Filed Pursuant to Rule 424(b)(5)

Registration No. 333-222868

CALCULATION OF REGISTRATION FEE

Title of Each Class of Securities to be Registered	Amount to be Registered(1)	Proposed Maximum Offering Price Per Share	Proposed Maximum Aggregate Offering Price	Amount of Registration Fee(2)
Common Stock, par value $0.001 per share	2,530,000	$94.46	$238,983,800	$29,753.48

(1) Includes 2,200,000 shares of common stock to be sold to the underwriters plus an option to purchase up to an additional 330,000 shares of common stock.

(2) Calculated pursuant to Rule 457(a) under the Securities Act of 1933, as amended (the “Securities Act”). Payment of the registration fee at the time of filing of the Registrant’s registration statement on Form S-3, filed with the Securities and Exchange Commission on February 5, 2018, was deferred pursuant to Rules 456(b) and 457(r) under the Securities Act and is paid herewith.

PROSPECTUS SUPPLEMENT TO PROSPECTUS DATED FEBRUARY 5, 2018

2,200,000 Shares

Common Stock

We are offering 2,200,000 shares of our common stock pursuant to this prospectus supplement and the accompanying prospectus.

We have granted the underwriters a 30-day option to purchase up to 330,000 additional shares of our common stock from us at the public offering price, less underwriting discounts and commissions.

Our common stock is listed on The Nasdaq Global Select Market under the symbol “ANAB.” The last sale price of our common stock on The Nasdaq Global Select Market on September 25, 2018 was $94.46 per share.

We are an “emerging growth company” as the term is used in the Jumpstart Our Business Startups Act of 2012 and, as such, have elected to comply with certain reduced public company reporting requirements.

An investment in our common stock involves a high degree of risk. You should carefully consider the information under the heading “Risk Factors” beginning on page S-13 of this prospectus supplement and in the documents incorporated by reference into this prospectus supplement before investing in our securities.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

	Price to Public	Underwriting Discounts and Commissions(1)	Proceeds to AnaptysBio, Inc.
Per Share	$94.46	$4.8659	$89.5941
Total	$207,812,000	$10,704,980	$197,107,020

(1) See “Underwriting” beginning on page S-26 for additional information regarding underwriting compensation. The underwriters will receive an aggregate underwriting discount of up to $1,605,747 on the shares sold pursuant to the exercise of the underwriters’ option to purchase additional shares.

If the underwriters exercise the option in full, the total underwriting discounts and commissions payable by us will be up to $12,310,727, and the total proceeds to us, before expenses, will be at least $226,673,073.

The underwriters expect to deliver the shares of common stock on or about September 28, 2018.

Credit Suisse	J.P. Morgan	Jefferies
Cantor	Guggenheim Securities	Wedbush PacGrow

The date of this prospectus supplement is September 25, 2018

TABLE OF CONTENTS

Prospectus Supplement

	Page
ABOUT THIS PROSPECTUS SUPPLEMENT		S-1
PROSPECTUS SUPPLEMENT SUMMARY		S-2
THE OFFERING		S-12
RISK FACTORS		S-13
FORWARD-LOOKING STATEMENTS		S-15
USE OF PROCEEDS		S-17
PRICE RANGE OF COMMON STOCK		S-18
DIVIDEND POLICY		S-19
DILUTION		S-20
MATERIAL UNITED STATES FEDERAL INCOME TAX CONSEQUENCES FOR NON-U.S. HOLDERS OF OUR COMMON STOCK		S-21
UNDERWRITING		S-26
LEGAL MATTERS		S-38
EXPERTS		S-38
WHERE YOU CAN FIND MORE INFORMATION		S-38
INCORPORATION OF INFORMATION BY REFERENCE		S-39

Prospectus

	Page
ABOUT THIS PROSPECTUS		1
PROSPECTUS SUMMARY		2
RATIO OF EARNINGS TO FIXED CHARGES		5
RISK FACTORS		6
FORWARD-LOOKING STATEMENTS		6
WHERE YOU CAN FIND MORE INFORMATION		7
INCORPORATION OF INFORMATION BY REFERENCE		7
USE OF PROCEEDS		8
PLAN OF DISTRIBUTION		9
DESCRIPTION OF CAPITAL STOCK		11
DESCRIPTION OF DEBT SECURITIES		16
DESCRIPTION OF WARRANTS		23
DESCRIPTION OF SUBSCRIPTION RIGHTS		25
DESCRIPTION OF UNITS		26
LEGAL MATTERS		26
EXPERTS		26

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ABOUT THIS PROSPECTUS SUPPLEMENT

On February 5, 2018, we filed with the Securities and Exchange Commission, or SEC, a “shelf” registration statement on Form S-3 utilizing a shelf registration process relating to the securities described in this prospectus supplement, which registration statement became automatically effective upon filing. Under this shelf registration process, we may, from time to time, sell common stock and other securities, of which this offering is a part.

This document is in two parts. The first part is this prospectus supplement, including the documents incorporated by reference herein, which describes the specific terms of this offering and also adds to and updates the information contained in the accompanying prospectus and the documents incorporated by reference. The second part, the accompanying prospectus, including the documents incorporated by reference therein, provides more general information, some of which may not apply to this offering. Generally, when we refer to this prospectus, we are referring to both parts of this document combined. Before you invest, you should carefully read this prospectus supplement, the accompanying prospectus and the information incorporated by reference herein and therein, as well as the additional information described in this prospectus supplement under “Where You Can Find More Information.” This prospectus supplement may add, update or change information contained in the accompanying prospectus. To the extent that any statement we make in this prospectus supplement is inconsistent with statements made in the accompanying prospectus or any documents incorporated by reference therein, the statements made in this prospectus supplement will be deemed to modify or supersede those made in the accompanying prospectus and such documents incorporated by reference therein.

We are offering to sell, and seeking offers to buy, shares of our common stock only in jurisdictions where offers and sales are permitted. The distribution of this prospectus supplement and the offering of the common stock in certain jurisdictions may be restricted by law. Persons outside the United States who come into possession of this prospectus supplement must inform themselves about, and observe any restrictions relating to, the offering of the common stock and the distribution of this prospectus supplement outside the United States. This prospectus supplement does not constitute, and may not be used in connection with, an offer to sell, or a solicitation of an offer to buy, any securities offered by this prospectus supplement by any person in any jurisdiction in which it is unlawful for such person to make such an offer or solicitation.

This prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein and therein include trademarks, service marks and trade names owned by us or other companies. All trademarks, service marks and trade names included or incorporated by reference into this prospectus supplement or the accompanying prospectus are the property of their respective owners.

We and the underwriters have not authorized anyone to provide you with information different than that contained or incorporated by reference in this prospectus supplement, the accompanying prospectus or any free writing prospectus that we have authorized for use in connection with this offering. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. You should assume that the information appearing in this prospectus supplement, the accompanying prospectus, the documents incorporated by reference herein and therein, and in any free writing prospectus that we have authorized for use in connection with this offering is accurate only as of the date of those respective documents. Our business, financial condition, results of operations and prospects may have changed since those dates. You should read this prospectus supplement, the accompanying prospectus, the documents incorporated by reference herein and therein, and any free writing prospectus that we have authorized for use in connection with this offering in their entirety before making an investment decision. You should also read and consider the information in the documents to which we have referred you in the sections of this prospectus supplement entitled “Where You Can Find More Information” and “Incorporation of Information by Reference.”

In this prospectus supplement, unless the context otherwise requires, the terms “AnaptysBio” the “Company,” “we,” “us,” and “our” refer to AnaptysBio, Inc., a Delaware corporation.

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PROSPECTUS SUPPLEMENT SUMMARY

This summary highlights selected information about us, this offering and information appearing elsewhere in this prospectus supplement, in the accompanying prospectus and in the documents incorporated by reference herein and therein. This summary is not complete and does not contain all the information you should consider before investing in our common stock pursuant to this prospectus supplement and the accompanying prospectus. Before making an investment decision, to fully understand this offering and its consequences to you, you should carefully read this entire prospectus supplement, the accompanying prospectus and the information incorporated by reference, including “Risk Factors,” the financial statements, and related notes, and the other information that we incorporate by reference herein and therein.

Company Overview

We are a clinical stage biotechnology company developing first-in-class antibody product candidates focused on unmet medical needs in inflammation. We develop our product candidates to address emerging biological targets using our proprietary antibody discovery technology platform, which is based upon a breakthrough understanding of the natural process of antibody generation, known as somatic hypermutation, or SHM, and replicates this natural process of antibody generation in vitro. Our strategy is to advance the development and commercialization of our proprietary product candidates, and for certain programs, establish partnerships with leading biopharmaceutical companies where we retain certain development and commercialization rights in the United States.

Our most advanced wholly-owned antibody programs, etokimab and ANB019, neutralize therapeutic targets that are genetically associated with severe inflammatory disorders in humans. Etokimab is the nonproprietary name adopted by the United States Adopted Names Council, in consultation with the World Health Organization International Nonproprietary Names Expert Committee, for our anti-IL-33 antibody drug candidate previously referred to as ANB020. Etokimab inhibits the activity of the interleukin-33 cytokine, or IL-33, which we believe is broadly applicable to the treatment of atopic inflammatory disorders, such as moderate-to-severe atopic dermatitis, eosinophilic asthma, chronic rhinosinusitis with nasal polyps and potentially other allergic conditions. We have completed a Phase 1 trial of etokimab in healthy volunteers in Australia, the results of which were presented at the 2017 American Academy of Dermatology, or AAD, Annual Meeting and the American Academy of Allergy, Asthma and Immunology, or AAAAI, 2017 Annual Meeting in March 2017. We believe the results of this Phase 1 trial demonstrate a favorable safety profile of etokimab, which was well-tolerated and for which no dose-limiting toxicities were observed, and favorable pharmacodynamic properties of etokimab, where a single dose was sufficient to suppress IL-33 function for approximately three months post-dosing as measured by an ex vivo pharmacodynamic assay.

We have subsequently completed a Phase 2a trial of etokimab in 12 moderate-to-severe adult atopic dermatitis patients, under an approved Clinical Trial Authorisation, or CTA, with the U.K. Medicines and Healthcare Products Regulatory Agency, or MHRA, announced top-line data from an interim analysis of this trial in October 2017 and presented data upon completion of this trial at the 2018 AAD Annual Meeting in February 2018 and the 2018 European Academy of Allergy and Clinical Immunology, or EAACI, Congress in May 2018. This Phase 2a proof-of-concept trial enrolled 12 moderate-to-severe adult atopic dermatitis patients, who were initially administered a single intravenous dose of placebo within 14 days of enrollment, followed by a single intravenous 300mg dose of etokimab one week subsequent to placebo. Prior to enrollment in the study, patients were not permitted any systemic or topical medications during a wash-out period. Patients were permitted to take a monitored amount of topical corticosteroids as rescue therapy during the course of the study. Clinical response was assessed by a number of endpoints, including the improvement of each patient’s Eczema Area Severity Index, or EASI, score, a tool used to measure the extent and severity of atopic dermatitis, at key time points

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following etokimab administration relative to their enrollment baseline. Additional efficacy endpoints measured during the trial included the 5-dimensional pruritus, or 5-D pruritus, scale which measures itchiness, the 5-point Investigator’s Global Assessment, or IGA, scale, Dermatology Life Quality Index, or DLQI, and the SCORing Atopic Dermatitis, or SCORAD, scale. The average baseline EASI score at enrollment amongst all 12 patients was 32. All 12 patients were inadequately controlled by topical corticosteroids and seven of these 12 patients were treated with systemic non-biologic anti-inflammatory therapy prior to the screening washout period of this trial and exhibited an average EASI baseline score of 36 upon enrollment, while the remaining five of 12 enrolled patients did not require systemic immuno-modulators pre-study and exhibited an average EASI baseline score of 27. Biomarkers included blood eosinophil levels, an ex vivo pharmacodynamic assay measuring IL-33 mediated interferon-gamma release, granulocyte infiltration and cytokine levels in localized skin lesions measured five days after placebo administration and five days after etokimab administration. We believe the data from this trial demonstrate proof-of-concept for etokimab in moderate-to-severe adult atopic dermatitis and suggest that etokimab may provide meaningful differentiation in terms of patient convenience. Based on our analysis of publicly available data sources and interviews with physicians and key opinion leaders in the field, atopic dermatitis affects approximately 1.4 million adults in the United States, and we estimate that 280,000 of these patients have moderate-to-severe atopic dermatitis.

As further development in atopic dermatitis, we are enrolling a Phase 2b randomized, double-blinded, placebo-controlled, multi-dose study in 300 adults patients with moderate-to-severe atopic dermatitis, also referred to as the ATLAS trial, to assess different dose levels and dosing frequencies of subcutaneously-administered etokimab for a 16-week treatment period followed by an eight-week follow-up period, with top-line data expected in the second half of 2019. Sixty patients are being randomized into each of five arms in the ATLAS trial where dosing will occur as follows: (i) initial 600mg loading dose followed by 300mg monthly doses of etokimab, (ii) initial 300mg loading dose followed by 150mg monthly doses of etokimab, (iii) initial 300mg loading dose followed by 150mg doses of etokimab every eight weeks, (iv) monthly 20mg doses of etokimab and (v) monthly doses of placebo.

We are conducting, under a CTA with the MHRA in the United Kingdom and under an Investigational New Drug Application, or IND, with the U.S. Food and Drug Administration, or FDA, a randomized, placebo-controlled Phase 2a trial of etokimab in 25 severe adult eosinophilic asthma patients, who were randomized between a single 300mg intravenous dose of etokimab or placebo upon enrollment (Day 1) at six sites located in the United States and the United Kingdom. Upon screening, which occurred 7 to 14 days prior to enrollment, patients were required to have a blood eosinophil count of at least 300 per microliter, confirmed clinical diagnosis of severe asthma according to the Global Initiative for Asthma, or GINA, 2016, pre-bronchodilator Forced Expiratory Volume in One Second, or FEV1, of less than 80% of predicted and at least one asthma exacerbation within the past 12 months requiring use of rescue medication. Patients were required to be stably maintained on high-dose inhaled corticosteroids, or ICS, and long-acting beta-2-agonists, or LABA, for at least three months prior to screening and were required to continue ICS/LABA therapy during the course of this trial. Baseline clinical assessments were conducted for each patient on Day 1 prior to etokimab or placebo dose, and patients completed follow-up clinical assessments on Days 2, 8, 22, 36 and 64 as of an interim analysis. The last follow-up visit for each patient will occur on Day 127 post-dose. Baseline parameters of etokimab-dosed patients (n=12) were 545 blood eosinophils per microliter, 2.5 liters FEV1 and 65% predicted FEV1, while placebo-dosed patients (n=13) had 705 blood eosinophils per microliter, 2.5 liters FEV1 and 66% predicted FEV1. Nine of 12 (75%) etokimab-dosed patients were male with an average age of 41, while nine of 13 (69%) placebo-dosed patients were male with an average age of 36.

We announced top-line data from this Phase 2a trial in September 2018, which we believe demonstrated proof-of-concept for etokimab in severe adult eosinophilic asthma patients with rapid and sustained FEV1 improvement. Etokimab-dosed patients rapidly improved lung function by Day 2, where FEV1 increased by 8% over placebo. FEV1 increase was sustained at Day 64, where etokimab-dosed patients demonstrated 11%

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increase over placebo. Blood eosinophil reduction, which is a biomarker illustrative of etokimab’s mechanistic breadth, was observed at 31% over placebo at Day 2 and sustained to 46% over placebo at Day 64. This reduction correlated with FEV1 improvement and was consistent with the blood eosinophil effects observed in a prior single dose etokimab trial in moderate-to-severe atopic dermatitis patients. Etokimab was generally well-tolerated by all patients and no serious adverse events have been reported to date. No treatment-emergent adverse events were deemed to be etokimab-related, and the most frequent treatment-emergent adverse events reported were single occurrences of moderate strep throat in two etokimab-dosed patients and single occurrences of mild vomiting in two placebo-dosed patients. No exacerbations or rescue therapy usage has been reported as of the interim analysis. This Phase 2a trial is currently ongoing and the company plans to report full data from this trial at a medical conference in 2019 following trial completion. In addition, we plan to continue development of etokimab in eosinophilic asthma with a multi-dose Phase 2b randomized, double-blinded, placebo-controlled trial, which is expected to be initiated in 2019. We estimate that approximately 1.1 million adults in the United States are diagnosed with severe asthma that is uncontrolled through standard-of-care, and 50% of these patients have eosinophilic asthma.

The following table summarizes the key top-line data we announced in September 2018:

Parameter	Timepoint		Change Relative to Day 1 Baseline
			Etokimab (n=12)			Placebo (n=13)			Net
FEV1 Increase (%)		Day 2		12	%		4	%		8	%
		Day 8		9	%		5	%		4	%
		Day 22		16	%		8	%		8	%
		Day 36		14	%		8	%		6	%
		Day 64		15	%		4	%		11	%
Blood Eosinophil Level (%)		Day 2		-22	%		9	%		-31	%
		Day 8		-34	%		-15	%		-19	%
		Day 22		-30	%		-10	%		-20	%
		Day 36		-43	%		1	%		-44	%
		Day 64		-40	%		6	%		-46	%

We have submitted an IND to the FDA to enable initiation of a randomized, placebo-controlled Phase 2 trial of etokimab in approximately 100 adult patients with chronic rhinosinusitis with nasal polyps, or CRSwNP, which is a debilitating atopic disorder associated with elevated IL-33 pathway signaling. We expect that patients in this trial, also known as the ECLIPSE trial, will be randomized between three cohorts, which include two different subcutaneous dosing frequencies of etokimab, or placebo, each in combination with mometasone furoate nasal spray as background therapy, for a treatment period of 16 weeks followed by an eight-week follow-up period, where efficacy will be assessed at week 16 post-dosing using the bilateral endoscopic Nasal Polyp Score and Sino-Nasal Outcome Test. We plan to initiate the ECLIPSE trial by the end of 2018, and anticipate top-line data to be available in the second half of 2019. Based on publicly available data sources, CRSwNP affects approximately 1.3 million adults in the United States, and we estimate that 400,000 of these patients are inadequately controlled with standard-of-care.

As a result of market assessment regarding the adoption of the peanut oral food challenge in future commercial usage of etokimab in peanut allergy patients, we have has decided to deprioritize further company-sponsored clinical development of etokimab in moderate-to-severe baseline adult peanut allergy patients. We therefore do not intend to utilize our capital or clinical development resources to pursue a Phase 2b clinical trial of etokimab in peanut allergy, however we may pursue potential investigator-sponsored trials related to this indication.

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ANB019 inhibits the interleukin-36 receptor, or IL-36R, for the treatment of rare inflammatory diseases including generalized pustular psoriasis, or GPP, and palmoplantar pustulosis, or PPP, previously referred to as palmo-plantar pustular psoriasis. We have completed, under an approved Clinical Trial Notification, or CTN, a Phase 1 clinical trial in healthy volunteers for which we announced positive top-line results from an interim analysis of this trial and subsequently presented completed data from this trial at the 2018 EAACI Congress. In the double-blinded, placebo-controlled healthy volunteer Phase 1 trial, 36 subjects were administered a single subcutaneous or intravenous dose of ANB019 ranging between 10 mg and 750 mg, 18 subjects were administered multiple ascending doses of ANB019 intravenously ranging between 40 mg and 300 mg weekly for four consecutive weeks and 18 subjects were dosed with placebo. ANB019 was well-tolerated by all subjects and no dose-limiting toxicities were observed. The most frequent treatment-emergent adverse events observed in the single ascending dose cohorts were upper respiratory tract infections in 10 of 36 (28%) subjects dosed with ANB019 versus six of 12 (50%) subjects dosed with placebo, and headache in 10 of 36 (28%) subjects dosed with ANB019 versus three of 12 (25%) subjects dosed with placebo. In the multiple ascending dose cohorts, the most frequent treatment-emerging adverse events observed were headache in seven of 18 (39%) subjects dosed with ANB019 versus one of six (17%) subjects dosed with placebo. No serious adverse events were reported among any subjects in the trial. The in vivo half-life of ANB019 was approximately 28 days for both subcutaneous and intravenous routes of administration, with bioavailability of approximately 90 percent. A single dose of ANB019 at certain dose levels was able to completely suppress IL-36 cytokine function for 85 days, as measured by IL-36 cytokine-mediated release of IL-8 using an ex vivo pharmacodynamic assay. The favorable pharmacokinetics and pharmacodynamic properties of ANB019 and other results demonstrated by this Phase 1 trial support advancement of ANB019 into Phase 2 studies for GPP and PPP.

We have received clearance of a CTA filing with the MHRA and an IND filing with the FDA, and have initiated a 10-patient open-label multi-dose Phase 2 trial of ANB019 in GPP patients, also referred to as the GALLOP trial, where top-line data are anticipated by early 2019. Patients in the GALLOP study are dosed with a 750mg intravenous loading dose of ANB019 upon enrollment, followed by 100mg subcutaneously-administered monthly doses of ANB019 for a treatment period of up to 16 weeks post enrollment and then monitored for a total of 8 weeks. We have cleared an IND with the FDA and have initiated, in the United States, a randomized, double-blind, placebo-controlled approximately 50-patient multi-dose trial of ANB019 in PPP, also referred to as the POPLAR trial. We intend to submit a CTA filing to the MHRA to permit expansion of the POPLAR trial in the United Kingdom, where top-line data is anticipated in the second half of 2019.

In addition to etokimab and ANB019, our wholly-owned pipeline includes novel anti-inflammatory checkpoint receptor modulator antibodies that we believe is applicable for treatment of certain autoimmune diseases where immune checkpoint receptors are insufficiently activated, where we anticipate an IND for the first such antibody in the second half of 2019.

In addition to our wholly-owned antibody programs, multiple AnaptysBio-developed antibody programs have been advanced to preclinical and clinical milestones under our collaborations. Our collaborations include an immuno-oncology-focused collaboration with TESARO, Inc. and TESARO Development, Ltd., or collectively, TESARO and an inflammation-focused collaboration with Celgene Corporation, or Celgene.

Our company is led by a strong management team with deep experience in antibody discovery and development, collaborations, operations and corporate finance.

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Our Product Candidates

We have developed, and will continue to develop, antibody product candidates that leverage emerging insights into biological mechanisms to treat severe diseases with unmet medical need. The following table summarizes certain key information about our wholly-owned and partnered product candidates:

Our most advanced, wholly-owned product candidates are summarized below:

• Etokimab is a potentially first-in-class antibody that inhibits the activity of IL-33, a pro-inflammatory cytokine that multiple studies have indicated is a central mediator of atopic diseases, including moderate-to-severe atopic dermatitis, severe eosinophilic asthma, chronic rhinosinusitis with nasal polyps and potentially other allergic conditions. IL-33 directly mediates release of disease-associated cytokines, which recruit pro-inflammatory cells that mediate atopic disease. Because etokimab inhibits IL-33 function, and acts upstream broadly across the key cell types and cytokines involved in atopy, we believe that its mechanism has advantages in the treatment of atopic diseases over competing agents that block only a subset of the cytokines responsible for atopic diseases. The role of IL-33 signaling in asthma has been genetically validated through human studies published in the medical literature. We have completed a Phase 1 trial of etokimab in healthy volunteers in Australia, which demonstrated a favorable safety, pharmacokinetic and pharmacodynamic profile of etokimab, and we presented these results at the 2017 AAD Annual Meeting and the American Academy of Allergy, Asthma and Immunology 2017 Annual Meeting in March 2017. We subsequently completed a Phase 2a trial of etokimab in 12 moderate-to-severe adult atopic dermatitis patients, under an approved CTA with the MHRA, announced top-line data from an interim analysis of this trial in October 2017 and presented data upon completion of this trial at the 2018 AAD Annual Meeting in February 2018 and the 2018 EAACI Congress in May 2018. We believe the data from this trial demonstrate proof-of-concept for etokimab in moderate-to-severe adult atopic dermatitis and suggest that etokimab may provide meaningful differentiation from available therapies in terms of patient convenience. As further development in atopic dermatitis, we are enrolling a Phase 2b randomized, double-blinded, placebo-controlled, multi-dose study in 300 adults patients with moderate-to-severe atopic dermatitis, also referred to as the ATLAS trial, to

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assess different dose levels and dosing frequencies of subcutaneously-administered etokimab for a 16-week treatment period followed by an eight-week follow-up period, with top-line data expected in the second half of 2019. Based on our analysis of publicly available data sources and interviews with physicians and key opinion leaders in the field, atopic dermatitis affects approximately 1.4 million adults in the United States, and we estimate that 280,000 of these patients have moderate-to-severe atopic dermatitis. We are conducting, under a CTA with the MHRA in the United Kingdom and under an IND with the FDA, a randomized, placebo-controlled 25-patient single dose Phase 2a trial of etokimab versus placebo, each in combination with inhaled corticosteroids and long-acting beta agonists as background therapy, where efficacy will be assessed using improvement in FEV1. An interim analysis of this Phase 2a trial was disclosed in September 2018, which we believe demonstrated proof-of-concept for etokimab in severe adult eosinophilic asthma patients with rapid and sustained FEV1 improvement. This Phase 2a trial is currently ongoing and the company plans to report full data from this trial at a medical conference in 2019 following trial completion. In addition, we plan to continue development of etokimab in eosinophilic asthma with a multi-dose Phase 2b randomized, double-blinded, placebo-controlled trial, which is expected to be initiated in 2019. Based on our analysis of publicly available data sources and interviews with physicians and key opinion leaders in the field, we estimate that approximately 1.1 million adults in the United States are diagnosed with severe asthma that is uncontrolled through standard-of-care, and 50% of these patients have eosinophilic asthma. We have submitted an IND to the FDA to enable initiation of a randomized, placebo-controlled Phase 2 trial of etokimab in approximately 100 adult patients, also known as the ECLIPSE trial, with CRSwNP, which is a debilitating atopic disorder associated with elevated IL-33 pathway signaling. We plan to initiate the ECLIPSE trial by the end of 2018, and anticipate top-line data to be available in the second half of 2019. Based on our analysis of publicly available data sources and interviews with physicians and key opinion leaders in the field, CRSwNP affects approximately 1.3 million adults in the United States, and we estimate that 400,000 of these patients are inadequately controlled with standard-of-care.

• ANB019 is an antibody that inhibits the function of IL-36R, which we are initially developing as a potential first-in-class therapy for GPP and PPP patients. GPP is a life-threatening, rare, systemic inflammatory disorder that, based on our analysis of publicly available data sources and interviews with physicians and key opinion leaders in the field, we estimate affects approximately 3,000 patients in the United States with no approved therapies for treatment of this disorder. Studies have shown that GPP can be associated in some patients with mutations that lead to abnormally high signaling through the IL-36R, which we believe can be addressed by treatment with ANB019 irrespective of whether a GPP patient has a mutated IL-36R signaling pathway. PPP is a non-fatal form of pustular psoriasis that we estimate affects approximately 150,000 patients in the United States alone. PPP is believed to be caused by increased systemic levels of interleukin-36 resulting in inflammatory pustules on the hands and feet of patients that cause significant inability to stand, walk or do manual work, which we believe can be addressed by treatment with ANB019. We have completed, under an approved CTN, a Phase 1 clinical trial in healthy volunteers which showed favorable safety, pharmacokinetic and pharmacodynamic properties that support advancement of ANB019 into Phase 2 studies for GPP and PPP. We have received clearance of a CTA filing to the MHRA and an IND filing with the FDA, and have subsequently initiated a 10-patient open-label multi-dose Phase 2 study of ANB019 in GPP patients, the GALLOP trial, where efficacy will be assessed using the modified Japanese Dermatology Association Severity Index. We believe that positive results from the GALLOP trial may enable initiation of a subsequent registration study enrolling less than 100 GPP patients. We have cleared an IND with the FDA and have initiated, in the United States, a randomized, double-blind, placebo-controlled approximately 50-patient multi-dose trial of ANB019 in PPP, also referred to as the POPLAR trial, where efficacy will be assessed using the Palmoplantar Pustulosis Severity Index. We intend to submit a CTA filing to the MHRA to permit expansion of the POPLAR trial in the United Kingdom, where top-line data is anticipated in the second half of 2019. We plan to seek FDA Orphan Drug Designation for the treatment of GPP and PPP. The

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FDA may grant Orphan Drug Designation to a drug intended to treat a disease or condition that generally affects fewer than 200,000 individuals in the United States.

• Checkpoint receptor agonist antibodies are being developed by us to multiple different novel anti-inflammatory checkpoint receptor modulator antibodies for the treatment of certain autoimmune diseases where we believe checkpoint receptor function is insufficiently activated. Known human immune checkpoint receptors include CTLA-4, PD-1, LAG-3, BTLA and TIGIT. We anticipate that, subsequent to regulatory clearance, one of our wholly-owned checkpoint receptor antibodies will initiate human testing during the second half of 2019.

The Advantages of Our SHM Platform

Our approach to developing novel therapeutic antibody product candidates is based upon SHM, a critical, endogenous process that generates the essential antibody diversity required to develop a natural immune response to pathogens. Our proprietary antibody generation platform is designed to replicate the natural process of SHM in vitro. Competing antibody discovery technologies include mouse immunization methodologies, microbial antibody display and human B-cell screening. We believe our SHM platform overcomes several key limitations associated with these competing technologies and has the following competitive advantages:

• Diversity against difficult targets. By applying SHM without the constraints of an in vivo environment we are able to generate an unprecedented diversity of antibodies. This enables us to develop antibodies against human targets that we believe have not otherwise been accessible to other technologies.

• High potency. Because our platform generates highly-potent antibodies, we are potentially able to modulate every extracellular target associated with human disease, and believe only small therapeutic doses may be required to mediate therapeutic effect in vivo.

• Functional activity selection. Our mammalian cell system simultaneously displays and secretes antibodies during the antibody discovery process, allowing us to incorporate functional assays throughout the process and focus on producing product candidates that are optimized for the desired therapeutic activity.

• Speed. Our platform technology has enabled us to generate therapeutic-grade antibodies and initiate subsequent preclinical manufacturing and toxicology studies, typically in less than 12 months. We believe this timeline is significantly shorter than conventional antibody discovery approaches based upon mouse immunization and microbial display systems.

• Manufacturability. By utilizing our mammalian cell display system, we believe our approach increases the probability of success in manufacturing and commercialization by mitigating the risks associated with antibody expression, formulation and stability during the antibody generation process.

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Our Collaborations

We have established collaborations with pharmaceutical and biotechnology companies that have provided us with $76.6 million in payments through June 30, 2018. Multiple antibodies, generated by us prior to or during a strategic collaboration, are currently being advanced through development by our collaborators. Our collaborations with TESARO and Celgene are described below:

TESARO Programs

Under our immuno-oncology collaboration with TESARO, we have granted exclusive rights to TESARO to develop and commercialize antibodies generated using our SHM platform consisting of the following antibody product candidates:

• Anti-PD-1 Monospecific Antagonist Antibody (TSR-042): Registration program initiated for metastatic microsatellite instability high (MSI-H) endometrial cancer;

• Anti-TIM-3 Monospecific Antagonist Antibody (TSR-022): Dose escalation completed in Phase 1, combination trial with TSR-042 is ongoing;

• Anti-LAG-3 Monospecific Antagonist Antibody (TSR-033): Phase 1 trial dose escalation and combination trial with TSR-042 is ongoing, and

• Anti-PD-1/LAG-3  Bispecific Antagonist Antibody (TSR-075): lead candidate identified, IND-enabling studies on-going.

Celgene Programs

Under our collaboration with Celgene, we developed therapeutic antibodies against multiple targets. We granted Celgene the option to obtain worldwide commercial rights to antibodies generated against each of the targets under the agreement, which option was triggered on a target-by-target basis by our delivery of antibodies meeting certain pre-specified parameters pertaining to each target under collaboration. Celgene is currently advancing two AnaptysBio-generated anti-inflammatory antibody programs, where one of these programs is an anti-PD-1 agonist antibody (CC-90006) currently in a Phase 1 trial for psoriasis.

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Milestones

Below is a list of key milestones relating to our wholly-owned pipeline programs:

Program	Milestone	Timing
Etokimab (anti-IL-33)	Moderate-to-Severe Adult Atopic Dermatitis Phase 2a Trial	Top-line data announced October 2017 Detailed data presented at AAD and EAACI 2018
	ATLAS: Moderate-to-Severe Adult Atopic Dermatitis Phase 2b Trial	Initiated H1 2018 Top-line data anticipated in H2 2019
	Severe Adult Eosinophilic Asthma Phase 2a Trial	Top-line data presented September 2018 Detailed data to be presented in 2019
	Eosinophilic Asthma Phase 2b Trial	To be initiated in 2019
ANB019 (anti-IL-36R)	ECLIPSE: Adult Chronic Rhinosinusitis with Nasal Polyps Phase 2 Trial	To be initiated by end 2018 Top-line data anticipated in H2 2019
	Healthy Volunteer Top-line Phase I Trial	Top-line data announced November 2017 Detailed data presented at EAACI 2018
	GALLOP: GPP Phase 2 Trial	Initiated H1 2018 Top-line data anticipated in early 2019
	POPLAR: PPP Phase 2 Trial	Initiated H2 2018 Top-line data anticipated in H2 2019

Our Strategy

We are a leading antibody development company with a pipeline of novel therapeutic antibodies, which is being further expanded by applying our technology platform to emerging biological targets. The key elements of our strategy include:

• Advancing our wholly-owned lead product candidates to clinical milestones. We are working to demonstrate the safety and efficacy of our wholly-owned pipeline programs, and have completed a Phase 1 trial of etokimab in healthy volunteers in Australia, which we believe has demonstrated favorable safety and ex vivo pharmacodynamic properties. We have completed a Phase 2a trial of etokimab in patients with moderate-to-severe adult atopic dermatitis where top-line data efficacy was announced in October 2017 and completed trial data was presented at the 2018 AAD Annual Meeting and the 2018 EAACI Congress. In September 2018, we announced top-line data from an interim analysis of an ongoing randomized, double-blinded placebo-controlled Phase 2a trial of etokimab in severe adult eosinophilic asthma patients and plan to initiate a randomized, placebo-controlled Phase 2 trial of etokimab in approximately 100 adult patients with CRSwNP. We are also enrolling a Phase 2b randomized, double-blinded, placebo-controlled, multi-dose study in 300 adults patients with moderate-to-severe atopic dermatitis. We have conducted, under an approved CTN, a Phase 1 clinical trial in healthy volunteers to assess the safety, pharmacokinetics and pharmacodynamics of ANB019 and announced top-line data from this trial in November 2017. We have received clearance of a CTA filing to the MHRA and an IND with

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the FDA, and have subsequently initiated a 10-patient open-label multi-dose Phase 2 trial of ANB019 in GPP patients, and have received clearance of an IND with the FDA, and subsequently initiated in the United States, a randomized, double-blind, placebo-controlled approximately 50-patient multi-dose trial of ANB019 in PPP.

• Continuing to expand our proprietary pipeline by generating new product candidates using our technology platform. Using our proprietary SHM antibody generation platform, we are able to rapidly develop novel antibodies against biological targets. Our goal is to continue expanding our wholly-owned new therapeutic antibody program pipeline by innovating one or more wholly-owned novel pipeline antibodies to potentially first-in-class immune-related targets.

• Identifying emerging opportunities in key therapeutic areas. We intend to remain at the forefront of discovery and development of new therapeutic opportunities in inflammation by understanding and translating biological breakthroughs into first-in-class therapeutic antibodies. Our approach includes translational biology assessments, such as human genetics, ex vivo tissue pathology and target expression patterns, to understand the relevance of emerging targets to patients with unmet medical needs. We plan to leverage this knowledge to create new product candidates and position our current and future programs for rapid initial efficacy assessment.

• Retaining rights to strategic products in key commercial markets. We intend to retain ownership and control of our pipeline programs to key preclinical and clinical data inflection points. We may build sales and marketing capabilities in the United States with a focused commercial organization. For certain programs, we plan to seek strategic collaborations that provide us with funding, infrastructure and marketing resources to advance through development and commercialization.

Corporate Information

We were incorporated under the laws of the State of Delaware in November 2005. Our principal executive offices are located at 10421 Pacific Center Court, Suite 200, San Diego, California 92121, and our telephone number is (858) 362-6295. Our website address is www.anaptysbio.com. The information contained on, or that can be accessed through, our website is not part of, and is not incorporated by reference into, this prospectus supplement. Investors should not rely on any such information in deciding whether to purchase our common stock.

JOBS Act

We are an “emerging growth company” as defined in the Jumpstart Our Business Startups Act of 2012, or the JOBS Act. We will remain an emerging growth company until the earlier of the last day of the fiscal year following the fifth anniversary of the completion of our initial public offering in January 2017, the last day of the fiscal year in which we have total annual gross revenue of at least $1.07 billion, the date on which we are deemed to be a large accelerated filer (this means that at the end of a fiscal year we have been public for at least 12 months, have filed at least one annual report and the market value of our common stock that is held by non-affiliates exceeds $700 million as of the end of the second quarter of that fiscal year), or the date on which we have issued more than $1.0 billion in nonconvertible debt securities during the prior three-year period. We will cease to be an “emerging growth company” as of December 31, 2018 as a result of our public float exceeding $700 million as of June 30, 2018.

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THE OFFERING

Common stock offered by us 2,200,000 Shares

Common stock to be outstanding after this offering 26,228,504 Shares

Option to purchase additional shares We have granted the underwriters a 30-day option to purchase up to 330,000 additional shares from us at the public offering price, less underwriting discounts and commissions.

Public offering price $94.46 per share

Use of proceeds We intend to use the net proceeds that we receive in this offering to fund research and development activities for our clinical development programs, our ongoing preclinical, discovery and research programs, and for working capital and other general corporate purposes. We may use a portion of the proceeds to acquire other complementary businesses or technologies, although we have no present commitments or agreements to do so. See “Use of Proceeds” for a more complete description of the intended use of proceeds from this offering.

Risk factors You should read the “Risk Factors” section of this prospectus supplement for a discussion of factors to consider carefully before deciding to invest in shares of our common stock.

Nasdaq Global Select Market symbol “ANAB”

The number of shares of our common stock to be outstanding immediately after this offering as shown above is based on 24,028,504 shares outstanding as of June 30, 2018 and excludes:

• 2,455,234 shares of common stock issuable upon exercise of outstanding options as of June 30, 2018, with a weighted-average exercise price of $22.50 per share;

• 65,100 shares of common stock issuable upon the exercise of options granted after June 30, 2018, with a weighted-average exercise price of $82.01 per share;

• 2,081,558 shares of common stock reserved for future issuance under our 2017 Equity Incentive Plan as of June 30, 2018; and

• 455,913 shares of common stock reserved for future issuance under our 2017 Employee Stock Purchase Plan as of June 30, 2018.

Except as otherwise indicated, all information in this prospectus supplement assumes no exercise of the outstanding options or warrants described above and no exercise of the underwriters’ option to purchase additional shares of common stock.

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RISK FACTORS

An investment in our securities involves a high degree of risk. Prior to making a decision about investing in our securities, you should carefully consider the risk factors described below together with all of the risks, uncertainties and assumptions discussed under Part II, Item 1A, “Risk Factors,” in our Annual Report on Form 10-K for the year ended December 31, 2017 and our most recent Quarterly Report on Form 10-Q for the quarter ended June 30, 2018, which is incorporated herein by reference, and may be amended, supplemented or superseded from time to time by other reports we file with the SEC in the future. If any of the risks incorporated by reference or set forth below occurs, our business, operations and financial condition could suffer significantly. As a result, you could lose some or all of your investment in our common stock. The risks and uncertainties we have described are not the only ones we face. Additional risks and uncertainties not presently known to us or that we currently deem immaterial may also affect our business, operations and financial condition, or cause the value of our common stock to decline.

Risks Related to this Offering

Our management will have broad discretion as to the use of the proceeds from this offering and we may not use the proceeds effectively.

Our management will have broad discretion in the application of the net proceeds from this offering and could spend the proceeds in ways that do not improve our results of operations or enhance the value of our common stock. You will be relying on the judgment of our management concerning these uses and you will not have the opportunity, as part of your investment decision, to assess whether the proceeds are being used appropriately. The failure of our management to apply these funds effectively could result in unfavorable returns and uncertainty about our prospects, each of which could cause the price of our common stock to decline.

If you purchase shares of common stock sold in this offering you will experience immediate and substantial dilution in your investment. You will experience further dilution if we issue additional equity securities in the future.

Since the price per share of our common stock being offered is substantially higher than the net tangible book value per share of our common stock, you will suffer substantial dilution with respect to the net tangible book value of the shares of common stock you purchase in this offering. Based on the public offering price of $94.46 per share, and our net tangible book value as of June 30, 2018, if you purchase shares of common stock in this offering, you will suffer immediate and substantial dilution of $76.08 per share with respect to the net tangible book value of the common stock. See “Dilution” for a more detailed discussion of the dilution you will incur if you purchase shares of common stock in this offering.

In addition, we have a significant number of stock options outstanding, and may also choose to issue additional common stock, or securities convertible into or exchangeable for common stock, in the future. In the event that the outstanding options are exercised, or that we make additional issuances of common stock or other convertible or exchangeable securities, you could experience additional dilution.

Future sales of a substantial number of shares of our common stock by our existing stockholders could cause our stock price to decline.

The market price of our common stock could decline as a result of sales of substantial amounts of our common stock in the public market after the closing of this offering, or the perception that these sales could occur. For example, certain of our stockholders possess rights with respect to the registration of their shares under the Securities Act of 1933, as amended, or the Securities Act. Registration of these shares under the Securities Act would result in the shares becoming freely tradable without restriction under the Securities Act.

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In addition, we have a significant number of stock options outstanding. If a substantial number of shares of common stock underlying these options are sold, or if it is perceived that they will be sold, in the public market, the trading price of our common stock could decline.

Risks Related to Discovery and Development of Our Product Candidates

Results from our initial Phase 2a clinical trials of etokimab may not be representative of the results we will experience in later Phase 2b and registration trials. If our later clinical trials are unsuccessful, etokimab may be delayed in development or fail entirely, which would have a material adverse impact on our business.

We have elected to structure our initial Phase 2a clinical trials in etokimab as investigational studies that enroll a relatively limited number of patients and are intended to allow us to better assess patient responses and potential efficacy results before designing and commencing Phase 2b clinical trials. We believe the results we have observed in the initial Phase 2a clinical trials of etokimab in atopic dermatitis and severe adult eosinophilic asthma suggest a reasonable basis for continuing development of etokimab in these indications through larger Phase 2b clinical trials. However, our Phase 2a trials involve relatively small patient populations, for example 12 patients in our Phase 2a trial in atopic dermatitis and 25 patients in our Phase 2a trial in severe adult eosinophilic asthma. The results we have observed in these smaller patient populations may not be predictive of results we will experience in later studies. Furthermore, the average results reported from our Phase 2a trials (for example, the average change in FEV1 reported in connection with our Phase 2a trial in severe adult eosinophilic asthma) are subject to significant variability due to the small number of patients enrolled, and are not expected to be, and are unlikely to be, statistically significant.

In addition, later studies may also include different design elements that could contribute to us experiencing different results than we have observed in our Phase 2a trials. In addition, the initial results we have reported from our completed Phase 2a clinical trials have included interim analyses and top-line results, which may not accurately predict the final results of the clinical trial or the results of future clinical trials. For instance, while we expect FEV1 to be an important endpoint in our later studies, our data from our Phase 2a study of severe adult eosinophilic asthma are from a single dose of drug evaluated only at timepoints through Day 64 and not at the planned Day 127 timepoint.

If our later clinical trials of etokimab are unsuccessful, whether for one of the reasons mentioned above or otherwise, etokimab may be delayed in development or fail entirely, which would have a material adverse impact on our business.

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FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying prospectus and the documents incorporated herein by reference contain “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. These forward-looking statements involve a number of risks and uncertainties. We caution readers that any forward-looking statement is not a guarantee of future performance and that actual results could differ materially from those contained in the forward-looking statement. The words “believe,” “may,” “will,” “potentially,” “estimate,” “continue,” “anticipate,” “intend,” “could,” “would,” “project,” “plan” “expect,” and similar expressions that convey uncertainty of future events or outcomes are intended to identify forward-looking statements.

These statements are based on current expectations of future events. Such statements include, but are not limited to:

• the success, cost and timing of our product candidate development activities and ongoing and planned clinical trials;

• our plans to develop and commercialize antibodies, including our lead product candidates etokimab for patients with severe allergic and atopic diseases and ANB019 for patients with GPP and PPP;

• the likelihood that the clinical data generated in any study we are performing or plan to perform in a non-U.S. jurisdiction will be subsequently accepted by the FDA and its foreign regulatory authorities outside of the jurisdiction where the study was being performed;

• the timing and ability of our collaborators to develop and commercialize our partnered product candidates;

• the potential benefits and advantages of our product candidates and approaches versus those of our competitors;

• our ability to execute on our strategy, including advancing our lead product candidates, identifying emerging opportunities in key therapeutic areas, continuing to expand our wholly-owned pipeline and retaining rights to strategic products in key commercial markets;

• our ability to obtain funding for our operations, including funding necessary to complete further development and commercialization of our product candidates;

• the timing of and our ability to obtain and maintain regulatory approvals for etokimab and ANB019 and our other product candidates;

• our ability to develop our product candidates;

• the rate and degree of market acceptance and clinical utility of any approved product candidates;

• the size and growth potential of the markets for any approved product candidates, and our ability to serve those markets;

• our commercialization, marketing and manufacturing capabilities and strategy;

• our ability to obtain and maintain intellectual property protection for our product candidates;

• our ability to avoid infringing upon the intellectual property rights of others;

• regulatory developments in the United States, the United Kingdom, Australia and other foreign countries;

• the success of competing therapies that are or may become available;

• our ability to attract and retain key scientific or management personnel;

• our use of the net proceeds from this offering;

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• our ability to identify additional products or product candidates with significant commercial potential that are consistent with our commercial objectives; and

• our estimates regarding expenses, future revenue, capital requirements and needs for additional financing.

These forward-looking statements are based on the current beliefs and expectations of our management and are subject to significant risks and uncertainties. If underlying assumptions prove inaccurate or unknown risks or uncertainties materialize, actual results may differ materially from current expectations and projections. Factors that might cause such a difference include those discussed under the section titled “Risk Factors” and elsewhere in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference into this prospectus supplement or the accompanying prospectus. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date made.

All subsequent written or oral forward-looking statements attributable to us or any person acting on our behalf are expressly qualified in their entirety by the cautionary statements contained or referred to in this section. We do not undertake any obligation to release publicly any revisions to these forward-looking statements to reflect events or circumstances after the date of this prospectus supplement or to reflect the occurrence of unanticipated events, except as may be required under applicable U.S. securities law. If we do update one or more forward-looking statements, no inference should be drawn that we will make additional updates with respect to those or other forward-looking statements.

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USE OF PROCEEDS

We estimate that we will receive net proceeds of approximately $197.1 million from the sale of 2,200,000 shares of our common stock in this offering, after deducting underwriting discounts and commissions and estimated offering expenses payable by us. If the underwriters exercise their option to purchase up to 330,000 additional shares in full, we estimate that the net proceeds of the shares we sell in this offering will be at least $226.7 million.

We currently intend to use the net proceeds we receive from this offering, together with our existing cash, cash equivalents and investments, to fund research and development activities for our clinical development programs, including, but not limited to, our ongoing and planned clinical trials for etokimab and ANB019, including related manufacturing costs, and our ongoing preclinical, discovery and research programs, and for working capital and other general corporate purposes.

Based on our planned use of the net proceeds, we believe that the funds from this offering, together with our existing cash, cash equivalents and investments, will be sufficient to fund our operating expenses and capital expenditure requirements through at least the end of 2020.

The expected use of the net proceeds from this offering represents our intentions based upon our current plans and business conditions. As of the date of this prospectus supplement, we cannot predict with any certainty all of the particular uses for the net proceeds or the amounts that we will actually spend on the uses set forth above. We may use a portion of the net proceeds for the acquisition of, or investment in, technologies, solutions or businesses that complement our business, although we have no present commitments or agreements to do so.

The amounts and timing of our clinical expenditures and the extent of clinical development may vary significantly depending on numerous factors, including the status, results and timing of our current and planned preclinical studies and clinical trials, product approval process with the FDA and other regulatory agencies, our current collaborations and any new collaborations we may enter into with third parties and any unforeseen cash needs. As a result, our management will retain broad discretion over the allocation of the net proceeds from this offering.

The expected net proceeds of this offering will not be sufficient for us to fund any of our product candidates through regulatory approval, and we will need to raise substantial additional capital to complete the development and commercialization of our product candidates.

Pending their use as described above, we intend to invest the net proceeds from this offering in short term and long-term, investment-grade interest-bearing securities such as money market accounts, certificates of deposit, commercial paper and guaranteed obligations of the U.S. government.

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PRICE RANGE OF COMMON STOCK

Our common stock is listed on The Nasdaq Global Select Market under the symbol “ANAB.” The following table sets forth, for the periods indicated, the reported high and low sales prices per share of our common stock as reported by The Nasdaq Global Select Market:

	HIGH		LOW
Fiscal Year ending December 31, 2017
First Quarter (beginning January 26, 2017)	$	29.96	$	15.17
Second Quarter	$	28.40	$	18.15
Third Quarter	$	37.62	$	20.12
Fourth Quarter	$	102.63	$	34.56
Fiscal Year ended December 31, 2018
First Quarter	$	134.00	$	91.01
Second Quarter	$	108.57	$	66.39
Third Quarter (through September 25, 2018)	$	110.00	$	67.91

The last reported sales price of our common stock on The Nasdaq Global Select Market on September 25, 2018 was $94.46 per share. On September 25, 2018, there were 17 holders of record of our common stock.

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DIVIDEND POLICY

We have never declared or paid cash dividends on our common stock. We currently intend to retain all available funds and any future earnings for use in the operation of our business and do not anticipate paying any dividends on our common stock in the foreseeable future. Any future determination to declare dividends will be made at the discretion of our board of directors and will depend on our financial condition, operating results, capital requirements, general business conditions and other factors that our board of directors may deem relevant. In addition, under the terms of our current credit facility, we are prohibited from paying cash dividends without the consent of our lenders.

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DILUTION

If you invest in our common stock, your interest will be diluted to the extent of the difference between the public offering price per share of our common stock and the as adjusted net tangible book value per share of our common stock immediately after this offering.

Our net tangible book value as of June 30, 2018 was approximately $285.0 million, or $11.86 per share. Net tangible book value per share is determined by dividing our total tangible assets, less total liabilities, by the number of shares of our common stock outstanding as of June 30, 2018. Dilution with respect to net tangible book value per share represents the difference between the amount per share paid by purchasers of shares of common stock in this offering and the net tangible book value per share of our common stock immediately after this offering.

After giving effect to the sale of 2,200,000 shares of our common stock at the public offering price of $94.46 per share, and after deducting underwriting discounts and commissions and estimated offering expenses, our as adjusted net tangible book value as of June 30, 2018 would have been approximately $482.1 million, or $18.38 per share. This represents an immediate increase in net tangible book value of $6.52 per share to existing stockholders and immediate dilution of $76.08 per share to investors purchasing our common stock in this offering. The following table illustrates this dilution on a per share basis:

Public offering price per share			$	94.46
Net tangible book value per share as of June 30, 2018	$	11.86
Increase in net tangible book value per share attributable to investors purchasing our common stock in this offering	$	6.52
As adjusted net tangible book value per share as of June 30, 2018 after this offering			$	18.38
Dilution per share to investors purchasing our common stock in this offering			$	76.08

If the underwriters exercise their option to purchase 330,000 additional shares in full, the as adjusted net tangible book value per share of our common stock after giving effect to this offering would be $19.26 per share, and the dilution in net tangible book value per share to investors purchasing common stock in this offering would be $75.20 per share.

The table and discussion above are based on 24,028,504 shares outstanding as of June 30, 2018 and excludes:

• 2,455,234 shares of common stock issuable upon exercise of outstanding options as of June 30, 2018, with a weighted-average exercise price of $22.50 per share;

• 65,100 shares of common stock issuable upon the exercise of options granted after June 30, 2018, with a weighted-average exercise price of $82.01 per share;

• 2,081,558 shares of common stock reserved for future issuance under our 2017 Equity Incentive Plan as of June 30, 2018; and

• 455,913 shares of common stock reserved for future issuance under our 2017 Employee Stock Purchase Plan as of June 30, 2018.

To the extent that outstanding options or warrants have been or may be exercised or other shares are issued, investors purchasing our common stock in this offering may experience further dilution. In addition, we may choose to issue additional common stock, or securities convertible into or exchangeable for common stock, in the future. The issuance of these securities could result in further dilution for investors purchasing our common stock in this offering.

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MATERIAL UNITED STATES FEDERAL INCOME TAX CONSEQUENCES

FOR NON-U.S. HOLDERS OF OUR COMMON STOCK

This section summarizes the material U.S. federal income tax considerations relating to the acquisition, ownership and disposition of our common stock acquired in this offering by “non-U.S. holders” (as defined below). This summary does not provide a complete analysis of all potential U.S. federal income tax considerations relating thereto. The information provided below is based upon provisions of the Internal Revenue Code of 1986, as amended, or the Code, Treasury regulations promulgated thereunder, administrative rulings and judicial decisions currently in effect. These authorities may change at any time, possibly retroactively, or the Internal Revenue Service, or IRS, might interpret the existing authorities differently. In either case, the tax considerations of owning or disposing of our common stock could differ from those described below. As a result, we cannot assure you that the tax consequences described in this discussion will not be challenged by the IRS or will be sustained by a court if challenged by the IRS.

This summary does not address the tax considerations arising under the laws of any non-U.S., state or local jurisdiction, or under U.S. federal gift and estate tax laws, except to the limited extent provided below. In addition, this discussion does not address tax considerations applicable to an investor’s particular circumstances or to investors that may be subject to special tax rules, including, without limitation:

• banks, insurance companies or other financial institutions;

• partnerships or other entities treated as partnerships or pass-through entities for U.S. federal tax purposes (or investors in such entities);

• corporations that accumulate earnings to avoid U.S. federal income tax;

• persons subject to the alternative minimum tax or the Medicare contribution tax on net investment income;

• tax-exempt organizations or tax-qualified retirement plans;

• controlled foreign corporations or passive foreign investment companies;

• persons who acquired our common stock as compensation for services;

• dealers in securities or currencies;

• traders in securities that elect to use a mark-to-market method of accounting for their securities holdings;

• persons that own, or are deemed to own, more than 5% of our capital stock (except to the extent specifically set forth below);

• certain former citizens or long-term residents of the United States;

• persons who hold our common stock as a position in a hedging transaction, “straddle,” “conversion transaction” or other risk reduction transaction;

• persons who do not hold our common stock as a capital asset within the meaning of Section 1221 of the Code (generally, for investment purposes);

• accrual method taxpayers subject to special tax accounting rules under Section 451(b) of the Code; or

• persons deemed to sell our common stock under the constructive sale provisions of the Code.

In addition, if a partnership or entity classified as a partnership or other pass-through entity for U.S. federal income tax purposes is a beneficial owner of our common stock, the tax treatment of a partner in the partnership or an owner of the entity will depend upon the status of the partner or other owner and the activities of the partnership or other entity. Accordingly, this summary does not address tax considerations applicable to partnerships that hold our common stock, and partners in such partnerships should consult their tax advisors.

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INVESTORS CONSIDERING THE PURCHASE OF OUR COMMON STOCK SHOULD CONSULT THEIR OWN TAX ADVISORS REGARDING THE APPLICATION OF THE U.S. FEDERAL INCOME AND ESTATE TAX LAWS TO THEIR PARTICULAR SITUATIONS AND THE CONSEQUENCES OF FOREIGN, STATE OR LOCAL LAWS, AND TAX TREATIES.

Non-U.S. Holder Defined

For purposes of this summary, a “non-U.S. holder” is any beneficial owner of our common stock, other than a partnership, that is not:

• an individual who is a citizen or resident of the United States;

• a corporation, or other entity taxable as a corporation for U.S. federal income tax purposes, created or organized under the laws of the United States, any state therein or the District of Columbia;

• a trust if it (i) is subject to the primary supervision of a U.S. court and one of more U.S. persons have authority to control all substantial decisions of the trust or (ii) has a valid election in effect under the applicable Treasury regulations to be treated as a U.S. person; or

• an estate whose income is subject to U.S. income tax regardless of source.

If you are a non-U.S. citizen who is an individual, you may, in some cases, be deemed to be a resident alien, as opposed to a nonresident alien, by virtue of being present in the United States for at least 31 days in the calendar year and for an aggregate of at least 183 days during a three-year period ending in the current calendar year. Generally, for this purpose, all the days present in the current year, one-third of the days present in the immediately preceding year, and one-sixth of the days present in the second preceding year are counted. Resident aliens are subject to U.S. federal income tax as if they were U.S. citizens. Such an individual is urged to consult his or her own tax advisor regarding the U.S. federal income tax consequences of the ownership or disposition of our common stock.

Dividends

We do not expect to declare or make any distributions on our common stock in the foreseeable future. If we do pay dividends on shares of our common stock, however, such distributions will constitute dividends for U.S. federal income tax purposes to the extent paid from our current or accumulated earnings and profits, as determined under U.S. federal income tax principles. Distributions in excess of our current and accumulated earnings and profits will constitute a return of capital that is applied against and reduces, but not below zero, a non-U.S. holder’s adjusted tax basis in shares of our common stock. Any remaining excess will be treated as gain realized on the sale or other disposition of our common stock. See “—Sale of Common Stock.”

Any dividend paid to a non-U.S. holder on our common stock that is not effectively connected with a non-U.S. holder’s conduct of a trade or business in the United States will generally be subject to U.S. withholding tax at a 30% rate. The withholding tax might apply at a reduced rate, however, under the terms of an applicable income tax treaty between the United States and the non-U.S. holder’s country of residence. You should consult your tax advisor regarding your entitlement to benefits under a relevant income tax treaty. Generally, in order for us or our paying agent to withhold tax at a lower treaty rate, a non-U.S. holder must certify its entitlement to treaty benefits. A non-U.S. holder generally can meet this certification requirement by providing a Form W-8BEN or Form W-8BEN-E (or any successor of such forms) or appropriate substitute form to us or our paying agent. If the non-U.S. holder holds the stock through a financial institution or other agent acting on the holder’s behalf, the holder will be required to provide appropriate documentation to the agent. The holder’s agent will then be required to provide certification to us or our paying agent, either directly or through other intermediaries. If you are eligible for a reduced rate of U.S. federal withholding tax under an income tax treaty, you may obtain a refund or credit of any excess amounts withheld by filing an appropriate claim for a refund with the IRS in a timely manner.

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Dividends received by a non-U.S. holder that are effectively connected with a U.S. trade or business conducted by the non-U.S. holder, and if required by an applicable income tax treaty between the United States and the non-U.S. holder’s country of residence, are attributable to a permanent establishment maintained by the non-U.S. holder in the United States, are not subject to U.S. withholding tax. To obtain this exemption, a non-U.S. holder must provide us or our paying agent with an IRS Form W-8ECI properly certifying such exemption. Such effectively connected dividends, although not subject to withholding tax, are taxed at the same graduated rates applicable to U.S. persons, net of certain deductions and credits. In addition, dividends received by corporate non-U.S. holders that are effectively connected with a U.S. trade or business of the corporate non-U.S. holder may also be subject to a branch profits tax at a rate of 30% or such lower rate as may be specified by an applicable tax treaty.

See also the sections below titled “—Foreign Account Tax Compliance Act” and “—Backup Withholding and Information Reporting” for additional withholding rules that may apply to dividends.

Sale of Common Stock

Subject to the discussions below regarding Backup Withholding and Information Reporting and the Foreign Account Tax Compliance Act, non-U.S. holders will generally not be subject to U.S. federal income tax on any gains realized on the sale, exchange or other disposition of our common stock unless:

• the gain (i) is effectively connected with the conduct by the non-U.S. holder of a U.S. trade or business and (ii) if required by an applicable income tax treaty between the United States and the non-U.S. holder’s country of residence, is attributable to a permanent establishment maintained by the non-U.S. holder in the United States (in which case the special rules described below apply);

• the non-U.S. holder is an individual who is present in the United States for 183 days or more in the taxable year of the sale, exchange or other disposition of our common stock, and certain other requirements are met (in which case the gain would be subject to a flat 30% tax, or such reduced rate as may be specified by an applicable income tax treaty, which may be offset by certain U.S. source capital losses, even though the individual is not considered a resident of the United States); or

• the rules of the Foreign Investment in Real Property Tax Act, or FIRPTA, treat the gain as effectively connected with a U.S. trade or business.

The FIRPTA rules may apply to a sale, exchange or other disposition of our common stock if we are, or were within the shorter of the five-year period preceding the disposition and the non-U.S. holder’s holding period, a “U.S. real property holding corporation,” or USRPHC. In general, we would be a USRPHC if interests in U.S. real estate comprised at least half of the value of our business assets. We do not believe that we are a USRPHC and we do not anticipate becoming one in the future. Even if we become a USRPHC, gain realized by a Non U.S. Holder on a disposition of our common stock will not be subject to U.S. federal income tax so long as (1) the Non U.S. Holder owned, directly, indirectly or constructively, no more than five percent of our common stock at all times within the shorter of (i) the five year period preceding the disposition or (ii) the holder’s holding period and (2) our common stock is regularly traded on an established securities market.

If any gain from the sale, exchange or other disposition of our common stock, (i) is effectively connected with a U.S. trade or business conducted by a non-U.S. holder and (ii) if required by an applicable income tax treaty between the United States and the non-U.S. holder’s country of residence, is attributable to a permanent establishment maintained by such non-U.S. holder in the United States, then the gain generally will be subject to U.S. federal income tax at the same graduated rates applicable to U.S. persons, net of certain deductions and credits. If the non-U.S. holder is a corporation, under certain circumstances, that portion of its earnings and profits that is effectively connected with its U.S. trade or business, subject to certain adjustments, generally would be subject also to a “branch profits tax.” The branch profits tax rate is 30%, although an applicable income

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tax treaty between the United States and the non-U.S. holder’s country of residence might provide for a lower rate.

U.S. Federal Estate Tax

The estates of nonresident alien individuals generally are subject to U.S. federal estate tax on property with a U.S. situs. Because we are a U.S. corporation, our common stock will be U.S. situs property and therefore will be included in the taxable estate of a nonresident alien decedent, unless an applicable estate tax treaty between the United States and the decedent’s country of residence provides otherwise. The terms “resident” and “nonresident” are defined differently for U.S. federal estate tax purposes than for U.S. federal income tax purposes. Investors are urged to consult their own tax advisors regarding the U.S. federal estate tax consequences of the ownership or disposition of our common stock.    

Backup Withholding and Information Reporting

The Code and the Treasury regulations require those who make specified payments to report the payments to the IRS. Among the specified payments are dividends and proceeds paid by brokers to their customers. The required information returns enable the IRS to determine whether the recipient properly included the payments in income. This reporting regime is reinforced by “backup withholding” rules. These rules require the payors to withhold tax from payments subject to information reporting if the recipient fails to cooperate with the reporting regime by failing to provide his taxpayer identification number to the payor, furnishing an incorrect identification number, or failing to report interest or dividends on his returns. The backup withholding tax rate is currently 24%. The backup withholding rules do not apply to payments to corporations, whether domestic or foreign, provided they establish such exemption.

Payments to non-U.S. holders of dividends on common stock generally will not be subject to backup withholding, and payments of proceeds made to non-U.S. holders by a broker upon a sale of common stock will not be subject to information reporting or backup withholding, in each case so long as the non-U.S. holder certifies its nonresident status (and we or our paying agent do not have actual knowledge or reason to know the holder is a U.S. person or that the conditions of any other exemption are not, in fact, satisfied) or otherwise establishes an exemption. The certification procedures to claim treaty benefits described under “—Dividends” will generally satisfy the certification requirements necessary to avoid the backup withholding tax. We must report annually to the IRS any dividends paid to each non-U.S. holder and the tax withheld, if any, with respect to these dividends. Copies of these reports may be made available to tax authorities in the country where the non-U.S. holder resides.

Under the Treasury regulations, the payment of proceeds from the disposition of shares of our common stock by a non-U.S. holder made to or through a U.S. office of a broker generally will be subject to information reporting and backup withholding unless the beneficial owner certifies, under penalties of perjury, among other things, its status as a non-U.S. holder (and the broker does not have actual knowledge or reason to know the holder is a U.S. person) or otherwise establishes an exemption. The payment of proceeds from the disposition of shares of our common stock by a non-U.S. holder made to or through a non-U.S. office of a broker generally will not be subject to backup withholding and information reporting, except as noted below. Information reporting, but not backup withholding, will apply to a payment of proceeds, even if that payment is made outside of the United States, if you sell our common stock through a non-U.S. office of a broker that is:

• a U.S. person (including a foreign branch or office of such person);

• a “controlled foreign corporation” for U.S. federal income tax purposes;

• a foreign person 50% or more of whose gross income from certain periods is effectively connected with a U.S. trade or business; or

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• a foreign partnership if at any time during its tax year (a) one or more of its partners are U.S. persons who, in the aggregate, hold more than 50% of the income or capital interests of the partnership or (b) the foreign partnership is engaged in a U.S. trade or business; unless the broker has documentary evidence that the beneficial owner is a non-U.S. holder and certain other conditions are satisfied, or the beneficial owner otherwise establishes an exemption (and the broker has no actual knowledge or reason to know to the contrary).

Backup withholding is not an additional tax. Any amounts withheld from a payment to a holder of common stock under the backup withholding rules can be credited against any U.S. federal income tax liability of the holder and may entitle the holder to a refund, provided that the required information is furnished to the IRS in a timely manner.

Foreign Account Tax Compliance Act

A U.S. federal withholding tax of 30% may apply to dividends and the gross proceeds of a disposition of our common stock paid to a foreign financial institution (as specifically defined by the applicable rules) unless such institution enters into an agreement with the U.S. government to withhold on certain payments and to collect and provide to the U.S. tax authorities substantial information regarding U.S. account holders of such institution (which includes certain equity holders of such institution, as well as certain account holders that are foreign entities with U.S. owners). This U.S. federal withholding tax of 30% will also apply to dividends and the gross proceeds of a disposition of our common stock paid to a non-financial foreign entity unless such entity provides the withholding agent with either a certification that it does not have any substantial direct or indirect U.S. owners or provides information regarding direct and indirect U.S. owners of the entity. The 30% federal withholding tax described in this paragraph cannot be reduced under an income tax treaty with the United States or by providing an IRS Form W-8BEN or similar documentation. The withholding tax described above will not apply, however, if the foreign financial institution or non-financial foreign entity otherwise qualifies for an exemption from the rules. Under certain circumstances, a non-U.S. holder might be eligible for refunds or credits of such taxes. Holders should consult with their own tax advisors regarding the possible implications of the withholding described herein. Foreign financial institutions located in jurisdictions that have an intergovernmental agreement with the United States governing FATCA may be subject to different rules.

The withholding provisions described above generally will apply to proceeds from a sale or other disposition of common stock if such sale or other disposition occurs on or after January 1, 2019 and currently apply to payments of dividends on our common stock.

EACH PROSPECTIVE INVESTOR SHOULD CONSULT ITS OWN TAX ADVISOR REGARDING THE PARTICULAR U.S. FEDERAL, STATE, LOCAL AND FOREIGN TAX CONSEQUENCES OF PURCHASING, HOLDING AND DISPOSING OF OUR COMMON STOCK, INCLUDING THE CONSEQUENCES OF ANY RECENTLY ADOPTED AND PROPOSED CHANGES IN APPLICABLE LAWS.

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UNDERWRITING

Under the terms and subject to the conditions contained in an underwriting agreement dated September 25, 2018, we have agreed to sell to the underwriters named below, for whom Credit Suisse Securities (USA) LLC, J.P. Morgan Securities LLC and Jefferies LLC are acting as representatives, the following respective numbers of shares of common stock:

Underwriter	Number of Shares
Credit Suisse Securities (USA) LLC		660,000
J.P. Morgan Securities LLC		660,000
Jefferies LLC		484,000
Cantor Fitzgerald & Co.		132,000
Guggenheim Securities, LLC		132,000
Wedbush Securities Inc.		132,000
Total		2,200,000

The underwriting agreement provides that the underwriters are obligated to purchase all the shares of common stock in the offering if any are purchased, other than those shares covered by the option to purchase additional shares described below. The underwriting agreement also provides that if an underwriter defaults the purchase commitments of non-defaulting underwriters may be increased or the offering may be terminated.

We have granted to the underwriters a 30-day option to purchase on a pro rata basis up to 330,000 additional shares of common stock at the public offering price less underwriting discounts and commissions.

The underwriters propose to offer the shares of common stock initially at the public offering price on the cover page of this prospectus supplement and to selling group members at that price less a selling concession of $2.9195 per share. After the public offering the underwriters may change the public offering price and concession and discount to broker/dealers.

The following table summarizes the compensation we will pay:

	Per Share				Total
	Without Option to Purchase Additional Shares		With Option to Purchase Additional Shares		Without Option to Purchase Additional Shares		With Option to Purchase Additional Shares
Underwriting Discounts and Commissions paid by us(1)	$	4.8659	$	4.8659	$	10,704,980	$	12,310,727

(1) The underwriters will receive an aggregate underwriting discount of up to $1,605,747 on the shares sold pursuant to the exercise of the underwriters’ option to purchase additional shares.

We estimate that our out of pocket expenses for this offering will be approximately $300,000. We have also agreed to reimburse the underwriters for up to $35,000 for their FINRA counsel fee. In accordance with FINRA Rule 5110, this reimbursed fee is deemed underwriting compensation for this offering. In addition, the underwriters have agreed to reimburse us for certain expenses.

We have agreed with the underwriters that, for a period of 90 days after the date of this prospectus supplement, and our executive officers, directors and their affiliates have agreed with the underwriters that, for a period of 45 days after the date of this prospectus supplement, subject to certain exceptions, we and they will not (1) offer, sell, pledge, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, lend, or otherwise transfer or dispose of (or enter into any transaction which is designed to, or might reasonably be expected to, result in the disposition), directly or indirectly, including the filing (or participation in the filing) with the SEC of a registration statement under the Securities Act to register, any shares of our common stock or any securities convertible into or exercisable or

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exchangeable for our common stock or warrants or other rights to acquire shares of our common stock of which such officer, director or holder is now, or may in the future become, the beneficial owner (within the meaning of Rule 13d-3 under the Exchange Act), or (2) enter into any swap or other derivatives transaction that transfers to another, in whole or in part, directly or indirectly, any of the economic benefits or risks of ownership of such common stock, securities, warrants or other rights to acquire common stock, whether any such transaction described in clause (1) or (2) above is to be settled by delivery of common stock or other securities, in cash or otherwise, or (3) publicly disclose the intention to enter into any transaction described in clause (1) or (2) above, except with the prior written consent of Credit Suisse Securities (USA) LLC, J.P. Morgan Securities LLC and Jefferies LLC.

The restrictions on our executive officers and directors and their affiliates above do not apply to the following, subject to certain limitations set forth in the lock-up agreements:

• transfers of securities as a bona fide gift;

• transfers or dispositions of securities to any trust for the direct or indirect benefit of the lock-up signatory or any member of the immediate family of the lock-up signatory;

• transfers of securities to affiliates;

• transfers of securities by will, other testamentary document or intestate succession to the legal representative, heir, beneficiary or a member of the immediate family of the lock-up signatory;

• transfers or dispositions of shares of our common stock or securities convertible or exchangeable into shares of our common stock acquired in open market purchases after the closing of this offering;

• entry into any trading plan established pursuant to Rule 10b5-1 under the Exchange Act;

• exercise of options, warrants or other rights to acquire shares of common stock in accordance with their terms pursuant to an employee benefit plan, option, warrant or other right;

• transfers pursuant to a court order or settlement agreement related to the distribution of assets in connection with the dissolution of a marriage or civil union;

• transfers to us pursuant to agreements under which we have the option to repurchase such shares or a right of first refusal with respect to transfers of such shares upon termination of service of the lock-up signatory;

• transfers by certain stockholders of shares purchased in this offering; or

• transfers of shares of our common stock or any security convertible into or exercisable or exchangeable for common stock pursuant to a liquidation, tender offer, merger, consolidation or similar transaction that results in all of our stockholders having the right to exchange their securities for cash, securities or other property.

We have agreed to indemnify the underwriters against liabilities under the Securities Act, or contribute to payments that the underwriters may be required to make in that respect.

Our common stock is listed on The Nasdaq Global Select Market under the symbol “ANAB.”

In connection with the offering the underwriters may engage in stabilizing transactions, over-allotment transactions, syndicate covering transactions and penalty bids and passive market making in accordance with Regulation M under the Securities Exchange Act of 1934, as amended, or the Exchange Act.

• Stabilizing transactions permit bids to purchase the underlying security so long as the stabilizing bids do not exceed a specified maximum.

• Over-allotment involves sales by the underwriters of shares in excess of the number of shares the underwriters are obligated to purchase, which creates a syndicate short position. The short position may

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be either a covered short position or a naked short position. In a covered short position, the number of shares over-allotted by the underwriters is not greater than the number of additional shares that they have the option to purchase. In a naked short position, the number of shares involved is greater than the number of additional shares that they have the option to purchase. The underwriters may close out any covered short position by either exercising their option to purchase additional shares and/or purchasing shares in the open market.

• Syndicate covering transactions involve purchases of the common stock in the open market after the distribution has been completed in order to cover syndicate short positions. In determining the source of shares to close out the short position, the underwriters will consider, among other things, the price of shares available for purchase in the open market as compared to the price at which they may purchase additional shares through their option. If the underwriters sell more shares than could be covered by the option to purchase additional shares, a naked short position, the position can only be closed out by buying shares in the open market. A naked short position is more likely to be created if the underwriters are concerned that there could be downward pressure on the price of the shares in the open market after pricing that could adversely affect investors who purchase in the offering.

• Penalty bids permit the representatives to reclaim a selling concession from a syndicate member when the common stock originally sold by the syndicate member is purchased in a stabilizing or syndicate covering transaction to cover syndicate short positions.

• In passive market making, market makers in the common stock who are underwriters or prospective underwriters may, subject to limitations, make bids for or purchases of our common stock until the time, if any, at which a stabilizing bid is made.

These stabilizing transactions, syndicate covering transactions and penalty bids may have the effect of raising or maintaining the market price of our common stock or preventing or retarding a decline in the market price of the common stock. As a result the price of our common stock may be higher than the price that might otherwise exist in the open market. These transactions may be effected on The Nasdaq Global Select Market or otherwise and, if commenced, may be discontinued at any time.

A prospectus in electronic format may be made available on the web sites maintained by one or more of the underwriters, or selling group members, if any, participating in this offering and one or more of the underwriters participating in this offering may distribute prospectuses electronically. The representatives may agree to allocate a number of shares to underwriters and selling group members for sale to their online brokerage account holders. Internet distributions will be allocated by the underwriters and selling group members that will make internet distributions on the same basis as other allocations.

The underwriters and their respective affiliates are full-service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, investment research, principal investment, hedging, financing and brokerage activities. Certain of the underwriters and their respective affiliates have, from time to time, performed, and may in the future perform, various financial advisory and investment banking services for us, for which they received or will receive customary fees and expenses.

In addition, in the ordinary course of their business activities, the underwriters and their affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers. These investments and securities activities may involve securities and/or instruments of ours or our affiliates. The underwriters and their affiliates may also make investment recommendations and/or publish or express independent research views in respect of such securities or financial instruments and may hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

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Selling Restrictions:

General

Other than in the United States, no action has been taken by us or the underwriters that would permit a public offering of the securities offered by this prospectus supplement in any jurisdiction where action for that purpose is required. The securities offered by this prospectus supplement may not be offered or sold, directly or indirectly, nor may this prospectus supplement or any other offering material or advertisements in connection with the offer and sale of any such securities be distributed or published in any jurisdiction, except under circumstances that will result in compliance with the applicable rules and regulations of that jurisdiction. Persons into whose possession this prospectus supplement comes are advised to inform themselves about and to observe any restrictions relating to the offering and the distribution of this prospectus supplement. This prospectus supplement does not constitute an offer to sell or a solicitation of an offer to buy any securities offered by this prospectus supplement in any jurisdiction in which such an offer or a solicitation is unlawful.

Notice to Prospective Investors in Switzerland

This document is not intended to constitute an offer or solicitation to purchase or invest in the securities described herein. The securities may not be publicly offered, sold or advertised, directly or indirectly, in, into or from Switzerland and will not be listed on the SIX Swiss Exchange or on any other exchange or regulated trading facility in Switzerland. Neither this document nor any other offering or marketing material relating to the securities constitutes a prospectus as such term is understood pursuant to article 652a or article 1156 of the Swiss Code of Obligations or a listing prospectus within the meaning of the listing rules of the SIX Swiss Exchange or any other regulated trading facility in Switzerland, and neither this document nor any other offering or marketing material relating to the securities may be publicly distributed or otherwise made publicly available in Switzerland.

Neither this document nor any other offering or marketing material relating to the offering, nor the Company nor the securities have been or will be filed with or approved by any Swiss regulatory authority. The securities are not subject to the supervision by any Swiss regulatory authority, e.g., the Swiss Financial Markets Supervisory Authority FINMA (FINMA), and investors in the securities will not benefit from protection or supervision by such authority.

Notice to Prospective Investors in the European Economic Area

Any distributor subject to MiFID II that is offering, selling or recommending the shares is responsible for undertaking its own target market assessment in respect of the shares and determining its own distribution channels for the purposes of the MiFID product governance rules under Commission Delegated Directive (EU) 2017/593 (“Delegated Directive”). Neither the issuer nor the underwriters make any representations or warranties as to a distributor’s compliance with the Delegated Directive.

In relation to each Member State of the European Economic Area which has implemented the Prospectus Directive (each, a Relevant Member State), each underwriter represents and agrees that with effect from and including the date on which the Prospectus Directive is implemented in that Relevant Member State, it has not made and will not make an offer of securities which are the subject of the offering contemplated by this prospectus supplement to the public in that Relevant Member State other than:

(a) to any legal entity which is a qualified investor as defined in the Prospectus Directive;

(b) to fewer than 100 or, if the Relevant Member State has implemented the relevant provision of the 2010 PD Amending Directive, 150, natural or legal persons (other than qualified investors as defined in the Prospectus Directive), as permitted under the Prospectus Directive, subject to obtaining the prior consent of the representatives for any such offer; or

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(c) in any other circumstances falling within Article 3(2) of the Prospectus Directive, provided that no such offer of securities shall require us or any underwriter to publish a prospectus pursuant to Article 3 of the Prospectus Directive.

For the purposes of this provision, the expression an “offer to the public” in relation to any securities in any Relevant Member State means the communication in any form and by any means of sufficient information on the terms of the offer and the securities to be offered so as to enable an investor to decide to purchase or subscribe the securities, as the same may be varied in that Member State by any measure implementing the Prospectus Directive in that Member State, the expression Prospectus Directive means Directive 2003/71/EC (and amendments thereto, including the 2010 PD Amending Directive, to the extent implemented in the Relevant Member State), and includes any relevant implementing measure in the Relevant Member State and the expression “2010 PD Amending Directive” means Directive 2010/73/EU.

Notice to Prospective Investors in the United Kingdom

In the United Kingdom, this document is being distributed only to, and is directed only at, and any offer subsequently made may only be directed at persons who are “qualified investors” (as defined in the Prospectus Directive) (i) who have professional experience in matters relating to investments falling within Article 19(5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005, as amended (the “Order”) and/or (ii) who are high net worth companies (or persons to whom it may otherwise be lawfully communicated) falling within Article 49(2)(a) to (d) of the Order (all such persons together being referred to as “relevant persons”) or otherwise in circumstances which have not resulted and will not result in an offer to the public of the shares in the United Kingdom within the meaning of the Financial Services and Markets Act 2000.

Any person in the United Kingdom that is not a relevant person should not act or rely on the information included in this document or use it as basis for taking any action. In the United Kingdom, any investment or investment activity that this document relates to may be made or taken exclusively by relevant persons.

Notice to Canadian Residents

Resale Restrictions

The distribution of shares of common stock offered hereby in Canada is being made only in the provinces of Ontario, Quebec, Alberta and British Columbia on a private placement basis exempt from the requirement that we prepare and file a prospectus with the securities regulatory authorities in each province where trades of these securities are made. Any resale of the shares offered hereby in Canada must be made under applicable securities laws which may vary depending on the relevant jurisdiction, and which may require resales to be made under available statutory exemptions or under a discretionary exemption granted by the applicable Canadian securities regulatory authority. Purchasers are advised to seek legal advice prior to any resale of the shares.

Representations of Canadian Purchasers

By purchasing shares of common stock offered hereby in Canada and accepting delivery of a purchase confirmation, a purchaser is representing to us and the dealer from whom the purchase confirmation is received that:

• the purchaser is entitled under applicable provincial securities laws to purchase the shares without the benefit of a prospectus qualified under those securities laws as it is an “accredited investor” as defined under National Instrument 45-106—Prospectus Exemptions,

• the purchaser is a “permitted client” as defined in National Instrument 31-103—Registration Requirements, Exemptions and Ongoing Registrant Obligations,

• where required by law, the purchaser is purchasing as principal and not as agent, and

• the purchaser has reviewed the text above under Resale Restrictions.

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Conflicts of Interest

Canadian purchasers are hereby notified that the underwriters are relying on the exemption set out in section 3A.3 or 3A.4, if applicable, of National Instrument 33-105—Underwriting Conflicts from having to provide certain conflict of interest disclosure in this document.

Statutory Rights of Action

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if the offering memorandum (including any amendment thereto) such as this document contains a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser’s province or territory. The purchaser of these securities in Canada should refer to any applicable provisions of the securities legislation of the purchaser’s province or territory for particulars of these rights or consult with a legal advisor.

Enforcement of Legal Rights

All of our directors and officers as well as the experts named herein may be located outside of Canada and, as a result, it may not be possible for Canadian purchasers to effect service of process within Canada upon us or those persons. All or a substantial portion of our assets and the assets of those persons may be located outside of Canada and, as a result, it may not be possible to satisfy a judgment against us or those persons in Canada or to enforce a judgment obtained in Canadian courts against us or those persons outside of Canada.

Taxation and Eligibility for Investment

Canadian purchasers of shares of common stock offered hereby should consult their own legal and tax advisors with respect to the tax consequences of an investment in the shares in their particular circumstances and about the eligibility of the shares for investment by the purchaser under relevant Canadian legislation.

Notice to Prospective Investors in France

Neither this prospectus supplement nor any other offering material relating to the securities described in this prospectus supplement has been submitted to the clearance procedures of the Autorité des Marchés Financiers or of the competent authority of another member state of the European Economic Area and notified to the Autorité des Marchés Financiers. The securities have not been offered or sold and will not be offered or sold, directly or indirectly, to the public in France. Neither this prospectus supplement nor any other offering material relating to the securities has been or will be:

• to any legal entity which is a qualified investor as defined in the Prospectus Directive;

• to fewer than 100 or, if the relevant member state has implemented the relevant provision of the 2010 PD Amending Directive, 150 natural or legal persons (other than qualified investors as defined in the Prospectus Directive), as permitted under the Prospectus Directive, subject to obtaining the prior consent of the relevant Dealer or Dealers nominated by us for any such offer; or

• in any other circumstances falling within Article 3(2) of the Prospectus Directive,

• released, issued, distributed or caused to be released, issued or distributed to the public in France; or

• used in connection with any offer for subscription or sale of the securities to the public in France.

Such offers, sales and distributions will be made in France only:

• to qualified investors (investisseurs qualifiés) and/or to a restricted circle of investors (cercle restreint d’investisseurs), in each case investing for their own account, all as defined in, and in accordance with articles L.411-2, D.411-1, D.411-2, D.734-1, D.744-1, D.754-1 and D.764-1 of the French Code monétaire et financier;

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• to investment services providers authorized to engage in portfolio management on behalf of third parties; or

• in a transaction that, in accordance with article L.411-2-II-1° -or-2° -or 3° of the French Code monétaire et financier and article 211-2 of the General Regulations (Règlement Général) of the Autorité des Marchés Financiers, does not constitute a public offer (appel public à l’épargne).

The securities may be resold directly or indirectly, only in compliance with articles L.411-1, L.411-2, L.412-1 and L.621-8 through L.621-8-3 of the French Code monétaire et financier.

Notice to Prospective Investors in the Republic of Italy

The offering of securities has not been registered with the Commissione Nazionale per le Società e la Borsa (“CONSOB”) pursuant to Italian securities legislation and, accordingly, no securities may be offered, sold or delivered, nor copies of this prospectus supplement, the accompanying prospectus or any other documents relating to the securities may not be distributed in Italy except:

(a) to “qualified investors”, as referred to in Article 100 of Legislative Decree No. 58 of 24 February 1998, as amended (the “Decree No. 58”) and defined in Article 26, paragraph 1, letter d) of CONSOB Regulation No. 16190 of 29 October 2007, as amended (“Regulation No. 16190”) pursuant to Article 34-ter, paragraph 1, letter. b) of CONSOB Regulation No. 11971 of 14 May 1999, as amended (“Regulation No. 11971”); or

(b) in any other circumstances where an express exemption from compliance with the offer restrictions applies, as provided under Decree No. 58 or Regulation No. 11971.

Any offer, sale or delivery of the securities or distribution of copies of this prospectus supplement, the accompanying prospectus or any other documents relating to the securities in the Republic of Italy must be:

(a) made by investment firms, banks or financial intermediaries permitted to conduct such activities in the Republic of Italy in accordance with Legislative Decree No. 385 of 1 September 1993, as amended (the “Banking Law”), Decree No. 58 and Regulation No. 16190 and any other applicable laws and regulations;

(b) in compliance with Article 129 of the Banking Law, and the implementing guidelines of the Bank of Italy, as amended; and

(c) in compliance with any other applicable notification requirement or limitation which may be imposed, from time to time, by CONSOB or the Bank of Italy or other competent authority.

Please note that, in accordance with Article 100-bis of Decree No. 58, where no exemption from the rules on public offerings applies, the subsequent distribution of the securities on the secondary market in Italy must be made in compliance with the public offer and the prospectus requirement rules provided under Decree No. 58 and Regulation No. 11971.

Furthermore, securities which are initially offered and placed in Italy or abroad to qualified investors only but in the following year are regularly (“sistematicamente”) distributed on the secondary market in Italy to non-qualified investors become subject to the public offer and the prospectus requirement rules provided under Decree No. 58 and Regulation No. 11971. Failure to comply with such rules may result in the sale of the securities being declared null and void and in the liability of the intermediary transferring the securities for any damages suffered by such non-qualified investors.

Notice to Prospective Investors in Germany

This prospectus supplement does not constitute a Prospectus Directive-compliant prospectus in accordance with the German Securities Prospectus Act (Wertpapierprospektgesetz) and does therefore not allow any public

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offering in the Federal Republic of Germany (“Germany”) or any other Relevant Member State pursuant to § 17 and § 18 of the German Securities Prospectus Act. No action has been or will be taken in Germany that would permit a public offering of the securities, or distribution of a prospectus or any other offering material relating to the securities. In particular, no securities prospectus (Wertpapierprospekt) within the meaning of the German Securities Prospectus Act or any other applicable laws of Germany, has been or will be published within Germany, nor has this prospectus supplement been filed with or approved by the German Federal Financial Supervisory Authority (Bundesanstalt für Finanzdienstleistungsaufsicht) for publication within Germany.

Each manager will represent, agree and undertake, (i) that it has not offered, sold or delivered and will not offer, sell or deliver the securities within Germany other than in accordance with the German Securities Prospectus Act (Wertpapierprospektgesetz) and any other applicable laws in Germany governing the issue, sale and offering of securities, and (ii) that it will distribute in Germany any offering material relating to the securities only under circumstances that will result in compliance with the applicable rules and regulations of Germany.

This prospectus supplement is strictly for use of the person who has received it. It may not be forwarded to other persons or published in Germany.

Notice to Prospective Investors in the United Arab Emirates

The securities have not been, and are not being, publicly offered, sold, promoted or advertised in the United Arab Emirates (“U.A.E.”) other than in compliance with the laws of the U.A.E. Prospective investors in the Dubai International Financial Centre should have regard to the specific notice to prospective investors in the Dubai International Financial Centre set out above.

The information contained in this prospectus supplement and the accompanying prospectus do not constitute a public offer of securities in the U.A.E. in accordance with the Commercial Companies Law (Federal Law No. 8 of 1984 of the U.A.E., as amended) or otherwise and is not intended to be a public offer. This prospectus supplement and the accompanying prospectus have not been approved by or filed with the Central Bank of the United Arab Emirates, the Emirates Securities and Commodities Authority or the Dubai Financial Services Authority, or DFSA. If you do not understand the contents of this prospectus supplement or the accompanying prospectus, you should consult an authorized financial adviser. This prospectus supplement and the accompanying prospectus are provided for the benefit of the recipient only, and should not be delivered to, or relied on by, any other person.

Notice to Prospective Investors in the Dubai International Financial Centre

This document relates to an exempt offer in accordance with the Offered Securities Rules of the Dubai Financial Services Authority. This document is intended for distribution only to persons of a type specified in those rules. It must not be delivered to, or relied on by, any other person. The Dubai Financial Services Authority has no responsibility for reviewing or verifying any documents in connection with exempt offers. The Dubai Financial Services Authority has not approved this document nor taken steps to verify the information set out in it, and has no responsibility for it. The notes which are the subject of the offering contemplated by this offering memorandum may be illiquid and/or subject to restrictions on their resale. Prospective purchasers of the notes offered should conduct their own due diligence on the notes. If you do not understand the contents of this document you should consult an authorized financial advisor.

Notice to Prospective Investors in the Kingdom of Saudi Arabia

This prospectus supplement may not be distributed in the Kingdom of Saudi Arabia except to such persons as are permitted under the Offers of Securities Regulations issued by the Capital Market Authority of Saudi Arabia (the “Capital Market Authority”). The Capital Market Authority does not make any representations as to the accuracy or completeness of this prospectus supplement, and expressly disclaims any liability whatsoever for

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any loss arising from, or incurred in reliance upon, any part of this prospectus supplement. Prospective purchasers of the securities offered hereby should conduct their own due diligence on the accuracy of the information relating to the securities. If a prospective purchaser does not understand the contents of this prospectus supplement he or she should consult an authorised financial adviser. By accepting this prospectus supplement and other information relating to the offering of the securities in the Kingdom of Saudi Arabia, each recipient represents that he is a “sophisticated investor”, as set out in the prospectus supplement.

Notice to Prospective Investors in Israel

This prospectus supplement does not constitute a prospectus under the Israeli Securities Law, 5728-1968, and has not been filed with or approved by the Israel Securities Authority. In Israel, this prospectus supplement is being distributed only to, and is directed only at, investors listed in the first addendum, or the Addendum, to the Israeli Securities Law, consisting primarily of joint investment in trust funds, provident funds, insurance companies, banks, portfolio managers, investment advisors, members of the Tel Aviv Stock Exchange, underwriters purchasing for their own account, venture capital funds, entities with equity in excess of NIS 50 million and qualified individuals, each as defined in the Addendum (as it may be amended from time to time), collectively referred to as qualified investors. Qualified investors may be required to submit written confirmation that they meet the criteria for one of the categories of investors set forth in the prospectus supplement.

Notice to Prospective Investors in South Africa

Due to restrictions under the securities laws of South Africa, the securities are not offered, and the offer of our securities shall not be transferred, sold, renounced or delivered, in South Africa or to a person with an address in South Africa, unless one or other of the following exemptions applies:

(i) the offer, transfer, sale, renunciation or delivery is to duly registered banks, mutual banks, financial services provider, financial institution, the Public Investment Corporation (in each case registered as such in South Africa), a person who deals with securities in their ordinary course of business, or a wholly owned subsidiary of a bank, mutual bank, authorized services provider or financial institution, acting as agent in the capacity of an authorized portfolio manager for a pension fund (duly registered in South Africa), or as manager for a collective investment scheme(registered in South Africa); or

(ii) the contemplated acquisition cost of the securities, for any single addressee acting as principal is equal to or greater than R1,000,000.

This document does not, nor is it intended to, constitute an “offer to the public” (as that term is defined in the South African Companies Act, 2008 (the “SA Companies Act”) and does not, nor is it intended to, constitute a prospectus prepared and registered under the SA Companies Act. This document is not an “offer to the public” and must not be acted on or relied on by persons who do not fall within Section 96(1)(a) of the SA Companies Act (such persons being referred to as “relevant persons”). Any investment or investment activity to which this document relates is available only to relevant persons and will be engaged in only with relevant persons. A South African resident person or company or any non-South African company which is a subsidiary of a South African company is not permitted to acquire the securities unless such person has obtained exchange control approval to do so.

Notice to Prospective Investors in Hong Kong

The securities may not be offered or sold in Hong Kong by means of any document other than (i) to “professional investors” as defined in the Securities and Futures Ordinance (Cap.571) of Hong Kong and any rules made under that Ordinance, or (ii) in other circumstances which do not result in the document being a “prospectus” as defined in the Companies Ordinance (Cap.32) of Hong Kong or which do not constitute an offer to the public within the meaning of that Ordinance. No advertisement, invitation or document relating to the depositary securities may be issued or may be in the possession of any person for the purpose of issue, whether in Hong Kong or elsewhere, which is directed at, or the contents of which are likely to be accessed or read by, the

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public of Hong Kong (except if permitted to do so under the securities laws of Hong Kong) other than with respect to depositary securities which are or are intended to be disposed of only to persons outside Hong Kong or only to “professional investors” as defined in the Securities and Futures Ordinance and any rules made under that Ordinance.

Notice to Prospective Investors in Singapore

This prospectus supplement has not been registered as a prospectus with the Monetary Authority of Singapore. Accordingly, this prospectus supplement and any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of securities may not be circulated or distributed, nor may the securities be offered or sold, or be made the subject of an invitation for subscription or purchase, whether directly or indirectly, to persons in Singapore other than

(i) to an institutional investor under Section 274 of the Securities and Futures Act, Chapter 289 of Singapore (the “SFA”), (ii) to a relevant person pursuant to Section 275(1), or any person pursuant to Section 275(1A), and in accordance with the conditions specified in Section 275, of the SFA, or

(ii) otherwise pursuant to, and in accordance with the conditions of, any other applicable provision of the SFA.

Where the securities are subscribed or purchased under Section 275 of the SFA by a relevant person which is:

(a) a corporation (which is not an accredited investor (as defined in Section 4A of the SFA)) the sole business of which is to hold investments and the entire share capital of which is owned by one or more individuals, each of whom is an accredited investor; or

(b) a trust (where the trustee is not an accredited investor) whose sole purpose is to hold investments and each beneficiary of the trust is an individual who is an accredited investor, securities (as defined in Section 239(1) of the SFA) of that corporation or the beneficiaries’ rights and interest (howsoever described) in that trust shall not be transferred within six months after that corporation or that trust has acquired the securities pursuant to an offer made under Section 275 of the SFA except:

(a) to an institutional investor or to a relevant person defined in Section 275(2) of the SFA, or to any person arising from an offer referred to in Section 275(1A) or Section 276(4)(i)(B) of the SFA;

(b) where no consideration is or will be given for the transfer;

(c) where the transfer is by operation of law;

(d) as specified in Section 276(7) of the SFA; or

(e) as specified in Regulation 32 of the Securities and Futures (Offers of Investments) (Shares and Debentures) Regulations 2005 of Singapore.

Notice to Prospective Investors in Japan

The securities have not been and will not be registered under the Financial Instruments and Exchange Law of Japan (Law No. 25 of 1948, as amended) and accordingly, will not be offered or sold, directly or indirectly, in Japan, or for the benefit of any Japanese Person or to others for re-offering or resale, directly or indirectly, in Japan or to any Japanese Person, except in compliance with all applicable laws, regulations and ministerial guidelines promulgated by relevant Japanese governmental or regulatory authorities in effect at the relevant time. For the purposes of this paragraph, “Japanese Person” shall mean any person resident in Japan, including any corporation or other entity organized under the laws of Japan.

Notice to Residents of Malaysia

The securities may not be offered for subscription or purchase and no invitation to subscribe for or purchase such Certificates in Malaysia may be made, directly or indirectly, and this prospectus supplement or any

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document or other materials in connection therewith may not be distributed in Malaysia other than to persons falling within the categories specified under Schedule 6 or Section 229(l)(b), Schedule 7 or Section 230(l)(b) and Schedule 8 or Section 257(3) of the Capital Market and Services Act, 2007 of Malaysia. The Securities Commission of Malaysia shall not be liable for any non-disclosure on the part of the Issuer and assumes no responsibility for the correctness of any statements made or opinions or reports expressed in this prospectus supplement.

Notice to Prospective Investors in China

This prospectus supplement does not constitute a public offer of the securities offered by this prospectus supplement, whether by sale or subscription, in the People’s Republic of China, or the PRC. The securities are not being offered or sold directly or indirectly in the PRC to or for the benefit of, legal or natural persons of the PRC.

Further, no legal or natural persons of the PRC may directly or indirectly purchase any of the securities without obtaining all prior PRC’s governmental approvals that are required, whether statutorily or otherwise. Persons who come into possession of this document are required by the issuer and its representatives to observe these restrictions.

Notice to Prospective Investors in Korea

The securities have not been and will not be registered under the Financial Investments Services and Capital Markets Act of Korea and the decrees and regulations thereunder, or the FSCMA, and the securities have been and will be offered in Korea as a private placement under the FSCMA. None of the securities may be offered, sold or delivered directly or indirectly, or offered or sold to any person for re-offering or resale, directly or indirectly, in Korea or to any resident of Korea except pursuant to the applicable laws and regulations of Korea, including the FSCMA and the Foreign Exchange Transaction Law of Korea and the decrees and regulations thereunder, or the FETL. The securities have not been listed on any of securities exchanges in the world including, without limitation, the Korea Exchange in Korea. Furthermore, the purchaser of the securities shall comply with all applicable regulatory requirements (including but not limited to requirements under the FETL) in connection with the purchase of the securities. By the purchase of the securities, the relevant holder thereof will be deemed to represent and warrant that if it is in Korea or is a resident of Korea, it purchased the securities pursuant to the applicable laws and regulations of Korea.

Notice to Prospective Investors in Taiwan

The securities have not been and will not be registered with the Financial Supervisory Commission of Taiwan pursuant to relevant securities laws and regulations and may not be sold, issued or offered within Taiwan through a public offering or in circumstances which constitutes an offer within the meaning of the Securities and Exchange Act of Taiwan that requires a registration or approval of the Financial Supervisory Commission of Taiwan. No person or entity in Taiwan has been authorised to offer, sell, give advice regarding or otherwise intermediate the offering and sale of the securities in Taiwan.

Notice to Prospective Investors in Australia

No placement document, prospectus, product disclosure statement or other disclosure document has been lodged with the Australian Securities and Investments Commission (“ASIC”), in relation to the offering. This prospectus supplement does not constitute a prospectus, product disclosure statement or other disclosure document under the Corporations Act 2001 (the “Corporations Act”), and does not purport to include the information required for a prospectus, product disclosure statement or other disclosure document under the Corporations Act.

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Any offer in Australia of the securities may only be made to persons (the “Exempt Investors”) who are “sophisticated investors” (within the meaning of section 708(8) of the Corporations Act), “professional investors” (within the meaning of section 708(11) of the Corporations Act) or otherwise pursuant to one or more exemptions contained in section 708 of the Corporations Act so that it is lawful to offer the securities without disclosure to investors under Chapter 6D of the Corporations Act. The securities applied for by Exempt Investors in Australia must not be offered for sale in Australia in the period of 12 months after the date of allotment under the offering, except in circumstances where disclosure to investors under Chapter 6D of the Corporations Act would not be required pursuant to an exemption under section 708 of the Corporations Act or otherwise or where the offer is pursuant to a disclosure document which complies with Chapter 6D of the Corporations Act. Any person acquiring securities must observe such Australian on-sale restrictions. This prospectus supplement contains general information only and does not take account of the investment objectives, financial situation or particular needs of any particular person. It does not contain any securities recommendations or financial product advice. Before making an investment decision, investors need to consider whether the information in this prospectus supplement is appropriate to their needs, objectives and circumstances, and, if necessary, seek expert advice on those matters.

Notice to Prospective Investors in the Cayman Islands

This prospectus supplement does not constitute an invitation or offer to the public in the Cayman Islands of the securities, whether by way of sale or subscription. The underwriters have not offered or sold, and will not offer or sell, directly or indirectly, any securities in the Cayman Islands.

Notice to Prospective Investors in Bermuda

The securities offered by this prospectus supplement may be offered or sold in Bermuda only in compliance with the provisions of the Investment Business Act of 2003 of Bermuda which regulates the sale of securities in Bermuda. Additionally, non-Bermudian persons (including companies) may not carry on or engage in any trade or business in Bermuda unless such persons are permitted to do so under applicable Bermuda legislation.

Notice to Prospective Investors in the British Virgin Islands

The securities are not being, and may not be offered to the public or to any person in the British Virgin Islands for purchase or subscription by us or on our behalf. The securities may be offered to companies incorporated under the BVI Business Companies Act, 2004 (British Virgin Islands) (each a BVI Company), but only where the offer will be made to, and received by, the relevant BVI Company entirely outside of the British Virgin Islands.

This prospectus supplement has not been, and will not be, registered with the Financial Services Commission of the British Virgin Islands. No registered prospectus has been or will be prepared in respect of the securities for the purposes of the Securities and Investment Business Act, 2010, or SIBA or the Public Issuers Code of the British Virgin Islands.

The securities may be offered to persons located in the British Virgin Islands who are “qualified investors” for the purposes of SIBA. Qualified investors include (i) certain entities which are regulated by the Financial Services Commission in the British Virgin Islands, including banks, insurance companies, licensees under SIBA and public, professional and private mutual funds; (ii) a company, any securities of which are listed on a recognised exchange; and (iii) persons defined as “professional investors” under SIBA, which is any person (a) whose ordinary business involves, whether for that person’s own account or the account of others, the acquisition or disposal of property of the same kind as the property, or a substantial part of our property; or (b) who has signed a declaration that he, whether individually or jointly with his spouse, has net worth in excess of US$1,000,000 and that he consents to being treated as a professional investor.

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LEGAL MATTERS

The validity of the shares of common stock offered hereby will be passed upon for us by Fenwick & West LLP, San Francisco, California. Certain legal matters relating to the offering will be passed upon for the underwriters by Cooley LLP, San Diego, California.

EXPERTS

The consolidated financial statements of AnaptysBio, Inc. as of December 31, 2017 and 2016, and for each of the years in the three-year period ended December 31, 2017, have been incorporated by reference herein and in the registration statement in reliance upon the report of KPMG LLP, an independent registered public accounting firm, incorporated by reference herein, and upon the authority of said firm as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

We are subject to the informational requirements of the Securities Exchange Act of 1934, as amended, and are required to file annual, quarterly and other reports, proxy statements and other information with the SEC. You may request copies of these reports, proxy statements and other information without charge, by written or telephonic request directed to AnaptysBio, Inc., Attn: Investor Relations, 10421 Pacific Center Court, Suite 200, San Diego, CA 92121, telephone (858) 362-6295. You may also inspect and copy these reports, proxy statements and other information at the public reference facilities maintained by the SEC in Washington, D.C., 100 F Street N.E., Washington, D.C. 20549. Copies of such materials can be obtained from the SEC’s public reference section at prescribed rates. You may obtain information on the operation of the public reference rooms by calling the SEC at (800) SEC-0330. Additionally, the SEC maintains an Internet site (https://www.sec.gov) that contains reports, proxy and information statements, and various other information about us. You may also inspect the documents described herein at our principal executive offices, 10421 Pacific Center Court, Suite 200, San Diego, CA 92121, during normal business hours.

Information about us is also available at our website at https://www.anaptysbio.com. However, the information on, or that can be accessed through, our website is not a part of this prospectus supplement or the accompanying prospectus and is not incorporated by reference into this prospectus supplement (other than those filings with the SEC that we specifically incorporate by reference into this prospectus supplement or accompanying prospectus).

Any statement contained herein or in a document incorporated or deemed to be incorporated by reference into this document will be deemed to be modified or superseded for purposes of the document to the extent that a statement contained in this document or any other subsequently filed document that is deemed to be incorporated by reference into this document modifies or supersedes the statement.

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INCORPORATION OF INFORMATION BY REFERENCE

The SEC allows us to “incorporate by reference” information that we file with the SEC, which means that we can disclose important information to you by referring you to those other documents. The information incorporated by reference is an important part of this prospectus supplement and the accompanying prospectus, and information we file later with the SEC will automatically update and supersede this information. We incorporate by reference the documents listed below and any future filings we make with the SEC under Section 13(a), 13(c), 14, or 15(d) of the Exchange Act prior to the termination of any offering of securities made by this prospectus supplement:

• our Annual Report on Form 10-K for the fiscal year ended December 31, 2017 filed with the SEC on March 5, 2018 (as amended on September 14, 2018), including certain information incorporated by reference therein from our Definitive Proxy Statement for our 2018 annual meeting of stockholders filed with the SEC on April 26, 2018;

• our Quarterly Reports on Form 10-Q for the fiscal quarters ended March 31, 2018 and June 30, 2018, filed with the SEC on May 8, 2018 (as amended on September 14, 2018) and August 7, 2018 (as amended on September 14, 2018), respectively

• our Current Reports on Form 8-K filed with the SEC on February 1, 2018, March 5, 2018, March 20, 2018, May 23, 2018 and June 12, 2018 (in each case, except for information contained therein that is furnished rather than filed); and

• the description of our common stock contained in our registration statement on Form 8-A filed with the SEC on January 17, 2017 under Section 12 of the Exchange Act, including any amendment or report filed for the purpose of updating such description.

Upon written or oral request, we will provide without charge to each person, including any beneficial owner, to whom this prospectus supplement and the accompanying prospectus are delivered, a copy of any or all of such information that has been incorporated herein by reference (other than exhibits to such documents unless such exhibits are specifically incorporated by reference into the documents that this prospectus supplement and accompanying prospectus incorporates). Written or oral requests for copies should be directed AnaptysBio, Inc., Attn: Investor Relations, 10421 Pacific Center Court, Suite 200, San Diego, CA 92121, telephone (858) 362-6295. See the section of this prospectus supplement entitled “Where You Can Find More Information” for information concerning how to read and obtain copies of materials that we file with the SEC at the SEC’s public offices.

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PROSPECTUS

AnaptysBio, Inc.

Common Stock, Preferred Stock,

Debt Securities, Warrants, Subscription Rights and Units

From time to time, we may offer our common stock or preferred stock, debt securities, warrants to purchase our common stock, preferred stock or debt securities, subscription rights to purchase our common stock, preferred stock or debt securities and/or units consisting of some or all of these securities, in any combination, together or separately, in one or more offerings, in amounts, at prices and on the terms that we will determine at the time of the offering and which will be set forth in a prospectus supplement and any related free writing prospectus. The prospectus supplement and any related free writing prospectus may also add, update or change information contained in this prospectus.

You should read this prospectus, the information incorporated, or deemed to be incorporated, by reference in this prospectus, and any applicable prospectus supplement and related free writing prospectus carefully before you invest.

Our common stock is traded on the Nasdaq Global Market under the symbol “ANAB.”

An investment in our securities involves a high degree of risk. You should carefully consider the information under the heading “Risk Factors” beginning on page 6 of this prospectus before investing in our securities.

Common stock, preferred stock, debt securities, warrants, subscription rights and/or units may be sold by us to or through underwriters or dealers, directly to purchasers or through agents designated from time to time. For additional information on the methods of sale, you should refer to the section entitled “Plan of Distribution” in this prospectus. If any underwriters, dealers or agents are involved in the sale of any securities with respect to which this prospectus is being delivered, the names of such underwriters or agents and any applicable fees, discounts or commissions, details regarding over-allotment options, if any, and the net proceeds to us will be set forth in a prospectus supplement. The price to the public of such securities and the net proceeds we expect to receive from such sale will also be set forth in a prospectus supplement.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus is February 5, 2018

TABLE OF CONTENTS

	PAGE
ABOUT THIS PROSPECTUS		1
PROSPECTUS SUMMARY		2
RATIO OF EARNINGS TO FIXED CHARGES		5
RISK FACTORS		6
FORWARD-LOOKING STATEMENTS		6
WHERE YOU CAN FIND MORE INFORMATION		7
INCORPORATION OF INFORMATION BY REFERENCE		7
USE OF PROCEEDS		8
PLAN OF DISTRIBUTION		9
DESCRIPTION OF CAPITAL STOCK		11
DESCRIPTION OF DEBT SECURITIES		16
DESCRIPTION OF WARRANTS		23
DESCRIPTION OF SUBSCRIPTION RIGHTS		25
DESCRIPTION OF UNITS		26
LEGAL MATTERS		26
EXPERTS		26

i

ABOUT THIS PROSPECTUS

This prospectus is part of an automatic shelf registration statement that we filed with the Securities and Exchange Commission (the SEC) as a “well-known seasoned issuer” as defined in Rule 405 under the Securities Act of 1933, as amended (Securities Act) using a “shelf” registration process. Under this shelf registration process, from time to time, we may sell any combination of the securities described in this prospectus in one or more offerings, in amounts, at prices, and on the terms that we will determine at the time of the offering and which will be set forth in a prospectus supplement and any related free writing prospectus. Each time we offer our securities under this prospectus, we will provide a prospectus supplement that will contain more specific information about the terms of the offering. We may also add, update or change in a prospectus supplement any of the information contained in this prospectus or in documents we have incorporated by reference into this prospectus. Any statement that we make in this prospectus will be modified or superseded by any inconsistent statement made by us in a prospectus supplement. This prospectus, together with the applicable prospectus supplements and the documents incorporated by reference into this prospectus, includes all material information relating to this offering. You should carefully read both this prospectus and the applicable prospectus supplement, together with the additional information described under the headings “Incorporation of Information by Reference” and “Where You Can Find More Information” before buying any of our securities in this offering.

You should rely only on the information contained in or incorporated by reference into this prospectus or any applicable prospectus supplement. No dealer, salesperson or any other person is authorized to give any information or to make any representation other than the information and representations contained in or incorporated by reference into this prospectus or any applicable prospectus supplement. If different information is given or different representations are made, you may not rely on that information or those representations as having been authorized by us. You may not imply from the delivery of this prospectus and any applicable prospectus supplement, nor from a sale made under this prospectus and any applicable prospectus supplement, that our affairs are unchanged since the date of this prospectus and any applicable prospectus supplement or that the information contained in any document incorporated by reference is accurate as of any date other than the date of the document incorporated by reference, regardless of the time of delivery of this prospectus and any applicable prospectus supplement or any sale of a security. This prospectus and any applicable prospectus supplement may only be used where it is legal to sell the securities.

THIS PROSPECTUS MAY NOT BE USED TO OFFER AND SELL SECURITIES UNLESS IT IS ACCOMPANIED BY A PROSPECTUS SUPPLEMENT.

In this prospectus, unless the context otherwise requires, the terms “AnaptysBio,” the “Company,” “we,” “us,” and “our” refer to AnaptysBio, Inc., a Delaware corporation.

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PROSPECTUS SUMMARY

This summary may not contain all the information that you should consider before investing in securities. You should read the entire prospectus and the information incorporated by reference in this prospectus carefully, including “Risk Factors” and the financial data and related notes and other information incorporated by reference, before making an investment decision.

Company Overview

We are a clinical stage biotechnology company developing first-in-class antibody product candidates focused on unmet medical needs in inflammation. We develop our product candidates to address emerging biological targets using our proprietary antibody discovery technology platform, which is based upon a breakthrough understanding of the natural process of antibody generation, known as somatic hypermutation, or SHM, and replicates this natural process of antibody generation in vitro. Our strategy is to advance the development and commercialization of our proprietary product candidates, and for certain programs, establish partnerships with leading biopharmaceutical companies where we retain certain development and commercialization rights in the United States.

Our most advanced wholly-owned antibody programs, ANB020 and ANB019, neutralize therapeutic targets that are genetically associated with severe inflammatory disorders in humans. ANB020 inhibits the activity of the interleukin-33 cytokine, or IL-33, for the treatment of moderate-to-severe adult atopic dermatitis, severe adult peanut allergy and severe adult eosinophilic asthma. We have completed a Phase 1 trial of ANB020 in healthy volunteers in Australia, the results of which were presented at the 2017 American Academy of Dermatology Annual Meeting and the American Academy of Allergy, Asthma and Immunology 2017 Annual Meeting in March 2017. We believe the results of this Phase 1 trial demonstrate a favorable safety profile of ANB020, which was well-tolerated and for which no dose-limiting toxicities were observed, and favorable pharmacodynamic properties of ANB020, where a single dose was sufficient to suppress IL-33 function for approximately three months post-dosing as measured by an ex vivo pharmacodynamic assay. We have subsequently completed enrollment of a Phase 2a trial of ANB020 in 12 moderate-to-severe adult atopic dermatitis patients, under an approved Clinical Trial Authorisation, or CTA, with the U.K. Medicines and Healthcare Products Regulatory Agency, or MHRA, and announced top-line data from an interim analysis of this trial in October 2017.

The Phase 2a proof-of-concept trial enrolled 12 moderate-to-severe adult atopic dermatitis patients, who were initially administered a single intravenous dose of placebo within 14 days of enrollment, followed by a single intravenous 300mg dose of ANB020 one week subsequent to placebo. Prior to enrollment in the study, patients were not permitted any systemic or topical medications during a wash-out period. Patients were permitted to take a monitored amount of topical corticosteroids as rescue therapy during the course of the study. Clinical response was assessed by a number of endpoints, including the improvement of each patient’s Eczema Area Severity Index, or EASI, score, a tool used to measure the extent and severity of atopic dermatitis, at key time points following ANB020 administration relative to their enrollment baseline. Pruritus, also known as itchiness, as measured by the 5-D pruritus scale score, was also assessed for each patient. Exploratory mechanistic biomarkers included granulocyte infiltration and cytokine levels in localized skin lesions measured five days after placebo administration and five days after ANB020 administration.

Top-line data indicated rapid and sustained clinical achievement of EASI-50, which is 50% or better improvement in EASI score relative to enrollment baseline, in 83% of patients at Day 29, and the 5-D pruritus score was reduced by 32% relative to enrollment baseline. As early as Day 15 post-ANB020 administration 75% of patients reached EASI-50 and pruritus was reduced by 28%, which was sustained until Day 57 when 75% of patients achieved EASI-50; pruritus was reduced by 22% at Day 57. All 12 patients achieved EASI-50 at one or more time points through Day 57 post-ANB020 administration. Exploratory biomarker assessment indicated

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reduction of granulocyte infiltration into localized skin lesions by an average of 30% amongst all patients and 60% among the 10 patients achieving EASI-50 at 29 days post-ANB020 administration, while exploratory cytokine biomarker levels were below detection limit and therefore inconclusive. ANB020 was generally well-tolerated by all patients and no severe adverse events have been reported to date. The most frequent treatment-emergent adverse events reported were mild dizziness in two patients subsequent to placebo dosing, and mild headache in two patients post-ANB020 administration. We plan to report full data from this trial, including results on additional clinical measures, at a medical conference following study completion and further data analysis.

We believe these data demonstrate proof-of-concept for ANB020 in moderate-to-severe adult atopic dermatitis and suggest that ANB020 may provide meaningful differentiation in terms of patient convenience. As further development in atopic dermatitis, we plan to initiate, during the first half of 2018, a Phase 2b randomized, double-blinded, placebo-controlled study in 200-300 adults patients with moderate-to-severe atopic dermatitis to evaluate multi-dose subcutaneous administration of ANB020, with data expected in 2019.

We are continuing to enroll, under our Investigational New Drug application, or IND, with the U.S. Food and Drug Administration, or FDA, a Phase 2a trial of ANB020 with 20 severe adult peanut allergy patients where efficacy is assessed by measuring the cumulative dose of peanut tolerated in an oral food challenge before and after a single dose of ANB020 or placebo. As of October 31, 2017, we completed 75 percent enrollment of this trial and top-line data are expected in the first quarter of 2018. We have also initiated enrollment, under a CTA with MHRA, of a Phase 2a trial of ANB020 in 24 severe adult eosinophilic asthma patients, where efficacy will be assessed using improvement in Forced Expiratory Volume in One Second after administration of a single dose of ANB020 or placebo. Top-line data are anticipated during the second quarter of 2018.

ANB019 inhibits the interleukin-36 receptor, or IL-36R, for the treatment of rare inflammatory diseases including generalized pustular psoriasis, or GPP, and palmo-plantar pustular psoriasis, or PPP. We are currently conducting, under an approved Clinical Trial Notification, or CTN, a Phase 1 clinical trial in healthy volunteers, where 54 subjects are dosed with ANB019 and 18 are dosed with placebo in single and multi-dose cohorts at various subcutaneous and intravenously administered dose levels. In November 2017, we announced positive top-line results from an interim analysis, which showed favorable safety, pharmacokinetics and pharmacodynamic properties that support advancement of ANB019 into Phase 2 studies for generalized pustular psoriasis and palmo-plantar pustular psoriasis during 2018. In addition to ANB020 and ANB019, our wholly-owned pipeline includes novel checkpoint receptor agonist antibodies that we believe are applicable for treatment of certain autoimmune diseases where immune checkpoint receptors are insufficiently activated, and have demonstrated efficacy in an animal model of graft-versus-host disease. During December 2017, we submitted a CTA filing to the MHRA supporting the initiation of a 10-patient open-label multi-dose Phase 2 study of ANB019 in GPP patients. We anticipated filing an additional CTA application to support the initiation of a placebo-controlled multi-dose study of ANB019 in PPP.

In addition to our wholly-owned antibody programs, multiple AnaptysBio-developed antibody programs have been advanced to preclinical and clinical milestones under our collaborations. Our collaborations include an immuno-oncology-focused collaboration with TESARO, Inc. and TESARO Development, Ltd., or collectively, TESARO and an inflammation-focused collaboration with Celgene Corporation, or Celgene.

Under our TESARO collaboration, TESARO has initiated a registration program under an IND with the FDA of an AnaptysBio-generated anti-PD-1 antagonist antibody (TSR-042) in metastatic microsatellite high endometrial cancer patients. TESARO has completed dose escalation of an AnaptysBio-generated anti-TIM-3 antagonist antibody (TSR-022) in patients under an IND and has subsequently initiated a combination study of TSR-022 and TSR-042. In addition, TESARO has initiated a Phase 1 study of an AnaptysBio-generated

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anti-LAG-3 antibody (TSR-033), and TESARO has initiated IND-enabling preclinical studies for an AnaptysBio generated PD-1/LAG-3 bispecific antibody, which has exhibited similar levels of T-cell activation in vitro as a combination of TSR-042 and TSR-033.

Under our Celgene partnership, Celgene is conducting a Phase 1 study of an AnaptysBio-generated anti-PD-1 agonist antibody (CC-90006) in healthy volunteers, and an undisclosed second AnaptysBio-generated antibody is currently under preclinical development.

The Securities We May Offer

With this prospectus, we may offer common stock, preferred stock, debt securities, warrants, subscription rights to purchase our common stock, preferred stock or debt securities, and/or units consisting of some or all of these securities in any combination. Each time we offer securities with this prospectus, we will provide offerees with a prospectus supplement that will contain the specific terms of the securities being offered. The following is a summary of the securities we may offer with this prospectus.

Common Stock

We may offer shares of our common stock, par value $0.001 per share.

Preferred Stock

We may offer shares of our preferred stock, par value $0.001 per share, in one or more series. Our board of directors or a committee designated by the board will determine the dividend, voting, conversion and other rights of the series of shares of preferred stock being offered. Each series of preferred stock will be more fully described in the particular prospectus supplement that will accompany this prospectus, including redemption provisions, rights in the event of our liquidation, dissolution or the winding up, voting rights and rights to convert into common stock.

Debt Securities

We may offer general obligations, which may be secured or unsecured, senior or subordinated and convertible into shares of our common stock or preferred stock. In this prospectus, we refer to the senior debt securities and the subordinated debt securities together as the “debt securities.” Our board of directors will determine the terms of each series of debt securities being offered.

We will issue the debt securities under an indenture between us and a trustee. In this document, we have summarized general features of the debt securities from the indenture. We encourage you to read the indenture, which is an exhibit to the registration statement of which this prospectus is a part.

Warrants

We may offer warrants for the purchase of debt securities, shares of preferred stock or shares of common stock. We may issue warrants independently or together with other securities. Our board of directors will determine the terms of the warrants.

Subscription Rights

We may offer subscription rights for the purchase of common stock, preferred stock or debt securities. We may issue subscription rights independently or together with other securities. Our board of directors will determine the terms of the subscription rights.

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Units

We may offer units consisting of some or all of the securities described above, in any combination, including common stock, preferred stock, warrants and/or debt securities. The terms of these units will be set forth in a prospectus supplement. The description of the terms of these units in the related prospectus supplement will not be complete. You should refer to the applicable form of unit and unit agreement for complete information with respect to these units.

* * *

We were incorporated under the laws of the State of Delaware in November 2005. Our principal executive offices are located at 10421 Pacific Center Court, Suite 200, San Diego, California 92121, and our telephone number is (858) 362-6295. Our website address is www.anaptysbio.com. The information contained on, or that can be accessed through, our website is not part of, and is not incorporated by reference into, this prospectus.

RATIO OF EARNINGS TO FIXED CHARGES

The following table sets forth our dollar coverage deficiency. Any time we offer debt securities pursuant to this prospectus, we will provide an updated table setting forth our ratio of earnings to fixed charges on a historical basis in the applicable prospectus supplement, if required. Any time we offer shares of preferred stock pursuant to this prospectus, we will provide a table setting forth our ratio of combined fixed charges and preferred stock dividends to earnings, if required.

	Year Ended December 31, 2014		Year Ended December 31, 2015		Year Ended December 31, 2016		Nine Months Ended September 30, 2017
Ratio of earnings to fixed charges(1)		*		*		*		*

⁽¹⁾  The ratio of earnings to fixed charges is computed by dividing earnings by fixed charges. Earnings consist of income before income taxes plus fixed charges. Fixed charges consist of interest expense, including amortized discounts, premiums and capitalized expenses related to indebtedness.

* Earnings were inadequate to cover fixed charges for all periods presented.

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RISK FACTORS

An investment in our securities involves a high degree of risk. The prospectus supplement applicable to each offering of securities will contain a discussion of the risks applicable to an investment in our securities. Prior to making a decision about investing in our securities, you should carefully consider the specific factors discussed under the heading “Risk Factors” in the applicable prospectus supplement, together with all of the other information contained or incorporated by reference in the prospectus supplement or appearing or incorporated by reference in this prospectus. You should also consider the risks, uncertainties and assumptions discussed under Part II, Item 1A, “Risk Factors,” in our Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2017, which is incorporated herein by reference, and may be amended, supplemented or superseded from time to time by other reports we file with the SEC in the future. The risks and uncertainties we have described are not the only ones we face. Additional risks and uncertainties not presently known to us or that we currently deem immaterial may also affect our operations.

FORWARD-LOOKING STATEMENTS

This prospectus and documents incorporated herein by reference contain “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. These forward-looking statements involve a number of risks and uncertainties. We caution readers that any forward-looking statement is not a guarantee of future performance and that actual results could differ materially from those contained in the forward-looking statement. These statements are based on current expectations of future events. Such statements include, but are not limited to, statements about future financial and operating results, plans, objectives, expectations and intentions, costs and expenses, interest rates, outcome of contingencies, financial condition, results of operations, liquidity, cost savings, objectives of management, business strategies, debt financing, clinical trial timing and plans, the achievement of clinical and commercial milestones, the advancement of our technologies and our proprietary and partnered products and product candidates, and other statements that are not historical facts. You can find many of these statements by looking for words like “believes,” “expects,” “anticipates,” “estimates,” “may,” “might,” “should,” “will,” “could,” “plan,” “intend,” “project,” “seek” or similar expressions in this prospectus or in documents incorporated by reference into this prospectus. We intend that such forward-looking statements be subject to the safe harbors created thereby.

These forward-looking statements are based on the current beliefs and expectations of our management and are subject to significant risks and uncertainties. If underlying assumptions prove inaccurate or unknown risks or uncertainties materialize, actual results may differ materially from current expectations and projections. Factors that might cause such a difference include those discussed in Part II, Item 1A, “Risk Factors,” in our Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2017, as well as those discussed in this prospectus and in the documents incorporated by reference into this prospectus. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date of this prospectus or, in the case of documents referred to or incorporated by reference, the date of those documents.

All subsequent written or oral forward-looking statements attributable to us or any person acting on our behalf are expressly qualified in their entirety by the cautionary statements contained or referred to in this section. We do not undertake any obligation to release publicly any revisions to these forward-looking statements to reflect events or circumstances after the date of this prospectus or to reflect the occurrence of unanticipated events, except as may be required under applicable U.S. securities law. If we do update one or more forward-looking statements, no inference should be drawn that we will make additional updates with respect to those or other forward-looking statements.

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WHERE YOU CAN FIND MORE INFORMATION

We are subject to the informational requirements of the Securities Exchange Act of 1934, as amended (the Exchange Act) and are required to file annual, quarterly and other reports, proxy statements and other information with the SEC. You may inspect and copy these reports, proxy statements and other information at the public reference facilities maintained by the SEC in Washington, D.C., 100 F Street N.E., Washington, D.C. 20549. Copies of such materials can be obtained from the SEC’s public reference section at prescribed rates. You may obtain information on the operation of the public reference rooms by calling the SEC at (800) SEC-0330. Additionally, the SEC maintains an Internet site (http://www.sec.gov) that contains reports, proxy and information statements, and various other information about us.

Information about us is also available at our website at http://www.anaptysbio.com. However, the information on our website is not a part of this prospectus and is not incorporated by reference into this prospectus.

INCORPORATION OF INFORMATION BY REFERENCE

The SEC allows us to “incorporate by reference” information that we file with the SEC, which means that we can disclose important information to you by referring you to those other documents. The information incorporated by reference is an important part of this prospectus, and information we file later with the SEC will automatically update and supersede this information. A Current Report (or portion thereof) furnished, but not filed, on Form 8-K shall not be incorporated by reference into this prospectus. We incorporate by reference the documents listed below and any future filings we make with the SEC under Section 13(a), 13(c), 14, or 15(d) of the Exchange Act prior to the termination of any offering of securities made by this prospectus:

• our Annual Report on Form 10-K for the fiscal year ended December 31, 2016 filed with the SEC on March 8, 2017;

• our Quarterly Report on Form 10-Q for the quarter ended March 31, 2017 and filed with the SEC on May 12, 2017;

• our Quarterly Report on Form 10-Q for the quarter ended June 30, 2017 and filed with the SEC on August 10, 2017;

• our Quarterly Report on Form 10-Q for the quarter ended September 30, 2017 and filed with the SEC on November 7, 2017;

• our Current Reports on Form 8-K filed on March 2, 2017, July 27, 2017, August 24, 2017 and February 1, 2018; and

• the description of our common stock contained in our registration statement on Form 8-A filed with the SEC on January 17, 2017 under Section 12 of the Exchange Act, including any amendment or report filed for the purpose of updating such description.

Upon written or oral request, we will provide without charge to each person, including any beneficial owner, to whom this prospectus is delivered, a copy of any or all of such information that has been incorporated herein by reference (other than exhibits to such documents unless such exhibits are specifically incorporated by reference into the documents that this prospectus incorporates). Written or oral requests for copies should be directed to AnaptysBio, Inc., Attn: Investor Relations, 10421 Pacific Center Court, telephone number (858) 362-6295. See the section of this prospectus entitled “Where You Can Find More Information” for information concerning how to read and obtain copies of materials that we file with the SEC at the SEC’s public offices.

Any statement contained in this prospectus, or in a document all or a portion of which is incorporated by reference, shall be modified or superseded for purposes of this prospectus to the extent that a statement contained

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in this prospectus, any prospectus supplement or any document incorporated by reference modifies or supersedes such statement. Any such statement so modified or superseded shall not, except as so modified or superseded, constitute a part of this prospectus.

USE OF PROCEEDS

We will retain broad discretion over the use of the net proceeds to us from the sale of our securities under this prospectus. Unless otherwise provided in the applicable prospectus supplement, we intend to use the net proceeds from the sale of securities under this prospectus for general corporate purposes, which may include funding research and development for our clinical development and ongoing preclinical, discovery and research programs, increasing our working capital, acquisitions or investments in businesses, products or technologies that are complementary to our own and capital expenditures. We will set forth in the prospectus supplement our intended use for the net proceeds received from the sale of any securities. Pending the application of the net proceeds, we intend to invest the net proceeds in short-term or long-term, investment-grade, interest-bearing securities.

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PLAN OF DISTRIBUTION

We may sell the securities covered by this prospectus to one or more underwriters for public offering and sale by them, and may also sell the securities to investors directly or through agents. We will name any underwriter or agent involved in the offer and sale of securities in the applicable prospectus supplement. We have reserved the right to sell or exchange securities directly to investors on our own behalf in jurisdictions where we are authorized to do so. We may distribute the securities from time to time in one or more transactions:

• at a fixed price or prices, which may be changed;

• at market prices prevailing at the time of sale;

• at prices related to such prevailing market prices; or

• at negotiated prices.

We may directly solicit offers to purchase the securities being offered by this prospectus. We may also designate agents to solicit offers to purchase the securities from time to time. We will name in a prospectus supplement any agent involved in the offer or sale of our securities. Unless otherwise indicated in a prospectus supplement, an agent will be acting on a best efforts basis, and a dealer will purchase securities as a principal for resale at varying prices to be determined by the dealer.

If we utilize an underwriter in the sale of the securities being offered by this prospectus, we will execute an underwriting agreement with the underwriter at the time of sale and we will provide the name of any underwriter in the prospectus supplement that the underwriter will use to make resales of the securities to the public. In connection with the sale of the securities, we, or the purchasers of securities for whom the underwriter may act as agent, may compensate the underwriter in the form of underwriting discounts or commissions. The underwriter may sell the securities to or through dealers, and those dealers may receive compensation in the form of discounts, concessions or commissions from the underwriters or commissions from the purchasers for whom they may act as agent.

We will provide in the applicable prospectus supplement any compensation we pay to underwriters, dealers, or agents in connection with the offering of the securities, and any discounts, concessions or commissions allowed by underwriters to participating dealers. Underwriters, dealers and agents participating in the distribution of the securities may be deemed to be underwriters within the meaning of the Securities Act of 1933 (the Securities Act), and any discounts and commissions received by them and any profit realized by them on resale of the securities may be deemed to be underwriting discounts and commissions. We may enter into agreements to indemnify underwriters, dealers and agents against civil liabilities, including liabilities under the Securities Act, and to reimburse them for certain expenses. We may grant underwriters who participate in the distribution of our securities under this prospectus an option to purchase additional securities to cover any over-allotments in connection with the distribution.

The securities we offer under this prospectus may or may not be listed through the Nasdaq Global Market or any other securities exchange. To facilitate the offering of securities, certain persons participating in the offering may engage in transactions that stabilize, maintain or otherwise affect the price of the securities. This may include short sales of the securities, which involves the sale by persons participating in the offering of more securities than we sold to them. In these circumstances, these persons would cover such short positions by making purchases in the open market or by exercising their option to purchase additional securities. In addition, these persons may stabilize or maintain the price of the securities by bidding for or purchasing securities in the open market or by imposing penalty bids, whereby selling concessions allowed to dealers participating in the offering may be reclaimed if securities sold by them are repurchased in connection with stabilization transactions. The effect of these transactions may be to stabilize or maintain the market price of the securities at a level above that which might otherwise prevail in the open market. These transactions may be discontinued at any time.

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We will file a prospectus supplement to describe the terms of any offering of our securities covered by this prospectus. The prospectus supplement will disclose:

• the terms of the offer;

• the names of any underwriters, including any managing underwriters, as well as any dealers or agents;

• the purchase price of the securities from us;

• the net proceeds to us from the sale of the securities;

• any delayed delivery arrangements;

• any over-allotment or other options under which underwriters, if any, may purchase additional securities from us;

• any underwriting discounts, commissions or other items constituting underwriters’ compensation, and any commissions paid to agents;

• in a subscription rights offering, whether we have engaged dealer-managers to facilitate the offering or subscription, including their name or names and compensation;

• any public offering price; and

• other facts material to the transaction.

We will bear all or substantially all of the costs, expenses and fees in connection with the registration of our securities under this prospectus. The underwriters, dealers and agents may engage in transactions with us, or perform services for us, in the ordinary course of business.

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DESCRIPTION OF CAPITAL STOCK

General

We are authorized to issue 510,000,000 shares of all classes of capital stock, of which 500,000,000 shares are common stock, $0.001 par value per share, and 10,000,000 shares are preferred stock, $0.001 par value per share. Our capital is stated in U.S. dollars. As of September 30, 2017, we had 20,496,288 outstanding shares of common stock and no outstanding shares of preferred stock.

Common Stock

Dividend Rights

Subject to preferences that may apply to any shares of preferred stock outstanding at the time, the holders of our common stock are entitled to receive dividends out of funds legally available if our board of directors, in its discretion, determines to issue dividends and then only at the times and in the amounts that our board of directors may determine. See “Dividend Policy” above.

Voting Rights

Holders of our common stock are entitled to one vote for each share held on all matters submitted to a vote of stockholders. We have not provided for cumulative voting for the election of directors in our restated certificate of incorporation. Accordingly, pursuant to our restated certificate of incorporation, holders of a majority of the shares of our common stock can elect all of our directors. Our restated certificate of incorporation establishes a classified board of directors, divided into three classes with staggered three-year terms. Only one class of directors is elected at each annual meeting of our stockholders, with the other classes continuing for the remainder of their respective three-year terms.

No Preemptive or Similar Rights

Our common stock is not entitled to preemptive rights, and is not subject to conversion, redemption or sinking fund provisions.

Right to Receive Liquidation Distributions

Upon our liquidation, dissolution or winding-up, the assets legally available for distribution to our stockholders would be distributable ratably among the holders of our common stock and any participating preferred stock outstanding at that time, subject to prior satisfaction of all outstanding debt and liabilities and the preferential rights of and the payment of liquidation preferences, if any, on any outstanding shares of preferred stock.

Registration Rights

According to the terms of our amended and restated investors’ rights agreement entered into in July 2015, certain of our common stockholders are entitled to demand, piggyback and Form S-3 registration rights.

Demand Registration Rights. At any point, the holders of at least a majority of the then-outstanding registrable securities may make a written request to us for the registration of any of the registrable securities under the Securities Act. Within 30 days of such request, we are obligated to provide written notice of such request to all stockholders to file a registration statement under the Securities Act covering all registrable securities that the initiating holders requested to be registered and any additional registrable securities requested to be included in such registration by any other holders. We are only required to file two registration statements that are declared effective upon exercise of these demand registration rights. We may postpone taking action with

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respect to such filing not more than once during any 12-month period for a total period of not more than 60 days if our board of directors determines in its good faith judgment that it would be seriously detrimental to us and our stockholders for such registration statement to be effected at such time.

Piggyback Registration Rights. If we register any of our securities for public sale in an offering, holders of registrable securities will have the right to include their shares in the registration statement. However, this right does not apply to a registration relating to employee benefit plans, a registration relating to a corporate reorganization or a registration of only common stock issuable upon conversion of debt securities that are also being registered. We have the right to terminate any registration we have initiated before the effective date of such registration, whether or not any holder has elected to include registrable securities in such registration. The underwriters of any underwritten offering will have the right to limit the number of shares registered by these holders if they determine in good faith that marketing factors require limitation, in which case the number of shares to be registered will be apportioned pro rata among these holders, according to the total amount of securities entitled to be included by each holder, or in a manner mutually agreed upon by the holders. However, in any underwriting not in connection with an initial public offering, the number of shares to be registered by these holders cannot be reduced below 30% of the total shares covered by the registration statement.

Form S-3 Registration Rights. Any holder of then-outstanding registrable securities can request that we register all or part of their shares on Form S-3 if we are eligible to file a registration statement on Form S-3 and if the aggregate price to the public of the shares offered is at least $2,000,000. The stockholders may only require us to effect two registration statements on Form S-3 in a 12-month period. We may postpone taking action with respect to such filing once during any 12-month period for a total cumulative period of not more than 90 days if our board of directors determines in its good faith judgment that the filing would be materially detrimental to us and our stockholders.

Expenses of Registration. We generally will pay all expenses, other than underwriting discounts and commissions.

Expiration of Registration Rights. The registration rights described above will expire, with respect to any particular holder of these rights, on the earlier of the fifth anniversary of the closing of our initial public offering, a merger, consolidation, sale or disposition of our company or a sale by a holder of equity securities representing at least a majority of the voting power of our company, when that holder holds less than 1% of our outstanding common stock and can sell all of its registrable securities in a three-month period without restriction under Rule 144 of the Securities Act.

Preferred Stock

As of September 30, 2017, no shares of our preferred stock are issued and outstanding and no such shares were subject to outstanding options or other rights to purchase or acquire. However, shares of preferred stock may be issued in one or more series from time to time by our board of directors, and the board of directors is expressly authorized to fix by resolution or resolutions the designations and the powers, preferences and rights, and the qualifications, limitations and restrictions thereof, of the shares of each series of preferred stock. Subject to the determination of our board of directors, any shares of our preferred stock that may be issued in the future would generally have preferences over our common stock with respect to the payment of dividends and the distribution of assets in the event of our liquidation, dissolution or winding up.

Anti-Takeover Effect of Unissued Shares of Capital Stock

Common Stock. Our shares of authorized and unissued common stock are available for future issuance without additional stockholder approval. While these additional shares are not designed to deter or prevent a change of control, under some circumstances we could use the additional shares to create voting impediments or to frustrate persons seeking to effect a takeover or otherwise gain control by, for example, issuing those shares in private placements to purchasers who might side with our board of directors in opposing a hostile takeover bid.

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Preferred Stock. Our certificate of incorporation grants our board of directors the authority, without any further vote or action by our stockholders, to issue preferred stock in one or more series and to fix the number of shares constituting any such series and the preferences, limitations and relative rights, including dividend rights, dividend rate, voting rights, terms of redemption, redemption price or prices, conversion rights and liquidation preferences of the shares constituting any series. The existence of authorized but unissued preferred stock could reduce our attractiveness as a target for an unsolicited takeover bid since we could, for example, issue shares of preferred stock to parties who might oppose such a takeover bid or shares that contain terms the potential acquirer may find unattractive. This may have the effect of delaying or preventing a change in control, may discourage bids for the common stock at a premium over the market price of the common stock, and may adversely affect the market price of, and the voting and other rights of the holders of, common stock.

Anti-Takeover Provisions

The provisions of Delaware law, our restated certificate of incorporation and our restated bylaws could have the effect of delaying, deferring or discouraging another person from acquiring control of our company. These provisions, which are summarized below, may have the effect of discouraging takeover bids. They are also designed, in part, to encourage persons seeking to acquire control of us to negotiate first with our board of directors. We believe that the benefits of increased protection of our potential ability to negotiate with an unfriendly or unsolicited acquirer outweigh the disadvantages of discouraging a proposal to acquire us because negotiation of these proposals could result in an improvement of their terms.

Delaware Law

We are subject to the provisions of Section 203 of the Delaware General Corporation Law regulating corporate takeovers. This section prevents some Delaware corporations, including us, from engaging, under some circumstances, in a business combination, which includes a merger or sale of at least 10% of the corporation’s assets with any interested stockholder, meaning a stockholder who, together with affiliates and associates, owns or, within three years prior to the determination of interested stockholder status, did own 15% or more of the corporation’s outstanding voting stock, unless:

• prior to the date of the transaction, the board of directors of the corporation approved either the business combination or the transaction which resulted in the stockholder becoming an interested stockholder;

• upon consummation of the transaction which resulted in the stockholder becoming an interested stockholder, the interested stockholder owned at least 85% of the voting stock of the corporation outstanding at the time the transaction commenced; or

• at or subsequent to such time that the stockholder became an interested stockholder, the business combination is approved by the board of directors and authorized at an annual or special meeting of stockholders by at least two-thirds of the outstanding voting stock not owned by the interested stockholder.

A Delaware corporation may “opt out” of these provisions with an express provision in its original certificate of incorporation or an express provision in its certificate of incorporation or bylaws resulting from a stockholders’ amendment approved by at least a majority of the outstanding voting shares. We have not and do not plan to “opt out” of these provisions. The statute could prohibit or delay mergers or other takeover or change in control attempts and, accordingly, may discourage attempts to acquire us.

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Restated Certificate of Incorporation and Restated Bylaw Provisions

Our restated certificate of incorporation and our restated bylaws include a number of provisions that may have the effect of deterring hostile takeovers or delaying or preventing changes in control, including the following:

• Board of Directors Vacancies. Our restated certificate of incorporation and restated bylaws authorize only our board of directors to fill vacant directorships, including newly created seats. In addition, the number of directors constituting our board of directors is permitted to be set only by a resolution adopted by a majority vote of our entire board of directors. These provisions would prevent a stockholder from increasing the size of our board of directors and then gaining control of our board of directors by filling the resulting vacancies with its own nominees. This makes it more difficult to change the composition of our board of directors but promotes continuity of management.

• Classified Board. Our restated certificate of incorporation and restated bylaws provide that our board is classified into three classes of directors, each with staggered three-year terms. A third party may be discouraged from making a tender offer or otherwise attempting to obtain control of us as it is more difficult and time consuming for stockholders to replace a majority of the directors on a classified board of directors.

• Stockholder Action; Special Meetings of Stockholders. Our restated certificate of incorporation provides that our stockholders may not take action by written consent, but may only take action at annual or special meetings of our stockholders. As a result, a holder controlling a majority of our capital stock would not be able to amend our restated bylaws or remove directors without holding a meeting of our stockholders called in accordance with our restated bylaws. Further, our restated bylaws provide that special meetings of our stockholders may be called only by a majority of our board of directors, the chairman of our board of directors, our Chief Executive Officer or our President, thus prohibiting a stockholder from calling a special meeting. These provisions might delay the ability of our stockholders to force consideration of a proposal or for stockholders controlling a majority of our capital stock to take any action, including the removal of directors.

• Advance Notice Requirements for Stockholder Proposals and Director Nominations. Our restated bylaws provide advance notice procedures for stockholders seeking to bring business before our annual meeting of stockholders or to nominate candidates for election as directors at our annual meeting of stockholders. Our restated bylaws also specify certain requirements regarding the form and content of a stockholder’s notice. These provisions might preclude our stockholders from bringing matters before our annual meeting of stockholders or from making nominations for directors at our annual meeting of stockholders if the proper procedures are not followed. We expect that these provisions might also discourage or deter a potential acquirer from conducting a solicitation of proxies to elect the acquirer’s own slate of directors or otherwise attempting to obtain control of our company.

• No Cumulative Voting. The Delaware General Corporation Law provides that stockholders are not entitled to the right to cumulate votes in the election of directors unless a corporation’s certificate of incorporation provides otherwise. Our restated certificate of incorporation and restated bylaws do not provide for cumulative voting.

• Directors Removed Only for Cause. Our restated certificate of incorporation provides that stockholders may remove directors only for cause and only by the affirmative vote of the holders of at least two-thirds of our outstanding common stock.

• Amendment to Certificate of Incorporation and Bylaws. Any amendment of the above provisions in our restated certificate of incorporation and restated bylaws requires approval by holders of at least two-thirds of our then-outstanding capital stock entitled to vote in the election of directors.

• Issuance of Undesignated Preferred Stock. Our board of directors has the authority, without further action by the stockholders, to issue up to 10,000,000 shares of undesignated preferred stock with rights

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and preferences, including voting rights, designated from time to time by our board of directors. The existence of authorized but unissued shares of preferred stock would enable our board of directors to render more difficult or to discourage an attempt to obtain control of us by merger, tender offer, proxy contest or other means.

• Choice of Forum. Our restated certificate of incorporation provides that the Court of Chancery of the State of Delaware will be the exclusive forum for any derivative action or proceeding brought on our behalf; any action asserting a breach of fiduciary duty; any action asserting a claim against us arising pursuant to the Delaware General Corporation Law, our restated certificate of incorporation or our restated bylaws; or any action asserting a claim against us that is governed by the internal affairs doctrine.

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is American Stock Transfer & Trust Company, LLC.

Listing

Our common stock is quoted on the Nasdaq Global Market under the trading symbol “ANAB.”

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DESCRIPTION OF DEBT SECURITIES

General

We will issue the debt securities offered by this prospectus and any accompanying prospectus supplement under an indenture to be entered into between us and the trustee identified in the applicable prospectus supplement. The terms of the debt securities will include those stated in the indenture and those made part of the indenture by reference to the Trust Indenture Act of 1939, as in effect on the date of the indenture. We have filed a copy of the form of indenture as an exhibit to the registration statement in which this prospectus is included. The indenture will be subject to and governed by the terms of the Trust Indenture Act of 1939. Unless otherwise specified in the applicable prospectus supplement, the debt securities will represent our direct, unsecured obligations and will rank equally with all of our other unsecured indebtedness.

We may issue the debt securities in one or more series with the same or various maturities, at par, at a premium, or at a discount. We will describe the particular terms of each series of debt securities in a prospectus supplement relating to that series, which we will file with the SEC. The prospectus supplement relating to the particular series of debt securities being offered will specify the particular amounts, prices and terms of those debt securities. These terms may include:

• the title of the series;

• the aggregate principal amount, and, if a series, the total amount authorized and the total amount outstanding;

• the issue price or prices, expressed as a percentage of the aggregate principal amount of the debt securities;

• any limit on the aggregate principal amount;

• the date or dates on which principal is payable;

• the interest rate or rates (which may be fixed or variable) or, if applicable, the method used to determine such rate or rates;

• the date or dates from which interest, if any, will be payable and any regular record date for the interest payable;

• the place or places where principal and, if applicable, premium and interest, is payable;

• the terms and conditions upon which we may, or the holders may require us to, redeem or repurchase the debt securities;

• the denominations in which such debt securities may be issuable, if other than denominations of $1,000 or any integral multiple of that number;

• whether the debt securities are to be issuable in the form of certificated securities (as described below) or global securities (as described below);

• the portion of principal amount that will be payable upon declaration of acceleration of the maturity date if other than the principal amount of the debt securities;

• the currency of denomination;

• the designation of the currency, currencies or currency units in which payment of principal and, if applicable, premium and interest, will be made;

• if payments of principal and, if applicable, premium or interest, on the debt securities are to be made in one or more currencies or currency units other than the currency of denomination, the manner in which the exchange rate with respect to such payments will be determined;

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• if amounts of principal and, if applicable, premium and interest may be determined by reference to an index based on a currency or currencies or by reference to a commodity, commodity index, stock exchange index or financial index, then the manner in which such amounts will be determined;

• the provisions, if any, relating to any collateral provided for such debt securities;

• any addition to or change in the covenants and/or the acceleration provisions described in this prospectus or in the indenture;

• any events of default, if not otherwise described below under “Events of Default”;

• the terms and conditions, if any, for conversion into or exchange for shares of our common stock or preferred stock;

• any depositaries, interest rate calculation agents, exchange rate calculation agents or other agents; and

• the terms and conditions, if any, upon which the debt securities shall be subordinated in right of payment to our other indebtedness.

We may issue discount debt securities that provide for an amount less than the stated principal amount to be due and payable upon acceleration of the maturity of such debt securities in accordance with the terms of the indenture. We may also issue debt securities in bearer form, with or without coupons. If we issue discount debt securities or debt securities in bearer form, we will describe material U.S. federal income tax considerations and other material special considerations which apply to these debt securities in the applicable prospectus supplement.

We may issue debt securities denominated in or payable in a foreign currency or currencies or a foreign currency unit or units. If we do, we will describe the restrictions, elections, and general tax considerations relating to the debt securities and the foreign currency or currencies or foreign currency unit or units in the applicable prospectus supplement.

Debt securities offered under this prospectus and any prospectus supplement will be subordinated in right of payment to certain of our outstanding senior indebtedness. In addition, we will seek the consent of the holders of any such senior indebtedness prior to issuing any debt securities under this prospectus to the extent required by the agreements evidencing such senior indebtedness.

Registrar and Paying Agent

The debt securities may be presented for registration of transfer or for exchange at the corporate trust office of the security registrar or at any other office or agency that we maintain for those purposes. In addition, the debt securities may be presented for payment of principal, interest and any premium at the office of the paying agent or at any office or agency that we maintain for those purposes.

Conversion or Exchange Rights

Debt securities may be convertible into or exchangeable for shares of our common stock. The terms and conditions of conversion or exchange will be stated in the applicable prospectus supplement. The terms will include, among others, the following:

• the conversion or exchange price;

• the conversion or exchange period;

• provisions regarding the convertibility or exchangeability of the debt securities, including who may convert or exchange;

• events requiring adjustment to the conversion or exchange price;

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• provisions affecting conversion or exchange in the event of our redemption of the debt securities; and

• any anti-dilution provisions, if applicable.

Registered Global Securities

If we decide to issue debt securities in the form of one or more global securities, then we will register the global securities in the name of the depositary for the global securities or the nominee of the depositary, and the global securities will be delivered by the trustee to the depositary for credit to the accounts of the holders of beneficial interests in the debt securities.

The prospectus supplement will describe the specific terms of the depositary arrangement for debt securities of a series that are issued in global form. None of us, the trustee, any payment agent or the security registrar will have any responsibility or liability for any aspect of the records relating to or payments made on account of beneficial ownership interests in a global debt security or for maintaining, supervising or reviewing any records relating to these beneficial ownership interests.

No Protection in the Event of Change of Control

The indenture does not have any covenants or other provisions providing for a put or increased interest or otherwise that would afford holders of our debt securities additional protection in the event of a recapitalization transaction, a change of control or a highly leveraged transaction. If we offer any covenants or provisions of this type with respect to any debt securities covered by this prospectus, we will describe them in the applicable prospectus supplement.

Covenants

Unless otherwise indicated in this prospectus or the applicable prospectus supplement, our debt securities will not have the benefit of any covenants that limit or restrict our business or operations, the pledging of our assets or the incurrence by us of indebtedness. We will describe in the applicable prospectus supplement any material covenants in respect of a series of debt securities.

Merger, Consolidation or Sale of Assets

The form of indenture provides that we will not consolidate with or merge into any other person or convey, transfer, sell or lease our properties and assets substantially as an entirety to any person, unless:

• we are the surviving person of such merger or consolidation, or if we are not the surviving person, the person formed by the consolidation or into or with which we are merged or the person to which our properties and assets are conveyed, transferred, sold or leased, is a corporation organized and existing under the laws of the U.S., any state or the District of Columbia or a corporation or comparable legal entity organized under the laws of a foreign jurisdiction and has expressly assumed all of our obligations, including the payment of the principal of and, premium, if any, and interest on the debt securities and the performance of the other covenants under the indenture; and

• immediately before and immediately after giving effect to the transaction on a pro forma basis, no event of default, and no event which, after notice or lapse of time or both, would become an event of default, has occurred and is continuing under the indenture.

Events of Default

Unless otherwise specified in the applicable prospectus supplement, the following events will be events of default under the indenture with respect to debt securities of any series:

• we fail to pay any principal or premium, if any, when it becomes due;

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• we fail to pay any interest within 30 days after it becomes due;

• we fail to observe or perform any other covenant in the debt securities or the indenture for 60 days after written notice specifying the failure from the trustee or the holders of not less than 25% in aggregate principal amount of the outstanding debt securities of that series; and

• certain events involving bankruptcy, insolvency or reorganization of us or any of our significant subsidiaries.

The trustee may withhold notice to the holders of the debt securities of any series of any default, except in payment of principal of or premium, if any, or interest on the debt securities of a series, if the trustee considers it to be in the best interest of the holders of the debt securities of that series to do so.

If an event of default (other than an event of default resulting from certain events of bankruptcy, insolvency or reorganization) occurs, and is continuing, then the trustee or the holders of not less than 25% in aggregate principal amount of the outstanding debt securities of any series may accelerate the maturity of the debt securities. If this happens, the entire principal amount, plus the premium, if any, of all the outstanding debt securities of the affected series plus accrued interest to the date of acceleration will be immediately due and payable. At any time after the acceleration, but before a judgment or decree based on such acceleration is obtained by the trustee, the holders of a majority in aggregate principal amount of outstanding debt securities of such series may rescind and annul such acceleration if:

• all events of default (other than nonpayment of accelerated principal, premium or interest) have been cured or waived;

• all lawful interest on overdue interest and overdue principal has been paid; and

• the rescission would not conflict with any judgment or decree.

In addition, if the acceleration occurs at any time when we have outstanding indebtedness that is senior to the debt securities, the payment of the principal amount of outstanding debt securities may be subordinated in right of payment to the prior payment of any amounts due under the senior indebtedness, in which case the holders of debt securities will be entitled to payment under the terms prescribed in the instruments evidencing the senior indebtedness and the indenture.

If an event of default resulting from certain events of bankruptcy, insolvency or reorganization occurs, the principal, premium and interest amount with respect to all of the debt securities of any series will be due and payable immediately without any declaration or other act on the part of the trustee or the holders of the debt securities of that series.

The holders of a majority in principal amount of the outstanding debt securities of a series will have the right to waive any existing default or compliance with any provision of the indenture or the debt securities of that series and to direct the time, method and place of conducting any proceeding for any remedy available to the trustee, subject to certain limitations specified in the indenture.

No holder of any debt security of a series will have any right to institute any proceeding with respect to the indenture or for any remedy under the indenture, unless:

• the holder gives to the trustee written notice of a continuing event of default;

• the holders of at least 25% in aggregate principal amount of the outstanding debt securities of the affected series make a written request and offer reasonable indemnity to the trustee to institute a proceeding as trustee;

• the trustee fails to institute a proceeding within 60 days after such request; and

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• the holders of a majority in aggregate principal amount of the outstanding debt securities of the affected series do not give the trustee a direction inconsistent with such request during such 60-day period.

These limitations do not, however, apply to a suit instituted for payment on debt securities of any series on or after the due dates expressed in the debt securities.

We will periodically deliver certificates to the trustee regarding our compliance with our obligations under the indenture.

Modification and Waiver

From time to time, we and the trustee may, without the consent of holders of the debt securities of one or more series, amend the indenture or the debt securities of one or more series, or supplement the indenture, for certain specified purposes, including:

• to provide that the surviving entity following a change of control permitted under the indenture will assume all of our obligations under the indenture and debt securities;

• to provide for certificated debt securities in addition to uncertificated debt securities;

• to comply with any requirements of the SEC under the Trust Indenture Act of 1939;

• to provide for the issuance of and establish the form and terms and conditions of debt securities of any series as permitted by the indenture;

• to cure any ambiguity, defect or inconsistency, or make any other change that does not materially and adversely affect the rights of any holder; and

• to appoint a successor trustee under the indenture with respect to one or more series.

From time to time we and the trustee may, with the consent of holders of at least a majority in principal amount of an outstanding series of debt securities, amend or supplement the indenture or the debt securities series, or waive compliance in a particular instance by us with any provision of the indenture or the debt securities. We may not, however, without the consent of each holder affected by such action, modify or supplement the indenture or the debt securities or waive compliance with any provision of the indenture or the debt securities in order to:

• reduce the amount of debt securities whose holders must consent to an amendment, supplement, or waiver to the indenture or such debt security;

• reduce the rate of or change the time for payment of interest or reduce the amount of or postpone the date for payment of sinking fund or analogous obligations;

• reduce the principal of or change the stated maturity of the debt securities;

• make any debt security payable in money other than that stated in the debt security;

• change the amount or time of any payment required or reduce the premium payable upon any redemption, or change the time before which no such redemption may be made;

• waive a default in the payment of the principal of, premium, if any, or interest on the debt securities or a redemption payment;

• waive a redemption payment with respect to any debt securities or change any provision with respect to redemption of debt securities; or

• take any other action otherwise prohibited by the indenture to be taken without the consent of each holder affected by the action.

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Defeasance of Debt Securities and Certain Covenants in Certain Circumstances

The indenture permits us, at any time, to elect to discharge our obligations with respect to one or more series of debt securities by following certain procedures described in the indenture. These procedures will allow us either:

• to defease and be discharged from any and all of our obligations with respect to any debt securities except for the following obligations (which discharge is referred to as “legal defeasance”):

1. to register the transfer or exchange of such debt securities;

2. to replace temporary or mutilated, destroyed, lost or stolen debt securities;

3. to compensate and indemnify the trustee; or

4. to maintain an office or agency in respect of the debt securities and to hold monies for payment in trust; or

• to be released from our obligations with respect to the debt securities under certain covenants contained in the indenture, as well as any additional covenants which may be contained in the applicable supplemental indenture (which release is referred to as “covenant defeasance”).

In order to exercise either defeasance option, we must irrevocably deposit with the trustee or other qualifying trustee, in trust for that purpose:

• money;

• U.S. Government Obligations (as described below) or Foreign Government Obligations (as described below) that through the scheduled payment of principal and interest in accordance with their terms will provide money; or a combination of money and/or U.S. Government Obligations and/or Foreign Government Obligations sufficient in the written opinion of a nationally-recognized firm of independent accountants to provide money;

• that, in each case specified above, provides a sufficient amount to pay the principal of, premium, if any, and interest, if any, on the debt securities of the series, on the scheduled due dates or on a selected date of redemption in accordance with the terms of the indenture.

In addition, defeasance may be effected only if, among other things:

• in the case of either legal or covenant defeasance, we deliver to the trustee an opinion of counsel, as specified in the indenture, stating that as a result of the defeasance neither the trust nor the trustee will be required to register as an investment company under the Investment Company Act of 1940;

• in the case of legal defeasance, we deliver to the trustee an opinion of counsel stating that we have received from, or there has been published by, the Internal Revenue Service a ruling to the effect that, or there has been a change in any applicable federal income tax law with the effect that (and the opinion shall confirm that), the holders of outstanding debt securities will not recognize income, gain or loss for U.S. federal income tax purposes solely as a result of such legal defeasance and will be subject to U.S. federal income tax on the same amounts, in the same manner, including as a result of prepayment, and at the same times as would have been the case if legal defeasance had not occurred;

• in the case of covenant defeasance, we deliver to the trustee an opinion of counsel to the effect that the holders of the outstanding debt securities will not recognize income, gain or loss for U.S. federal income tax purposes as a result of covenant defeasance and will be subject to U.S. federal income tax on the same amounts, in the same manner and at the same times as would have been the case if covenant defeasance had not occurred; and

• certain other conditions described in the indenture are satisfied.

If we fail to comply with our remaining obligations under the indenture and applicable supplemental indenture after a covenant defeasance of the indenture and applicable supplemental indenture, and the debt

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securities are declared due and payable because of the occurrence of any undefeased event of default, the amount of money and/or U.S. Government Obligations and/or Foreign Government Obligations on deposit with the trustee could be insufficient to pay amounts due under the debt securities of the affected series at the time of acceleration. We will, however, remain liable in respect of these payments.

The term “U.S. Government Obligations” as used in the above discussion means securities that are direct obligations of or non-callable obligations guaranteed by the United States of America for the payment of which obligation or guarantee the full faith and credit of the United States of America is pledged.

The term “Foreign Government Obligations” as used in the above discussion means, with respect to debt securities of any series that are denominated in a currency other than U.S. dollars, (1) direct obligations of the government that issued or caused to be issued such currency for the payment of which obligations its full faith and credit is pledged or (2) obligations of a person controlled or supervised by or acting as an agent or instrumentality of such government the timely payment of which is unconditionally guaranteed as a full faith and credit obligation by that government, which in either case under clauses (1) or (2), are not callable or redeemable at the option of the issuer.

Regarding the Trustee

We will identify the trustee with respect to any series of debt securities in the prospectus supplement relating to the applicable debt securities. You should note that if the trustee becomes a creditor of ours, the indenture and the Trust Indenture Act of 1939 limit the rights of the trustee to obtain payment of claims in certain cases, or to realize on certain property received in respect of any such claim, as security or otherwise. The trustee and its affiliates may engage in, and will be permitted to continue to engage in, other transactions with us and our affiliates. If, however, the trustee acquires any “conflicting interest” within the meaning of the Trust Indenture Act of 1939, it must eliminate such conflict or resign.

The holders of a majority in principal amount of the then outstanding debt securities of any series may direct the time, method and place of conducting any proceeding for exercising any remedy available to the trustee. If an event of default occurs and is continuing, the trustee, in the exercise of its rights and powers, must use the degree of care and skill of a prudent person in the conduct of his or her own affairs. Subject to that provision, the trustee will be under no obligation to exercise any of its rights or powers under the indenture at the request of any of the holders of the debt securities, unless they have offered to the trustee reasonable indemnity or security.

No Individual Liability of Incorporators, Stockholders, Officers or Directors

Each indenture provides that no incorporator and no past, present or future stockholder, officer or director of our company or any successor corporation in those capacities will have any individual liability for any of our obligations, covenants or agreements under the debt securities or such indenture.

Governing Law

The indentures and the debt securities will be governed by, and construed in accordance with, the laws of the State of New York.

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DESCRIPTION OF WARRANTS

General

We may issue warrants for the purchase of our debt securities, preferred stock, common stock, or any combination thereof. Warrants may be issued independently or together with our debt securities, preferred stock or common stock and may be attached to or separate from any offered securities. Each series of warrants will be issued under a separate warrant agreement to be entered into between us and a bank or trust company, as warrant agent. The warrant agent will act solely as our agent in connection with the warrants. The warrant agent will not have any obligation or relationship of agency or trust for or with any holders or beneficial owners of warrants. This summary of certain provisions of the warrants is not complete. For the terms of a particular series of warrants, you should refer to the prospectus supplement for that series of warrants and the warrant agreement for that particular series.

Debt Warrants

The prospectus supplement relating to a particular issue of warrants to purchase debt securities will describe the terms of the debt warrants, including the following:

• the title of the debt warrants;

• the offering price for the debt warrants, if any;

• the aggregate number of the debt warrants;

• the designation and terms of the debt securities, including any conversion rights, purchasable upon exercise of the debt warrants;

• if applicable, the date from and after which the debt warrants and any debt securities issued with them will be separately transferable;

• the principal amount of debt securities that may be purchased upon exercise of a debt warrant and the exercise price for the warrants, which may be payable in cash, securities or other property;

• the dates on which the right to exercise the debt warrants will commence and expire;

• if applicable, the minimum or maximum amount of the debt warrants that may be exercised at any one time;

• whether the debt warrants represented by the debt warrant certificates or debt securities that may be issued upon exercise of the debt warrants will be issued in registered or bearer form;

• information with respect to book-entry procedures, if any;

• the currency or currency units in which the offering price, if any, and the exercise price are payable;

• if applicable, a discussion of material U.S. federal income tax considerations;

• the antidilution provisions of the debt warrants, if any;

• the redemption or call provisions, if any, applicable to the debt warrants;

• any provisions with respect to the holder’s right to require us to repurchase the debt warrants upon a change in control or similar event; and

• any additional terms of the debt warrants, including procedures and limitations relating to the exchange, exercise, and settlement of the debt warrants.

Debt warrant certificates will be exchangeable for new debt warrant certificates of different denominations. Debt warrants may be exercised at the corporate trust office of the warrant agent or any other office indicated in

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the prospectus supplement. Prior to the exercise of their debt warrants, holders of debt warrants will not have any of the rights of holders of the debt securities purchasable upon exercise and will not be entitled to payment of principal or any premium, if any, or interest on the debt securities purchasable upon exercise.

Equity Warrants

The prospectus supplement relating to a particular series of warrants to purchase our common stock or preferred stock will describe the terms of the warrants, including the following:

• the title of the warrants;

• the offering price for the warrants, if any;

• the aggregate number of warrants;

• the designation and terms of the common stock or preferred stock that may be purchased upon exercise of the warrants;

• if applicable, the designation and terms of the securities with which the warrants are issued and the number of warrants issued with each security;

• if applicable, the date from and after which the warrants and any securities issued with the warrants will be separately transferable;

• the number of shares of common stock or preferred stock that may be purchased upon exercise of a warrant and the exercise price for the warrants;

• the dates on which the right to exercise the warrants shall commence and expire;

• if applicable, the minimum or maximum amount of the warrants that may be exercised at any one time;

• the currency or currency units in which the offering price, if any, and the exercise price are payable;

• if applicable, a discussion of material U.S. federal income tax considerations;

• the antidilution provisions of the warrants, if any;

• the redemption or call provisions, if any, applicable to the warrants;

• any provisions with respect to a holder’s right to require us to repurchase the warrants upon a change in control or similar event; and

• any additional terms of the warrants, including procedures and limitations relating to the exchange, exercise and settlement of the warrants.

Holders of equity warrants will not be entitled:

• to vote, consent, or receive dividends;

• receive notice as stockholders with respect to any meeting of stockholders for the election of our directors or any other matter; or

• exercise any rights as stockholders.

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DESCRIPTION OF SUBSCRIPTION RIGHTS

We may issue subscription rights to purchase our common stock, preferred stock or debt securities. These subscription rights may be offered independently or together with any other security offered hereby and may or may not be transferable by the stockholder receiving the subscription rights in such offering. In connection with any offering of subscription rights, we may enter into a standby arrangement with one or more underwriters or other purchasers pursuant to which the underwriters or other purchasers may be required to purchase any securities remaining unsubscribed for after such offering.

The prospectus supplement relating to any subscription rights we offer, if any, will, to the extent applicable, include specific terms relating to the offering, including some or all of the following:

• the price, if any, for the subscription rights;

• the exercise price payable for our common stock, preferred stock or debt securities upon the exercise of the subscription rights;

• the number of subscription rights to be issued to each stockholder;

• the number and terms of our common stock, preferred stock or debt securities which may be purchased per each subscription right;

• the extent to which the subscription rights are transferable;

• any other terms of the subscription rights, including the terms, procedures and limitations relating to the exchange and exercise of the subscription rights;

• the date on which the right to exercise the subscription rights shall commence, and the date on which the subscription rights shall expire;

• the extent to which the subscription rights may include an over-subscription privilege with respect to unsubscribed securities or an over-allotment privilege to the extent the securities are fully subscribed; and

• if applicable, the material terms of any standby underwriting or purchase arrangement which may be entered into by us in connection with the offering of subscription rights.

The description in the applicable prospectus supplement of any subscription rights we offer will not necessarily be complete and will be qualified in its entirety by reference to the applicable subscription rights certificate, which will be filed with the SEC if we offer subscription rights. We urge you to read the applicable subscription rights certificate and any applicable prospectus supplement in their entirety.

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DESCRIPTION OF UNITS

We may issue units consisting of some or all of the securities described above, in any combination, including common stock, preferred stock, warrants and/or debt securities. The terms of these units will be set forth in a prospectus supplement. The description of the terms of these units in the related prospectus supplement will not be complete. You should refer to the applicable form of unit and unit agreement for complete information with respect to these units.

LEGAL MATTERS

Fenwick & West LLP, Mountain View, California, will issue an opinion about certain legal matters with respect to the securities. Any underwriters or agents will be advised about legal matters relating to any offering by their own counsel.

EXPERTS

The consolidated financial statements of AnaptysBio, Inc. as of December 31, 2016 and 2015, and for each of the years in the three-year period ended December 31, 2016, have been incorporated by reference herein in reliance upon the report of KPMG LLP, an independent registered public accounting firm, incorporated by reference herein, and upon the authority of said firm as experts in accounting and auditing.

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2,200,000 Shares

AnaptysBio, Inc.

Common Stock

PROSPECTUS SUPPLEMENT

Credit Suisse

J.P. Morgan

Jefferies

Cantor

Guggenheim Securities

Wedbush PacGrow

September 25, 2018