Filed Pursuant to Rule 424(b)(5)
 Registration No. 333-233601​

PROSPECTUS SUPPLEMENT
(To Prospectus Dated September 5, 2019)

Up to $25,000,000

Common Stock

We have entered into an At-the-Market Sales Agreement, or the Sales Agreement with Virtu Americas LLC, or Virtu, relating to shares of our common stock offered by this prospectus supplement and the accompanying prospectus. In accordance with the terms of the Sales Agreement, from time to time we may offer and sell shares of our common stock having an aggregate offering price of up to $25.0 million through Virtu, acting as sales agent.

Our common stock is traded on the Nasdaq Capital Market under the symbol “ARDS.” On January 14, 2022, the last reported sale price of our common stock was $1.54 per share.

Sales of our common stock, if any, under this prospectus may be made in sales deemed to be “at-the-market” equity offerings as defined in Rule 415(a)(4) promulgated under the Securities Act of 1933, as amended, including sales made directly on or through The Nasdaq Capital Market, or any other existing trading market for our common stock. Virtu will act as a sales agent on a best efforts basis using commercially reasonable efforts consistent with its normal trading and sales practices, on mutually agreed terms between Virtu and us. There is no arrangement for funds to be received in any escrow, trust or similar arrangement.

The compensation to Virtu for sales of shares of common stock sold pursuant to the Sales Agreement will be an amount up to 3.0% of the gross proceeds of any shares of common stock sold under the Sales Agreement. In connection with the sale of the shares of common stock on our behalf, Virtu will be deemed to be an “underwriter” within the meaning of the Securities Act, and the compensation of Virtu will be deemed to be underwriting commissions or discounts. We have also agreed to provide indemnification and contribution to Virtu with respect to certain liabilities, including liabilities under the Securities Act.

Investing in our common stock involves a high degree of risk. Please read the information contained in and incorporated by reference under the heading “Risk Factors” on page S-6 of this prospectus, and under similar headings in the other documents that are filed after the date hereof and incorporated by reference into this prospectus.

Neither the U.S. Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities, or passed upon the adequacy or accuracy of this prospectus or any accompanying prospectus supplement. Any representation to the contrary is a criminal offense.

The date of this prospectus is January 19, 2022.

TABLE OF CONTENTS

Prospectus Supplement

​	Page
ABOUT THIS PROSPECTUS SUPPLEMENT	​	S-1
PROSPECTUS SUPPLEMENT SUMMARY	​	S-2
RISK FACTORS	​	S-6
DISCLOSURE REGARDING FORWARD-LOOKING STATEMENTS	​	S-8
USE OF PROCEEDS	​	S-10
DILUTION	​	S-11
PLAN OF DISTRIBUTION	​	S-12
LEGAL MATTERS	​	S-13
EXPERTS	​	S-13
WHERE YOU CAN FIND MORE INFORMATION	​	S-13
INCORPORATION OF DOCUMENTS BY REFERENCE	​	S-13

Prospectus

About This Prospectus	1
Summary	2
Risk Factors	7
Forward-Looking Statements	7
Use of Proceeds	9
Description of Capital Stock	10
Description of Debt Securities	13
Description of Warrants	19
Description of Rights	21
Description of Units	22
Legal Ownership of Securities	23
Plan of Distribution	27
Legal Matters	30
Experts	30
Where You Can Find More Information	30
Incorporation of Documents by Reference	31

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ABOUT THIS PROSPECTUS SUPPLEMENT

This prospectus supplement and the accompanying prospectus are part of a shelf registration statement that we filed with the Securities and Exchange Commission (the “Commission”) using a “shelf” registration process. This prospectus supplement amends and supplements the information contained in the prospectus filed as a part of our registration statement on Form S-3 (File No. 333-233601), which was declared effective as of September 5, 2019 (our “Registration Statement”). This document is in two parts. The first part is the prospectus supplement, including the documents incorporated by reference, which describes the specific terms of this offering. The second part, the accompanying prospectus, including the documents incorporated by reference, provides more general information. Generally, when we refer to this prospectus supplement, we are referring to both parts of this document combined. We urge you to carefully read this prospectus supplement and the accompanying prospectus, and the documents incorporated by reference herein and therein, before buying any of the securities being offered under this prospectus supplement. This prospectus supplement may add, update or change information contained in the accompanying prospectus. To the extent that any statement that we make in this prospectus supplement is inconsistent with statements made in the accompanying prospectus or any documents incorporated by reference therein filed prior to the date of this prospectus supplement, 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.

You should rely only on the information contained or incorporated herein by reference in this prospectus supplement and contained or incorporated therein by reference in the accompanying prospectus. We have not authorized anyone to provide you with different or additional information. If anyone provides you with different, additional or inconsistent information, you should not rely on it.

We are offering to sell the securities only in jurisdictions where such offers and sales are permitted. The distribution of this prospectus supplement and the accompanying prospectus and the offering of the securities in certain jurisdictions or to certain persons within such jurisdictions may be restricted by law. Persons outside the United States who come into possession of this prospectus supplement and the accompanying prospectus must inform themselves about and observe any restrictions relating to the offering of the securities and the distribution of this prospectus supplement and the accompanying prospectus outside the United States. This prospectus supplement and the accompanying prospectus do 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 and the accompanying prospectus by any person in any jurisdiction in which it is unlawful for such person to make such an offer or solicitation.

You should assume that the information in this prospectus supplement and the accompanying prospectus is accurate only as of the date on the front of the applicable document and that any information we have incorporated by reference is accurate only as of the date of the document incorporated by reference, regardless of the time of delivery of this prospectus supplement or the accompanying prospectus, or any sale of a security. Our business, financial condition, results of operations and prospects may have changed since those dates. You should read this prospectus supplement, the accompanying prospectus and the documents incorporated by reference in this prospectus supplement and the accompanying prospectus when making your investment decision. You should also read and consider the information in the documents we have referred you to in the sections of this prospectus supplement and the accompanying prospectus titled “Where You Can Find More Information” and “Incorporation of Documents by Reference.”

The representations, warranties and covenants made by us in any agreement that is filed as an exhibit to any document that is incorporated by reference herein or in the accompanying prospectus were made solely for the benefit of the parties to such agreement, including, in some cases, for the purpose of allocating risk among the parties to such agreements, and should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be relied on as accurately representing the current state of our affairs.

This prospectus supplement, the accompanying prospectus, and the information incorporated herein and therein by reference includes 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.

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PROSPECTUS SUPPLEMENT SUMMARY

This summary highlights certain information about us, this offering and selected information contained elsewhere in or incorporated by reference into this prospectus. This summary is not complete and does not contain all of the information that you should consider before deciding whether to invest in our common stock. For a more complete understanding of our company and this offering, we encourage you to read and consider carefully the more detailed information in this prospectus and the accompanying prospectus, including the information incorporated by reference into this prospectus and the accompanying prospectus, and the information referred to under the heading “Risk Factors” in this prospectus on page S-6 and on page 7 of the accompanying prospectus, and in the documents incorporated by reference into this prospectus and the accompanying prospectus.

The Company

We are a late-stage biopharmaceutical company focused on the discovery and development of novel anti-infectives. A significant focus of ours is on targeted immunotherapy using fully human monoclonal antibodies, or mAbs, to treat life-threatening infections. mAbs represent an innovative treatment approach that harnesses the human immune system to fight infections and are designed to overcome the deficiencies associated with current therapies, such as rise in drug resistance, short duration of response, limited tolerability, negative impact on the human microbiome, and lack of differentiation among the treatment alternatives. The majority of our product candidates are derived by employing our differentiated antibody discovery platforms. Our proprietary product pipeline comprises fully human mAbs targeting specific pathogens associated with life-threatening bacterial infections, primarily nosocomial pneumonia, and viral infections such as COVID-19.

In July 2021, we announced that our COVID-19 mAb cocktail AR-712 binds and neutralizes the Delta variant virus SARS COV2 at a highly effective level (~20ng/mL). In vitro neutralization data using authentic SARS-CoV2 virus showed that AR-712 was effective against all major variants on the U.S. Center for Disease Control’s Variants of Interest and Variants of Concern lists. The dual antibody cocktail will be delivered as an inhaled treatment and is expected to provide broad coverage of all known high-risk variants. In addition, we announced the preclinical development services support from the National Institute of Allergy and Infectious Diseases (NIAID) at the National Institutes of Health (NIH) provided further demonstration of strong therapeutic activity of inhaled delivery in a SARS-COV2 hamster challenge model. This achieved reversal of disease in infected animals at an inhaled dose of 1mg/kg, equivalent to a 10mg dose in humans from a nebulizer. These results confirmed our studies showing highly efficient dosing by inhalation. For reference purposes, the dose of commercially available COVID antibody therapies is in the range of 500mg to 1,200mg. AR-712 is being developed as a self-administered, at-home inhaled treatment for COVID-19 patients who are not yet hospitalized. The product candidate is designed to substantially lower the barrier to treatment of COVID-19 patients and encourage treatment much earlier in the course of their disease within the patients’ own homes.

In December 2021, we announced that our COVID-19 mAb cocktail AR-701 is broadly reactive against the Omicron and other COVID-19 (SARS-CoV-2) variants, SARS (Severe Acute Respiratory Syndrome), MERS (Middle East Respiratory Syndrome Coronavirus), and seasonal (‘common cold’) human coronaviruses. AR-701 consists of AR-703 and AR-720 mAbs, each neutralizes coronaviruses using distinct mechanisms of action, namely inhibition of viral fusion and entry into human cells (AR-703) and blockage of viral binding to the human ‘ACE2’ receptor (AR-720). In vivo data with multiple animal challenge models that are widely used to evaluate COVID-19 treatments support AR-701’s broad efficacy. The two mAbs complement and enhance each other in a synergistic fashion, creating a potent first-in-class cocktail. AR-701 is engineered to be long-acting, and is expected to provide relevant drug levels for up to 1 year from prophylactic or therapeutic treatment. The dual antibody cocktail will be delivered as an intramuscular and inhaled treatment, and is expected to provide broad coverage of all known high-risk variants. A clinical Phase 1/2 study is expected to be launched in the second half of 2022.

Our lead product candidate, AR-301 has exhibited promising preclinical data and clinical data from a Phase 1/2a clinical study in patients. AR-301 targets the alpha toxin produced by gram-positive bacteria Staphylococcus aureus, or S. aureus, a common pathogen associated with HAP and VAP. In contrast to other programs targeting S. aureus toxins, we are developing AR-301 as a treatment of pneumonia, rather than prevention of S. aureus colonized patients from progression to pneumonia. In January 2019, we initiated a Phase 3 pivotal trial evaluating AR-301 for the treatment of VAP. This AR-301 Phase 3 study remains blinded,

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and the independent Data Monitoring Committee with access to unblinded data continues to monitor study subjects for safety and has not conveyed any safety concerns (i.e., thus far an un-remarkable safety profile). The on-going COVID-19 pandemic has caused an impact on patient enrollment globally and the rate of clinical site activation. The activation of AR-301 clinical trial sites progressed globally during the pandemic, but the patient enrollment slowed due to the prioritization of the intensive care units (“ICU”) around the world to COVID-19 patients. As countries start to emerge from the pandemic, we expect patient enrollment to improve, and enrollment to be complete in late first half of 2022. At this rate, the Phase 3 interim futility analysis would be completed too close to the completion of patient enrollment to be useful. As such, we expect to elect to forgo the interim futility analysis and focus on accelerating patient enrollment to deliver top-line data by approximately mid-2022.

In July 2021, we announced an in-licensing agreement with AstraZeneca for the worldwide commercial rights to suvratoxumab, which is a half-life extended human IgG1 monoclonal antibody that also targets the alpha toxin produced by S. aureus. This product is given the product code ‘AR-320’. As with AR-301, AR-320’s mode of action is independent of the antibiotic resistance profile of S. aureus, and it is active against infections caused by both MRSA and MSSA. Suvratoxumab and AR-301 are complementary products. Suvratoxumab’s focus on preventive treatment of S. aureus pneumonia complements Aridis’ AR-301 Phase 3 mAb program which is being developed as a therapeutic treatment of S. aureus pneumonia. A multinational, randomized, double blinded, placebo controlled Phase 2 study conducted by AstraZeneca (n=196 patients) showed that mechanically ventilated ICU patients colonized with S. aureus who are treated with suvratoxumab saw a relative risk reduction of pneumonia by 32% in the overall intend to treat (“ITT”) study population, and by 47% in the under 65 year old population, which is the target population in the planned Phase 3 study. The relative risk reduction in the target population reached statistical significance, and was also associated with a substantial reduction in the duration of care needed in the ICU and hospital [see https://www.thelancet.com/​journals/laninf/article/PIIS1473-3099(20)30995-6/fulltext]. We believe that AR-320 will be first-line treatment, first to market, first-in-class pre-emptive treatment of S. aureus colonized patients. The same first-line, first to market and first-in-class strategy applies to the acute treatment with the monoclonal antibody AR-301, which we believe makes us a global leader in this space.

To complement and diversify our portfolio of targeted mAbs, we are developing a broad spectrum small molecule non-antibiotic anti-infective agent gallium citrate (AR-501). AR-501 is being developed in collaboration with the Cystic Fibrosis Foundation (“CFF”) as a chronic inhaled therapy to treat lung infections in cystic fibrosis patients. In 2018, AR-501 was granted Orphan Drug, Fast Track and Qualified Infectious Disease Product (“QIDP”) designations by the Food and Drug Administration (“FDA”). During the third quarter of 2019, the European Medicines Agency (“EMA”) granted the program Orphan Drug Designation. We initiated a Phase 1/2a clinical trial in December 2018 of the inhalable formulation of gallium citrate, which is being evaluated for the treatment of chronic lung infections associated with cystic fibrosis. In June 2020, we announced positive results from the Phase 1 portion of our Phase 1/2a clinical trial of AR-501 in which healthy subjects were enrolled. The Safety Monitoring Committee (“SMC’) and Data Safety Monitoring Board (“DSMB”) from the Cystic Fibrosis Foundation supported that the study proceed at all dose levels to the Phase 2a portion of the Phase 1/2a trial in adult subjects with cystic fibrosis (“CF”). The on-going COVID-19 pandemic has caused an impact on the rate of clinical site activation. We provisionally expect to complete enrollment of the Phase 2a portion with cystic fibrosis subjects in early 2022 with top-line data available shortly afterward.

In September 2020, we announced that we reached an agreement with the FDA to simplify our AR-501 Phase 2 trial design for the treatment of chronic lung infections associated with CF. We proposed, and the FDA agreed, to streamline AR-501’s forthcoming Phase 2a clinical trial in CF patients, by removing the single ascending dose (“SAD”) portion of the study and only conducting a multiple ascending dose (“MAD”) regimen. Furthermore, the FDA also concurred with our proposal to expand the originally planned Phase 2a protocol design into a Phase 2a/2b study. This Phase 2a/2b design will enable seamless and efficient advancement of the study from Phase 2a into Phase 2b using the same clinical study protocol. The data from the Phase 2a will inform the dose selection and sample size expansion to achieve statistical significance in efficacy in Phase 2b.

To date, we have devoted substantially all of our resources to research and development efforts relating to our therapeutic candidates, including conducting clinical trials and developing manufacturing capabilities,

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in-licensing related intellectual property, protecting our intellectual property and providing general and administrative support for these operations. We have generated revenue from payments under our collaboration strategic research and development contracts and federal awards and grants, as well as awards and grants from not-for-profit entities and fee for service to third-party entities. Since our inception, we have funded our operations primarily through these sources and the issuance of common stock, convertible preferred stock, and debt securities. Current clinical development activities are focused on AR-301, AR-712 and AR-501.

Recent Developments

On September 1, 2021, Cantor Fitzgerald & Co. (“Cantor”) filed a complaint in the Supreme Court of the State of New York, County of New York, against us alleging that we breached a letter agreement with Cantor. On December 8, 2021, we participated in a mediation with Cantor during which we agreed to a settlement of the litigation. In addition, on January 10, 2022, we notified Cantor of our intent to terminate, which became effective on January 18, 2022, the Controlled Equity Offering Sales Agreement dated as of September 3, 2019 between us and Cantor in connection with our at-the-market offering of up to $25.0 million.

Corporate History and Information

We were formed under the name “Aridis, LLC” in the State of California on April 24, 2003 as a limited liability company. On August 30, 2004, we changed our name to “Aridis Pharmaceuticals, LLC.” On May 21, 2014, we converted into a Delaware corporation named “Aridis Pharmaceuticals, Inc.” Our fiscal year end is December 31. Our principal executive offices are located at 983 University Avenue, Bldg. B, Los Gatos, California 95032. Our telephone number is (408) 385-1742. Our website address is www.aridispharma.com. The information contained on, or that can be accessed through, our website is not a part of this prospectus supplement or the accompanying prospectus.

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The Offering

Common stock offered by us

Shares of our common stock having an aggregate offering price of up to $25,000,000.

Common stock to be outstanding
  after this offering

 
Up to 33,935,358 shares (as more fully described in the notes following this table), assuming sales of 16,233,766 shares of our common stock in this offering at an assumed offering price of $1.54 per share, which was the last reported sale price of our common stock on the Nasdaq Capital Market on January 14, 2022. The actual number of shares issued in connection with this offering will vary depending on how many shares of our common stock we choose to sell and the prices at which such sales occur.

Plan of Distribution

“At the market offering” that may be made from time to time through our sales agent, Virtu. See “Plan of Distribution” on page S-12.

Use of Proceeds

We intend to use the net proceeds, if any, from this offering for working capital and general corporate purposes, including research and development. See “Use of Proceeds” on page S-10.

Risk Factors

You should read the “Risk Factors” section of this prospectus supplement and in the documents incorporated by reference in this prospectus supplement for a discussion of factors to consider before deciding to purchase shares of our common stock.

Nasdaq Capital Market symbol

“ARDS”

The number of shares of common stock to be outstanding after this offering is based on 14,054,036 shares of common stock outstanding as of September 30, 2021, and also includes 3,647,556 shares of common stock issued upon exercise of pre-funded warrants in December 2021, and excludes the following:

•

1,739,743 shares of our common stock issuable upon exercise of outstanding stock options under our stock incentive plans at a weighted average exercise price of $9.12 per share;

•

4,106,569 shares of our common stock issuable upon exercise of outstanding warrants at a weighted average exercise price of $7.97 per share; and

•

393,815 shares of common stock reserved for future grants and awards under our stock incentive plans.

In addition, unless we specifically state otherwise, all information in this prospectus assumes no exercise of stock options or warrants outstanding at September 30, 2021

Unless otherwise stated, all information contained in this prospectus reflects an assumed public offering price of $1.54 per share, which was the last reported sale price of our common stock on the Nasdaq Capital Market on January 14, 2022.

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RISK FACTORS

Investing in our common stock involves a high degree of risk. Before deciding whether to invest in our common stock, you should consider carefully the risks and uncertainties described below and discussed under the section entitled “Risk Factors” on page 7 of the accompanying prospectus. You should also consider the risks, uncertainties and assumptions discussed under the heading “Risk Factors” included in our most recent Annual Report on Form 10-K, as revised or supplemented by our most recent Quarterly Report on Form 10-Q, each of which are on file with the SEC and are incorporated herein by reference, and which may be amended, supplemented or superseded from time to time by other reports we file with the SEC in the future. There may be other unknown or unpredictable economic, business, competitive, regulatory or other factors that could have material adverse effects on our future results. If any of these risks actually occurs, our business, business prospects, financial condition or results of operations could be seriously harmed. This could cause the trading price of our common stock to decline, resulting in a loss of all or part of your investment. Please also read carefully the section below entitled “Disclosure Regarding Forward-Looking Statements.”

Additional Risks Related to This Offering and Ownership of our Common Stock

Management will have broad discretion as to the use of the proceeds from this offering, and may not use the proceeds effectively.

Because we have not designated the amount of net proceeds from this offering to be used for any particular purpose, our management will have broad discretion as to the application of the net proceeds from this offering and could use them for purposes other than those contemplated at the time of the offering. Our management may use the net proceeds for corporate purposes that may not improve our financial condition or market value.

You may experience immediate and substantial dilution.

The offering price per share in this offering may exceed the net tangible book value per share of our common stock outstanding prior to this offering. Assuming that an aggregate of 16,233,766 shares of our common stock are sold during the term of the Sales Agreement at an assumed public offering price of $1.54 per share, the last reported sale price of our common stock on The Nasdaq Capital Market on January 14, 2022, for aggregate gross proceeds of $25,000,000, after deducting commissions and estimated aggregate offering expenses payable by us, you will experience immediate dilution of $0.94 per share, representing the difference between our pro forma as adjusted net tangible book value per share as of September 30, 2021 after giving effect to (i) the issuance of 3,647,556 shares of common stock upon exercise of a pre-funded warrant in December 2021 and (ii) this offering and the assumed offering price. The exercise of outstanding stock options and warrants may result in further dilution of your investment. See the section entitled “Dilution” below for a more detailed illustration of the dilution you would incur if you participate in this offering.

You may experience future dilution as a result of future equity offerings.

In order to raise additional capital, we may in the future offer additional shares of our common stock or other securities convertible into or exchangeable for our common stock at prices that may not be the same as the price per share in this offering. We may sell shares or other securities in any other offering at a price per share that is less than the price per share paid by investors in this offering, and investors purchasing shares or other securities in the future could have rights superior to existing stockholders. The price per share at which we sell additional shares of our common stock, or securities convertible or exchangeable into common stock, in future transactions may be higher or lower than the price per share paid by investors in this offering.

The actual number of shares of common stock we will issue under the Sales Agreement, at any one time or in total, is uncertain.

Subject to certain limitations in the Sales Agreement and compliance with applicable law, we have the discretion to deliver a placement notice to Virtu at any time throughout the term of the Sales Agreement. The number of shares that are sold by Virtu after delivering a placement notice will fluctuate based on the market price of our common stock during the sales period and limits we set with Virtu. Because the price per share of

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each share sold will fluctuate based on the market price of our common stock during the sales period, it is not possible at this stage to predict the number of shares that will be ultimately issued.

The common stock offered hereby will be sold in “at the market offerings,” and investors who buy shares at different times will likely pay different prices.

Investors who purchase shares in this offering at different times will likely pay different prices, and so may experience different outcomes in their investment results. We will have discretion, subject to market demand, to vary the timing, prices and numbers of shares sold, and there is no minimum or maximum sales price. Investors may experience a decline in the value of their shares as a result of share sales made at prices lower than the prices they paid.

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DISCLOSURE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying prospectus and the documents we incorporate by reference in this prospectus supplement contain forward-looking statements within the meaning of Section 27A of the Securities Act, and Section 21E of the Exchange Act, and may involve material risks, assumptions and uncertainties. Statements that are not purely historical should be considered forward-looking statements. Often they can be identified by the use of forward-looking words and phrases, such as “may,” “will,” “believe,” “anticipate,” “expect,” “should,” “optimistic” or “continue,” “estimate,” “intend,” “plan,” “would,” “could,” “guidance,” “potential,” “opportunity,” “project,” “forecast,” “confident,” “projections,” “schedule,” “designed,” “future” and the like. These forward-looking statements reflect our current expectations and projections about future events and financial trends that we believe may affect our business, financial condition and results of operations. These forward-looking statements are subject to a number of risks, uncertainties and assumptions described under the section entitled “Risk Factors.”

These statements are not guarantees of future performance and involve risks and uncertainties that are difficult to predict or are beyond our control. A number of important factors could cause actual outcomes and results to differ materially from those expressed in these forward-looking statements. Consequently, readers should not place undue reliance on such forward-looking statements. In addition, these forward-looking statements relate to the date on which they are made.

The forward-looking statements reflect our current expectations and are based on information currently available to us and on assumptions we believe to be reasonable. Forward-looking information is subject to known and unknown risks, uncertainties and other factors that may cause our actual results, activities, performance or achievements to be materially different from that expressed or implied by such forward-looking statements. These forward-looking statements include, but are not limited to:

•

the timing of regulatory submissions;

•

our ability to obtain and maintain regulatory approval of our existing product candidates and any other product candidates we may develop, and the labeling under any approval we may obtain;

•

approvals for clinical trials may be delayed or withheld by regulatory agencies;

•

preclinical and clinical studies will not be successful or confirm earlier results, meet expectations, meet regulatory requirements, or meet performance thresholds for commercial success;

•

risks relating to the timing and costs of clinical trials, the timing and costs of other expenses;

•

risks associated with obtaining third-party funding;

•

risks associated with delays, increased costs and funding shortages caused by or resulting from the COVID-19 pandemic;

•

management and employee operations and execution risks;

•

loss of key personnel;

•

competition;

•

risks related to market acceptance of products;

•

intellectual property risks;

•

assumptions regarding the size of the available market, benefits of our products, product pricing, and timing of product launches;

•

risks associated with the uncertainty of future financial results;

•

our ability to attract collaborators and partners; and

•

risks associated with our reliance on third-party organizations.

Although we have attempted to identify important factors that could cause actual actions, events or results to differ materially from those described in forward-looking information, there may be other factors that cause actions, events or results to differ from those anticipated, estimated or intended. Other than as

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required by law, we do not assume any obligation to update any forward-looking information, whether as a result of new information, future events or results or otherwise.

You should also read the matters described in “Risk Factors” and the other cautionary statements made in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference into this prospectus supplement. The forward-looking statements in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference into this prospectus supplement may not prove to be accurate and therefore you are encouraged not to place undue reliance on forward-looking statements. You should read this prospectus supplement, the accompanying prospectus and the documents incorporated by reference into this prospectus supplement completely.

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USE OF PROCEEDS

We may issue and sell shares of our common stock having aggregate sales proceeds of up to $25.0 million from time to time. The amount of proceeds from this offering will depend upon the number of shares of our common stock sold and the market price at which they are sold. There can be no assurance that we will be able to sell any shares under or fully utilize the Sales Agreement with Virtu as a source of financing. We intend to use the net proceeds, if any, from this offering for working capital and general corporate purposes, including research and development.

The amounts and timing of our use of the net proceeds from this offering will depend on a number of factors, such as the timing and progress of our research and development efforts, the timing and progress of any collaborative or strategic partnering efforts, and the competitive environment for our planned products. As of the date of this prospectus, we cannot specify with certainty all of the particular uses for the net proceeds to us from this offering. Accordingly, our management will have broad discretion in the timing and application of these proceeds. Pending application of the net proceeds as described above, we intend to temporarily invest the proceeds in short-term, interest-bearing instruments.

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DILUTION

If you purchase our common stock in this offering, your interest will be diluted to the extent of the difference between the public offering price per share and the net tangible book value per share of our common stock after this offering. We calculate net tangible book value per share by dividing our net tangible assets (tangible assets less total liabilities) by the number of shares of our common stock issued and outstanding as of September 30, 2021.

Our net tangible book value at September 30, 2021 was a deficit of $(4.2) million, or $(0.30) 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 September 30, 2021. Dilution in 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 as adjusted net tangible book value per share of our common stock immediately after giving effect to this offering.

Our pro forma net tangible book value as of September 30, 2021 was a deficit of $(4.2) million, or $(0.24) per share of common stock. Pro forma net tangible book value represents the amount of our total tangible assets less our total liabilities after giving effect to the issuance of 3,647,556 shares of common stock upon exercise of pre-funded warrants in December 2021.

After giving effect to the sale of our common stock during the term of the Sales Agreement with Virtu in the aggregate amount of $25.0 million at an assumed public offering price of $1.54 per share, the last reported sale price of our common stock on the Nasdaq Capital Market on January 14, 2022, and after deducting commissions and estimated aggregate offering expenses payable by us, our pro forma as adjusted net tangible book value as of September 30, 2021 would have been $20.3 million, or $0.60 per share of common stock. This represents an immediate increase in the pro forma as adjusted net tangible book value of $0.90 per share to our existing stockholders and an immediate dilution of $0.94 per share to new investors. The following table illustrates this per share dilution:

Assumed public offering price per share	​	​	​	$	1.54
Pro forma net tangible book value per share as of September 30, 2021	​	$	(0.24)	​	​
Increase in pro forma as adjusted net tangible book value per share attributable to this offering	​	$	0.84	​	​
Pro forma as adjusted net tangible book value per share as of September 30, 2021, after giving effect to this offering				$	0.60
Dilution per share to new investors purchasing shares in this offering				$	0.94

The number of shares of common stock to be outstanding after this offering is based on 14,054,036 shares of common stock outstanding as of September 30, 2021, and also includes 3,647,556 shares of common stock issued upon exercise of pre-funded warrants in December 2021, and excludes the following:

•

1,739,743 shares of our common stock issuable upon exercise of outstanding stock options under our stock incentive plans at a weighted average exercise price of $9.12 per share;

•

4,106,569 shares of our common stock issuable upon exercise of outstanding warrants at a weighted average exercise price of $7.97 per share; and

•

393,815 shares of common stock reserved for future grants and awards under our stock incentive plans.

In addition, unless we specifically state otherwise, all information in this prospectus assumes no exercise of stock options or warrants outstanding at September 30, 2021.

To the extent that options or warrants as of September 30, 2021 have been or are exercised, or other shares are issued, investors purchasing shares in this offering could experience further dilution. In addition, we may choose to raise additional capital due to market conditions or strategic considerations, even if we believe we have sufficient funds for our current or future operating plans. To the extent that additional capital is raised through the sale of equity or convertible debt securities, the issuance of these securities could result in further dilution to our stockholders.

S-11

PLAN OF DISTRIBUTION

We have entered into an At-the-Market Sales Agreement, or the Sales Agreement, with Virtu Americas LLC, or Virtu, pursuant to which we may issue and sell shares of our common stock, $0.0001 par value per share, through Virtu, acting as our sales agent. Pursuant to this prospectus supplement, we may issue and sell up to $25.0 million shares of our common stock. This summary of the material provisions of the Sales Agreement does not purport to be a complete statement of its terms and conditions. A copy of the Sales Agreement will be filed as an exhibit to a Current Report on Form 8-K and will be incorporated by reference into the registration statement of which this prospectus supplement is a part. See “Where You Can Find More Information” below.

Upon delivery of a placement notice and subject to the terms and conditions of the Sales Agreement, Virtu may sell our common stock by any method permitted by law deemed to be an “at the market offering” as defined in Rule 415(a)(4) promulgated under the Securities Act, including sales made directly on the Nasdaq Capital Market or any other existing trading market for our common stock. We or Virtu may suspend the offering of our common stock upon notice and subject to other conditions.

We will pay Virtu in cash, upon each sale of our common stock pursuant to the Sales Agreement, a commission in an amount of up to 3.0% of the gross sales price per share for any shares of common stock sold through Virtu acting as our sales agent under the Sales Agreement. Because there is no minimum offering amount required as a condition to close this offering, the actual total public offering amount, commissions and proceeds to us, if any, are not determinable at this time. We have also agreed to reimburse Virtu for certain specified expenses, in an aggregate amount not exceeding $50,000, including the fees and disbursements of its legal counsel. We estimate that the total expenses for the offering, excluding compensation and reimbursements payable to Virtu under the terms of the Sales Agreement, will be approximately $60,000. Virtu may agree to a fee sharing arrangement with Arcadia Securities, LLC, or Arcadia, pursuant to which Arcadia will be entitled to receive a percentage of the net commissions payable to Virtu in consideration for their services to us as a financial advisor under this offering. Other than serving as a financial advisor to us, Arcadia will have no other obligation or responsibility in connection with the sale of the common stock covered by this prospectus supplement.

Settlement for sales of common stock will occur on the second business day following the date on which any sales are made, or on another date that is agreed upon by us and Virtu in connection with a particular transaction, in return for payment of the net proceeds to us. Sales of our common stock as contemplated in this prospectus supplement will be settled through the facilities of The Depository Trust Company or by such other means as we and Virtu may agree upon. There is no arrangement for funds to be received in an escrow, trust or similar arrangement.

Virtu will use its commercially reasonable efforts, consistent with its sales and trading practices, to solicit offers to purchase shares of our common stock under the terms and subject to the conditions set forth in the Sales Agreement. In connection with the sale of the common stock on our behalf, Virtu will be deemed to be an “underwriter” within the meaning of the Securities Act, and the compensation of Virtu will be deemed to be underwriting commissions or discounts. We have agreed to provide indemnification and contribution to Virtu against certain civil liabilities, including liabilities under the Securities Act.

The offering of our common stock pursuant to the Sales Agreement will terminate upon the termination of the Sales Agreement as permitted therein. We and Virtu may each terminate the Sales Agreement at any time upon ten days’ prior notice.

We have agreed to indemnify Virtu and specified other persons against certain liabilities relating to or arising out of Virtu’s activities under the Sales Agreement and to contribute to payments that Virtu may be required to make in respect of such liabilities.

Virtu and its affiliates may in the future provide various investment banking, commercial banking and other financial services for us and our affiliates, for which services they may in the future receive customary fees. To the extent required by Regulation M, Virtu will not engage in any market making activities involving our common stock while the offering is ongoing under this prospectus supplement.

This prospectus supplement and the accompanying prospectus in electronic format may be made available on a website maintained by Virtu, and Virtu may distribute this prospectus supplement and the accompanying prospectus electronically.

S-12

LEGAL MATTERS

The validity of the shares of our common stock offered in this prospectus supplement will be passed upon for us by Sheppard, Mullin, Richter & Hampton LLP, New York, NY. Virtu Americas LLC is being represented in connection with this offering by Cooley LLP, New York, New York..

EXPERTS

The consolidated financial statements as of and for the years ended December 31, 2020 and 2019, included in our Annual Report on Form 10-K for the year ended December 31, 2020, have been audited by Mayer Hoffman McCann P.C., independent registered public accounting firm, as set forth in their report (which report includes an explanatory paragraph regarding the existence of substantial doubt about the Company’s ability to continue as a going concern), and have been incorporated herein by reference in reliance on the report of Mayer Hoffman McCann P.C., given on the authority of such firm as experts in auditing and accounting in giving said reports.

WHERE YOU CAN FIND MORE INFORMATION

This prospectus supplement constitutes a part of the registration statement on Form S-3 that we have filed with the SEC under the Securities Act. As permitted by the SEC’s rules, this prospectus supplement and any accompanying prospectus, which forms a part of the registration statement, do not contain all of the information that is included in the registration statement. You will find additional information about us in the registration statement. Any statement made in this prospectus supplement or any accompanying prospectus concerning legal documents are not necessarily complete and you should read the documents that are filed as exhibits to the registration statement or otherwise filed with the SEC for a more complete understanding of the document or matter.

We are subject to the reporting requirements of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and file annual, quarterly and current reports, proxy statements and other information with the SEC. You can read our SEC filings, including the registration statement, over the Internet at the SEC’s website at www.sec.gov. We also maintain a website at www.aridispharma.com, at which you may access these materials free of charge as soon as reasonably practicable after they are electronically filed with, or furnished to, the SEC. The information contained in, or that can be accessed through, our website is not part of this prospectus. You may also request a copy of these filings, at no cost, by writing or telephoning us at: 983 University Avenue, Bldg. B, Los Gatos, California 95032, (408) 385-1742.

INCORPORATION OF DOCUMENTS BY REFERENCE

The SEC allows us to “incorporate by reference” the information we file with them which means that we can disclose important information to you by referring you to those documents instead of having to repeat the information in this prospectus. The information incorporated by reference is considered to be part of this prospectus, and later information that we file with the SEC will automatically update and supersede this information. This prospectus incorporates by reference the documents listed below:

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The Company’s Annual Report on Form 10-K for the year ended December 31, 2020, filed with the SEC on March 30, 2021;

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Amendment No. 1 to the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on April 30, 2021;

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The Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2021, filed with the SEC on May 11, 2021;

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Amendment No. 1 to the Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2020, filed with the SEC on April 30, 2021;

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The Company’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2021, filed with the SEC on August 12, 2021;

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The Company’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2021, filed with the SEC on November 10, 2021;

S-13

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The Company’s Definitive Proxy Statement filed with the SEC on April 16, 2021;

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The Company’s Current Reports on Form 8-K filed with the SEC on February 23, 2021, March 8, 2021, March 15, 2021, March 16, 2021 (8-K/A), May 24, 2021, June 2, 2021, June 3, 2021, July 13, 2021, July 19, 2021, July 26, 2021, August 4, 2021, November 30, 2021, and December 21, 2021; and

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The description of the Company’s common stock contained in the registration statement on Form 8-A filed with the SEC on August 13, 2018 pursuant to Section 12 of the Exchange Act of 1934, as amended (the “Exchange Act”), including any amendment or report filed for the purpose of updating that description.

We also incorporate by reference all documents (other than Current Reports furnished under Item 2.02 or Item 7.01 of Form 8-K and exhibits filed on such form that are related to such items) that are subsequently filed by us with the Securities and Exchange Commission pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act prior to the termination of the offering of the securities made by this prospectus (including documents filed after the date of the initial Registration Statement of which this prospectus is a part and prior to the effectiveness of the Registration Statement). These documents include periodic reports, such as Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, as well as proxy statements.

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

S-14

PROSPECTUS

Aridis Pharmaceuticals, Inc.

Common Stock

Preferred Stock
Debt Securities
Warrants
Rights
Units

We may offer and sell, from time to time in one or more offerings, any combination of common stock, preferred stock, debt securities, warrants to purchase common stock, preferred stock or debt securities, or any combination of the foregoing, either individually or as units comprised of one or more of the other securities, having an aggregate initial offering price not exceeding $100,000,000.

This prospectus provides a general description of the securities we may offer. Each time we sell a particular class or series of securities, we will provide specific terms of the securities offered in a supplement to this prospectus. The prospectus supplement and any related free writing prospectus may also add, update or change information contained in this prospectus. We may also authorize one or more free writing prospectuses to be provided to you in connection with these offerings. You should read carefully this prospectus, the applicable prospectus supplement and any related free writing prospectus, as well as any documents incorporated by reference herein or therein before you invest in any of our securities.

The specific terms of any securities to be offered, and the specific manner in which they may be offered, will be described in one or more supplements to this prospectus. This prospectus may not be used to consummate sales of any of these securities unless it is accompanied by a prospectus supplement. Before investing, you should carefully read this prospectus and any related prospectus supplement.

Our common stock is presently listed on The Nasdaq Capital Market under the symbol “ARDS.” On August 30, 2019, the last reported sale price of our common stock was $11.68 per share. The applicable prospectus supplement will contain information, where applicable, as to any other listing on The Nasdaq Capital Market or any securities market or other exchange of the securities, if any, covered by the prospectus supplement. Prospective purchasers of our securities are urged to obtain current information as to the market prices of our securities, where applicable

These securities may be sold directly by us, through dealers or agents designated from time to time, to or through underwriters, dealers, or through a combination of these methods on a continuous or delayed basis. See “Plan of Distribution” in this prospectus. We may also describe the plan of distribution for any particular offering of our securities in a prospectus supplement. If any agents, underwriters or dealers are involved in the sale of any securities in respect of which this prospectus is being delivered, we will disclose their names and the nature of our arrangements with them in a prospectus supplement. The price to the public of such securities and the net proceeds we expect to receive from any such sale will also be included in a prospectus supplement.

Investing in our securities involves various risks. See “Risk Factors” contained herein for more information on these risks. Additional risks will be described in the related prospectus supplements under the heading “Risk Factors.” You should review that section of the related prospectus supplements for a discussion of matters that investors in our securities should consider.

Neither the U.S. Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities, or passed upon the adequacy or accuracy of this prospectus or any accompanying prospectus supplement. Any representation to the contrary is a criminal offense.

The date of this prospectus is September 5, 2019.

TABLE OF CONTENTS

​	Page
ABOUT THIS PROSPECTUS	​	1
SUMMARY	​	2
RISK FACTORS	​	7
FORWARD-LOOKING STATEMENTS	​	7
USE OF PROCEEDS	​	9
DESCRIPTION OF CAPITAL STOCK	​	10
DESCRIPTION OF DEBT SECURITIES	​	13
DESCRIPTION OF WARRANTS	​	19
DESCRIPTION OF RIGHTS	​	21
DESCRIPTION OF UNITS	​	22
LEGAL OWNERSHIP OF SECURITIES	​	23
PLAN OF DISTRIBUTION	​	27
LEGAL MATTERS	​	30
EXPERTS	​	30
WHERE YOU CAN FIND MORE INFORMATION	​	30
INCORPORATION OF DOCUMENTS BY REFERENCE	​	31

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ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we filed with the U.S. Securities and Exchange Commission, or SEC, using a “shelf” registration process. Under this shelf registration statement, we may sell from time to time in one or more offerings of common stock and preferred stock, various series of debt securities and/or warrants to purchase any of such securities, either individually or as units comprised of a combination of one or more of the other securities in one or more offerings up to a total dollar amount of $100,000,000. This prospectus provides you with a general description of the securities we may offer. Each time we sell any type or series of securities under this prospectus, we will provide a prospectus supplement that will contain more specific information about the terms of that offering.

This prospectus does not contain all of the information included in the registration statement. For a more complete understanding of the offering of the securities, you should refer to the registration statement, including its exhibits. We may add, update or change in a prospectus supplement or free writing prospectus any of the information contained in this prospectus or in the documents we have incorporated by reference into this prospectus. We may also authorize one or more free writing prospectuses to be provided to you that may contain material information relating to these offerings. This prospectus, together with the applicable prospectus supplement, any related free writing prospectus and the documents incorporated by reference into this prospectus and the applicable prospectus supplement, will include all material information relating to the applicable offering. You should carefully read both this prospectus and the applicable prospectus supplement and any related free writing prospectus, together with the additional information described under “Where You Can Find More Information,” before buying any of the securities being offered.

We have not authorized any dealer, agent or other person to give any information or to make any representation other than those contained or incorporated by reference in this prospectus, any accompanying prospectus supplement or any related free writing prospectus that we may authorize to be provided to you. You must not rely upon any information or representation not contained or incorporated by reference in this prospectus or an accompanying prospectus supplement, or any related free writing prospectus that we may authorize to be provided to you. This prospectus, the accompanying prospectus supplement and any related free writing prospectus, if any, do not constitute an offer to sell or the solicitation of an offer to buy any securities other than the registered securities to which they relate, nor do this prospectus, the accompanying prospectus supplement or any related free writing prospectus, if any, constitute an offer to sell or the solicitation of an offer to buy securities in any jurisdiction to any person to whom it is unlawful to make such offer or solicitation in such jurisdiction. You should not assume that the information contained in this prospectus, any applicable prospectus supplement or any related free writing prospectus is accurate on any date subsequent to the date set forth on the front of the document or that any information we have incorporated by reference is correct on any date subsequent to the date of the document incorporated by reference (as our business, financial condition, results of operations and prospects may have changed since that date), even though this prospectus, any applicable prospectus supplement or any related free writing prospectus is delivered or securities are sold on a later date.

We further note that the representations, warranties and covenants made by us in any agreement that is filed as an exhibit to any document that is incorporated by reference in this prospectus were made solely for the benefit of the parties to such agreement, including, in some cases, for the purpose of allocating risk among the parties to such agreements, and should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be relied on as accurately representing the current state of our affairs.

This prospectus may not be used to consummate sales of our securities, unless it is accompanied by a prospectus supplement. To the extent there are inconsistencies between any prospectus supplement, this prospectus and any documents incorporated by reference, the document with the most recent date will control.

As permitted by the rules and regulations of the SEC, the registration statement, of which this prospectus forms a part, includes additional information not contained in this prospectus. You may read the registration statement and the other reports we file with the SEC at the SEC’s web site or at the SEC’s offices described below under the heading “Where You Can Find Additional Information.”

Company References

In this prospectus “the Company,” “we,” “us,” and “our” refer to Aridis Pharmaceuticals, Inc., a Delaware corporation, and its subsidiaries, unless the context otherwise requires.

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SUMMARY

Overview

We are a late-stage biopharmaceutical company focused on the discovery and development of targeted immunotherapy using fully human monoclonal antibodies, or mAbs, to treat life-threatening infections. mAbs represent a fundamentally new treatment approach in the infectious disease market and are designed to overcome key issues associated with current therapies, including drug resistance, short duration of response, negative impact on the human microbiome, and lack of differentiation between treatment alternatives. Our proprietary product pipeline is comprised of fully human mAbs targeting specific pathogens associated with life-threatening bacterial infections, primarily hospital-acquired pneumonia, or HAP, and ventilator-associated pneumonia, or VAP. Two of our product candidates have exhibited promising preclinical data and clinical data are available from two completed studies and are in pivotal trial stage. Our lead product candidate, AR-301, targets the alpha toxin produced by gram-positive bacteria Staphylococcus aureus, or S. aureus, a common pathogen associated with HAP and VAP. In contrast to other programs targeting S. aureus toxins, we are developing AR-301 as a treatment of pneumonia, rather than prevention of S. aureus colonized patients from progression to pneumonia. We have conducted an end-of-Phase 2 meeting with the US Food and Drug Administration, or FDA, and initiated a Phase 3 pivotal trial for AR-301 in January 2019.

The majority of candidates from our product pipeline are derived by employing our differentiated antibody discovery platform called MabIgX. This platform is designed to comprehensively screen the B-cell repertoire and isolate human antibody-producing B-cells from individuals who have either successfully overcome an infection by a particular pathogen or have been vaccinated against a particular pathogen. We believe that B-cells from these patients are the ideal source of highly protective and efficacious mAbs which can been administered safely to other patients. MabIgX also allows for rapid, high-throughput screening of B-cells and direct manufacturing of mAbs. As a result, we can significantly reduce time for antibody discovery and manufacturing compared to conventional approaches.

Our initial clinical indication is for adjunctive therapeutic treatment with standard of care, or SOC, antibiotics for HAP and VAP. Mortality and morbidity associated with HAP and VAP in the intensive care units, or ICU, remain high despite aggressive treatment with SOC antibiotics. Current SOC antibiotics used to treat HAP and VAP typically involve a combination of several broad spectrum antibiotics that are prescribed empirically at the start of treatment. The specific empirical antibiotic regimens that are prescribed vary widely among physicians, and generally resulted in modest clinical benefits due to a number of reasons, including the frequent mismatch of the antibiotics regimen to the etiologic agent and/or infection by an antibiotic resistant strain. Recently, rapid diagnostic tests have been introduced that allow the identification of infection-causing agents within hours. These increasingly common tests allow physicians to prescribe a targeted anti-infective drug, rather than a broad-spectrum antibiotic. This evidenced-based treatment approach is designed to remove issues associated with SOC antibiotics treatment practices, and to improve the effectiveness of SOC antibiotics, while not competing directly with antibiotics. In contrast to the lack of differentiation among SOC antibiotics, mAbs are highly differentiated from SOC antibiotics in mechanism of action and pharmacodynamic profile, and thus are well suited to complement antibiotics action and are effective against antibiotic resistant bacteria. To emphasize the benefits of our product candidates as an adjunctive therapy, we design clinical trials based on superiority endpoints.

HAP and VAP pose serious challenges in the hospital setting, as SOC antibiotics are becoming inadequate in treating infected patients. There are approximately 3,000,000 cases of pneumonia reported in the U.S. per year and approximately 628,000 annual cases of HAP and VAP caused by Gram negative bacteria and MRSA (DRG, 2016). These patients are typically at high risk of mortality, which is compounded by other life-threatening co-morbidities and the rise in antibiotic resistance. Epidemiology studies estimate that the probability of death attributed to S. aureus ranges from 29% to 55% and P. aeruginosa ranges from 24% to 76%. In addition, pneumonia infections can prolong patient stays in ICUs and the use of mechanical ventilation, creating a major economic burden on patients, hospital systems and payors. For example, ICU cost of care for a ventilated pneumonia patient is approximately $10,000 per day, and the duration of ICU stay is typically twice that of a non-ventilated patient (Infection Control and Hospital Epidemiology. 2010, vol. 31, pp. 509-515). The average cost of care per pneumonia patient is approximately $41,250 which increases

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86% for HAP/VAP patients to approximately $76,730. We estimate that our two clinical mAb candidates have an addressable market of $25 billion and the potential to address approximately 325,000 HAP and VAP patients in the U.S.

Our proprietary pipeline is primarily focused on severe lung infections and is comprised of six wholly-owned product candidates which are highlighted below.

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AR-301 is a fully human immunoglobulin 1, or IgG1, mAb targeting the gram-positive bacteria S. aureus alphatoxin. We are developing AR-301 initially as an adjunctive immunotherapy in combination with SOC antibiotics to treat acute pneumonia caused by S. aureus infection. We filed an Investigational New Drug Application, or IND for AR-301 on June 5, 2015. We completed a randomized, double-blind, placebo-controlled Phase 2a trial in 48 HAP and VAP patients. The trial met its primary endpoint of tolerability. AR-301 was generally well tolerated with no serious adverse events, or SAEs, related to the product candidate, and its pharmacokinetic properties were consistent with that of human IgG1. In addition, the trial showed trends towards benefit in various patient benefits related endpoints, including improvements in time on ventilator for VAP patients, microbiological eradication rate, time to microbiological eradication, and overall ICU and hospital stays for AR-301 plus SOC antibiotics compared to antibiotics alone. We initiated a Phase 3 pivotal trial in VAP patients in January 2019. AR-301 has been granted Fast-Track designation by the FDA and orphan drug designation in the EU.

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AR-101 is a fully human immunoglobulin M, or IgM, mAb targeting the gram-negative bacteria P. aeruginosa serotype O11. We filed an Investigational Medicinal Product Dossier, or IMPD, with the EU on October 22, 2004. We plan to file an IND after the initiation of our Phase 2/3 pivotal trial described below. We have completed a Phase 1 trial in healthy adults and a Phase 2a trial in 27 HAP and VAP patients. In the Phase 2a trial, AR-101 plus SOC antibiotics was generally well tolerated. The per protocol population demonstrated numeric improvement over standalone antibiotics across multiple clinical endpoints, including initial clinical resolution rate, time to initial clinical resolution, time on ventilator or in ICU and all-cause mortality was seen. AR-101 has been granted orphan drug designation in the U.S. and in the EU.

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AR-401 is our mAb discovery program aimed at treating infections caused by Acinetobacter baumannii, a gram-negative bacterium that is increasingly prevalent in blood stream, lung and skin infections. We used our MabIgX technology to identify novel targets and select several fully human mAb candidates that bind to outer membrane proteins of the bacteria. We intend to select a development candidate for additional preclinical studies.

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AR-201 is a fully human IgG1 mAb with high affinity for respiratory syncytial virus, or RSV, glycoprotein F and neutralizes diverse clinical isolates of RSV. In in vivo preclinical studies, AR-201

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has shown to be 12-fold more potent than Synagis in a head-to-head comparison study, a currently marketed drug for pediatric RSV. AR-201 has also been shown to bind to RSV strains that are resistant to Synagis.

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AR-501 (Panaecin) is a broad spectrum small molecule anti-infective we are developing in addition to our targeted mAb product candidates. This product candidate is currently in a phase 1/2a clinical study and is funded by the Cystic Fibrosis Foundation. AR-501 is administered as an inhalable aerosol to treat lung infections in cystic fibrosis patients. Preclinical studies have shown that mice infected with P. aeruginosa can be rescued with a single inhalation exposure of aerosolized AR-501. We filed the IND, application and subsequently initiated a Phase 1/2a trial in December 2018. We expect to report top-line Phase 1 study results in the first quarter of 2020. AR-501 has been granted Fast-Track and Qualified Infectious Disease Product (QIDP) designations by the FDA.

The Securities We May Offer

We may offer shares of our common stock and preferred stock, various series of debt securities and warrants or rights to purchase any of such securities, either individually or in units, from time to time under this prospectus, together with any applicable prospectus supplement and related free writing prospectus, at prices and on terms to be determined by market conditions at the time of offering. If we issue any debt securities at a discount from their original stated principal amount, then, for purposes of calculating the total dollar amount of all securities issued under this prospectus, we will treat the initial offering price of the debt securities as the total original principal amount of the debt securities. Each time we offer securities under this prospectus, we will provide offerees with a prospectus supplement that will describe the specific amounts, prices and other important terms of the securities being offered, including, to the extent applicable:

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designation or classification;

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aggregate principal amount or aggregate offering price;

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maturity, if applicable;

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original issue discount, if any;

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rates and times of payment of interest or dividends, if any;

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redemption, conversion, exchange or sinking fund terms, if any;

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conversion or exchange prices or rates, if any, and, if applicable, any provisions for changes to or adjustments in the conversion or exchange prices or rates and in the securities or other property receivable upon conversion or exchange;

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ranking;

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restrictive covenants, if any;

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voting or other rights, if any; and

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important United States federal income tax considerations.

A prospectus supplement and any related free writing prospectus that we may authorize to be provided to you may also add, update, or change information contained in this prospectus or in documents we have incorporated by reference. However, no prospectus supplement or free writing prospectus will offer a security that is not registered and described in this prospectus at the time of the effectiveness of the registration statement of which this prospectus is a part.

We may sell the securities to or through underwriters, dealers or agents or directly to purchasers. We, as well as any agents acting on our behalf, reserve the sole right to accept and to reject in whole or in part any proposed purchase of securities. Each prospectus supplement will set forth the names of any underwriters, dealers or agents involved in the sale of securities described in that prospectus supplement and any applicable fee, commission or discount arrangements with them, details regarding any over-allotment option granted to them, and net proceeds to us. The following is a summary of the securities we may offer with this prospectus.

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Common Stock

We currently have authorized 100,000,000 shares of common stock, par value $0.0001 per share. As of August 30, 2019, 8,912,227 shares of common stock were issued and outstanding. We may offer shares of our common stock either alone or underlying other registered securities convertible into or exercisable for our common stock. Holders of our common stock are entitled to such dividends as our board of directors (the “Board of Directors” or “Board”) may declare from time to time out of legally available funds, subject to the preferential rights of the holders of any shares of our preferred stock that are outstanding or that we may issue in the future. Currently, we do not pay any dividends on our common stock. Each holder of our common stock is entitled to one vote per share. In this prospectus, we provide a general description of, among other things, the rights and restrictions that apply to holders of our common stock.

Preferred Stock

We currently have authorized 60,000,000 shares of preferred stock, par value $0.0001. There are currently no shares of preferred stock outstanding. Any authorized and undesignated shares of preferred stock may be issued from time to time in one or more additional series pursuant to a resolution or resolutions providing for such issue duly adopted by our Board of Directors (authority to do so being hereby expressly vested in the Board of Directors). The Board of Directors is further authorized, subject to limitations prescribed by law, to fix by resolution or resolutions the designations, powers, preferences and rights, and the qualifications, limitations or restrictions thereof, of any wholly unissued series of preferred stock, including without limitation authority to fix by resolution or resolutions the dividend rights, dividend rate, conversion rights, voting rights, rights and terms of redemption (including sinking fund provisions), redemption price or prices, and liquidation preferences of any such series, and the number of shares constituting any such series and the designation thereof, or any of the foregoing.

The rights, preferences, privileges, and restrictions granted to or imposed upon any series of preferred stock that we offer and sell under this prospectus and applicable prospectus supplements will be set forth in a certificate of designation relating to the series. We will incorporate by reference into the registration statement of which this prospectus is a part the form of any certificate of designation that describes the terms of the series of preferred stock we are offering before the issuance of shares of that series of preferred stock. You should read any prospectus supplement and any free writing prospectus that we may authorize to be provided to you related to the series of preferred stock being offered, as well as the complete certificate of designation that contains the terms of the applicable series of preferred stock.

Debt Securities

We may offer general debt obligations, which may be secured or unsecured, senior or subordinated, and convertible into shares of our common stock. In this prospectus, we refer to the senior debt securities and the subordinated debt securities together as the “debt securities.” We may issue debt securities under a note purchase agreement or under an indenture to be entered between us and a trustee and forms of the senior and subordinated indentures are included as an exhibit to the registration statement of which this prospectus is a part. The indentures do not limit the amount of securities that may be issued under it and provides that debt securities may be issued in one or more series. The senior debt securities will have the same rank as all of our other indebtedness that is not subordinated. The subordinated debt securities will be subordinated to our senior debt on terms set forth in the applicable prospectus supplement. In addition, the subordinated debt securities will be effectively subordinated to creditors and preferred stockholders of our subsidiaries. Our Board of Directors will determine the terms of each series of debt securities being offered. This prospectus contains only general terms and provisions of the debt securities. The applicable prospectus supplement will describe the particular terms of the debt securities offered thereby. You should read any prospectus supplement and any free writing prospectus that we may authorize to be provided to you related to the series of debt securities being offered, as well as the complete note agreements and/or indentures that contain the terms of the debt securities. Forms of indentures have been filed as exhibits to the registration statement of which this prospectus is a part, and supplemental indentures and forms of debt securities containing the terms of debt securities being offered will be incorporated by reference into the registration statement of which this prospectus is a part from reports we file with the SEC.

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Warrants

We may offer warrants for the purchase of shares of our common stock or preferred stock or of debt securities. We may issue the warrants by themselves or together with common stock, preferred stock or debt securities, and the warrants may be attached to or separate from any offered securities. Any warrants issued under this prospectus may be evidenced by warrant certificates. Warrants may be issued under a separate warrant agreement to be entered into between us and the investors or a warrant agent. Our Board of Directors will determine the terms of the warrants. This prospectus contains only general terms and provisions of the warrants. The applicable prospectus supplement will describe the particular terms of the warrants being offered thereby. You should read any prospectus supplement and any free writing prospectus that we may authorize to be provided to you related to the series of warrants being offered, as well as the complete warrant agreements that contain the terms of the warrants. Specific warrant agreements will contain additional important terms and provisions and will be incorporated by reference into the registration statement of which this prospectus is a part from reports we file with the SEC.

Rights

We may issue rights to our stockholders to purchase shares of our common stock, preferred stock or the other securities described in this prospectus. We may offer rights separately or together with one or more additional rights, debt securities, preferred stock, common stock or warrants, or any combination of those securities in the form of units, as described in the applicable prospectus supplement. Each series of rights will be issued under a separate rights agreement to be entered into between us and a bank or trust company, as rights agent. The rights agent will act solely as our agent in connection with the certificates relating to the rights of the series of certificates and will not assume any obligation or relationship of agency or trust for or with any holders of rights certificates or beneficial owners of rights. The following description sets forth certain general terms and provisions of the rights to which any prospectus supplement may relate. The particular terms of the rights to which any prospectus supplement may relate and the extent, if any, to which the general provisions may apply to the rights so offered will be described in the applicable prospectus supplement. To the extent that any particular terms of the rights, rights agreement or rights certificates described in a prospectus supplement differ from any of the terms described below, then the terms described below will be deemed to have been superseded by that prospectus supplement. Specific rights agreements will contain additional important terms and provisions and will be incorporated by reference into the registration statement of which this prospectus is a part from reports we file with the SEC.

Units

We may offer units consisting of our common stock or preferred stock, debt securities and/or warrants to purchase any of these securities in one or more series. We may evidence each series of units by unit certificates that we will issue under a separate agreement. We may enter into unit agreements with a unit agent. Each unit agent will be a bank or trust company that we select. We will indicate the name and address of the unit agent in the applicable prospectus supplement relating to a particular series of units. This prospectus contains only a summary of certain general features of the units. The applicable prospectus supplement will describe the particular features of the units being offered thereby. You should read any prospectus supplement and any free writing prospectus that we may authorize to be provided to you related to the series of units being offered, as well as the complete unit agreements that contain the terms of the units. Specific unit agreements will contain additional important terms and provisions and will be incorporated by reference into the registration statement of which this prospectus is a part from reports we file with the SEC.

Corporate Information

We were formed under the name “Aridis, LLC” in the State of California on April 24, 2003 as a limited liability company. On August 30, 2004, we changed our name to “Aridis Pharmaceuticals, LLC.” On May 21, 2014, we converted into a Delaware corporation named “Aridis Pharmaceuticals, Inc.” Our fiscal year end is December 31. Our principal executive offices are located at 5941 Optical Court, San Jose, California 95138. Our telephone number is (408) 385-1742. Our website address is www.aridispharma.com. The information contained on, or that can be accessed through, our website is not a part of this registration statement or the accompanying prospectus.

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RISK FACTORS

An investment in our securities involves a high degree of risk. This prospectus contains, and the prospectus supplement applicable to each offering of our 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 this prospectus and 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 Item 1A, “Risk Factors,” in our Annual Report on Form 10-K for the fiscal year ended December 31, 2018, filed with the SEC on March 28, 2019, and any updates described in our Quarterly Reports on Form 10-Q, all of which are 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 and any prospectus supplement related to a particular offering. 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. The occurrence of any of these known or unknown risks might cause you to lose all or part of your investment in the offered securities.

FORWARD-LOOKING STATEMENTS

This prospectus and any accompanying prospectus supplement, including the documents that we incorporate by reference, contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”) and Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). Any statements in this prospectus and any accompanying prospectus supplement about our expectations, beliefs, plans, objectives, assumptions or future events or performance are not historical facts and are forward-looking statements. These statements are often, but not always, made through the use of words or phrases such as “believe,” “will,” “expect,” “anticipate,” “estimate,” “intend,” “plan,” and “would.” For example, statements concerning financial condition, possible or assumed future results of operations, growth opportunities, industry ranking, plans and objectives of management, markets for our common stock and future management and organizational structure are all forward-looking statements. Forward-looking statements are not guarantees of performance. They involve known and unknown risks, uncertainties and assumptions that may cause actual results, levels of activity, performance or achievements to differ materially from any results, levels of activity, performance or achievements expressed or implied by any forward-looking statement.

Any forward-looking statements are qualified in their entirety by reference to the risk factors discussed throughout this prospectus and any accompanying prospectus supplement. Some of the risks, uncertainties and assumptions that could cause actual results to differ materially from estimates or projections contained in the forward-looking statements include, but are not limited to:

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the timing of regulatory submissions;

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our ability to obtain and maintain regulatory approval of our existing product candidates and any other product candidates we may develop, and the labeling under any approval we may obtain;

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approvals for clinical trials may be delayed or withheld by regulatory agencies;

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preclinical and clinical studies will not be successful or confirm earlier results or meet expectations or meet regulatory requirements or meet performance thresholds for commercial success;

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risks relating to the timing and costs of clinical trials, the timing and costs of other expenses;

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risks associated with obtaining funding from third parties;

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management and employee operations and execution risks;

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loss of key personnel;

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competition;

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risks related to market acceptance of products;

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intellectual property risks;

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assumptions regarding the size of the available market, benefits of our products, product pricing, and timing of product launches;

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risks associated with the uncertainty of future financial results;

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our ability to attract collaborators and partners; and

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risks associated with our reliance on third party organizations.

The foregoing list sets forth some, but not all, of the factors that could affect our ability to achieve results described in any forward-looking statements. You should read this prospectus and any accompanying prospectus supplement and the documents that we reference herein and therein and have filed as exhibits to the registration statement, of which this prospectus is part, completely and with the understanding that our actual future results may be materially different from what we expect. You should assume that the information appearing in this prospectus and any accompanying prospectus supplement is accurate as of the date on the front cover of this prospectus or such prospectus supplement only. Because the risk factors referred to on page 7 of this prospectus and incorporated herein by reference, could cause actual results or outcomes to differ materially from those expressed in any forward-looking statements made by us or on our behalf, you should not place undue reliance on any forward-looking statements. Further, any forward-looking statement speaks only as of the date on which it is made, and we undertake no obligation to update any forward-looking statement to reflect events or circumstances after the date on which the statement is made or to reflect the occurrence of unanticipated events. New factors emerge from time to time, and it is not possible for us to predict which factors will arise. In addition, we cannot assess the impact of each factor on our business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements. We qualify all of the information presented in this prospectus and any accompanying prospectus supplement, and particularly our forward-looking statements, by these cautionary statements.

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USE OF PROCEEDS

Except as described in any prospectus supplement and any free writing prospectus in connection with a specific offering, we currently intend to use the net proceeds from the sale of the securities offered under this prospectus for general corporate purposes, including the development and commercialization of our products, research and development, general and administrative expenses, license or technology acquisitions, and working capital and capital expenditures. We may also use the net proceeds to repay any debts and/or invest in or acquire complementary businesses, products, or technologies, although we have no current commitments or agreements with respect to any such investments or acquisitions as of the date of this prospectus. We have not determined the amount of net proceeds to be used specifically for the foregoing purposes. As a result, our management will have broad discretion in the allocation of the net proceeds and investors will be relying on the judgment of our management regarding the application of the proceeds of any sale of the securities. Pending use of the net proceeds, we intend to invest the proceeds in short-term, investment-grade, interest-bearing instruments.

Each time we offer securities under this prospectus, we will describe the intended use of the net proceeds from that offering in the applicable prospectus supplement. The actual amount of net proceeds we spend on a particular use will depend on many factors, including, our future capital expenditures, the amount of cash required by our operations, and our future revenue growth, if any. Therefore, we will retain broad discretion in the use of the net proceeds.

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DESCRIPTION OF CAPITAL STOCK

General

The following description of our capital stock, together with any additional information we include in any applicable prospectus supplement or any related free writing prospectus, summarizes the material terms and provisions of our common stock and the preferred stock that we may offer under this prospectus. While the terms we have summarized below will apply generally to any future common stock or preferred stock that we may offer, we will describe the particular terms of any class or series of these securities in more detail in the applicable prospectus supplement. For the complete terms of our common stock and preferred stock, please refer to our Certificate of Incorporation, as amended and restated (the “Certificate of Incorporation”) and our bylaws, as amended and restated (the “Bylaws”) that are incorporated by reference into the registration statement of which this prospectus is a part or may be incorporated by reference in this prospectus or any applicable prospectus supplement. The terms of these securities may also be affected by Delaware General Corporation Law (the “DGCL”). The summary below and that contained in any applicable prospectus supplement or any related free writing prospectus are qualified in their entirety by reference to our Certificate of Incorporation and our amended and restated bylaws.

As of the date of this prospectus, our authorized capital stock consisted of 100,000,000 shares of common stock, $0.0001 par value per share, and 60,000,000 shares of preferred stock, $0.0001 par value per share. Our Board may establish the rights and preferences of the preferred stock from time to time. As of August 30, 2019, there were 8,912,227 shares of our common stock issued and outstanding and no shares of preferred stock issued and outstanding.

Common Stock

We are authorized to issue up to a total of 100,000,000 shares of common stock, par value $0.0001 per share. Holders of our common stock are entitled to one vote for each share held on all matters submitted to a vote of our stockholders. Holders of our common stock have no cumulative voting rights. All shares of common stock offered hereby will, when issued, be fully paid and nonassessable, including shares of common stock issued upon the exercise of common stock warrants or subscription rights, if any.

Further, holders of our common stock have no preemptive or conversion rights or other subscription rights. Upon our liquidation, dissolution or winding- up, holders of our common stock are entitled to share in all assets remaining after payment of all liabilities and the liquidation preferences of any of our outstanding shares of preferred stock. Subject to preferences that may be applicable to any outstanding shares of preferred stock, holders of our common stock are entitled to receive dividends, if any, as may be declared from time to time by our Board of Directors out of our assets which are legally available. Such dividends, if any, are payable in cash, in property or in shares of capital stock.

The holders of a majority of the shares of our capital stock, represented in person or by proxy, are necessary to constitute a quorum for the transaction of business at any meeting. If a quorum is present, an action by stockholders entitled to vote on a matter is approved if the number of votes cast in favor of the action exceeds the number of votes cast in opposition to the action, with the exception of the election of directors, which requires a plurality of the votes cast.

Preferred Stock

Our board of directors has the authority, without further action by the stockholders, to issue up to 60,000,000 shares of preferred stock in one or more series and to fix the designations, powers, preferences, privileges, and relative participating, optional, or special rights as well as the qualifications, limitations, or restrictions of the preferred stock, including dividend rights, conversion rights, voting rights, terms of redemption, and liquidation preferences, any or all of which may be greater than the rights of the common stock. Our board of directors, without stockholder approval, can issue convertible preferred stock with voting, conversion, or other rights that could adversely affect the voting power and other rights of the holders of common stock. Preferred stock could be issued quickly with terms calculated to delay or prevent a change of control or make removal of management more difficult. Additionally, the issuance of preferred stock may

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have the effect of decreasing the market price of our common stock, and may adversely affect the voting and other rights of the holders of common stock. At present, we have no plans to issue any shares of preferred stock following this offering.

Anti-Takeover Effects of Provisions of Delaware State Law

We are governed by the provisions of Section 203 of the Delaware General Corporation Law. In general, Section 203 prohibits a public Delaware corporation from engaging in a “business combination” with an “interested stockholder” for a period of three years after the date of the transaction in which the person became an interested stockholder, unless:

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the transaction was approved by the board of directors prior to the time that the stockholder became an interested stockholder;

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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, excluding shares owned by directors who are also officers of the corporation and shares owned by employee stock plans in which employee participants do not have the right to determine confidentially whether shares held subject to the plan will be tendered in a tender or exchange offer; or

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at or subsequent to the time the stockholder became an interested stockholder, the business combination was approved by the board of directors and authorized at an annual or special meeting of the stockholders, and not by written consent, by the affirmative vote of at least two-thirds of the outstanding voting stock which is not owned by the interested stockholder.

In general, Section 203 defines a “business combination” to include mergers, asset sales and other transactions resulting in financial benefit to a stockholder and an “interested stockholder” as a person who, together with affiliates and associates, owns, or within three years did own, 15% or more of the corporation’s outstanding voting stock. These provisions may have the effect of delaying, deferring or preventing changes in control of our company.

Our certificate of incorporation and our bylaws include a number of provisions that could deter hostile takeovers or delay or prevent changes in control of our board of directors or management team, including the following:

Board of Directors Vacancies.   Our 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 will be 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 will make it more difficult to change the composition of our board of directors and will promote continuity of management.

Classified Board.   Our bylaws provide that our board of directors is classified into three classes of directors. 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. See the section titled “Management — Classified Board of Directors.”

Stockholder Action; Special Meeting of Stockholders.   Our bylaws provide that any action which may be taken at any annual or special meeting of stockholders, may, if such action has been earlier approved by the Board, be taken without a meeting. As a result, a holder controlling a majority of our capital stock would not be able to amend our bylaws or remove directors without holding a meeting of our stockholders called in accordance with our bylaws unless such action had been earlier approved by the Board. Our bylaws further provide that special meetings of our stockholders may be called only by our board of directors or the chairman of our board of directors, 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.

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Advance Notice Requirements for Stockholder Proposals and Director Nominations.   Our 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 bylaws will 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 may 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 cumulate votes in the election of directors unless a corporation’s certificate of incorporation provides otherwise. Our certificate of incorporation does not provide for cumulative voting.

Issuance of Undesignated Preferred Stock.   Our board of directors will have the authority, without further action by our stockholders, to issue up to 60,000,000 shares of undesignated preferred stock with rights 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 means of a merger, tender offer, proxy contest or other means.

Listing

Our common stock is listed on The Nasdaq Capital Market under the trading symbol “ARDS.”

Transfer Agent and Registrar

The Transfer Agent and Registrar for our common stock is Philadelphia Stock Transfer, Inc.

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DESCRIPTION OF DEBT SECURITIES

The following description, together with the additional information we include in any applicable prospectus supplements or free writing prospectuses, summarizes the material terms and provisions of the debt securities that we may offer under this prospectus. We may issue debt securities, in one or more series, as either senior or subordinated debt or as senior or subordinated convertible debt. While the terms we have summarized below will apply generally to any future debt securities we may offer under this prospectus, we will describe the particular terms of any debt securities that we may offer in more detail in the applicable prospectus supplement or free writing prospectus. The terms of any debt securities we offer under a prospectus supplement may differ from the terms we describe below. However, no prospectus supplement shall fundamentally change the terms that are set forth in this prospectus or offer a security that is not registered and described in this prospectus at the time of its effectiveness. As of the date of this prospectus, we have no outstanding registered debt securities. Unless the context requires otherwise, whenever we refer to the “indentures,” we also are referring to any supplemental indentures that specify the terms of a particular series of debt securities.

We will issue any senior debt securities under the senior indenture that we will enter into with the trustee named in the senior indenture. We will issue any subordinated debt securities under the subordinated indenture and any supplemental indentures that we will enter into with the trustee named in the subordinated indenture. We have filed forms of these documents as exhibits to the registration statement, of which this prospectus is a part, and supplemental indentures and forms of debt securities containing the terms of the debt securities being offered will be filed as exhibits to the registration statement of which this prospectus is a part or will be incorporated by reference from reports that we file with the SEC.

The indentures will be qualified under the Trust Indenture Act of 1939, as amended (the “Trust Indenture Act”). We use the term “trustee” to refer to either the trustee under the senior indenture or the trustee under the subordinated indenture, as applicable.

The following summaries of material provisions of the senior debt securities, the subordinated debt securities and the indentures are subject to, and qualified in their entirety by reference to, all of the provisions of the indenture and any supplemental indentures applicable to a particular series of debt securities. We urge you to read the applicable prospectus supplements and any related free writing prospectuses related to the debt securities that we may offer under this prospectus, as well as the complete indentures that contains the terms of the debt securities. Except as we may otherwise indicate, the terms of the senior indenture and the subordinated indenture are identical.

General

The terms of each series of debt securities will be established by or pursuant to a resolution of our Board of Directors and set forth or determined in the manner provided in an officers’ certificate or by a supplemental indenture. Debt securities may be issued in separate series without limitation as to aggregate principal amount. We may specify a maximum aggregate principal amount for the debt securities of any series. We will describe in the applicable prospectus supplement the terms of the series of debt securities being offered, including:

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the title;

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the principal amount being offered, and if a series, the total amount authorized and the total amount outstanding;

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any limit on the amount that may be issued;

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whether or not we will issue the series of debt securities in global form, and, if so, the terms and who the depositary will be;

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the maturity date;

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whether and under what circumstances, if any, we will pay additional amounts on any debt securities held by a person who is not a United States person for tax purposes, and whether we can redeem the debt securities if we have to pay such additional amounts;

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the annual interest rate, which may be fixed or variable, or the method for determining the rate and the date interest will begin to accrue, the dates interest will be payable and the regular record dates for interest payment dates or the method for determining such dates;

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whether or not the debt securities will be secured or unsecured, and the terms of any secured debt;

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the terms of the subordination of any series of subordinated debt;

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the place where payments will be made;

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restrictions on transfer, sale or other assignment, if any;

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our right, if any, to defer payment of interest and the maximum length of any such deferral period;

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the date, if any, after which, and the price at which, we may, at our option, redeem the series of debt securities pursuant to any optional or provisional redemption provisions and the terms of those redemption provisions;

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provisions for a sinking fund purchase or other analogous fund, if any, including the date, if any, on which, and the price at which we are obligated, pursuant thereto or otherwise, to redeem, or at the holder’s option, to purchase, the series of debt securities and the currency or currency unit in which the debt securities are payable;

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whether the indenture will restrict our ability or the ability of our subsidiaries, if any, to:

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incur additional indebtedness;

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issue additional securities;

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create liens;

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pay dividends or make distributions in respect of our capital stock or the capital stock of our subsidiaries;

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redeem capital stock;

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place restrictions on our subsidiaries’ ability to pay dividends, make distributions or transfer assets;

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make investments or other restricted payments;

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sell or otherwise dispose of assets;

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enter into sale-leaseback transactions;

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engage in transactions with stockholders or affiliates;

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issue or sell stock of our subsidiaries; or

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effect a consolidation or merger;

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whether the indenture will require us to maintain any interest coverage, fixed charge, cash flow-based, asset-based or other financial ratios;

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a discussion of certain material or special United States federal income tax considerations applicable to the debt securities;

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information describing any book-entry features;

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the applicability of the provisions in the indenture on discharge;

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whether the debt securities are to be offered at a price such that they will be deemed to be offered at an “original issue discount” as defined in paragraph (a) of Section 1273 of the Internal Revenue Code of 1986, as amended;

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the denominations in which we will issue the series of debt securities, if other than denominations of $1,000 and any integral multiple thereof;

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the currency of payment of debt securities if other than U.S. dollars and the manner of determining the equivalent amount in U.S. dollars; and

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any other specific terms, preferences, rights or limitations of, or restrictions on, the debt securities, including any additional events of default or covenants provided with respect to the debt securities, and any terms that may be required by us or advisable under applicable laws or regulations.

Conversion or Exchange Rights

We will set forth in the applicable prospectus supplement the terms under which a series of debt securities may be convertible into or exchangeable for our common stock, our preferred stock or other securities (including securities of a third party). We will include provisions as to whether conversion or exchange is mandatory, at the option of the holder or at our option. We may include provisions pursuant to which the number of shares of our common stock, our preferred stock or other securities (including securities of a third party) that the holders of the series of debt securities receive would be subject to adjustment.

Consolidation, Merger or Sale

Unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, the indentures will not contain any covenant that restricts our ability to merge or consolidate, or sell, convey, transfer or otherwise dispose of all or substantially all of our assets. However, any successor to or acquirer of such assets must assume all of our obligations under the indentures or the debt securities, as appropriate. If the debt securities are convertible into or exchangeable for our other securities or securities of other entities, the person with whom we consolidate or merge or to whom we sell all of our property must make provisions for the conversion of the debt securities into securities that the holders of the debt securities would have received if they had converted the debt securities before the consolidation, merger or sale.

Events of Default under the Indenture

Unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, the following are events of default under the indentures with respect to any series of debt securities that we may issue:

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if we fail to pay interest when due and payable and our failure continues for 90 days and the time for payment has not been extended;

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if we fail to pay the principal, premium or sinking fund payment, if any, when due and payable at maturity, upon redemption or repurchase or otherwise, and the time for payment has not been extended;

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if we fail to observe or perform any other covenant contained in the debt securities or the indentures, other than a covenant specifically relating to another series of debt securities, and our failure continues for 90 days after we receive notice from the trustee or we and the trustee receive notice from the holders of at least 25% in aggregate principal amount of the outstanding debt securities of the applicable series; and

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if specified events of bankruptcy, insolvency or reorganization occur.

We will describe in each applicable prospectus supplement any additional events of default relating to the relevant series of debt securities.

If an event of default with respect to debt securities of any series occurs and is continuing, other than an event of default specified in the last bullet point above, the trustee or the holders of at least 25% in aggregate principal amount of the outstanding debt securities of that series, by notice to us in writing, and to the trustee if notice is given by such holders, may declare the unpaid principal, premium, if any, and accrued interest, if any, due and payable immediately. If an event of default arises due to the occurrence of certain specified bankruptcy, insolvency or reorganization events, the unpaid principal, premium, if any, and accrued interest, if any, of each issue of debt securities then outstanding shall be due and payable without any notice or other action on the part of the trustee or any holder.

The holders of a majority in principal amount of the outstanding debt securities of an affected series may waive any default or event of default with respect to the series and its consequences, except defaults or events

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of default regarding payment of principal, premium, if any, or interest, unless we have cured the default or event of default in accordance with the indenture. Any waiver shall cure the default or event of default.

Subject to the terms of the indentures, if an event of default under an indenture shall occur and be continuing, the trustee will be under no obligation to exercise any of its rights or powers under such indenture at the request or direction of any of the holders of the applicable series of debt securities, unless such holders have offered the trustee reasonable indemnity or security satisfactory to it against any loss, liability or expense. The holders of a majority in principal amount of the outstanding debt securities of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the trustee, or exercising any trust or power conferred on the trustee, with respect to the debt securities of that series, provided that:

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the direction so given by the holder is not in conflict with any law or the applicable indenture; and

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subject to its duties under the Trust Indenture Act, the trustee need not take any action that might involve it in personal liability or might be unduly prejudicial to the holders not involved in the proceeding.

The indentures will provide that if an event of default has occurred and is continuing, the trustee will be required in the exercise of its powers to use the degree of care that a prudent person would use in the conduct of its own affairs. The trustee, however, may refuse to follow any direction that conflicts with law or the indenture, or that the trustee determines is unduly prejudicial to the rights of any other holder of the relevant series of debt securities, or that would involve the trustee in personal liability. Prior to taking any action under the indentures, the trustee will be entitled to indemnification against all costs, expenses and liabilities that would be incurred by taking or not taking such action.

A holder of the debt securities of any series will have the right to institute a proceeding under the indentures or to appoint a receiver or trustee, or to seek other remedies only if:

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the holder has given written notice to the trustee of a continuing event of default with respect to that series;

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the holders of at least 25% in aggregate principal amount of the outstanding debt securities of that series have made a written request and such holders have offered reasonable indemnity to the trustee or security satisfactory to it against any loss, liability or expense or to be incurred in compliance with instituting the proceeding as trustee; and

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the trustee does not institute the proceeding, and does not receive from the holders of a majority in aggregate principal amount of the outstanding debt securities of that series other conflicting directions within 90 days after the notice, request and offer.

These limitations do not apply to a suit instituted by a holder of debt securities if we default in the payment of the principal, premium, if any, or interest on, the debt securities, or other defaults that may be specified in the applicable prospectus supplement.

We will periodically file statements with the trustee regarding our compliance with specified covenants in the indentures.

The indentures will provide that if a default occurs and is continuing and is actually known to a responsible officer of the trustee, the trustee must mail to each holder notice of the default within the earlier of 90 days after it occurs and 30 days after it is known by a responsible officer of the trustee or written notice of it is received by the trustee, unless such default has been cured or waived. Except in the case of a default in the payment of principal or premium of, or interest on, any debt security or certain other defaults specified in an indenture, the trustee shall be protected in withholding such notice if and so long as the Board of Directors, the executive committee or a trust committee of directors, or responsible officers of the trustee, in good faith determine that withholding notice is in the best interests of holders of the relevant series of debt securities.

Modification of Indenture; Waiver

Subject to the terms of the indenture for any series of debt securities that we may issue, we and the trustee may change an indenture without the consent of any holders with respect to the following specific matters:

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to fix any ambiguity, defect or inconsistency in the indenture;

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to comply with the provisions described above under “Description of Debt Securities — Consolidation, Merger or Sale;”

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to comply with any requirements of the SEC in connection with the qualification of any indenture under the Trust Indenture Act;

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to add to, delete from or revise the conditions, limitations and restrictions on the authorized amount, terms or purposes of issue, authentication and delivery of debt securities, as set forth in the indenture;

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to provide for the issuance of, and establish the form and terms and conditions of, the debt securities of any series as provided under “Description of Debt Securities — General,” to establish the form of any certifications required to be furnished pursuant to the terms of the indenture or any series of debt securities, or to add to the rights of the holders of any series of debt securities;

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to evidence and provide for the acceptance of appointment hereunder by a successor trustee;

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to provide for uncertificated debt securities and to make all appropriate changes for such purpose;

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to add such new covenants, restrictions, conditions or provisions for the benefit of the holders, to make the occurrence, or the occurrence and the continuance, of a default in any such additional covenants, restrictions, conditions or provisions an event of default or to surrender any right or power conferred to us in the indenture; or

•

to change anything that does not adversely affect the interests of any holder of debt securities of any series in any material respect.

In addition, under the indentures, the rights of holders of a series of debt securities may be changed by us and the trustee with the written consent of the holders of at least a majority in aggregate principal amount of the outstanding debt securities of each series that is affected. However, subject to the terms of the indenture for any series of debt securities that we may issue or otherwise provided in the prospectus supplement applicable to a particular series of debt securities, we and the trustee may only make the following changes with the consent of each holder of any outstanding debt securities affected:

•

extending the stated maturity of the series of debt securities;

•

reducing the principal amount, reducing the rate of or extending the time of payment of interest, or reducing any premium payable upon the redemption or repurchase of any debt securities; or

•

reducing the percentage of debt securities, the holders of which are required to consent to any amendment, supplement, modification or waiver.

Discharge

Each indenture provides that, subject to the terms of the indenture and any limitation otherwise provided in the prospectus supplement applicable to a particular series of debt securities, we may elect to be discharged from our obligations with respect to one or more series of debt securities, except for specified obligations, including obligations to:

•

register the transfer or exchange of debt securities of the series;

•

replace stolen, lost or mutilated debt securities of the series;

•

maintain paying agencies;

•

hold monies for payment in trust;

•

recover excess money held by the trustee;

•

compensate and indemnify the trustee; and

•

appoint any successor trustee.

In order to exercise our rights to be discharged, we will deposit with the trustee money or government obligations sufficient to pay all the principal of, and any premium and interest on, the debt securities of the series on the dates payments are due.

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Form, Exchange and Transfer

We will issue the debt securities of each series only in fully registered form without coupons and, unless we otherwise specify in the applicable prospectus supplement, in denominations of $1,000 and any integral multiple thereof. The indentures will provide that we may issue debt securities of a series in temporary or permanent global form and as book-entry securities that will be deposited with, or on behalf of, The Depository Trust Company or another depositary named by us and identified in a prospectus supplement with respect to that series. See “Legal Ownership of Securities” below for a further description of the terms relating to any book-entry securities.

At the option of the holder, subject to the terms of the indentures and the limitations applicable to global securities described in the applicable prospectus supplement, the holder of the debt securities of any series can exchange the debt securities for other debt securities of the same series, in any authorized denomination and of like tenor and aggregate principal amount.

Subject to the terms of the indentures and the limitations applicable to global securities set forth in the applicable prospectus supplement, holders of the debt securities may present the debt securities for exchange or for registration of transfer, duly endorsed or with the form of transfer endorsed thereon duly executed if so required by us or the security registrar, at the office of the security registrar or at the office of any transfer agent designated by us for this purpose. Unless otherwise provided in the debt securities that the holder presents for transfer or exchange, we will make no service charge for any registration of transfer or exchange, but we may require payment of any taxes or other governmental charges.

We will name in the applicable prospectus supplement the security registrar, and any transfer agent in addition to the security registrar, that we initially designate for any debt securities. We may at any time designate additional transfer agents or rescind the designation of any transfer agent or approve a change in the office through which any transfer agent acts, except that we will be required to maintain a transfer agent in each place of payment for the debt securities of each series.

If we elect to redeem the debt securities of any series, we will not be required to:

•

issue, register the transfer of, or exchange any debt securities of that series during a period beginning at the opening of business 15 days before the day of mailing of a notice of redemption of any debt securities that may be selected for redemption and ending at the close of business on the day of the mailing; or

•

register the transfer of or exchange any debt securities so selected for redemption, in whole or in part, except the unredeemed portion of any debt securities we are redeeming in part.

Information Concerning the Trustee

The trustee, other than during the occurrence and continuance of an event of default under an indenture, undertakes to perform only those duties as are specifically set forth in the applicable indenture and is under no obligation to exercise any of the powers given it by the indentures at the request of any holder of debt securities unless it is offered reasonable security and indemnity against the costs, expenses and liabilities that it might incur. However, upon an event of default under an indenture, the trustee must use the same degree of care as a prudent person would exercise or use in the conduct of his or her own affairs.

Payment and Paying Agents

Unless we otherwise indicate in the applicable prospectus supplement, we will make payment of the interest on any debt securities on any interest payment date to the person in whose name the debt securities, or one or more predecessor securities, are registered at the close of business on the regular record date for the interest payment.

We will pay principal of and any premium and interest on the debt securities of a particular series at the office of the paying agents designated by us, except that unless we otherwise indicate in the applicable prospectus supplement, we will make interest payments by check that we will mail to the holder or by wire transfer to certain holders. Unless we otherwise indicate in the applicable prospectus supplement, we will designate the corporate trust office of the trustee as our sole paying agent for payments with respect to debt

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securities of each series. We will name in the applicable prospectus supplement any other paying agents that we initially designate for the debt securities of a particular series. We will maintain a paying agent in each place of payment for the debt securities of a particular series.

All money we pay to a paying agent or the trustee for the payment of the principal of or any premium or interest on any debt securities that remains unclaimed at the end of two years after such principal, premium or interest has become due and payable will be repaid to us, and the holder of the debt security thereafter may look only to us for payment thereof.

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, except to the extent that the Trust Indenture Act is applicable.

Ranking Debt Securities

The subordinated debt securities will be unsecured and will be subordinate and junior in priority of payment to certain other indebtedness to the extent described in a prospectus supplement. The subordinated indenture does not limit the amount of subordinated debt securities that we may issue. It also does not limit us from issuing any other secured or unsecured debt.

The senior debt securities will be unsecured and will rank equally in right of payment to all our other senior unsecured debt. The senior indenture does not limit the amount of senior debt securities that we may issue. It also does not limit us from issuing any other secured or unsecured debt.

DESCRIPTION OF WARRANTS

The following description, together with the additional information we may include in any applicable prospectus supplements and free writing prospectuses, summarizes the material terms and provisions of the warrants that we may offer under this prospectus, which may consist of warrants to purchase common stock, preferred stock or debt securities and may be issued in one or more series. Warrants may be offered independently or together with common stock, preferred stock or debt securities offered by any prospectus supplement, and may be attached to or separate from those securities. While the terms we have summarized below will apply generally to any warrants that we may offer under this prospectus, we will describe the particular terms of any series of warrants that we may offer in more detail in the applicable prospectus supplement and any applicable free writing prospectus. The terms of any warrants offered under a prospectus supplement may differ from the terms described below. However, no prospectus supplement will fundamentally change the terms that are set forth in this prospectus or offer a security that is not registered and described in this prospectus at the time of its effectiveness.

We may issue the warrants under a warrant agreement that we will enter into with a warrant agent to be selected by us. If selected, the warrant agent will act solely as an agent of ours in connection with the warrants and will not act as an agent for the holders or beneficial owners of the warrants. If applicable, we will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from a Current Report on Form 8-K that we file with the SEC, the form of warrant agreement, including a form of warrant certificate, that describes the terms of the particular series of warrants we are offering before the issuance of the related series of warrants. The following summaries of material provisions of the warrants and the warrant agreements are subject to, and qualified in their entirety by reference to, all the provisions of the warrant agreement and warrant certificate applicable to a particular series of warrants. We urge you to read the applicable prospectus supplement and any applicable free writing prospectus related to the particular series of warrants that we sell under this prospectus, as well as the complete warrant agreements and warrant certificates that contain the terms of the warrants.

General

We will describe in the applicable prospectus supplement the terms relating to a series of warrants, including:

•

the offering price and aggregate number of warrants offered;

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•

the currency for which the warrants may be purchased;

•

if applicable, the designation and terms of the securities with which the warrants are issued and the number of warrants issued with each such security or each principal amount of such security;

•

if applicable, the date on and after which the warrants and the related securities will be separately transferable;

•

in the case of warrants to purchase debt securities, the principal amount of debt securities purchasable upon exercise of one warrant and the price at, and currency in which, this principal amount of debt securities may be purchased upon such exercise;

•

in the case of warrants to purchase common stock or preferred stock, the number of shares of common stock or preferred stock, as the case may be, purchasable upon the exercise of one warrant and the price at which these shares may be purchased upon such exercise;

•

the effect of any merger, consolidation, sale or other disposition of our business on the warrant agreements and the warrants;

•

the terms of any rights to redeem or call the warrants;

•

any provisions for changes to or adjustments in the exercise price or number of securities issuable upon exercise of the warrants;

•

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

•

the manner in which the warrant agreements and warrants may be modified;

•

United States federal income tax consequences of holding or exercising the warrants;

•

the terms of the securities issuable upon exercise of the warrants; and

•

any other specific terms, preferences, rights or limitations of or restrictions on the warrants.

•

Before exercising their warrants, holders of warrants will not have any of the rights of holders of the securities purchasable upon such exercise, including:

•

in the case of warrants to purchase debt securities, the right to receive payments of principal of, or premium, if any, or interest on, the debt securities purchasable upon exercise or to enforce covenants in the applicable indenture; or

•

in the case of warrants to purchase common stock or preferred stock, the right to receive dividends, if any, or, payments upon our liquidation, dissolution or winding up or to exercise voting rights, if any.

Exercise of Warrants

Each warrant will entitle the holder to purchase the securities that we specify in the applicable prospectus supplement at the exercise price that we describe in the applicable prospectus supplement. Unless we otherwise specify in the applicable prospectus supplement, holders of the warrants may exercise the warrants at any time up to the specified time on the expiration date that we set forth in the applicable prospectus supplement. After the close of business on the expiration date, unexercised warrants will become void.

Holders of the warrants may exercise the warrants by delivering the warrant certificate representing the warrants to be exercised together with specified information, and paying the required amount to the warrant agent in immediately available funds, as provided in the applicable prospectus supplement. We will set forth on the reverse side of the warrant certificate and in the applicable prospectus supplement the information that the holder of the warrant will be required to deliver to us or the warrant agent as applicable.

Upon receipt of the required payment and the warrant certificate properly completed and duly executed at the corporate trust office of the warrant agent or any other office indicated in the applicable prospectus supplement, we will issue and deliver the securities purchasable upon such exercise. If fewer than all of the warrants represented by the warrant certificate are exercised, then we will issue a new warrant certificate for the remaining amount of warrants. If we so indicate in the applicable prospectus supplement, holders of the warrants may surrender securities as all or part of the exercise price for warrants.

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Enforceability of Rights by Holders of Warrants

If selected, each warrant agent will act solely as our agent under the applicable warrant agreement and will not assume any obligation or relationship of agency or trust with any holder of any warrant. A single bank or trust company may act as warrant agent for more than one issue of warrants. A warrant agent will have no duty or responsibility in case of any default by us under the applicable warrant agreement or warrant, including any duty or responsibility to initiate any proceedings at law or otherwise, or to make any demand upon us. Any holder of a warrant may, without the consent of the related warrant agent or the holder of any other warrant, enforce by appropriate legal action its right to exercise, and receive the securities purchasable upon exercise of, its warrants.

DESCRIPTION OF RIGHTS

General

We may issue rights to our stockholders to purchase shares of our common stock, preferred stock or the other securities described in this prospectus. We may offer rights separately or together with one or more additional rights, debt securities, preferred stock, common stock or warrants, or any combination of those securities in the form of units, as described in the applicable prospectus supplement. Each series of rights will be issued under a separate rights agreement to be entered into between us and a bank or trust company, as rights agent. The rights agent will act solely as our agent in connection with the certificates relating to the rights of the series of certificates and will not assume any obligation or relationship of agency or trust for or with any holders of rights certificates or beneficial owners of rights. The following description sets forth certain general terms and provisions of the rights to which any prospectus supplement may relate. The particular terms of the rights to which any prospectus supplement may relate and the extent, if any, to which the general provisions may apply to the rights so offered will be described in the applicable prospectus supplement. To the extent that any particular terms of the rights, rights agreement or rights certificates described in a prospectus supplement differ from any of the terms described below, then the terms described below will be deemed to have been superseded by that prospectus supplement. We encourage you to read the applicable rights agreement and rights certificate for additional information before you decide whether to purchase any of our rights. We will provide in a prospectus supplement the following terms of the rights being issued:

•

the date of determining the stockholders entitled to the rights distribution;

•

the aggregate number of shares of common stock, preferred stock or other securities purchasable upon exercise of the rights;

•

the exercise price;

•

the aggregate number of rights issued;

•

whether the rights are transferrable and the date, if any, on and after which the rights may be separately transferred;

•

the date on which the right to exercise the rights will commence, and the date on which the right to exercise the rights will expire;

•

the method by which holders of rights will be entitled to exercise;

•

the conditions to the completion of the offering, if any;

•

the withdrawal, termination and cancellation rights, if any;

•

whether there are any backstop or standby purchaser or purchasers and the terms of their commitment, if any;

•

whether stockholders are entitled to oversubscription rights, if any;

•

any applicable material U.S. federal income tax considerations; and

•

any other terms of the rights, including terms, procedures and limitations relating to the distribution, exchange and exercise of the rights, as applicable.

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Each right will entitle the holder of rights to purchase for cash the principal amount of shares of common stock, preferred stock or other securities at the exercise price provided in the applicable prospectus supplement. Rights may be exercised at any time up to the close of business on the expiration date for the rights provided in the applicable prospectus supplement.

Holders may exercise rights as described in the applicable prospectus supplement. Upon receipt of payment and the rights certificate properly completed and duly executed at the corporate trust office of the rights agent or any other office indicated in the prospectus supplement, we will, as soon as practicable, forward the shares of common stock, preferred stock or other securities, as applicable, purchasable upon exercise of the rights. If less than all of the rights issued in any rights offering are exercised, we may offer any unsubscribed securities directly to persons other than stockholders, to or through agents, underwriters or dealers or through a combination of such methods, including pursuant to standby arrangements, as described in the applicable prospectus supplement.

Rights Agent

The rights agent for any rights we offer will be set forth in the applicable prospectus supplement.

DESCRIPTION OF UNITS

The following description, together with the additional information we may include in any applicable prospectus supplements and free writing prospectuses, summarizes the material terms and provisions of the units that we may offer under this prospectus.

While the terms we have summarized below will apply generally to any units that we may offer under this prospectus, we will describe the particular terms of any series of units in more detail in the applicable prospectus supplement. The terms of any units offered under a prospectus supplement may differ from the terms described below. However, no prospectus supplement will fundamentally change the terms that are set forth in this prospectus or offer a security that is not registered and described in this prospectus at the time of its effectiveness.

We will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from a Current Report on Form 8-K that we file with the SEC, the form of unit agreement that describes the terms of the series of units we are offering, and any supplemental agreements, before the issuance of the related series of units. The following summaries of material terms and provisions of the units are subject to, and qualified in their entirety by reference to, all the provisions of the unit agreement and any supplemental agreements applicable to a particular series of units. We urge you to read the applicable prospectus supplements related to the particular series of units that we sell under this prospectus, as well as the complete unit agreement and any supplemental agreements that contain the terms of the units.

General

We may issue units comprised of one or more debt securities, shares of common stock, shares of preferred stock and warrants in any combination. Each unit will be issued so that the holder of the unit is also the holder of each security included in the unit. Thus, the holder of a unit will have the rights and obligations of a holder of each included security. The unit agreement under which a unit is issued may provide that the securities included in the unit may not be held or transferred separately, at any time or at any time before a specified date.

We will describe in the applicable prospectus supplement the terms of the series of units, including:

•

the designation and terms of the units and of the securities comprising the units, including whether and under what circumstances those securities may be held or transferred separately;

•

any provisions of the governing unit agreement that differ from those described below; and

•

any provisions for the issuance, payment, settlement, transfer or exchange of the units or of the securities comprising the units.

The provisions described in this section, as well as those described under “Description of Capital Stock,” “Description of Debt Securities” and “Description of Warrants” will apply to each unit and to any common stock, preferred stock, debt security or warrant included in each unit, respectively.

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Unit Agent

The name and address of the unit agent, if any, for any units we offer will be set forth in the applicable prospectus supplement.

Issuance in Series

We may issue units in such amounts and in numerous distinct series as we determine.

Enforceability of Rights by Holders of Units

Each unit agent will act solely as our agent under the applicable unit agreement and will not assume any obligation or relationship of agency or trust with any holder of any unit. A single bank or trust company may act as unit agent for more than one series of units. A unit agent will have no duty or responsibility in case of any default by us under the applicable unit agreement or unit, including any duty or responsibility to initiate any proceedings at law or otherwise, or to make any demand upon us. Any holder of a unit may, without the consent of the related unit agent or the holder of any other unit, enforce by appropriate legal action its rights as holder under any security included in the unit.

We, the unit agents and any of their agents may treat the registered holder of any unit certificate as an absolute owner of the units evidenced by that certificate for any purpose and as the person entitled to exercise the rights attaching to the units so requested, despite any notice to the contrary. See “Legal Ownership of Securities.”

LEGAL OWNERSHIP OF SECURITIES

We can issue securities in registered form or in the form of one or more global securities. We describe global securities in greater detail below. We refer to those persons who have securities registered in their own names on the books that we or any applicable trustee or depositary or warrant agent maintain for this purpose as the “holders” of those securities. These persons are the legal holders of the securities. We refer to those persons who, indirectly through others, own beneficial interests in securities that are not registered in their own names, as “indirect holders” of those securities. As we discuss below, indirect holders are not legal holders, and investors in securities issued in book-entry form or in street name will be indirect holders.

Book-Entry Holders

We may issue securities in book-entry form only, as we will specify in the applicable prospectus supplement. This means securities may be represented by one or more global securities registered in the name of a financial institution that holds them as depositary on behalf of other financial institutions that participate in the depositary’s book-entry system. These participating institutions, which are referred to as participants, in turn, hold beneficial interests in the securities on behalf of themselves or their customers.

Only the person in whose name a security is registered is recognized as the holder of that security. Global securities will be registered in the name of the depositary or its participants. Consequently, for global securities, we will recognize only the depositary as the holder of the securities, and we will make all payments on the securities to the depositary. The depositary passes along the payments it receives to its participants, which in turn pass the payments along to their customers who are the beneficial owners. The depositary and its participants do so under agreements they have made with one another or with their customers; they are not obligated to do so under the terms of the securities.

As a result, investors in a global security will not own securities directly. Instead, they will own beneficial interests in a global security, through a bank, broker or other financial institution that participates in the depositary’s book-entry system or holds an interest through a participant. As long as the securities are issued in global form, investors will be indirect holders, and not legal holders, of the securities.

Street Name Holders

We may terminate a global security or issue securities that are not issued in global form. In these cases, investors may choose to hold their securities in their own names or in “street name.” Securities held by an

23

investor in street name would be registered in the name of a bank, broker or other financial institution that the investor chooses, and the investor would hold only a beneficial interest in those securities through an account he or she maintains at that institution.

For securities held in street name, we or any applicable trustee or depositary will recognize only the intermediary banks, brokers and other financial institutions in whose names the securities are registered as the holders of those securities, and we or any such trustee or depositary will make all payments on those securities to them. These institutions pass along the payments they receive to their customers who are the beneficial owners, but only because they agree to do so in their customer agreements or because they are legally required to do so. Investors who hold securities in street name will be indirect holders, not legal holders, of those securities.

Legal Holders

Our obligations, as well as the obligations of any applicable trustee or third party employed by us or a trustee, run only to the legal holders of the securities. We do not have obligations to investors who hold beneficial interests in global securities, in street name or by any other indirect means. This will be the case whether an investor chooses to be an indirect holder of a security or has no choice because we are issuing the securities only in global form.

For example, once we make a payment or give a notice to the holder, we have no further responsibility for the payment or notice even if that holder is required, under agreements with its participants or customers or by law, to pass it along to the indirect holders but does not do so. Similarly, we may want to obtain the approval of the holders to amend an indenture, to relieve us of the consequences of a default or of our obligation to comply with a particular provision of an indenture, or for other purposes. In such an event, we would seek approval only from the legal holders, and not the indirect holders, of the securities. Whether and how the legal holders contact the indirect holders is up to the legal holders.

Special Considerations for Indirect Holders

If you hold securities through a bank, broker or other financial institution, either in book-entry form because the securities are represented by one or more global securities or in street name, you should check with your own institution to find out:

•

how it handles securities payments and notices;

•

whether it imposes fees or charges;

•

how it would handle a request for the holders’ consent, if ever required;

•

whether and how you can instruct it to send you securities registered in your own name so you can be a legal holder, if that is permitted in the future;

•

how it would exercise rights under the securities if there were a default or other event triggering the need for holders to act to protect their interests; and

•

if the securities are in book-entry form, how the depositary’s rules and procedures will affect these matters.

Global Securities

A global security is a security that represents one or any other number of individual securities held by a depositary. Generally, all securities represented by the same global securities will have the same terms.

Each security issued in book-entry form will be represented by a global security that we issue to, deposit with and register in the name of a financial institution or its nominee that we select. The financial institution that we select for this purpose is called the depositary. Unless we specify otherwise in the applicable prospectus supplement, The Depository Trust Company, New York, NY, known as DTC, will be the depositary for all securities issued in book-entry form.

A global security may not be transferred to or registered in the name of anyone other than the depositary, its nominee or a successor depositary, unless special termination situations arise. We describe those situations

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below under “— Special Situations When A Global Security Will Be Terminated.” As a result of these arrangements, the depositary, or its nominee, will be the sole registered owner and legal holder of all securities represented by a global security, and investors will be permitted to own only beneficial interests in a global security. Beneficial interests must be held by means of an account with a broker, bank or other financial institution that in turn has an account with the depositary or with another institution that does. Thus, an investor whose security is represented by a global security will not be a legal holder of the security, but only an indirect holder of a beneficial interest in the global security.

If the prospectus supplement for a particular security indicates that the security will be issued as a global security, then the security will be represented by a global security at all times unless and until the global security is terminated. If termination occurs, we may issue the securities through another book-entry clearing system or decide that the securities may no longer be held through any book-entry clearing system.

Special Considerations For Global Securities

As an indirect holder, an investor’s rights relating to a global security will be governed by the account rules of the investor’s financial institution and of the depositary, as well as general laws relating to securities transfers. We do not recognize an indirect holder as a holder of securities and instead deal only with the depositary that holds the global security.

If securities are issued only as global securities, an investor should be aware of the following:

•

an investor cannot cause the securities to be registered in his or her name, and cannot obtain non-global certificates for his or her interest in the securities, except in the special situations we describe below;

•

an investor will be an indirect holder and must look to his or her own bank or broker for payments on the securities and protection of his or her legal rights relating to the securities, as we describe above;

•

an investor may not be able to sell interests in the securities to some insurance companies and to other institutions that are required by law to own their securities in non-book-entry form;

•

an investor may not be able to pledge his or her interest in the global security in circumstances where certificates representing the securities must be delivered to the lender or other beneficiary of the pledge in order for the pledge to be effective;

•

the depositary’s policies, which may change from time to time, will govern payments, transfers, exchanges and other matters relating to an investor’s interest in the global security. We and any applicable trustee have no responsibility for any aspect of the depositary’s actions or for its records of ownership interests in the global security. We and the trustee also do not supervise the depositary in any way;

•

the depositary may, and we understand that DTC will, require that those who purchase and sell interests in the global security within its book-entry system use immediately available funds, and your broker or bank may require you to do so as well; and

•

financial institutions that participate in the depositary’s book-entry system, and through which an investor holds its interest in the global security, may also have their own policies affecting payments, notices and other matters relating to the securities. There may be more than one financial intermediary in the chain of ownership for an investor. We do not monitor and are not responsible for the actions of any of those intermediaries

Special Situations When A Global Security Will Be Terminated

In a few special situations described below, a global security will terminate and interests in it will be exchanged for physical certificates representing those interests. After that exchange, the choice of whether to hold securities directly or in street name will be up to the investor. Investors must consult their own banks or brokers to find out how to have their interests in securities transferred to their own names, so that they will be direct holders. We have described the rights of holders and street name investors above.

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A global security will terminate when the following special situations occur:

•

if the depositary notifies us that it is unwilling, unable or no longer qualified to continue as depositary for that global security and we do not appoint another institution to act as depositary within 90 days;

•

if we notify any applicable trustee that we wish to terminate that global security; or

•

if an event of default has occurred with regard to securities represented by that global security and has not been cured or waived.

The applicable prospectus supplement may also list additional situations for terminating a global security that would apply only to the particular series of securities covered by the prospectus supplement. When a global security terminates, the depositary, and neither we, nor any applicable trustee, is responsible for deciding the names of the institutions that will be the initial direct holders.

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PLAN OF DISTRIBUTION

We may sell the securities being offered hereby in one or more of the following ways from time to time:

•

through agents to the public or to investors;

•

to underwriters for resale to the public or to investors;

•

negotiated transactions;

•

block trades;

•

directly to investors; or

•

through a combination of any of these methods of sale.

As set forth in more detail below, the securities may be distributed 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 will set forth in a prospectus supplement the terms of that particular offering of securities, including:

•

the name or names of any agents or underwriters;

•

the purchase price of the securities being offered and the proceeds we will receive from the sale;

•

any over-allotment options under which underwriters may purchase additional securities from us;

•

any agency fees or underwriting discounts and other items constituting agents’ or underwriters’ compensation;

•

any initial public offering price;

•

any discounts or concessions allowed or re-allowed or paid to dealers; and

•

any securities exchanges or markets on which such securities may be listed.

Only underwriters named in an applicable prospectus supplement are underwriters of the securities offered by that prospectus supplement.

If underwriters are used in an offering, we will execute an underwriting agreement with such underwriters and will specify the name of each underwriter and the terms of the transaction (including any underwriting discounts and other terms constituting compensation of the underwriters and any dealers) in a prospectus supplement. The securities may be offered to the public either through underwriting syndicates represented by managing underwriters or directly by one or more investment banking firms or others, as designated. If an underwriting syndicate is used, the managing underwriter(s) will be specified on the cover of the prospectus supplement. If underwriters are used in the sale, the offered securities will be acquired by the underwriters for their own accounts and may be resold from time to time in one or more transactions, including negotiated transactions, at a fixed public offering price or at varying prices determined at the time of sale. Any public offering price and any discounts or concessions allowed or re-allowed or paid to dealers may be changed from time to time. Unless otherwise set forth in the prospectus supplement, the obligations of the underwriters to purchase the offered securities will be subject to conditions precedent and the underwriters will be obligated to purchase all of the offered securities if any are purchased.

We may grant to the underwriters options to purchase additional securities to cover over-allotments, if any, at the public offering price, with additional underwriting commissions or discounts, as may be set forth in a related prospectus supplement. The terms of any over-allotment option will be set forth in the prospectus supplement for those securities.

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If we use a dealer in the sale of the securities being offered pursuant to this prospectus or any prospectus supplement, we will sell the securities to the dealer, as principal. The dealer may then resell the securities to the public at varying prices to be determined by the dealer at the time of resale. The names of the dealers and the terms of the transaction will be specified in a prospectus supplement.

We may sell the securities directly or through agents we designate from time to time. We will name any agent involved in the offering and sale of securities and we will describe any commissions we will pay the agent in the prospectus supplement. Unless the prospectus supplement states otherwise, any agent will act on a best-efforts basis for the period of its appointment.

We may authorize agents or underwriters to solicit offers by institutional investors to purchase securities from us at the public offering price set forth in the prospectus supplement pursuant to delayed delivery contracts providing for payment and delivery on a specified date in the future. We will describe the conditions to these contracts and the commissions we must pay for solicitation of these contracts in the prospectus supplement.

In connection with the sale of the securities, underwriters, dealers or agents may receive compensation from us or from purchasers of the common stock for whom they act as agents in the form of discounts, concessions or commissions. Underwriters 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 agents. Underwriters, dealers and agents that participate in the distribution of the securities, and any institutional investors or others that purchase common stock directly and then resell the securities, may be deemed to be underwriters, and any discounts or commissions received by them from us and any profit on the resale of the common stock by them may be deemed to be underwriting discounts and commissions under the Securities Act.

We may provide agents and underwriters with indemnification against particular civil liabilities, including liabilities under the Securities Act, or contribution with respect to payments that the agents or underwriters may make with respect to such liabilities. Agents and underwriters may engage in transactions with, or perform services for, us in the ordinary course of business.

We may engage in at the market offerings into an existing trading market in accordance with Rule 415(a)(4) under the Securities Act. In addition, we may enter into derivative transactions with third parties (including the writing of options), or sell securities not covered by this prospectus to third parties in privately negotiated transactions. If the applicable prospectus supplement indicates, in connection with such a transaction, the third parties may, pursuant to this prospectus and the applicable prospectus supplement, sell securities covered by this prospectus and the applicable prospectus supplement. If so, the third party may use securities borrowed from us or others to settle such sales and may use securities received from us to close out any related short positions. We may also loan or pledge securities covered by this prospectus and the applicable prospectus supplement to third parties, who may sell the loaned securities or, in an event of default in the case of a pledge, sell the pledged securities pursuant to this prospectus and the applicable prospectus supplement. The third party in such sale transactions will be an underwriter and will be identified in the applicable prospectus supplement or in a post-effective amendment.

To facilitate an offering of a series of securities, persons participating in the offering may engage in transactions that stabilize, maintain, or otherwise affect the market price of the securities. This may include over-allotments or short sales of the securities, which involves the sale by persons participating in the offering of more securities than have been sold to them by us. In those circumstances, such persons would cover such over-allotments or short positions by purchasing in the open market or by exercising the over-allotment option granted to those persons. In addition, those 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 underwriters or dealers participating in any such 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. Such transactions, if commenced, may be discontinued at any time. We make no representation or prediction as to the direction or magnitude of any effect that the transactions described above, if implemented, may have on the price of our securities.

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Unless otherwise specified in the applicable prospectus supplement, each class or series of securities will be a new issue with no established trading market, other than our common stock, which is listed on The Nasdaq Capital Market. We may elect to list any other class or series of securities on any exchange or market, but we are not obligated to do so. It is possible that one or more underwriters may make a market in a class or series of securities, but the underwriters will not be obligated to do so and may discontinue any market making at any time without notice. We cannot give any assurance as to the liquidity of the trading market for any of the securities.

In order to comply with the securities laws of some U.S. states or territories, if applicable, the securities offered pursuant to this prospectus will be sold in those states only through registered or licensed brokers or dealers. In addition, in some states securities may not be sold unless they have been registered or qualified for sale in the applicable state or an exemption from the registration or qualification requirement is available and complied with.

Any underwriter may engage in overallotment, stabilizing transactions, short covering transactions and penalty bids in accordance with Regulation M under the Securities Exchange Act of 1934, as amended (the “Exchange Act”). Overallotment involves sales in excess of the offering size, which create a short position. Stabilizing transactions permit bids to purchase the underlying security so long as the stabilizing bids do not exceed a specified maximum. Short covering transactions involve purchases of the securities in the open market after the distribution is completed to cover short positions. Penalty bids permit the underwriters to reclaim a selling concession from a dealer when the securities originally sold by the dealer are purchased in a covering transaction to cover short positions. Those activities may cause the price of the securities to be higher than it would otherwise be. If commenced, the underwriters may discontinue any of these activities at any time.

Any underwriters who are qualified market makers on The Nasdaq Capital Market may engage in passive market making transactions in the securities on The Nasdaq Capital Market in accordance with Rule 103 of Regulation M, during the business day prior to the pricing of the offering, before the commencement of offers or sales of the securities. Passive market makers must comply with applicable volume and price limitations and must be identified as passive market makers. In general, a passive market maker must display its bid at a price not in excess of the highest independent bid for such security. If all independent bids are lowered below the passive market maker’s bid, however, the passive market maker’s bid must then be lowered when certain purchase limits are exceeded.

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LEGAL MATTERS

The validity of the issuance of the securities offered hereby will be passed upon for us by Sheppard, Mullin, Richter & Hampton LLP, New York, NY. Additional legal matters may be passed upon for us or any underwriters, dealers or agents, by counsel that we will name in the applicable prospectus supplement.

EXPERTS

Mayer Hoffman McCann P.C., our independent registered public accounting firm, has audited our consolidated balance sheets as of December 31, 2018 and 2017, and the related consolidated statements of operations, changes in convertible preferred stock and stockholders’ deficit and cash flows for each of the years ended December 31, 2018 and 2017, as set forth in their report, which is incorporated by reference in this prospectus and elsewhere in the registration statement. Our financial statements are incorporated by reference in reliance on Mayer Hoffman McCann P.C.’s report, given on their authority as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

This prospectus constitutes a part of a registration statement on Form S-3 filed under the Securities Act. As permitted by the SEC’s rules, this prospectus and any prospectus supplement, which form a part of the registration statement, do not contain all the information that is included in the registration statement. You will find additional information about us in the registration statement. Any statements made in this prospectus or any prospectus supplement concerning legal documents are not necessarily complete and you should read the documents that are filed as exhibits to the registration statement or otherwise filed with the SEC for a more complete understanding of the document or matter.

You may read and copy the registration statement, as well as our reports, proxy statements, and other information, at the SEC’s Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for more information about the operation of the Public Reference Room. The SEC maintains an Internet site that contains reports, proxy and information statements, and other information regarding issuers that file electronically with the SEC. The SEC’s Internet site can be found at http://www.sec.gov. You can also obtain copies of materials we file with the SEC from our website found at www.aridispharma.com. Information on our website does not constitute a part of, nor is it incorporated in any way, into this prospectus and should not be relied upon in connection with making an investment decision.

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INCORPORATION OF DOCUMENTS BY REFERENCE

The SEC allows us to “incorporate by reference” information that we file with them. Incorporation by reference allows us to 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 that we file later with the SEC will automatically update and supersede this information. We filed a registration statement on Form S-1 under the Securities Act with the SEC with respect to the securities being offered pursuant to this prospectus. This prospectus omits certain information contained in the registration statement, as permitted by the SEC. You should refer to the registration statement, including the exhibits, for further information about us and the securities being offered pursuant to this prospectus. Statements in this prospectus regarding the provisions of certain documents filed with, or incorporated by reference in, the registration statement are not necessarily complete and each statement is qualified in all respects by that reference. Copies of all or any part of the registration statement, including the documents incorporated by reference or the exhibits, may be obtained upon payment of the prescribed rates at the offices of the SEC listed above in “Where You Can Find More Information”. We are incorporating by reference the documents listed below, which we have already filed with the SEC, and all documents subsequently filed by us pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, except as to any portion of any future report or document that is not deemed filed under such provisions:

1.   The Company’s Annual Report on Form 10-K for the year ended December 31, 2018, filed with the SEC on March 28, 2019;

2.   Amendment No. 1 to the Company’s Annual Report on Form 10-K/A for the year ended December 31, 2018, filed with the SEC on April 19, 2019;

3.   Amendment No. 2 to the Company’s Annual Report on Form 10-K/A for the year ended December 31, 2018, filed with the SEC on June 12, 2019;

4.   The Company’s Quarterly Reports on Form 10-Q for the quarter ended March 31, 2019, filed with the SEC on May 14, 2019 and the quarter ended June 30, 2019, filed with the SEC on August 12, 2019;

5.   The Company’s Current Reports on Form 8-K filed on February 27, 2019, June 10, 2019, July 30, 2019, August 14, 2019 and September 3, 2019 and Form 8-K/A filed on August 12, 2019;

6.   The Company’s definitive proxy statement on Schedule 14A filed on July 2, 2019; and

7.   The description of the Company’s common stock contained in the registration statement in our prospectus that constitutes a part of the Registration Statement on Form S-1, as amended (File No. 333-226232), including any amendment or report filed for the purpose of updating that description.

We also incorporate by reference all documents (other than Current Reports furnished under Item 2.02 or Item 7.01 of Form 8-K and exhibits filed on such form that are related to such items) that are subsequently filed by us with the Securities and Exchange Commission pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act prior to the termination of the offering of the securities made by this prospectus (including documents filed after the date of the initial Registration Statement of which this prospectus is a part and prior to the effectiveness of the Registration Statement). These documents include periodic reports, such as Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, as well as proxy statements.

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

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You may request, and we will provide you with, a copy of these filings, at no cost, by calling us at (408) 385-1742 or by writing to us at the following address:

Aridis Pharmacueticals, Inc.
5941 Optical Ct.
San Jose, California
Attn.: Secretary

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Up to $25,000,000

Common Stock

PROSPECTUS SUPPLEMENT

January 19, 2022