tcon-8k_20180509.htm

(Address, including zip code, and telephone number, including area code of registrant’s principal executive offices)

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Approximate date of commencement of proposed sale to the public: From time to time after the effective date of this registration statement.

If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box. ☐

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box. ☒

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a registration statement pursuant to General Instruction I.D. or a post-effective amendment thereto that shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, check the following box. ☐

If this Form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box. ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of "large accelerated filer," "accelerated filer," "smaller reporting company," and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of Securities Act. ☒

The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment that specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, as amended, or until the registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

The information in this prospectus is not complete and may be changed. The selling stockholders may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities and it is not soliciting offers to buy these securities in any state where such offer or sale is not permitted.

This prospectus relates to the disposition from time to time of up to 27,392,134 shares of our common stock, which includes 15,461,609 shares of our common stock issuable upon the exercise of outstanding warrants, which are held by the selling stockholders named in this prospectus. We are not selling any common stock under this prospectus and will not receive any of the proceeds from the sale of shares by the selling stockholders. We will, however, receive the net proceeds of any warrants exercised for cash.

The selling stockholders identified in this prospectus, or their permitted transferees or other successors-in-interest that may be identified in a supplement to this prospectus or, if required, a post-effective amendment to the registration statement of which this prospectus is a part, may offer the shares from time to time through public or private transactions at fixed prices, at prevailing market prices, at varying prices determined at the time of sale, or at privately negotiated prices. We provide more information about how the selling stockholders may sell their shares of common stock in the section entitled “Plan of Distribution”. We have agreed to pay certain expenses incurred in connection with the registration of these shares, however, we will not be paying any commissions in connection with any offering of shares of common stock under this prospectus.

Our common stock is traded on The Nasdaq Global Market under the symbol “TCON.” On May 8, 2018, the last reported sales price of our common stock was $2.42 per share.

Investing in our common stock involves a high degree of risk. You should review carefully the risks and uncertainties described under the heading “Risk Factors” contained on page 3 of this prospectus, and under similar headings in the other documents that are incorporated by reference into this prospectus, including those filed after the date hereof.

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR DETERMINED IF THIS PROSPECTUS IS TRUTHFUL OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

This prospectus is part of a registration statement on Form S-3 that we filed with the Securities and Exchange Commission, or SEC, utilizing a “shelf” registration process. Under this shelf registration process, the selling stockholders may from time to time, in one or more offerings, sell the common stock described in this prospectus.

We have not authorized anyone to provide you with information other than the information contained in or incorporated by reference into this prospectus (as supplemented or amended). This document may only be used where it is legal to sell these securities. The information contained in this prospectus (and in any supplement or amendment to this prospectus) is accurate only as of the date on the front of the document, and 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 or any sale of our common stock. Our business, financial condition, results of operations and prospects may have changed since those dates.

We urge you to read carefully this prospectus (as supplemented and amended), together with the information incorporated herein by reference as described under the heading “Incorporation by Reference” before deciding whether to invest in any of the common stock being offered.

This prospectus incorporates by reference market data, industry statistics and other data that have been obtained from, or compiled from, information made available by third parties. We have not independently verified their data. This prospectus and the information incorporated herein 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 are the property of their respective owners.

This summary highlights selected information contained elsewhere in this prospectus or incorporated by reference in this prospectus and does not contain all of the information that you need to consider in making your investment decision. You should carefully read the entire prospectus (as supplemented and amended), including the financial data and related notes, risk factors and other information incorporated by reference in this prospectus before making an investment decision.

Unless the context indicates otherwise, as used in this prospectus, the terms “TRACON,” “the Company,” “we,” “us” and “our” refer to TRACON Pharmaceuticals, Inc., a Delaware corporation. This prospectus or information incorporated by reference in this prospectus contains references to our trademarks and to trademarks belonging to other entities. Solely for convenience, trademarks and trade names referred to or incorporated by reference in this prospectus, including logos, artwork and other visual displays, may appear without the ® or TM symbols, but such references are not intended to indicate, in any way, that their respective owners will not assert, to the fullest extent under applicable law, their rights thereto. We do not intend our use or display of other companies’ trade names or trademarks to imply a relationship with, or endorsement or sponsorship of us by, any other companies.

We are a biopharmaceutical company focused on the development and commercialization of novel targeted therapeutics for cancer and wet age-related macular degeneration, or wet AMD. We are a leader in the field of endoglin biology and are using our expertise to develop antibodies that bind to the endoglin receptor. Endoglin is essential to angiogenesis, the process of new blood vessel formation required for solid cancer growth and wet AMD. We are developing our lead product candidate, TRC105 (carotuximab), an endoglin antibody, for the treatment of multiple solid tumor types in combination with inhibitors of the vascular endothelial growth factor, or VEGF, pathway. The VEGF pathway regulates vascular development in the embryo, or vasculogenesis, and angiogenesis. We believe treatment with TRC105 in combination with VEGF inhibitors may improve survival in cancer patients when compared to treatment with a VEGF inhibitor alone. TRC105 has been studied in ten completed Phase 2 clinical trials and three completed Phase 1 clinical trials, and is currently being dosed in one Phase 3 clinical trial, five Phase 2 clinical trials and three Phase 1 clinical trials. Our TRC105 oncology clinical development plan is broad and involves a tiered approach. We are initially focused on angiosarcoma which is a tumor that highly expresses endoglin, the target of TRC105, and therefore may be more responsive to treatment with TRC105. We have seen complete durable responses in this tumor type and are currently enrolling the international multicenter Phase 3 TAPPAS trial in angiosarcoma. We obtained Special Protocol Assessment (SPA) agreement from the U.S. Food and Drug Administration (FDA) on our clinical trial design for the Phase 3 trial in angiosarcoma and also incorporated scientific advice from the European Medicines Agency (EMA) regarding the adequacy of the trial design. We also received orphan drug designation from the FDA and the EMA for TRC105 for the treatment of soft tissue sarcoma, including angiosarcoma, in 2016.

In March 2014, Santen Pharmaceutical Co. Ltd. (Santen) licensed from us exclusive worldwide rights to develop and commercialize our endoglin antibodies for ophthalmology indications, and in July 2017 Santen initiated dosing in a Phase 2 clinical trial of DE-122 in wet AMD. In December 2017, Ambrx, Inc. (Ambrx) licensed from us exclusive rights to develop and commercialize our endoglin antibodies in China (including Hong Kong and Macau) and Taiwan.

Our other product candidates are TRC102, which is a small molecule that is in Phase 2 clinical development for the treatment of mesothelioma and glioblastoma, and two compounds that we licensed from Janssen Pharmaceutica N.V. (Janssen) in September 2016: TRC253, which is a small molecule for which we initiated a Phase 1/2 clinical trial for the treatment of metastatic castration-resistant prostate cancer in March 2017, and TRC694, a small molecule in pre-clinical development for the treatment of hematologic malignancies, including myeloma.

We operate a clinical development model that emphasizes capital efficiency. Our experienced clinical operations and regulatory affairs groups enable us to eliminate the cost associated with hiring contract research organizations to manage clinical, regulatory and database aspects of our Phase 1 and Phase 2 clinical trials conducted in the United States. We have also collaborated with the NCI, which has selected TRC105 and TRC102 for federal funding of clinical development, Case Western Cancer Center (Case Western), the University of Alabama – Birmingham, and Cedars-Sinai Medical Center. Under these collaborations, NCI sponsored or is sponsoring ten completed or ongoing clinical trials of TRC105 and TRC102, Case Western sponsored two clinical trials of TRC102, the University of Alabama – Birmingham is sponsoring one clinical trial of TRC105 and Cedars-Sinai Medical Center is sponsoring one clinical trial of TRC105. All TRC105 NCI sponsored trials have been completed. If merited by Phase 2 data, we expect to fund additional Phase 3 clinical trials of TRC105 and TRC102 and, based on NCI’s past course of conduct with similarly situated pharmaceutical companies in which it has sponsored pivotal clinical trials following receipt of positive Phase 2 data, we anticipate that NCI will sponsor Phase 3 clinical trials in additional indications.

We were incorporated in the state of Delaware in October 2004 as Lexington Pharmaceuticals, Inc. and we subsequently changed our name to TRACON Pharmaceuticals, Inc. in March 2005, at which time we relocated to San Diego, California. Our principal executive offices are located at 4350 La Jolla Village Drive, Suite 800, San Diego, California 92122, and our telephone number is (858) 550‑0780. Our corporate website is www.traconpharma.com. The information on, or that can be accessed through, our website is not part of this prospectus, and you should not rely on any such information in making the decision whether to purchase our common stock.

We are an “emerging growth company,” as defined in the Jumpstart Our Business Startups Act of 2012. We will cease to be an emerging growth company on the date that is the earliest of (i) the last day of the fiscal year in which we have total annual gross revenues of $1.07 billion or more; (ii) December 31, 2020; (iii) the date on which we have issued more than $1.0 billion in non-convertible debt during the previous three years; or (iv) the last day of the fiscal year in which we are deemed to be a large accelerated filer under the rules of the SEC.

The selling stockholders named in this prospectus may offer and sell up to 27,392,134 shares of our common stock, which includes 15,461,609 shares of our common stock issuable upon the exercise of outstanding warrants. The shares issuable upon exercise of the warrants will become eligible for sale by the selling stockholders under this prospectus only as the warrants are exercised. Our common stock is currently listed on The Nasdaq Global Market under the symbol “TCON.” Shares of common stock that may be offered under this prospectus, when issued and paid for in the case of shares issuable upon exercise of the outstanding warrants, will be fully paid and non-assessable. We will not receive any of the proceeds of sales by the selling stockholders of any of the common stock covered by this prospectus. Throughout this prospectus, when we refer to the shares of our common stock being registered on behalf of the selling stockholders, we are referring to the shares and the shares underlying the warrants issued to the selling stockholders pursuant to the securities purchase agreement we entered into with the selling stockholders on March 22, 2018, and when we refer to the selling stockholders in this prospectus, we are referring to the purchasers under the securities purchase agreement and, as applicable, their permitted transferees or other successors-in-interest that may be identified in a supplement to this prospectus or, if required, a post-effective amendment to the registration statement of which this prospectus is a part.

Investing in our securities involves a high degree of risk. You should carefully review the risks and uncertainties described under the heading “Risk Factors” contained in our Annual Report on Form 10-K for the year ended December 31, 2017 filed with the SEC on March 1, 2018, as updated by our subsequent annual, quarterly and other reports and documents that are incorporated by reference into this prospectus, before deciding whether to purchase any of the securities being registered pursuant to the registration statement of which this prospectus is a part. Each of the risk factors could adversely affect our business, operating results and financial condition, as well as adversely affect the value of an investment in our securities, and the occurrence of any of these risks might cause you to lose all or part of your investment. Additional risks not presently known to us or that we currently believe are immaterial may also significantly impair our business operations.

This prospectus, each prospectus supplement and the information incorporated by reference in this prospectus and each prospectus supplement contain 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”) that involve a number of risks and uncertainties. Although our forward-looking statements reflect the good faith judgment of our management, these statements can only be based on facts and factors currently known by us. Consequently, these forward-looking statements are inherently subject to risks and uncertainties, and actual results and outcomes may differ materially from results and outcomes discussed in the forward-looking statements.

Forward-looking statements can be identified by the use of forward-looking words such as “believes,” “expects,” “hopes,” “may,” “will,” “plan,” “intends,” “estimates,” “could,” “should,” “would,” “continue,” “seeks,” “pro forma,” or “anticipates,” or other similar words (including their use in the negative), or by discussions of future matters such as the development of new products, technology enhancements, possible collaborations, possible changes in legislation and other statements that are not historical. These statements include but are not limited to statements under the captions “Business,” “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and in other sections incorporated by reference from our Annual Report on Form 10-K and Quarterly Reports on Form 10-Q, as applicable, as well as our other filings with the SEC. You should be aware that the occurrence of any of the events discussed under the heading “Risk Factors” in any applicable prospectus supplement and any documents incorporated by reference herein or therein could substantially harm our business, operating results and financial condition and that if any of these events occurs, it could adversely affect the value of an investment in our securities.

The cautionary statements made in this prospectus and the information incorporated by reference in this prospectus are intended to be applicable to all related forward-looking statements wherever they may appear in this prospectus or in any prospectus supplement or any documents incorporated by reference herein or therein. We urge you not to place undue reliance on these forward-looking statements, which speak only as of the date they are made. Except as required by law, we assume no obligation to update our forward-looking statements, even if new information becomes available in the future.

The selling stockholders will receive all of the net proceeds from sales of the common stock pursuant to this prospectus. However, in the case of warrants issued to the selling stockholders pursuant to the securities purchase agreement dated March 22, 2018, upon any exercise of these warrants for cash, the selling stockholders would pay us an exercise price of $2.70 per share of common stock or, in the case of pre-funded warrants, an exercise price of $0.01 per share of common stock, in each case, subject to any adjustment pursuant to the terms of the warrants. We expect to use any such warrant exercise proceeds primarily for working capital and general corporate purposes. These warrants are also exercisable on a cashless basis by net exercise under certain conditions contained therein. If any of these warrants are exercised on a cashless basis, we would not receive any cash payment from the applicable selling stockholder upon any such cashless exercise of a warrant.

On March 22, 2018, we entered into a securities purchase agreement with the selling stockholders pursuant to which we issued and sold in a private placement an aggregate of (a) 11,930,525 shares of our common stock, (b) pre-funded warrants to purchase 1,765,542 shares of common stock to certain selling stockholders whose purchase of shares of common stock would otherwise have resulted in such selling stockholder, together with its affiliates, beneficially owning more than either 9.99% or 19.99% of our outstanding shares of common stock immediately following closing, and (c) warrants to purchase 13,696,067 shares of common stock, for an aggregate purchase price of approximately $38.7 million. Pursuant to the securities purchase agreement, we agreed to file the registration statement of which this prospectus is a part to cover the resale of the shares of our

common stock and the warrant shares issuable upon exercise of the warrants issued to the selling stockholders pursuant to the securities purchase agreement, and to keep such registration statement effective with respect to each selling stockholder until the earlier to occur of (i) the third anniversary of the effective date of the registration statement of which this prospectus is a part, (ii) the date on which all of the shares and warrants shares held by such selling stockholder (other than a selling stockholder that would beneficially own more than 10% or more or our outstanding shares of common stock assuming all warrant shares held by such selling stockholder are outstanding) may be sold under Rule 144 under the Securities Act within a three month period or, (iii) immediately prior to the closing of a change in control. The pre-funded warrants are exercisable for a period of seven years and the common warrants are exercisable for a period of six years. The exercise price and number of shares of common stock issuable upon exercise of the warrants may be adjusted in certain circumstances, including stock splits, stock dividends, reclassifications and the like. The warrant shares issuable upon exercise of the warrants will become eligible for sale by the selling stockholders under this prospectus only as the warrants are exercised. We cannot predict when or whether any of the selling stockholders will exercise their Warrants.

We are registering the resale of the above-referenced shares to permit each of the selling stockholders identified below, or their permitted transferees or other successors-in-interest that may be identified in a supplement to this prospectus or, if required, a post-effective amendment to the registration statement of which this prospectus is a part, to resell or otherwise dispose of the shares in the manner contemplated under “Plan of Distribution” in this prospectus (as may be supplemented and amended). This prospectus covers the sale or other disposition by the selling stockholders of up to the total number of shares of common stock issued to the selling stockholders pursuant to the securities purchase agreement, plus the total number of shares of common stock issuable upon exercise of the warrants issued to the selling stockholders. Throughout this prospectus, when we refer to the shares of our common stock being registered on behalf of the selling stockholders, we are referring to the shares of our common stock and the warrant shares issuable upon exercise of the warrants issued to the selling stockholders pursuant to the securities purchase agreement, and when we refer to the selling stockholders in this prospectus, we are referring to the purchasers under the securities purchase agreement and, as applicable, their permitted transferees or other successors-in-interest that may be identified in a supplement to this prospectus or, if required, a post-effective amendment to the registration statement of which this prospectus is a part.

The selling stockholders may sell some, all or none of their shares. We do not know how long the selling stockholders will hold the shares before selling them, and we currently have no agreements, arrangements or understandings with the selling stockholders regarding the sale or other disposition of any of the shares. The shares of our common stock covered hereby may be offered from time to time by the selling stockholders.

The following table sets forth the name of each selling stockholder, the number and percentage of our common stock beneficially owned by the selling stockholders as of April 30, 2018, the number of shares of our common stock that may be offered under this prospectus, and the number and percentage of our common stock beneficially owned by the selling stockholders assuming all of the shares of our common stock registered hereunder are sold. Beneficial ownership is determined in accordance with the rules of the SEC and includes voting or investment power with respect to our common stock. Generally, a person “beneficially owns” shares of our common stock if the person has or shares with others the right to vote those shares or to dispose of them, or if the person has the right to acquire voting or disposition rights within 60 days. The number of shares of our common stock in the column “Number of Shares Offered” represents all of the shares of our common stock that a selling stockholder may offer and sell from time to time under this prospectus.

The information in the table below and the footnotes thereto regarding shares of common stock to be beneficially owned after the offering assumes that all of the selling stockholders have exercised the warrants in full pursuant to cash exercises and further assumes the sale of all shares being offered by the selling stockholders under this prospectus.

All information contained in the table below and the footnotes thereto is based upon information provided to us by the selling stockholders. The information in the table below and the footnotes thereto regarding shares of common stock to be beneficially owned after the offering assumes that all of the selling stockholders have exercised the warrants in full pursuant to cash exercises and further assumes the sale of all shares being offered by the selling stockholders under this prospectus. The percentage of shares owned prior to and after the offering is based on 29,731,331 shares of common stock outstanding as of April 30, 2018 and, with respect to the percentage of shares owned after the offering, on the assumption that all of the selling stockholders have exercised the warrants in full pursuant to cash exercises and therefore that all shares of common stock issuable upon exercise of the warrants were outstanding as of that date. Unless otherwise indicated in the footnotes to this table, we believe that each of the selling stockholders named in this table has sole voting and investment power with respect to the shares of common stock indicated as beneficially owned. Except as otherwise indicated below, based on the information provided to us by the selling stockholders, none of the selling stockholders is a broker-dealer or an affiliate of a broker-dealer.



	Prior to Offering			After Offering
Name and Address	Number of Shares Beneficially Owned(1)	Percentage of Shares Beneficially Owned(1)	Number of Shares Offered(2)	Number of Shares Beneficially Owned	Percentage of Shares Beneficially Owned
Puissance Cross-Border Opportunities IV LLC 950 3^rd Ave. 25^th Floor New York, NY 10022	3,539,822(3)	7.8%	3,539,822	—	*
Puissance Cross-Border Opportunities V LLC 950 3rd Ave. 25th Floor New York, NY 10022	5,663,7144)	12.5%	5,633,714	—	*
New Enterprise Associates 14, L.P. 1954 Greenspring Drive, Suite 600 Timonium, Maryland 21093	4,175,145(5)	9.2%	1,415,928	2,759,217	6.1%
683 Capital Partners, LP 3 Columbus Circle, Suite 2205 New York, New York 10019	3,977,876(6)	8.8%	2,477,876	1,500,000	3.3%
Linden Capital L.P. Victoria Place, 31 Victoria Street Hamilton HM10, Bermuda	9,216,038(7)	20.4%	9,216,038	—	*
Aspire Capital Fund, LLC 155 North Wacker Drive, Suite 1600 Chicago, IL 60606	2,541,840(8)	5.6%	2,123,892	417,948	*
Laurence Lytton 467 Central Park West New York, NY 10025	2,138,272(9)	4.7%	1,415,928	722,344	1.6%
Lincoln Park Capital Fund, LLC 440 N Wells St. Suite 410 Chicago, IL 60654	707,964 (10)	1.6%	707,964	—	*
Arcus Ventures Fund II, LP 60 E 42nd St. Suite 1610 New York, NY 10165	665,926(11)	1.5%	353,982	311,944	*
Investor Company ITF Rosalind Master Fund L.P. 77 Bloor St. W 3rd Floor Toronto, ON M5S 1M2	474,800(12)	1.0%	300,000	174,800	*
BioBrit, LLC 2223 Avenida de la Playa #108 La Jolla, CA 92037	225,053 (13)	*	176,990	48,053	*

(1) Under the terms of the warrants, the number of shares of our common stock that may be acquired by a selling stockholder upon any exercise of a warrant is generally limited to the extent necessary to ensure that, following such exercise, such selling stockholder would not, together with its affiliates and any other persons or entities whose beneficial ownership of our common stock would be aggregated with such selling stockholder for purposes of Section 13(d) of the Exchange Act, beneficially own in excess of a specified percentage of the total number of shares of our common stock then issued and outstanding and/or the then combined voting power of all of our voting securities (the “Blockers”). Certain of the Blockers are waivable by the selling stockholders’ on at least 60 days’ prior notice to us up to a specified maximum percentage. If the operation of the Blockers currently limits the beneficial ownership of a selling stockholder, such limitation is noted in the footnotes that follow. In addition, as noted in footnote (2), the number of shares shown under the column titled “Number of Shares Offered” is shown without regard to the foregoing limitations on exercise.

(2) The number of shares offered hereby, for each selling stockholder, consists solely of the shares issued to such selling stockholder pursuant to the securities purchase agreement and the shares issuable upon exercise of the warrants issued to such selling stockholder. The shares issuable upon exercise of the warrants will become eligible for sale by the selling stockholders under this prospectus only as the warrants are exercised. In addition, the number of shares offered hereby shown under the column titled “Number of Shares Offered” includes the maximum number of shares issuable upon the exercise of the warrants without regard to the limitations on exercise described in footnote (1) above.

(3) Represents 1,769,911 outstanding shares of common stock owned by Puissance Cross-Border IV, LLC and 1,769,911 shares of common stock issuable upon exercise of warrants. The warrants are only exercisable to the extent that the holders thereof and their affiliates would beneficially own no more than 19.99% of the outstanding common stock after exercise. Puissance Cross-Border Opportunities V, Puissance Cross-Border Opportunities IV, Puissance GP, Puissance Capital Management GP, and Theodore Wang, share voting and dispositive power with respect to the shares held by Puissance Capital Management. Theodore Wang, the managing member of Puissance, disclaims beneficial ownership of such shares except to the extent of his pecuniary interest therein.

(4) Represents 2,831,857 outstanding shares of common stock owned by Puissance Cross-Border V, LLC and 2,831,857 shares of common stock issuable upon exercise of warrants. The warrants are only exercisable to the extent that the holders thereof and their affiliates would beneficially own no more than 19.99% of the outstanding common stock after exercise. Puissance Cross-Border Opportunities V, Puissance Cross-Border Opportunities IV, Puissance GP, Puissance Capital Management GP, and Theodore Wang, share voting and dispositive power with respect to the shares held by Puissance Capital Management. Theodore Wang, the managing member of Puissance, disclaims beneficial ownership of such shares except to the extent of his pecuniary interest therein.

(5) Represents (a) 3,466,003 outstanding shares of common stock and 707,964 shares of common stock issuable upon exercise of warrants, beneficially owned by New Enterprise Associates 14, L.P., or NEA 14, and (b) 1,178 outstanding shares of common stock beneficially owned by NEA Ventures 2014, L.P., or Ven 2014. The warrants are only exercisable to the extent that the holders thereof and their affiliates would beneficially own no more than 9.99% of the outstanding common stock after exercise. The shares and warrants directly held by NEA 14 are indirectly held by NEA Partners 14, L.P., the sole general partner of NEA; NEA 14 GP, LTD, the sole general partner of NEA Partners 14, L.P.; and each of the individual directors of NEA 14 GP, LTD. The directors of NEA 14 GP, LTD are M. James Barrett, Peter J. Barris, Forest Baskett, Anthony A. Florence, Jr., Patrick J. Kerins, David M. Mott, Scott D. Sandell, Peter Sonsini, and Ravi Viswanathan. NEA 14, NEA Partners 14, L.P., NEA 14 GP, LTD and the directors of NEA 14 GP, LTD share voting and dispositive power with respect to the shares and warrants held by NEA 14. The shares directly held by Ven 2014 are indirectly held by Karen P. Welsh, the general partner of Ven 2014. Karen Welsh has voting and dispositive power with regard to the shares held by Ven 2014. Paul Walker, a partner at New Enterprise Associates, Inc., has no voting or dispositive power with regard to any of the above referenced shares and warrants and disclaims beneficial ownership of such shares and warrants except to the extent of his pecuniary interest therein, if any. All indirect holders of the above referenced shares and warrants disclaim beneficial ownership of all applicable shares and warrants except to the extent of their pecuniary interest therein.

(6) Represents 2,738,938 outstanding shares of common stock beneficially owned by 683 Capital Management, LLC and 1,238,938 shares of common stock issuable upon exercise of warrants. The warrants are only exercisable to the extent that the holders thereof and their affiliates would beneficially own no more than 9.99% of the outstanding common stock after exercise. The shares and warrants directly held by 683 Capital Management LLC are indirectly held by 683 Capital Partners LP and Ari Zweiman (Mr. Zweiman), the managing member of 683 Capital Management, LLC. 683 Capital Management, LLC, 683 Capital Partners LP and Mr. Zweiman share voting and dispositive power with respect to the shares held by 683 Capital Management, LLC.

(7) Represents 2,842,477 outstanding shares of common stock held by Linden Capital L.P., 4,608,019 shares of common stock issuable upon exercise of warrants, and 1,765,542 shares of common stock issuable upon exercise of pre-funded warrants. The warrants are only exercisable to the extent that the holders thereof and their affiliates would beneficially own no more than 9.99% of the outstanding common stock after exercise and the holders disclaim beneficial ownership of shares of common stock underlying their warrants to the extent that their beneficial ownership of common stock would exceed 9.99%. The shares and warrants directly held by Linden Capital L.P. are indirectly held by Linden Advisors LP, the investment manager of Linden Capital L.P., Linden GP LLC, the general partner of Linden Capital L.P., and Siu Min (Joe) Wong (Mr. Wong), the principle owner and controlling person of Linden Advisors and Linden GP LLC. Linden Capital L.P., Linden Advisors LP, Linden GP LLC and Mr. Wong share voting and dispositive power with respect to the shares held by Linden Capital L.P.

(8) Represents 1,479,894 outstanding shares of common stock beneficially owned by Aspire Capital Fund LLC, and 1,061,946 shares of common stock issuable upon exercise of warrants. The warrants are only exercisable to the extent that the holders thereof and their affiliates would beneficially own no more than 9.99% of the outstanding common stock after exercise and the holders disclaim beneficial ownership of shares of common stock underlying their warrants to the extent that their beneficial ownership of common stock would exceed 9.99%. Aspire Capital Partners LLC (“Aspire Partners”) is the Managing Member of Aspire Capital Fund LLC (“Aspire Fund”). SGM Holdings Corp (“SGM”) is the Managing Member of Aspire Partners. Mr. Steven G. Martin (“Mr. Martin”) is the president and sole shareholder of SGM, as well as a principal of Aspire Partners. Mr. Erik J. Brown (“Mr. Brown”) is the president and sole shareholder of Red Cedar Capital Corp (“Red Cedar”), which is a principal of Aspire Partners. Mr. Christos Komissopoulos (“Mr. Komissopoulos”) is president and sole shareholder of Chrisko Investors Inc. (“Chrisko”), which is a principal of Aspire Partners. Each of Aspire Partners, SGM, Red Cedar,

Chrisko, Mr. Martin, Mr. Brown, and Mr. Komissopoulos may be deemed to be a beneficial owner of common stock held by Aspire Fund. Each of Aspire Partners, SGM, Red Cedar, Chrisko, Mr. Martin, Mr. Brown, and Mr. Komissopoulos disclaims beneficial ownership of the common stock held by Aspire Fund.

(9) Represents 1,430,308 outstanding shares of common stock beneficially owned by Laurence W. Lytton and 707,964 shares of common stock issuable upon exercise of warrants. The warrants are only exercisable to the extent that the holders thereof and their affiliates would beneficially own no more than 9.99% of the outstanding common stock after exercise.

(10) Represents 353,982 outstanding shares of common stock beneficially owned by Lincoln Park Capital Fund, LLC and 353,982 shares of common stock issuable upon exercise of warrants. The warrants are only exercisable to the extent that the holders thereof and their affiliates would beneficially own no more than 9.99% of the outstanding common stock after exercise. Joshua Scheinfeld and Jonathan Cope, the principals of Lincoln Park Capital Fund, LLC are deemed to be beneficial owners of all the shares of common stock owned by Lincoln Park Capital Fund, LLC. Messrs. Scheinfeld and Cope have shared voting and dispositive power with respect to the shares held by Lincoln Park Capital Fund, LLC.

(11) Represents 488,935 outstanding shares of common stock beneficially owned by Arcus Ventures Fund II, LP and Arcus Ventures Fund, LP and 176,991 shares of common stock issuable upon exercise of warrants. The warrants are only exercisable to the extent that the holders thereof and their affiliates would beneficially own no more than 9.99% of the outstanding common stock after exercise. The shares and warrants held by Arcus Ventures Fund, LP and Arcus Ventures Fund II, LP are indirectly held by Arcus Ventures Management GP LP; the sole general partner of Arcus Ventures Fund, LP and Arcus Ventures Management GP II, LP; the sole general partner and each individual of the general partner Steven Soignet and James Dougherty. Steven Soignet and James Dougherty share voting and dispositive power with respect to the shares held by both Arcus Ventures Fund, LP and Arcus Ventures Fund II, LP.

(12) Represents 324,800 outstanding shares of common stock beneficially owned by Rosalind Master Fund L.P. and 150,000 shares of common stock issuable upon exercise of warrants. The warrants are only exercisable to the extent that the holders thereof and their affiliates would beneficially own no more than 9.99% of the outstanding common stock after exercise.

(13) Represents 136,558 outstanding shares of common stock beneficially owned by BioBrit, LLC and 88,495 shares of common stock issuable upon exercise of warrants. The warrants are only exercisable to the extent that the holders thereof and their affiliates would beneficially own no more than 9.99% of the outstanding common stock after exercise.

In April 2018, following the completion of the transactions contemplated by the securities purchase agreement, Theodore T. Wang, Ph.D., the Chief Investment Officer and Chief Executive Officer of Puissance Capital Management, was appointed to our board of directors. In connection with the transactions contemplated by the securities purchase agreement, we engaged Angel Pond Capital LLC as a placement agent and paid Angel Pond a placement agent fee of approximately $1.9 million. Angel Pond is affiliated through common control with Puissance Capital Management.

In March 2017, we entered into a common stock purchase agreement, or the Aspire Agreement, with Aspire Capital Fund, LLC, or Aspire, pursuant to which, upon the terms and subject to the conditions and limitations set forth in the Aspire Agreement, Aspire committed to purchase up to an aggregate of $21.0 million of shares of our common stock at our request from time to time over a thirty month period.

In November 2016, we completed an underwritten follow-on public offering pursuant to which we issued and sold an aggregate of 3,018,750 shares of our common stock, at a price to the public of $5.75 per share. New Enterprise Associates 14, L.P. purchased 869,565 shares of the common stock in the offering for a total purchase price of approximately $5.0 million. Mr. Paul Walker, a member of our board of directors, is affiliated with New Enterprise Associates.

Except with respect to the foregoing and the transactions contemplated by the securities purchase agreement as described above, none of the selling stockholders (or their control persons) has, or within the past three years has had, any position, office or other material relationship with us or any of our affiliates.

We are registering the shares of common stock issued to the selling stockholders and issuable upon exercise of the warrants issued to the selling stockholders to permit the resale of these shares of common stock by the selling stockholders from time to time from after the date of this prospectus. We will not receive any of the proceeds from the sale by the selling stockholders of

the shares of common stock. We will bear all fees and expenses incident to our obligation to register the shares of common stock.

Each selling stockholder may, from time to time, sell any or all of their shares of common stock covered hereby on The Nasdaq Global Market or any other stock exchange, market or trading facility on which the shares are traded or in private transactions. These sales may be at fixed prices, at prevailing market prices at the time of the sale, at varying prices determined at the time of sale, or privately negotiated prices. A selling stockholder may use any one or more of the following methods when selling shares:

• ordinary brokerage transactions and transactions in which the broker-dealer solicits purchasers;

• block trades in which the broker-dealer will attempt to sell the shares as agent but may position and resell a portion of the block as principal to facilitate the transaction;

• purchases by a broker-dealer as principal and resale by the broker-dealer for its account;

• an exchange distribution in accordance with the rules of the applicable exchange;

• in transactions through broker-dealers that agree with the selling stockholders to sell a specified number of such shares at a stipulated price per share;

• through the writing or settlement of options or other hedging transactions, whether through an options exchange or otherwise;

The selling stockholders may also sell the shares of common stock under Rule 144 under the Securities Act, if available, rather than under this prospectus.

Broker-dealers engaged by the selling stockholders may arrange for other brokers-dealers to participate in sales. Broker-dealers may receive commissions or discounts from the selling stockholders (or, if any broker-dealer acts as agent for the purchaser of shares, from the purchaser) in amounts to be negotiated, but, except as set forth in a supplement to this prospectus, in the case of an agency transaction not in excess of a customary brokerage commission in compliance with FINRA Rule 2440; and in the case of a principal transaction a markup or markdown in compliance with FINRA IM-2440-1.

In connection with the sale of the shares of common stock or interests therein, the selling stockholders may enter into hedging transactions with broker-dealers or other financial institutions, which may in turn engage in short sales of the shares of common stock in the course of hedging the positions they assume. The selling stockholders may also sell the shares of common stock short and deliver these securities to close out their short positions or to return borrowed shares in connection with such short sales, or loan or pledge the shares of common stock to broker-dealers that in turn may sell these securities. The selling stockholders may also enter into option or other transactions with broker-dealers or other financial institutions or create one or more derivative securities which require the delivery to such broker-dealer or other financial institution of shares of common stock offered by this prospectus, which shares such broker-dealer or other financial institution may resell pursuant to this prospectus (as supplemented or amended to reflect such transaction).

The selling stockholders and any broker-dealers or agents that are involved in selling the shares of common stock may be deemed to be “underwriters” within the meaning of the Securities Act in connection with such sales. In such event, any commissions received by such selling stockholders, broker-dealers or agents and any profit on the resale of the shares purchased by them may be deemed to be underwriting commissions or discounts under the Securities Act. Selling stockholders who are “underwriters” within the meaning of Section 2(a)(11) of the Securities Act will be subject to the prospectus delivery requirements of the Securities Act and may be subject to certain statutory liabilities of, including but not limited to, Sections 11, 12 and 17 of the Securities Act and Rule 10b-5 under the Exchange Act. In no event shall any broker-dealer receive fees, commissions and markups which, in the aggregate, would exceed eight percent (8%).

We are required to pay certain fees and expenses incurred by us incident to the registration of the shares. We have agreed to indemnify the selling stockholders against certain losses, claims, damages and liabilities, including liabilities under the Securities Act, and the selling stockholders may be entitled to contribution. We may be indemnified by the selling stockholders against certain losses, claims, damages and liabilities, including liabilities under the Securities Act that may arise from any written information furnished to us by the selling stockholders specifically for use in this prospectus, or we may be entitled to contribution.

The selling stockholders will be subject to the prospectus delivery requirements of the Securities Act including Rule 172 thereunder unless an exemption therefrom is available.

We agreed to cause the registration statement of which this prospectus is a part to remain effective with respect to each selling stockholder until the earlier to occur of (i) the third anniversary of the effective date of this Registration Statement, (ii) the date on which all of the shares and warrants shares held by such selling stockholder (other than a selling stockholder that would beneficially own more than 10% or more or our outstanding shares of common stock assuming all warrant shares held by such selling stockholder are outstanding) and registered for resale under this Registration Statement may be sold under Rule 144 under the Securities Act within a three month period or, (iii) immediately prior to the closing of a change in control. The shares of common stock will be sold only through registered or licensed brokers or dealers if required under applicable state securities laws. In addition, in certain states, the shares of common stock covered hereby 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 is complied with.

Under applicable rules and regulations under the Exchange Act, any person engaged in the distribution of the shares of common stock may not simultaneously engage in market making activities with respect to the shares of common stock for the applicable restricted period, as defined in Regulation M, prior to the commencement of the distribution. In addition, the selling stockholders will be subject to applicable provisions of the Exchange Act and the rules and regulations thereunder, including Regulation M, which may limit the timing of purchases and sales of shares of common stock by the selling stockholders or any other person. We will make copies of this prospectus available to the selling stockholders and have informed them of the need to deliver a copy of this prospectus at or prior to the time of the sale (including by compliance with Rule 172 under the Securities Act).

There can be no assurance that any selling stockholder will sell any or all of the shares of common stock we registered on behalf of the selling stockholders pursuant to the registration statement of which this prospectus forms a part.

Once sold under the registration statement of which this prospectus forms a part, the shares of common stock will be freely tradable in the hands of persons other than our affiliates.

The validity of the common stock being offered hereby has been passed upon for us by Cooley LLP, San Diego, California.

Ernst & Young LLP, independent registered public accounting firm, has audited our consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2017, as set forth in their report (which contains an explanatory paragraph describing conditions that raise substantial doubt about the Company’s ability to continue as a going concern as described in Note 1 to the consolidated financial statements) which is incorporated by reference in this prospectus and elsewhere in the registration statement. Our financial statements are incorporated by reference in reliance on Ernst & Young LLP’s report, given on their authority as experts in accounting and auditing.

This prospectus is part of a registration statement we filed with the SEC. This prospectus does not contain all of the information set forth in the registration statement and the exhibits to the registration statement. For further information with respect to us and the common stock we are offering under this prospectus, we refer you to the registration statement and the exhibits and schedules filed as a part of the registration statement. Neither we nor any agent, underwriter or dealer has authorized any person to provide you with different information. We are not making an offer of common stock in any state where the offer is not permitted. You should not assume that the information in this prospectus is accurate as of any date other than the date on the front page of this prospectus, regardless of the time of delivery of this prospectus or any sale of common

We file annual, quarterly and current reports, proxy statements and other information with the SEC. You may read and copy the registration statement, as well as any other document filed by us with the SEC, at the SEC’s Public Reference Room at 100 F Street NE, Washington, D.C. 20549. You can also request copies of these documents by writing to the SEC and paying a fee for the copying cost. You may obtain information on the operation of the Public Reference Room by calling the SEC at (800) SEC-0330. The SEC maintains a website that contains reports, proxy statements and other information regarding issuers that file electronically with the SEC, including Iridium. The address of the SEC website is www.sec.gov.

We maintain a website at www.traconpharma.com. Information contained in or accessible through our website does not constitute a part of this prospectus.

The SEC allows us to “incorporate by reference” information into this prospectus, which means that we can disclose important information to you by referring you to another document filed separately with the SEC. The documents incorporated by reference into this prospectus contain important information that you should read about us.

We also incorporate by reference into this prospectus 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 filed by us with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act (i) after the date of the initial filing of the registration statement of which this prospectus forms a part and prior to effectiveness of the registration statement, and (ii) after the date of this prospectus but prior to the termination of the offering. These documents including, without limitation, Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K, as well as proxy statements.

We will provide to each person, including any beneficial owner, to whom a prospectus is delivered, without charge upon written or oral request, a copy of any or all of the documents that are incorporated by reference into this prospectus but not delivered with the prospectus, including exhibits which are specifically incorporated by reference into such documents. You should direct any requests for documents by writing us at 4350 La Jolla Village Drive, Suite 800, San Diego, California 92122 or telephoning us at (858) 550-0780.

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

The following table sets forth the estimated costs and expenses, other than underwriting discounts and commissions, payable by us in connection with the offering of common stock being registered. The selling stockholders will not bear any portion of such expenses. All the amounts shown are estimates, except for the SEC registration fee.

We are incorporated under the laws of the State of Delaware. Section 145 of the Delaware General Corporation Law provides that a Delaware corporation may indemnify any persons who were, are, or are threatened to be made, parties to any threatened, pending or completed action, suit or proceeding, whether civil, criminal, administrative or investigative (other than an action by or in the right of such corporation), by reason of the fact that such person is or was an officer, director, employee or agent of such corporation, or is or was serving at the request of such corporation as an officer, director, employee or agent of another corporation or enterprise. The indemnity may include expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by such person in connection with such action, suit or proceeding, provided that such person acted in good faith and in a manner he or she reasonably believed to be in or not opposed to the corporation’s best interests and, with respect to any criminal action or proceeding, had no reasonable cause to believe that his or her conduct was illegal. A Delaware corporation may indemnify any persons who were, are, or are threatened to be made, a party to any threatened, pending or completed action or suit by or in the right of the corporation by reason of the fact that such person is or was a director, officer, employee or agent of such corporation, or is or was serving at the request of such corporation as a director, officer, employee or agent of another corporation or enterprise. The indemnity may include expenses (including attorneys’ fees) actually and reasonably incurred by such person in connection with the defense or settlement of such action or suit provided such person acted in good faith and in a manner he or she reasonably believed to be in or not opposed to the corporation’s best interests except that no indemnification is permitted without judicial approval if the officer or director is adjudged to be liable to the corporation. Where an officer or director is successful on the merits or otherwise in the defense of any action referred to above, the corporation must indemnify him or her against the expenses (including attorneys’ fees) actually and reasonably incurred.

Our amended and restated certificate of incorporation and amended and restated bylaws provide for the indemnification of our directors and officers to the fullest extent permitted under the Delaware General Corporation Law.

Section 102(b)(7) of the Delaware General Corporation Law permits a corporation to provide in its certificate of incorporation that a director of the corporation shall not be personally liable to the corporation or its stockholders for monetary damages for breach of fiduciary duties as a director, except for liability for any:

•act or omission not in good faith or that involves intentional misconduct or a knowing violation of law;

•breach of a director’s duty of loyalty to the corporation or its stockholders.

Our amended and restated certificate of incorporation includes such a provision. Expenses incurred by any officer or director in defending any such action, suit or proceeding in advance of its final disposition will be paid by us upon delivery to us of an undertaking, by or on behalf of such director or officer, to repay all amounts so advanced if it shall ultimately be determined that such director or officer is not entitled to be indemnified by us.

Section 174 of the Delaware General Corporation Law provides, among other things, that a director who willfully or negligently approves of an unlawful payment of dividends or an unlawful stock purchase or redemption, may be held liable for such actions. A director who was either absent when the unlawful actions were approved or dissented at the time may avoid liability by causing his or her dissent to such actions to be entered in the books containing minutes of the meetings of the board of directors at the time such action occurred or immediately after such absent director receives notice of the unlawful acts.

As permitted by the Delaware General Corporation Law, we have entered into, and continue to enter, into separate indemnity agreements with each of our directors and executive officers that require us to indemnify such persons against any and all costs and expenses (including attorneys’, witness or other professional fees) actually and reasonably incurred by such persons in connection with any action, suit or proceeding (including derivative actions), whether actual or threatened, to which any such person may be made a party by reason of the fact that such person is or was a director or officer or is or was acting or serving as an officer, director, employee or agent of ours or any of our affiliated enterprises. Under these agreements, we are not required to provide indemnification for certain matters, including:

The indemnification agreements also set forth certain procedures that will apply in the event of a claim for indemnification thereunder.

There is at present no pending litigation or proceeding involving any of our directors or executive officers as to which indemnification is required or permitted, and we are not currently aware of any threatened litigation or proceeding that may result in a claim for indemnification.

We have an insurance policy in place that covers our officers and directors with respect to certain liabilities, including liabilities arising under the Securities Act or otherwise.

The securities purchase agreement that we entered into with the selling stockholders identified in the prospectus included in this registration statement provides for cross indemnification in connection with registration of our common stock on behalf of such selling stockholder, including for certain liabilities arising under the Securities Act.

(1)To file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement:

provided, however, that the undertakings set forth in paragraphs (1)(i), (1)(ii) and (1)(iii) above do not apply if the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the Commission by the registrant pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 that are incorporated by reference in this registration statement or is contained in a form of prospectus filed pursuant to Rule 424(b) that is part of this registration statement.

(2)That, for the purpose of determining any liability under the Securities Act of 1933, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

(3)To remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering.

(4)That, for the purpose of determining liability under the Securities Act of 1933 to any purchaser:

(i)Each prospectus filed by the registrant pursuant to Rule 424(b)(3) shall be deemed to be part of the registration statement as of the date the filed prospectus was deemed part of and included in the registration statement; and

(ii)Each prospectus required to be filed pursuant to Rule 424(b)(2), (b)(5), or (b)(7) as part of a registration statement in reliance on Rule 430B relating to an offering made pursuant to Rule 415(a)(1)(i), (vii), or (x) for the purpose of providing the information required by Section 10(a) of the Securities Act of 1933 shall be deemed to be part of and included in the registration statement as of the earlier of the date such form of prospectus is first used after effectiveness or the date of the first contract of sale of securities in the offering described in the prospectus. As provided in Rule 430B, for liability purposes of the issuer and any person that is at that date an underwriter, such date shall be deemed to be a new effective date of the registration statement relating to the securities in the registration statement to which that prospectus relates, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof. Provided, however , that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale prior to such effective date, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such effective date.

(5)That, for the purpose of determining liability of the registrant under the Securities Act of 1933 to any purchaser in the initial distribution of the securities, the undersigned registrant undertakes that in a primary offering of securities of the undersigned registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned registrant will be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser: (i) any preliminary prospectus or prospectus of the undersigned registrant relating to the offering required to be filed pursuant to Rule 424; (ii) any free writing prospectus relating to the offering prepared by or on behalf of the undersigned registrant or used or referred to by the undersigned registrant; (iii) the portion of any other free writing prospectus relating to the offering containing material information about the undersigned registrant or its securities provided by or on behalf of the undersigned registrant; and (iv) any other communication that is an offer in the offering made by the undersigned registrant to the purchaser.

(6)That, for purposes of determining any liability under the Securities Act of 1933, each filing of the registrant’s annual report pursuant to Section 13(a) or 15(d) of the Securities Exchange Act of 1934 (and, where applicable, each filing of an employee benefit plan’s annual report pursuant to Section 15(d) of the Securities Exchange Act of 1934) that is incorporated by reference in the registration statement shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

Insofar as indemnification for liabilities arising under the Securities Act of 1933 may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, the registrant has been advised that in the opinion of the Commission such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act of 1933 and will be governed by the final adjudication of such issue.

Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of San Diego, State of California, on the 9^th day of May, 2018.

Know All Persons By These Presents , that each person whose signature appears below constitutes and appoints Charles P. Theuer, MD., Ph.D. and Patricia L. Bitar, and each or any one of them, as his or her true and lawful attorney-in-fact and agent, with full power of substitution and re-substitution, for him or her and in his or her name, place and stead, in any and all capacities, to sign any and all amendments (including post- effective amendments and registration statements filed pursuant to Rule 462 under the Securities Act) to this Registration Statement, and to file the same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in connection therewith, as fully to all intents and purposes as he or she might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents, or any of them, or their or his or her substitutes or substitute, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act, this registration statement has been signed by the following persons in the capacities and on the dates indicated.


Signature	Title	Date

/s/ Charles P. Theuer, M.D., Ph.D.	President, Chief Executive Officer and Member of the Board of Directors	May 9, 2018
Charles P. Theuer, M.D., Ph.D.	(Principal Executive Officer)

/s/ Patricia L. Bitar, CPA	Chief Financial Officer, Assistant Secretary and Treasurer	May 9, 2018
Patricia L. Bitar, CPA	(Principal Financial and Accounting Officer)

/s/ William R. LaRue	Member of the Board of Directors	May 9, 2018
William R. LaRue

/s/ Martin A. Mattingly, Pharm. D.	Member of the Board of Directors	May 9, 2018
Martin A. Mattingly, Pharm.D.

/s/ J. Rainer Twiford, J.D., Ph.D	Member of the Board of Directors	May 9, 2018
J. Rainer Twiford, J.D., Ph.D.

/s/ Paul Walker	Member of the Board of Directors	May 9, 2018
Paul Walker

/s/ Theodore T. Wang, Ph.D.	Member of the Board of Directors	May 9, 2018
Theodore T. Wang, Ph.D.

/s/ Stephen T. Worland, Ph.D.	Member of the Board of Directors	May 9, 2018
Stephen T. Worland, Ph.D.


ABOUT THIS PROSPECTUS	i
SUMMARY	1
RISK FACTORS	3
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS	3
USE OF PROCEEDS	3
SELLING STOCKHOLDERS	3
PLAN OF DISTRIBUTION	7
LEGAL MATTERS	9
EXPERTS	9
WHERE YOU CAN FIND MORE INFORMATION	9
INCORPORATION OF CERTAIN INFORMATION BY REFERENCE	11


SEC registration fee	$ 8,492
Accounting fees and expenses	15,000
Legal fees and expenses	25,000
Printing and miscellaneous expenses	5,000
Total	$ 53,492


3.1(1)	Amended and Restated Certificate of Incorporation
3.2(1)	Amended and Restated Bylaws
4.1(2)	Form of Common Stock Certificate
4.2(3)	Form of Pre-Funded Warrant
4.3(3)	Form of Common Warrant
5.1	Opinion of Cooley LLP
23.1	Consent of Independent Registered Public Accounting Firm
23.2	Consent of Cooley LLP (included in Exhibit 5.1)
24.1	Power of Attorney (included on signature page)