424B5

We are offering 2,500 shares of our Series D Convertible Preferred Stock (“Series D Preferred Stock”) and warrants to purchase up to 1,250,000 shares of our common stock (and the common stock issuable from time to time upon conversion of the Series D Preferred Stock and upon exercise of each of the warrants), pursuant to this prospectus supplement and the accompanying prospectus. Each investor will receive a warrant to purchase 500 shares of our common stock at an exercise price of $3.00 per share for each share of Series D Preferred Stock purchased. The Series D Preferred Stock and warrants are immediately separable and will be issued separately. The warrants will be exercisable immediately and will expire on the one year anniversary from the date of issuance.

Our common stock is listed on the NASDAQ Capital Market under the symbol “SNSS”. On October 24, 2017, the last reported sale price of our common stock was $1.85 per share. There is no established public trading market for the Series D Preferred Stock or the warrants and we do not expect a market to develop. In addition, we do not intend to apply for listing of the Series D Preferred Stock or the warrants on any securities exchange or recognized trading system.

Each share of Series D Preferred Stock is convertible into 1,000 shares of our common stock at any time at the option of the holder, provided that the holder will be prohibited from converting the Series D Preferred Stock into shares of our common stock if, as a result of such conversion, the holder, together with its affiliates, would own more than 9.98% of the total number of shares of our common stock then issued and outstanding. In the event of our liquidation, dissolution, or winding up, holders of our Series D Preferred Stock will receive a payment equal to $0.0001 per share of Series D Preferred Stock before any proceeds are distributed to the holders of our common stock. Shares of Series D Preferred Stock will generally have no voting rights, except as required by law and except that the consent of holders of a majority of the outstanding Series D Preferred Stock will be required to amend the terms of the Series D Preferred Stock.

Our business and an investment in our securities include significant risks. See “Risk Factors” beginning on page S-7 of this prospectus supplement and in our Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2017, which has been filed with the Securities and Exchange Commission and is incorporated by reference in this prospectus supplement and the accompanying prospectus.

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

The underwriters expect to deliver the shares of common stock and accompanying warrants against payment on or about October 27, 2017.

This document is in two parts. The first part is this prospectus supplement, which describes the specific terms of the offering and also adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference into this prospectus supplement and the accompanying prospectus. The second part, the accompanying prospectus dated June 10, 2014, including the documents incorporated by reference, provides more general information. Generally, when we refer to this prospectus, we are referring to both parts of this document combined. To the extent there is a conflict between the information contained in this prospectus supplement, on the one hand, and the information contained in the accompanying prospectus or in any document incorporated by reference that was filed with the Securities and Exchange Commission, or SEC, before the date of this prospectus supplement, on the other hand, you should rely on the information in this prospectus supplement. If any statement in one of these documents is inconsistent with a statement in another document having a later date—for example, a document incorporated by reference in the accompanying prospectus—the statement in the document having the later date modifies or supersedes the earlier statement. You should read this prospectus supplement and the accompanying prospectus, including the information incorporated by reference and any free writing prospectus that we have authorized for use in connection with this offering, in their entirety before making an investment decision.

You should rely only on the information contained or incorporated by reference in this prospectus supplement and the accompanying prospectus, along with the information contained in any free writing prospectus that we have authorized for use in connection with this offering. If the description of the offering varies between this prospectus supplement and the accompanying prospectus, you should rely on the information in this prospectus supplement. We and the underwriters have not authorized anyone to provide you with different or additional information. You should assume that the information appearing in this prospectus supplement, the accompanying prospectus, the documents incorporated by reference in this prospectus supplement and the accompanying prospectus, and in any free writing prospectus that we have authorized for use in connection with this offering is accurate only as of the respective dates of those documents. Our business, financial condition, results of operations and prospects may have changed since those dates.

This prospectus supplement contains summaries of certain provisions contained in some of the documents described herein, but reference is made to the actual documents for complete information. All of the summaries are qualified in their entirety by the actual documents. Copies of some of the documents referred to herein have been filed, will be filed or will be incorporated by reference as exhibits to the registration statement of which this prospectus supplement is a part, and you may obtain copies of those documents as described below under the heading “Where You Can Find More Information.”

PROSPECTUS SUPPLEMENT SUMMARY

This summary highlights certain information about us, this offering and information appearing elsewhere in this prospectus supplement, in the accompanying prospectus and in the documents we incorporate by reference. This summary is not complete and does not contain all of the information that you should consider before making an investment decision. To fully understand this offering and its consequences to you, you should read this entire prospectus supplement and the accompanying prospectus carefully, including the factors described under the headings “Risk Factors” in this prospectus supplement beginning on page S-7 and in our Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2017, together with any free writing prospectus we have authorized for use in connection with this offering and the financial statements and other information incorporated by reference in this prospectus supplement and the accompanying prospectus.

About Sunesis

Sunesis is a biopharmaceutical company focused on the development and commercialization of new oncology therapeutics for the treatment of solid and hematologic cancers. Our primary activities since incorporation have been conducting research and development internally and through corporate collaborators, in-licensing and out-licensing pharmaceutical compounds and technology, conducting clinical trials and raising capital.

In January 2014, we announced the expansion of our oncology pipeline through separate global licensing agreements for two preclinical kinase inhibitor programs. The first agreement, with Biogen Idec MA, Inc. (“Biogen”) is for global commercial rights to SNS-062, a selective non-covalently binding oral inhibitor of BTK. We filed a Clinical Trial Authorization application in the first quarter of 2016 in Belgium and enrolled the first patients in a Phase 1A study of SNS-062 in healthy volunteers. In September and again in in December 2016, we announced results from our Phase 1A study in healthy volunteers evaluating our oral non-covalent, reversible BTK inhibitor SNS-062. The study demonstrated a favorable safety, pharmacokinetic (“PK”) and pharmacodynamic (PD) profile for SNS-062 in healthy subjects. In December 2016 we filed an Investigational New Drug (“IND”) application with the FDA to conduct a Phase 1B/2 trial in patients with various B-cell malignancies. In January 2017, we announced that our IND application with the U.S. Food and Drug Administration (“FDA”), for SNS-062, is active and supports the initiation of the Phase 1B/2 study to assess the drug candidate’s safety and efficacy in patients with advanced B-cell malignancies after prior ibrutinib exposure, including in patients with C481S mutations. We expect to report interim data from the Phase 1B/2 study in the second quarter of 2018.

We are also developing a pre-clinical inhibitor of the novel target PDK1, which we believe to have the potential to be first-in-class. We are currently evaluating SNS-510, a PDK1 inhibitor, in pre-clinical absorption, distribution, metabolism and excretion, and toxicology studies, and we expect to complete such evaluation with the goal of declaring a development candidate before the end of 2017.

We are in a collaboration with Takeda for the development of TAK-580 (formerly MLN2480), an oral pan-RAF inhibitor, for which Takeda is conducting a multi-arm, open-label Phase 1B study in combination with: nivolumab, a PD-1 checkpoint inhibitor; TAK-228, an oral mTORC 1/2 inhibitor; alisertib, an oral aurora A kinase inhibitor; and several chemotherapeutic agents, in adult patients with advanced non-hematologic malignancies.

We also own the rights to QINPREZO^TM (vosaroxin), our product candidate for the potential treatment of acute myeloid leukemia (“AML”). Vosaroxin is an anticancer quinolone derivative (“AQD”) -a class of compounds that has not been used previously for the treatment of cancer.

In October 2014, we announced the results of a Phase 3, multi-national, randomized, double-blind, placebo-controlled trial of vosaroxin in combination with cytarabine in patients with relapsed or refractory AML, or the VALOR trial. The VALOR trial did not meet its primary endpoint of demonstrating a statistically significant improvement in overall survival. However, based upon the favorable results of other predefined analyses of the data, in November 2014, we submitted a letter of intent to the European Medicines Agency (“EMA”) describing our intention to file a marketing authorization application (“MAA”) for marketing authorization of vosaroxin plus cytarabine for the treatment of relapsed or refractory AML. In June 2015, we met separately with the Rapporteur and Co-Rapporteur, who are two appointed members of the EMA’s Committee for Medicinal Products for Human Use (“CHMP”). Based upon feedback from these meetings, we filed an MAA with the EMA at the end of 2015. In April 2016, we received a list of questions relating to our MAA filing (the “Day 120 Questions”), and we responded to these questions in October 2016, and in December 2016 received a list of outstanding issues (the “Day 180 LOI”). In March 2017, we submitted responses to the EMA Day 180 List of Outstanding Issues issued by the CMPH as part of the centralized review process of the MAA for vosaroxin as a treatment for relapsed/refractory acute myeloid leukemia (“AML”) in patients aged 60 years and older. In April 2017, we presented to the Scientific Advisory Group—Oncology (“SAG-O”) and also to the CHMP. As a result of these interactions, feedback from its CHMP rapporteurs and its retained regulatory consultants and an internal assessment, we announced on May 1, 2017 the withdrawal of our MAA. It is our intention to continue to support investigator-sponsored group trials with vosaroxin and to resume company-sponsored studies if a development partner can be secured.

Financial Update

On a preliminary unaudited basis, we expect our cash and cash equivalents as of September 30, 2017 to be approximately $12.5 million. The number of shares of our common stock outstanding as of September 30, 2017 was 23,998,692. This estimate of cash and cash equivalents is our preliminary estimate based on currently available information. It does not present all necessary information for an understanding of our financial condition as of September 30, 2017 or our results of operations for the three months ended September 30, 2017. As we complete our quarter-end financial close process and finalize our third quarter 2017 unaudited financial statements, we will be required to make significant judgments in a number of areas that may result in a the estimate provided herein being different than the final audited financial information. This preliminary estimate has been prepared by and is the responsibility of our management. Our independent registered public accounting firm has not audited, reviewed or performed any procedures with respect to this preliminary estimate or the accounting treatment thereof and does not express an opinion or any other form of assurance with respect thereto. We expect to complete our unaudited financial statements for the quarter ended September 30, 2017 subsequent to the completion of this offering. It is possible that we or our independent registered public accounting firm may identify items that require us to make adjustments to the preliminary estimated cash balance set forth above and those changes could be material. Accordingly, undue reliance should not be placed on this preliminary estimate. The preliminary estimate is not necessarily indicative of any future period and should be read together with the sections titled “Risk Factors,” “Special Note Regarding Forward-Looking Statements,” and our financial statements, related notes and other financial information incorporated by reference in this prospectus supplement.

Corporate Information

We were incorporated in Delaware in February 1998 as Mosaic Pharmaceuticals, Inc., and we subsequently changed our name to Sunesis Pharmaceuticals, Inc. The address of our principal executive office is 395 Oyster Point Boulevard, Suite 400, South San Francisco, California 94080, and our telephone number is (650) 266-3500. Our website address is www.sunesis.com. Information found

on our website is not incorporated by reference into this prospectus supplement or the accompanying prospectus. For further information regarding us and our financial information, you should refer to our recent filings with the SEC. See “Where You Can Find More Information” and “Incorporation of Certain Information By Reference.”

Concurrent Offering of Common Stock and Warrants to Purchase Common Stock

Concurrently with this offering of Series D Preferred Stock and warrants and pursuant to a separate prospectus supplement, we are offering 7,500,000 shares of our common stock and warrants to purchase up to 3,750,000 shares of our common stock (and the common stock issuable from time to time upon exercise of each of the warrants), which we refer to herein as the common stock and warrants offering. The common stock and warrants offering is being conducted as a separate public offering by means of a separate prospectus supplement. This offering is not contingent upon the completion of the common stock and warrants offering and the common stock and warrants offering is not contingent upon the completion of this offering. We cannot assure you that either or both of the offerings will be completed.

Unless expressly stated otherwise, all references in this prospectus supplement and the accompanying prospectus to “the Company,” “Sunesis,” “we,” “us,” “our,” or similar references mean Sunesis Pharmaceuticals, Inc. and our wholly owned subsidiaries on a consolidated basis. This prospectus supplement, the accompanying prospectus and the information incorporated 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 prospects, or included in any free writing prospectus that we have authorized for use in connection with this offering, are the property of their respective owners.

The Offering

Series D Preferred Stock offered by us

2,500 shares of Series D Preferred Stock. This prospectus also relates to the offering of the shares of common stock issuable upon conversion of the Series D Preferred Stock.

Conversion

Each share of our Series D Preferred Stock is convertible into 1,000 shares of our common stock at any time at the option of the holder, provided that the holder will be prohibited from converting Series D Preferred Stock into shares of our common stock if, as a result of such conversion, the holder, together with its affiliates, would own more than 9.98% of the total number of shares of our common stock then issued and outstanding.

Liquidation preferences

In the event of our liquidation, dissolution, or winding up, holders of our Series D Preferred Stock will receive a payment equal to $0.0001 per share of Series D Preferred Stock before any proceeds are distributed to the holders of our common stock.

Voting rights

Shares of Series D Preferred Stock will generally have no voting rights, except as required by law and except that the consent of holders of a majority of the outstanding Series D Preferred Stock will be required to amend the terms of the Series D Preferred Stock.

Dividends

Shares of Series D Preferred Stock will not be entitled to receive any dividends, unless and until specifically declared by our board of directors.

Warrants offered by us

Warrants to purchase up to 1,250,000 shares of our common stock, immediately exercisable, which expire on the first year anniversary from the date of issuance. The warrants have an exercise price of $3.00 per whole share of common stock, subject to adjustment. For more information, see the section entitled “Description of Securities We Are Offering — Warrants” on page S-15. Subject to applicable laws, the warrants are separately tradeable immediately after issuance at the option of the holders and may be transferred at the option of the holders. This prospectus supplement also relates to the offering of the shares of common stock issuable upon exercise of the warrants.

Common stock to be outstanding after this offering

23,513,194 shares (assuming none of the shares of Series D Preferred Stock has been converted and none of warrants issued in this offering are exercised).

Risk factors

Our business and an investment in our common stock include significant risks. See “Risk Factors” beginning on page S-7.

Use of proceeds

We currently intend to use the net proceeds from this offering and the concurrent common stock and warrants offering to fund the continued development of SNS-062 and additional kinase inhibitors and for working capital and general corporate purposes. See “Use of Proceeds” on page S-11.

Concurrent common stock and warrants offering

Concurrently with this offering of Series D Preferred Stock and warrants and pursuant to a separate prospectus supplement, we are offering 7,500,000 shares of our common stock and warrants to purchase up to 3,750,000 shares of our common stock (and the common stock issuable from time to time upon exercise of each of the warrants). The common stock and warrants offering is being conducted as a separate public offering by means of a separate prospectus supplement. This offering is not contingent upon the completion of the common stock and warrants offering and the common stock and warrants offering is not contingent upon the completion of this offering.

Listing

Our common stock is listed on the NASDAQ Capital Market under the trading symbol “SNSS.” There is no established public trading market for the offered Series D Preferred Stock or warrants and we do not expect a market to develop. In addition, we do not intend to apply for listing of the Series D Preferred Stock or warrants on any securities exchange or recognized trading system. The warrants will be issued in book-entry form pursuant to a warrant agency agreement between us and American Stock Transfer & Trust Company, as warrant agent.

The number of shares of common stock to be outstanding immediately after this offering as shown above is based on 23,513,194 shares of common stock outstanding as of the close of business on June 30, 2017. This number excludes, as of the close of business on June 30, 2017, the shares of common stock issuable upon exercise of the warrants offered hereby and also excludes:

∎

options representing the right to purchase a total of 2,629,325 shares of common stock at a weighted average exercise price of $12.56 per share;

∎

993,523 shares of common stock which were reserved for future equity awards that may be granted in the future under our equity incentive plans;

∎

202,773 shares of common stock which were reserved for issuance under our employee stock purchase plan;

∎

warrants representing the right to purchase a total of 218,247shares of common stock at exercise prices between $3.25 and $13.32 per share;

∎

2,723,168 shares of our common stock, issuable upon conversion of 16,339 shares of our Series B Convertible Preferred Stock;

∎

1,558,000 shares of our common stock issuable upon the conversion of 1,558 shares of our Series C Convertible Preferred Stock;

∎

7,500,000 shares of our common stock being offered by us in connection with our concurrent common stock and warrants offering;

∎

3,750,000 shares of common stock reserved for issuance upon exercise of warrants being offered by us in connection with our concurrent common stock and warrants offering; and

∎

up to $9,718,223 of common stock remaining available to sold pursuant to a Controlled Equity Offering^SM sales agreement we entered into with Cantor Fitzgerald & Co., or Cantor Fitzgerald; provided that no common stock may be issued prior to the expiration of the 60-day lock-up period following this offering.

Subsequent to September 30, 2017, we have sold an additional 2,749,630 shares of common stock pursuant to the Controlled Equity Offering^SM sales agreement with Cantor Fitzgerald, for gross proceeds of approximately $6.1 million, and the number of shares of our common stock outstanding as of the date of this prospectus supplement is 26,748,322.

You should consider carefully the risks described below and discussed under the section captioned “Risk Factors” contained in our Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2017, which are incorporated by reference in this prospectus supplement and the accompanying prospectus in their entirety, together with all of the other information included in this prospectus supplement, the accompanying prospectus, the documents incorporated by reference in this prospectus supplement and the accompanying prospectus, and in any free writing prospectus that we have authorized for use in connection with this offering, before making an investment decision. If any of these risks actually occurs, our business, financial condition, results of operations and future prospects would likely be materially and adversely affected. In these circumstances, the market price of our common stock would likely decline, and you may lose all or part of your investment.

Management will have broad discretion as to the use of the proceeds from this offering and our concurrent common stock and warrants offering, and we may not use the proceeds effectively.

We have not allocated specific amounts of the net proceeds from this offering and our concurrent common stock and warrants offering for any specific purpose. Our management will have significant flexibility in applying the net proceeds of this offering and our concurrent common stock and warrants offering. You will be relying on the judgment of our management with regard to the use of these net proceeds and you will not have the opportunity, as part of your investment decision, to assess whether the proceeds are being used appropriately. It is possible that the net proceeds will be invested in a way that does not yield a favorable, or any, return for us. The failure of our management to use such funds effectively could have a material adverse effect on our business, financial condition, operating results and cash flow.

If you purchase the Series D Preferred Stock sold in this offering, and assuming its conversion into shares of our common stock, you will experience immediate and substantial dilution in your investment.

Because the price per share of our Series D Preferred Stock being offered is substantially higher than the book value of the number of shares of our common stock into which a share of our Series D Preferred Stock will be convertible, you will suffer immediate and substantial dilution in the net tangible book value of the shares of our common stock into which the Series D Preferred Stock you purchase in this offering will be convertible. Assuming the conversion of shares of the Series D Preferred Stock into shares of common stock, and based on a public offering price of $2,000 per share and a net tangible book value per share of our common stock of $0.53 as of June 30, 2017, if you purchase shares of our Series D Preferred Stock in this offering you will suffer immediate and substantial dilution of $1.34 per share in the net tangible book value of the common stock into which a share of our Series D Preferred Stock will be convertible, excluding the issuance of shares of common stock in our concurrent common stock and warrants offering. See “Dilution” on page S-12 for a more detailed discussion of the dilution you will incur in connection with this offering.

Our stockholders will experience substantial additional dilution upon issuance of common stock and exercise of warrants to purchase common stock to be issued pursuant to our concurrent common stock and warrants offering.

The issuance of shares of our common stock and exercise of warrants to purchase common stock to be sold pursuant to the concurrent common stock and warrants offering would be substantially dilutive to the outstanding shares of common stock. Any dilution or potential dilution may cause our stockholders to sell their shares, which would contribute to a downward movement in the stock price of our common stock.

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

In order to raise additional capital, we may at any time, including during the pendency of this offering, 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.

There is no public market for the Series D Preferred Stock or warrants to purchase common stock in this offering.

There is no established public trading market for the Series D Preferred Stock or warrants being sold in this offering, and we do not expect a market to develop. In addition, we do not intend to apply to list the Series D Preferred Stock or warrants on any securities exchange or recognized trading system. Without an active market, the liquidity of the Series D Preferred Stock or warrants will be limited.

The warrants are a risky investment. You may not be able to recover your investment in the warrants, and the warrants may expire worthless.

The exercise price per share of the accompanying warrants being offered by this prospectus exceeds the last reported sale price of our common stock on the date of this prospectus supplement. The amount paid in excess of the value of our common stock represents the value of your investment in the warrants. The period the warrants are to be exercisable is only 12 months from the date of the issuance, which is a relatively short exercise period for warrants issued to the public.

If our common stock price does not increase to an amount sufficiently above the exercise prices of the warrants during the periods the warrants are exercisable, you will be unable to recover any of your investment in the warrants. There can be no assurance that any of the factors that could impact the trading price of our common stock will result in the trading price increasing to an amount that will exceed the exercise price or the price required for you to achieve a positive return on your investment in the warrants.

Holders of the warrants will have no rights as common stockholders until they acquire our common stock.

Until you acquire shares of our common stock upon exercise of the warrants, you will have no rights with respect to our common stock issuable upon exercise of the warrants, including the right to receive dividend payments, vote or respond to tender offers. Upon exercise of your warrants, you will be entitled to exercise the rights of a common stockholder only as to matters for which the record date occurs after the exercise date.

The statements in this prospectus supplement, the accompanying prospectus and the documents we have filed with the SEC that are incorporated by reference in this prospectus supplement contain “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended, or the Securities Act, Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act, or the “safe harbor” created by those sections. These statements involve known and unknown risks, uncertainties and important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements. All statements, other than statements of historical facts, are forward-looking statements for purposes of these provisions, including without limitation any statements relating to:

In some cases, you can identify forward-looking statements by terms such as “anticipates,” “believe,” “continue,” “could,” “estimates,” “expects,” “intend,” “look forward,” “may,” “could,” “plans,” “potential,” or “will” or the negative thereof or other comparable terminology intended to identify forward-looking statements. Discussions containing these forward-looking statements may be found, among other places, in the “Business” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” sections incorporated by reference from our most recent Annual Report on Form 10-K and our Quarterly Reports on Form 10-Q, as well as any amendments thereto reflected in subsequent filings with the SEC, and in Current Reports on Form 8-K filed with the SEC. Forward-looking statements reflect our current views with respect to future events, are based on assumptions and are subject to risks, uncertainties and other important factors. We discuss many of these risks, uncertainties and other important factors in greater detail under the heading “Risk Factors” in this prospectus supplement and in our Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2017, which are incorporated by reference in this prospectus supplement and the accompanying prospectus in their entirety. Given these risks, uncertainties and other important factors, you should not place undue reliance on these forward-looking statements. Also, these forward-looking statements represent our estimates and assumptions only as of the date such forward-looking statements are made. You should carefully read this prospectus supplement and the accompanying prospectus, together with the information incorporated herein by reference as described under the heading “Where You Can Find More Information,” in this prospectus supplement and the accompanying prospectus, completely and with the understanding that our actual future results may be materially different from what we expect. We can give no assurances that any of the events anticipated by the forward-looking statements will occur or, if any of them do, what impact they will have on our

business, results of operations and financial condition. We hereby qualify these forward looking statements by these cautionary statements.

In addition, statements that “we believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based upon information available to us as of the date of this prospectus supplement, and while we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted an exhaustive inquiry into, or review of, all potentially available relevant information. These statements are inherently uncertain and investors are cautioned not to unduly rely upon these statements.

Except as required by law, we assume no obligation to update these forward-looking statements publicly, or to update the reasons actual results could differ materially from those anticipated in these forward-looking statements, even if new information becomes available in the future. You are advised, however, to consult any further disclosures we make on related subjects in our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q and Current Reports on Form 8-K.

We estimate that the net proceeds from the sale of the 2,500 shares of Series D Preferred Stock and accompanying warrants that we are offering, excluding the proceeds, if any, from the exercise of the warrants issued in this offering, will be approximately $4.6 million based on the public offering price of $2,000 per share of Series D Preferred Stock (and accompanying warrants), after deducting the estimated underwriting discount and estimated offering expenses payable by us. In addition, we estimate that the net proceeds we will receive from our concurrent common stock and warrants offering will be approximately $13.9 million, after deducting the underwriting discount and estimated offering expenses payable by us. This offering is not contingent upon the completion of the common stock and warrants offering and the common stock and warrants offering is not contingent upon the completion of this offering. We cannot assure you that either or both of the offerings will be completed.

We currently intend to use the net proceeds from the sale of our securities primarily to fund the continued development of SNS-062 and additional kinase inhibitors and for working capital and general corporate purposes. As of the date of this prospectus supplement, we cannot specify with certainty all of the particular uses of the proceeds from this offering and our concurrent common stock and warrants offering. Accordingly, we will retain broad discretion over the use of such proceeds. Pending the use of the net proceeds from this offering and our concurrent common stock and warrants offering as described above, we intend to invest the net proceeds in investment-grade, interest-bearing instruments.

Our net tangible book value as of June 30, 2017 was $12.5 million, or $0.53 per share of common stock. Net tangible book value per share is calculated by subtracting our total liabilities from our total tangible assets, and dividing this amount by the number of shares of common stock outstanding.

After giving effect to our sale of 2,500 shares of Series D Preferred Stock and warrants to purchase an additional 1,250,000 shares of common stock offered by us at the public offering price of $2,000 per share and accompanying warrants, assuming the conversion of 2,500 shares of Series D Preferred Stock into 2,500,000 shares of our common stock (excluding the effect of exercise of warrants to purchase shares of our common stock, to be issued in this offering and in our concurrent common stock and warrants offering), after deducting the estimated underwriting discount and estimated offering expenses payable by us, our as adjusted net tangible book value as of June 30, 2017 would have been approximately $17.1 million, or $0.66 per share. Assuming the completion of the offering, this represents an immediate increase in net tangible book value of $0.13 per share to existing stockholders and immediate dilution in net tangible book value of $1.34 per share to new investors purchasing our Series D Preferred Stock and accompanying warrants in this offering at the public offering price. The following table illustrates this dilution on a per share basis:

The above discussion and table are based on 23,513,194 shares of our common stock outstanding as of the close of business on June 30, 2017. This number excludes, as of the close of business on June 30, 2017, the shares of our common stock issuable upon exercise of the warrants offered hereby and also excludes:

You will experience dilution after giving effect to our sale of 7,500,000 shares of common stock offered by us in the concurrent common stock and warrants offering. Giving effect to both this offering and the concurrent common stock and warrants offering, our as adjusted net tangible book value as of June 30, 2017, would have been approximately $31.0 million, or $0.93 per share of common stock (assuming conversion of all shares of Series D Preferred Stock offered). Assuming the completion of this offering and the concurrent common stock and warrants offering, this represents an immediate increase in net tangible book value of $18.6 per share to existing stockholders and immediate dilution in net tangible book value of $1.07 per share to new investors participating in this offering at the public offering price (assuming conversion of all shares of Series D Preferred Stock offered).

To the extent that outstanding options have been or may be exercised or other shares issued, including pursuant to our concurrent common stock and warrants offering, investors purchasing our Series D Preferred Stock in this offering may 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.

Concurrently with this offering of Series D Preferred Stock and warrants and pursuant to a separate prospectus supplement, we are offering 7,500,000 shares of our common stock and warrants to purchase up to 3,750,000 shares of our common stock (and the common stock issuable from time to time upon exercise of each of the warrants). Through this offering and our concurrent common stock and warrants offering we intend to raise gross proceeds of approximately $20 million based on the public offering price of $2,000 per share of Series D Preferred Stock and accompanying warrant and the public offering price of $2.00 per share of common stock and accompanying warrant. This offering is not contingent upon our common stock and warrants offering and our common stock and warrants offering is not contingent upon this offering. We cannot assure you that our common stock and warrants offering will be completed.

We are offering 2,500 shares of our Series D Preferred Stock and warrants to purchase an additional 1,250,000 shares of our common stock.

The Series D Preferred Stock and warrants will be sold together. Each share of Series D Preferred Stock will be sold with a warrant to purchase 500 shares of common stock.

The shares of Series D Preferred Stock and warrants are immediately separable and will be issued separately. The shares of common stock issuable from time to time upon conversion of the shares of Series D Preferred Stock and exercise of the warrants, if any, are also being offered pursuant to this prospectus.

The material terms and provisions of our common stock and each other class of our securities which qualifies or limits our common stock are described under the caption “Description of Capital Stock-Common Stock” starting on page 7 of the accompanying prospectus.

The following summary of certain terms and provisions of the Series D Preferred Stock offered in this offering is subject to, and qualified in its entirety by reference to, the terms and provisions set forth in our certificate of designation of preferences, rights and limitations of Series D Convertible Preferred Stock.

General. Our amended and restated certificate of incorporation authorizes our board of directors to issue up to 10,000,000 shares of our preferred stock, par value $0.0001 per share.

Subject to the limitations prescribed by our amended and restated certificate of incorporation, our board of directors is authorized to establish the number of shares constituting each series of preferred stock and to fix the designations, powers, preferences and rights of the shares of each of those series and the qualifications, limitations and restrictions of each of those series, all without any further vote or action by our stockholders. Our board of directors has designated 2,500 of the 10,000,000 authorized shares of preferred stock as Series D Preferred Stock. When issued, the shares of Series D Preferred Stock will be validly issued, fully paid and non-assessable.

in each case, as to distributions of assets upon our liquidation, dissolution or winding up whether voluntarily or involuntarily.

Conversion. Each share of the Series D Preferred Stock is convertible into 1,000 shares of our common stock (subject to adjustment as provided in the related certificate of designation of

preferences) at any time at the option of the holder, provided that the holder will be prohibited from converting the Series D Preferred Stock into shares of our common stock if, as a result of such conversion, the holder, together with its affiliates, would own more than 9.98% of the total number of shares of our common stock then issued and outstanding.

Liquidation Preference. In the event of our liquidation, dissolution, or winding up, holders of the Series D Preferred Stock will receive a payment equal to $0.0001 per share of Series D Preferred Stock before any proceeds are distributed to the holders of our common stock.

Voting Rights. The shares of Series D Preferred Stock will generally have no voting rights, except as required by law and except that the consent of holders of a majority of the outstanding Series D Preferred Stock will be required to amend the terms of the Series D Preferred Stock.

Dividends. The shares of Series D Preferred Stock will not be entitled to receive any dividends, unless and until specifically declared by our board of directors.

Redemption. We are not obligated to redeem or repurchase any shares of Series D Preferred Stock. The shares of Series D Preferred Stock are not otherwise entitled to any redemption rights, or mandatory sinking fund or analogous fund provisions.

Fundamental Transaction. If a fundamental transaction (as defined below) occurs while any of the Series D Preferred Stock is outstanding, then upon any subsequent conversion of this Series D Preferred Stock the holders shall have the right to receive, in lieu of the right to receive the shares of our common stock that would have been issuable upon such conversion immediately prior to the occurrence of such fundamental transaction, the same kind and amount of securities, cash or property as such holder would have been entitled to receive upon the occurrence of such fundamental transaction if it had been, immediately prior to such fundamental transaction, the holder of one share of our common stock, the Alternate Consideration. For purposes of any such subsequent conversion, the determination of the conversion ratio of the Series D Preferred Stock will be adjusted to apply to such Alternate Consideration based on the amount of Alternate Consideration issuable in respect of one share of our common stock in the fundamental transaction, and we will adjust the conversion ratio of the Series D Preferred Stock in a reasonable manner reflecting the relative value of any different components of the Alternate Consideration. If holders of our common stock are given any choice as to the securities, cash or property to be received in a fundamental transaction, then the holders of the Series D Preferred Stock will be given the same choice as to the Alternate Consideration they receive upon any conversion of this Series D Preferred Stock.

To the extent the surviving corporation following a fundamental traction is not our company, any successor or surviving entity in the fundamental transaction will file a new certificate of designations with the same terms and conditions and issue to the holders of the Series D Preferred Stock new preferred stock consistent with the foregoing provisions. The terms of any agreement to which we are a party and pursuant to which a fundamental transaction is effected shall include terms requiring any such successor or surviving entity to assume all our obligations set forth in the certificate of designations of the Series D Preferred Stock.

“Fundamental transaction” means (A) we affect any merger or consolidation with or into another person (other than a merger in which we are the surviving or continuing entity and our common stock is not exchanged for or converted into other securities, cash or property), (B) we effect any sale of all or substantially all of our assets in one transaction or a series of related transactions, (C) any tender offer or exchange offer (whether by us or another person) is completed pursuant to which all of our common stock is exchanged for or converted into other securities, cash or property, or (D) we effect any reclassification of our common stock or any compulsory share exchange pursuant (other than as a

result of specified dividends, subdivisions or combinations) to which our common stock is effectively converted into or exchanged for other securities, cash or property.

Exchange Listing. We do not plan on making an application to list the Series D Preferred Stock on the NASDAQ Capital Market, any national securities exchange or other nationally recognized trading system. We expect the common stock issuable upon conversion of the Series D Preferred Stock will be listed on the NASDAQ Capital Market.

The material terms and provisions of the warrants being issued in this offering are summarized below. The following description is subject to, and qualified in its entirety by, the form of warrant and the warrant agency agreement between us and the warrant agent, each of which will be filed as an exhibit to a Current Report on Form 8-K to be filed by us with the SEC in connection with this offering and incorporated by reference into the registration statement of which this prospectus forms a part. You should review the form of warrant and the warrant agency agreement for a complete description of the terms and conditions applicable to the warrants. See “Where You Can Find More Information” on page S-23.

Each purchaser of shares will receive, for each share of Series D Preferred Stock purchased on an as converted basis, a warrant representing the right to purchase 0.5 share of common stock.

Exercisability. The warrants may be exercised at any time after the date of the issuance and one year anniversary thereof. The warrants will be exercisable, at the option of each holder, in whole or in part by delivering to us or the warrant agent a duly executed exercise notice accompanied by payment in full for the number of shares of our common stock purchased upon such exercise. If there is no registration statement registering the issuance of the shares of our common stock upon exercise of the warrants under the Securities Act effective at the time of exercise, the warrants may only be exercised on a “cashless” basis.

Exercise Limitations. The warrants may be exercised only if a registration statement registering the issuance of the shares our common stock upon exercise of the warrants under the Securities Act is effective and available for issuance of such shares. In addition, certain holders of warrants will not have the right to exercise any portion of the warrant if the holder (together with its affiliates) would beneficially own in excess of 4.99% of the number of shares of our common stock outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the warrants. However, such holders may increase or decrease such percentage to any other percentage not in excess of 9.99% upon at least 61 days’ prior notice from the holder to us.

Exercise Price. The initial per share exercise price of the warrants is $3.00. The exercise price is subject to adjustment in the event of stock dividends and distributions, stock splits, stock combinations, reclassifications or similar events affecting our common stock.

Transferability. Subject to applicable laws, the warrants are separately tradeable immediately after issuance at the option of the holders and may be transferred at the option of the holders. The warrants will be issued in book-entry form under a warrant agency agreement between the warrant agent and us, and shall initially be represented by one or more book-entry certificates deposited with The Depository Trust Company, or DTC, and registered in the name of Cede & Co., a nominee of DTC, or as otherwise directed by DTC.

Listing. There is no established public trading market for the warrants and we do not expect a market to develop. In addition, we do not intend to apply for listing of the warrants on any securities

exchange or recognized trading system. Without an active market, the liquidity of the warrants will be limited.

Fundamental Transactions. In the event of a fundamental transaction, as described in the warrants and generally including any reorganization, recapitalization or reclassification of our common stock, the sale, transfer or other disposition of all or substantially all of our properties or assets, our consolidation or merger with or into another person, the acquisition of more than 50% of our outstanding common stock, or any person or group becoming the beneficial owner of 50% of the voting power represented by our outstanding common stock, the holders of the warrants will be entitled to receive upon exercise of the warrants the kind and amount of securities, cash or other property that the holders would have received had they exercised the warrants immediately prior to such fundamental transaction.

Rights as a Stockholder. Except as otherwise provided in the warrants or by virtue of a holder’s ownership of shares of our common stock, the holders of the warrants do not have the rights or privileges of holders of our common stock, including any voting rights, until they exercise their warrants.

Amendments. Amendments and waivers of the terms of each warrant require the written consent of the holder of such warrant and us.

The transfer agent and registrar for our common stock is American Stock Transfer & Trust Company. Its address is 6201 15th Avenue, Brooklyn, New York 11219. Its phone number is (718) 921-8124.

Our common stock is listed on the NASDAQ Capital Market under the symbol “SNSS.” There is no established public trading market for the Series D Preferred Stock or warrants, and we do not expect a market to develop. We do not plan on making an application to list the Series D Preferred Stock or the warrants on the NASDAQ Capital Market, any securities exchange or any recognized trading system. American Stock Transfer & Trust Company will act as the registrar and transfer agent for the warrants.

We have entered into an underwriting agreement with Cowen and Company, LLC and Wells Fargo Securities, LLC, as representatives of the underwriters, with respect to the Series D Preferred Stock and accompanying warrants being offered by this prospectus supplement. Subject to the terms and conditions of the underwriting agreement, each underwriter has severally agreed to purchase from us the number of shares of our Series D Preferred Stock and warrants to purchase common stock set forth opposite its name below.

The underwriting agreement provides that the obligations of the underwriters are subject to certain conditions precedent and that the underwriters have agreed to purchase all of the shares of Series D Preferred Stock and accompanying warrants sold under the underwriting agreement if any of these shares of Series D Preferred Stock and accompanying warrants are purchased. If the underwriters default, the underwriting agreement provides that the underwriting agreement may be terminated by us.

We have agreed to indemnify the underwriters against specified liabilities, including liabilities under the Securities Act, and to contribute to payments the underwriters may be required to make in respect thereof.

The underwriters are offering the shares of Series D Preferred Stock and accompanying warrants, subject to prior sale, when, as and if issued to and accepted by them, subject to approval of legal matters by their counsel and other conditions specified in the underwriting agreement. The underwriters reserve the right to withdraw, cancel or modify offers and to reject orders in whole or in part.

Discounts and commissions. The following table shows the public offering price, underwriting discount and proceeds, before expenses, to us.

We estimate that the total expenses of the offering, and the concurrent common stock and warrants offering, excluding the underwriting discount, will be approximately $440,000 and are payable by us.

The underwriters propose to offer the Series D Preferred Stock and accompanying warrants offered by us to the public at the public offering price set forth on the cover of this prospectus supplement. If all of the shares and accompanying warrants are not sold at the public offering price, the underwriters may change the offering price and other selling terms.

Discretionary accounts. The underwriters do not intend to confirm sales of the securities offered hereby to any accounts over which they have discretionary authority.

Passive market making. In connection with this offering, the underwriters may engage in passive market making transactions in our common stock on the NASDAQ Capital Market in accordance with Rule 103 of Regulation M under the Exchange Act during a period before the commencement of offers or sales of common stock and accompanying warrants and extending through the completion of the distribution. A passive market maker must display its bid at a price not in excess of the highest independent bid of that security. However, if all independent bids are lowered below the passive market maker’s bid, that bid must then be lowered when specified purchase limits are exceeded.

Lock-up agreements. Pursuant to certain “lock-up” agreements, we and our executive officers and directors and certain of our stockholders have agreed, subject to certain exceptions, not to offer, sell, assign, transfer, pledge, contract to sell, or otherwise dispose of or announce the intention to otherwise dispose of, or enter into any swap, hedge or similar agreement or arrangement that transfers, in whole or in part, the economic consequence of ownership of, directly or indirectly, or make any demand or request or exercise any right with respect to the registration of, or file with the SEC a registration statement under the Securities Act relating to, any common stock or securities convertible into or exchangeable or exercisable for any common stock without the prior written consent of Cowen and Company, LLC and Wells Fargo Securities, LLC, for a period of 60 days after the date of the pricing of the offering.

Switzerland. The securities will not be offered, directly or indirectly, to the public in Switzerland and this prospectus does not constitute a public offering prospectus as that term is understood pursuant to article 652a or 1156 of the Swiss Federal Code of Obligations.

Canada. The securities may be sold only to purchasers purchasing, or deemed to be purchasing, as principal that are accredited investors, as defined in National Instrument 45-106 Prospectus Exemptions or subsection 73.3(1) of the Securities Act (Ontario), and are permitted clients, as defined in National Instrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of the securities must be made in accordance with an exemption from, or in a transaction not subject to, the prospectus requirements of applicable securities laws.

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

Pursuant to section 3A.3 of National Instrument 33-105 Underwriting Conflicts (NI 33-105), the underwriters are not required to comply with the disclosure requirements of NI 33-105 regarding underwriter conflicts of interest in connection with this offering.

European Economic Area. In relation to each Member State of the European Economic Area (Iceland, Norway and Lichtenstein in addition to the member states of the European Union) that has implemented the Prospectus Directive (each, a Relevant Member State), the underwriters have represented and agreed that with effect from and including the date on which the Prospectus Directive is implemented in that Relevant Member State, or the Relevant Implementation Date, they have not made and will not make an offer of the securities to the public in that Relevant Member State prior to the publication of a prospectus in relation to the securities that has been approved by the competent authority in that Relevant Member State or, where appropriate, approved in another Relevant Member State and notified to the competent authority in that Relevant Member State, all in accordance with the Prospectus Directive, except that they may, with effect from and including the Relevant Implementation Date, make an offer of the securities to the public in that Relevant Member State at any time:

Each person in a Relevant Member State who receives any communication in respect of, or who acquires any securities under, the offer contemplated in this prospectus will be deemed to have represented, warranted and agreed to and with us and each underwriter that:

For the purposes of the provisions in the two immediately preceding paragraphs, the expression an “offer of the securities to the public” in relation to the securities in any Relevant Member State means the communication in any form and by any means of sufficient information on the terms of the offer and the securities to be offered so as to enable an investor to decide to purchase or subscribe for the securities, as the same may be varied in that Relevant Member State by any measure implementing

the Prospectus Directive in that Relevant Member State, and the expression “Prospectus Directive” means Directive 2003/71/EC and includes any relevant implementing measure in each Relevant Member State.

Electronic offer, sale and distribution of securities. A prospectus in electronic format may be made available on the website maintained by the underwriters participating in this offering and the underwriters participating in this offering may distribute prospectuses electronically. Other than the prospectus in electronic format, the information on an underwriter’s website is not part of this prospectus supplement, the accompanying prospectus or the registration statement of which the accompanying prospectus forms a part, has not been approved or endorsed by us or the underwriters in their capacity as underwriter, and should not be relied upon by investors.

Other relationships. The underwriters and their affiliates have provided, and may in the future provide, various investment banking, commercial banking and other financial services for us and our affiliates for which they have received, and may in the future receive, customary fees. In the ordinary course of their various business activities, the underwriters and certain of their respective affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers, and such investment and securities activities may involve securities and/or instruments of the issuer. The underwriters and certain of their respective affiliates may also make investment recommendations and/or publish or express independent research views in respect of such securities or instruments and may at any time hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

Cooley LLP, Palo Alto, California will pass upon the validity of the issuance of the securities offered by this prospectus supplement and the accompanying prospectus. The underwriters are being represented in connection with this offering by Goodwin Procter LLP, New York, New York.

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, 2016, as set forth in their report, which is incorporated by reference in this prospectus supplement 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.

We file annual, quarterly and special reports, proxy statements and other information with the SEC. You may read and copy any document we file 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, including Sunesis Pharmaceuticals, Inc. The SEC’s Internet site can be found at www.sec.gov.

The SEC allows us to “incorporate by reference” information from other documents that we file with it, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is considered to be part of this prospectus supplement and the accompanying prospectus. Information contained in this prospectus supplement and the accompanying prospectus and information that we file with the SEC in the future and incorporate by reference in this prospectus supplement and the accompanying prospectus will automatically update and supersede this information. We incorporate by reference the documents listed below and any future filings (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) we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act after the date of the prospectus supplement and prior to the termination of the offering of the securities covered by this prospectus supplement (Commission File No. 0-51531):

We will furnish without charge to you, upon written or oral request, a copy of any or all of the documents incorporated by reference, including exhibits to these documents. You should direct any requests for documents to:

From time to time, we may offer up to $200,000,000 of any combination of the securities described in this prospectus, either individually or in combination with other securities. We may also offer common stock or preferred stock upon conversion of debt securities, common stock upon conversion of preferred stock, or common stock, preferred stock or debt securities upon the exercise of warrants.

We will provide the specific terms of these offerings and securities in one or more supplements to this prospectus. We may also authorize one or more free writing prospectuses to be provided to you in connection with these offerings. The prospectus supplement and any related free writing prospectus may also add, update or change information contained in this prospectus. You should carefully read this prospectus, the applicable prospectus supplement and any related free writing prospectus, as well as any documents incorporated by reference, before buying any of the securities being offered.

Our common stock is listed on The NASDAQ Stock Market under the symbol “SNSS.” On May 6, 2014, the last reported sale price of our common stock was $5.02 per share. The applicable prospectus supplement will contain information, where applicable, as to any other listing, if any, on The NASDAQ Stock Market or any securities market or other exchange of the securities covered by the applicable prospectus supplement.

Investing in our securities involves a high degree of risk. You should review carefully the risks and uncertainties described under the heading “Risk Factors” contained in the applicable prospectus supplement and in any free writing prospectuses we have authorized for use in connection with a specific offering, and under similar headings in the documents that are incorporated by reference into this prospectus.

This prospectus may not be used to consummate a sale of securities unless it is accompanied by a prospectus supplement.

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

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

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, we may offer and sell shares of our common stock and preferred stock, various series of debt securities and/or warrants to purchase any of such securities, either individually or in combination with other securities, in one or more offerings, up to a total dollar amount of $200,000,000. This prospectus provides you with a general description of the securities we may offer.

Each time we offer securities under this prospectus, we will provide a prospectus supplement that will contain more specific information about the terms of that offering. We may also authorize one or more free writing prospectuses to be provided to you that may contain material information relating to these offerings. The prospectus supplement and any related free writing prospectus that we may authorize to be provided to you may also add, update or change any of the information contained in this prospectus or in the documents that we have incorporated by reference into this prospectus. We urge you to read carefully this prospectus, any applicable prospectus supplement and any free writing prospectuses we have authorized for use in connection with a specific offering, together with the information incorporated herein by reference as described under the section entitled “Incorporation of Certain Information by Reference,” before buying any of the securities being offered.

This prospectus may not be used to consummate a sale of securities unless it is accompanied by a prospectus supplement.

You should rely only on the information contained in, or incorporated by reference into, this prospectus and any applicable prospectus supplement, along with the information contained in any free writing prospectuses we have authorized for use in connection with a specific offering. We have not authorized anyone to provide you with different or additional information. This prospectus is an offer to sell only the securities offered hereby, but only under circumstances and in jurisdictions where it is lawful to do so.

The information appearing in this prospectus, any applicable prospectus supplement or any related free writing 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, any applicable prospectus supplement or any related free writing prospectus, or any sale of a security. Our business, financial condition, results of operations and prospects may have changed since those dates.

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 into 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 and the information incorporated herein by reference contain 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, any applicable prospectus supplement or any related free writing prospectus are the property of their respective owners.

PROSPECTUS SUMMARY

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, the applicable prospectus supplement and any related free writing prospectus, including the risks of investing in our securities discussed under the heading “Risk Factors” contained in the applicable prospectus supplement and any related free writing prospectus, and under similar headings in the other documents that are incorporated by reference into this prospectus. You also should carefully read the information incorporated by reference into this prospectus, including our financial statements, and the exhibits to the registration statement of which this prospectus is a part.

Sunesis Pharmaceuticals, Inc.

Overview

We are a biopharmaceutical company focused on the development and commercialization of new oncology therapeutics for the treatment of solid and hematologic cancers. Our efforts are currently focused primarily on the development and commercial planning for vosaroxin for the treatment of acute myeloid leukemia, or AML. Vosaroxin is a first-in-class anti-cancer quinolone derivative, or AQD—a class of compounds that has not been used previously for the treatment of cancer. AQDs have been shown to mediate anti-tumor activity by targeting mammalian topoisomerase II, an enzyme critical for cell replication. We have built a highly experienced cancer drug development organization committed to advancing vosaroxin in multiple indications to improve the lives of people with cancer.

We own worldwide development and commercialization rights to vosaroxin. In April 2012, the European Commission granted orphan drug designation to vosaroxin for the treatment of AML, which may provide for 10 years of marketing exclusivity in all member countries of the European Union following product approval for this indication in Europe. In 2009, vosaroxin received orphan drug designation for the treatment of AML from the U.S. Food and Drug Administration, or FDA. In February 2011, the FDA granted fast track designation to vosaroxin for the treatment of relapsed or refractory AML in combination with cytarabine. We have been granted, or notified of allowance of, a number of key patents for vosaroxin.

In December 2010, we commenced enrollment of a Phase 3, multi-national, randomized, double-blind, placebo-controlled, pivotal trial of vosaroxin in combination with cytarabine in patients with relapsed or refractory AML, or the VALOR trial. The VALOR trial is designed to evaluate the effect of vosaroxin in combination with cytarabine, a widely used chemotherapy in AML, on overall survival as compared to placebo in combination with cytarabine, and is being conducted at more than 100 study sites in the U.S., Canada, Europe, South Korea, Australia and New Zealand.

In September 2012, following the recommendation of the trial’s independent Data and Safety Monitoring Board, or DSMB, after the DSMB’s completion of a single, pre-planned interim analysis of unblinded efficacy and safety data sets from the VALOR trial, we implemented a one-time, 225 patient sample size increase to the VALOR trial, bringing target enrollment to 675 patients. This pre-specified sample size increase is designed to maintain adequate statistical power over a broader range of survival outcomes. In September 2013, we completed enrollment of 712 patients in the VALOR trial, which included a 5% over-enrollment factor. We anticipate unblinding of the VALOR trial in either the third or fourth quarter of 2014, after reaching 562 events in the VALOR trial and locking the final database.

We are also preparing the final clinical study reports and manuscripts for two completed clinical trials of vosaroxin: a Phase 1b/2 trial of vosaroxin in combination with cytarabine for the treatment of patients with

relapsed or refractory AML, and a Phase 2 trial in previously untreated patients age 60 years or older with AML, or REVEAL-1, which explored three dosing schedules of vosaroxin.

Company Information

The Securities We May Offer

We may offer shares of our common stock and preferred stock, various series of debt securities and/or warrants to purchase any of such securities, either individually or in combination with other securities, with a total value of up to $200,000,000 from time to time under this prospectus, together with any applicable prospectus supplement and any related free writing prospectus, at prices and on terms to be determined by market conditions at the time of any offering. This prospectus provides you with a general description of the securities we may offer. Each time we offer a type or series of securities under this prospectus, we will provide a prospectus supplement that will describe the specific amounts, prices and other important terms of the securities, including, to the extent applicable:

•

designation or classification;

•

aggregate principal amount or aggregate offering price;

•

maturity date, if applicable;

•

original issue discount, if any;

•

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

•

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

•

ranking;

•

restrictive covenants, if any;

•

voting or other rights, if any;

•

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; and

•

material or special U.S. federal income tax considerations, if any.

The applicable prospectus supplement and any related free writing prospectus that we may authorize to be provided to you also may 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.

THIS PROSPECTUS MAY NOT BE USED TO CONSUMMATE A SALE OF SECURITIES UNLESS IT IS ACCOMPANIED BY A PROSPECTUS SUPPLEMENT.

We may sell the securities directly to investors or to or through agents, underwriters or dealers. We, and our agents or underwriters, reserve the right to accept or reject all or part of any proposed purchase of securities. If we do offer securities to or through agents or underwriters, we will include in the applicable prospectus supplement:

•

the names of those agents or underwriters;

•

applicable fees, discounts and commissions to be paid to them;

•

details regarding over-allotment options, if any; and

•

the net proceeds to us.

Common Stock. We may issue shares of our common stock from time to time. The holders of our common stock are entitled to one vote for each share held of record on all matters submitted to a vote of stockholders. Subject to preferences that may be applicable to any outstanding shares of preferred stock, the holders of common stock are entitled to receive ratably such dividends as may be declared by our board of directors out of legally available funds. Upon our liquidation, dissolution or winding up, holders of our common stock are entitled to share ratably in all assets legally available for distribution to stockholders remaining after payment of liabilities and the liquidation preferences of any outstanding shares of preferred stock. Holders of common stock have no preemptive rights and no right to convert their common stock into any other securities. There are no redemption or sinking fund provisions applicable to our common stock. When we issue shares of common stock under this prospectus, the shares will be fully paid and non-assessable. The rights, preferences and privileges of the holders of common stock are subject to, and may be adversely affected by, the rights of the holders of shares of any series of preferred stock which we may designate in the future. In this prospectus, we have summarized certain general features of the common stock under “Description of Capital Stock — Common Stock.” We urge you, however, to read the applicable prospectus supplement (and any related free writing prospectus that we may authorize to be provided to you) related to any common stock being offered.

Preferred Stock. We may issue shares of our preferred stock from time to time, in one or more series. Under our certificate of incorporation, our board of directors has the authority to designate up to 10,000,000 shares of preferred stock in one or more series and to fix the privileges, preferences and rights of each series of preferred stock, any or all of which may be greater than the rights of the common stock. We are not offering any of the previously designated series of preferred stock under this prospectus. If we sell any new series of preferred stock under this prospectus and any applicable prospectus supplement, our board of directors will determine the designations, voting powers, preferences and rights of the preferred stock being offered, as well as the qualifications, limitations or restrictions thereof, including dividend rights, conversion rights, preemptive rights, terms of redemption or repurchase, liquidation preferences, sinking fund terms and the number of shares constituting any series or the designation of any series. Convertible preferred stock may be convertible into our common stock or exchangeable for our other securities. Conversion may be mandatory or at the holder’s option and would be at prescribed conversion rates. We will file as an exhibit to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the form of any certificate of designation that describes the terms of the series of preferred stock that we are offering before the issuance of the related series of preferred stock. In this prospectus, we have summarized certain general features of the preferred stock under “Description of Capital Stock — Preferred Stock.” We urge you, however, to read the applicable prospectus supplement (and any related 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 issue debt securities from time to time, in one or more series, as either senior or subordinated debt or as senior or subordinated convertible debt. The senior debt securities will rank equally with any other unsecured and unsubordinated debt. The subordinated debt securities will be subordinate and junior in right of payment, to the extent and in the manner described in the instrument governing the debt, to all

of our senior indebtedness. Convertible debt securities will be convertible into or exchangeable for our common stock or our other securities. Conversion may be mandatory or at the holder’s option and would be at prescribed conversion rates.

The debt securities will be issued under an indenture that we will enter into with a national banking association or other eligible party, as trustee. In this prospectus, we have summarized certain general features of the debt securities under “Description of Debt Securities.” We urge you, however, to read the applicable prospectus supplement (and any related 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 indenture and any supplemental indentures that contain the terms of the debt securities. We have filed a form of indenture as an exhibit 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.

Warrants. We may issue warrants for the purchase of common stock, preferred stock and/or debt securities in one or more series. We may issue warrants independently or in combination with common stock, preferred stock and/or debt securities. In this prospectus, we have summarized certain general features of the warrants under “Description of Warrants.” We urge you, however, to read the applicable prospectus supplement (and any related free writing prospectus that we may authorize to be provided to you) related to the particular series of warrants being offered, as well as the form of warrant and/or the warrant agreement and warrant certificate, as applicable, that contain the terms of the warrants. We have filed the forms of the warrant agreements and forms of warrant certificates containing the terms of the warrants that we may offer as exhibits to the registration statement of which this prospectus is a part. We will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the form of warrant and/or the warrant agreement and warrant certificate, as applicable, that describe the terms of the particular series of warrants we are offering, and any supplemental agreements, before the issuance of such warrants.

Warrants may be issued under a warrant agreement that we enter into with a warrant agent. We will indicate the name and address of the warrant agent, if any, in the applicable prospectus supplement relating to a particular series of warrants.

Use of Proceeds

Except as described in any applicable prospectus supplement or in any free writing prospectuses we have authorized for use in connection with a specific offering, we currently intend to use the net proceeds from this offering, if any, for working capital and general corporate purposes, including research and development expenses, general and administrative expenses and manufacturing expenses. See “Use of Proceeds” in this prospectus.

NASDAQ Stock Market Listing

Our common stock is listed on the NASDAQ Capital Market under the symbol “SNSS.”

Investing in our securities involves a high degree of risk. Before deciding whether to invest in our securities, you should consider carefully the risks and uncertainties described under the heading “Risk Factors” contained in the applicable prospectus supplement and any related free writing prospectus, and discussed under the section entitled “Risk Factors” contained in our most recent Annual Report on Form 10-K and in any subsequent Quarterly Report on Form 10-Q, as well as any amendments thereto reflected in subsequent filings with the SEC, which are incorporated by reference into this prospectus in their entirety, together with other information in this prospectus, the documents incorporated by reference and any free writing prospectus that we may authorize for use in connection with a specific offering. The risks described in these documents are not the only ones we face, but those that we consider to be material. There may be other unknown or unpredictable economic, business, competitive, regulatory or other factors that could have material adverse effects on our future results. Past financial performance may not be a reliable indicator of future performance, and historical trends should not be used to anticipate results or trends in future periods. If any of these risks actually occurs, our business, financial condition, results of operations or cash flow 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 “Forward-Looking Statements.”

This prospectus and the documents we have filed with the SEC that are incorporated by reference contain “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended, or the Securities Act, and Section 21E of the Exchange Act of 1934, as amended, or the Exchange Act. These statements relate to future events or to our future operating or financial performance and involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements to be materially different from any future results, performances or achievements expressed or implied by the forward-looking statements. Forward-looking statements may include, but are not limited to, statements about:

In some cases, you can identify forward-looking statements by terms such as “anticipates,” “believes,” “could,” “estimates,” “expects,” “intends,” “may,” “plans,” “potential,” “predicts,” “projects,” “should,” “will,” “would” and similar expressions intended to identify forward-looking statements. These statements reflect our current views with respect to future events and are based on assumptions and are subject to risks and uncertainties. Given these uncertainties, you should not place undue reliance on these forward-looking statements. We discuss in greater detail, and incorporate by reference into this prospectus in their entirety, many

of these risks under the heading “Risk Factors” contained in any applicable prospectus supplement, in any free writing prospectuses we may authorize for use in connection with a specific offering, and in our most recent Annual Report on Form 10-K and in our most recent Quarterly Report on Form 10-Q, as well as any amendments thereto reflected in subsequent filings with the SEC. Also, these forward-looking statements represent our estimates and assumptions only as of the date of the document containing the applicable statement. Unless required by law, we undertake no obligation to update or revise any forward-looking statements to reflect new information or future events or developments. Thus, you should not assume that our silence over time means that actual events are bearing out as expressed or implied in such forward-looking statements. You should read this prospectus, any applicable prospectus supplement, together with the documents we have filed with the SEC that are incorporated by reference and any free writing prospectus that we may authorize for use in connection with a specific offering completely and with the understanding that our actual future results may be materially different from what we expect. We qualify all of the forward-looking statements in the foregoing documents by these cautionary statements.

The following table sets forth our ratio of earnings to fixed charges for each of the periods presented. Our net losses were insufficient to cover fixed charges in each of the years ended December 31, 2009, 2010, 2011, 2012 and 2013. Because of these deficiencies, the ratio information is not applicable for those periods. The extent to which earnings were insufficient to cover fixed charges for those periods is shown below. Amounts shown are in thousands, except for ratios.

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 outcome of the VALOR trial, the timing and progress of any partnering and commercialization efforts, technological advances and the competitive environment for our 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.

As of the date of this prospectus, our amended and restated certificate of incorporation, as amended, authorizes us to issue 400,000,000 shares of common stock, $0.0001 par value per share, and 10,000,000 shares of preferred stock, $0.0001 par value per share. As of March 31, 2014, 60,162,665 shares of common stock were outstanding and no shares of preferred stock were outstanding.

The following summary describes the material terms of our capital stock. The description of our capital stock is based on the provisions of our amended and restated certificate of incorporation and amended bylaws, and the applicable provisions of the Delaware General Corporation Law, or DGCL. This information may not be complete in all respects and is qualified entirely by reference to our amended and restated certificate of incorporation, our amended and restated bylaws and the Delaware General Corporation Law. For more information on how to obtain copies of our amended and restated certificate of incorporation and our amended and restated bylaws which are incorporated by reference as exhibits into the registration statement of which this prospectus is a part, please see the section entitled “Where You Can Find More Information” in this prospectus.

The holders of common stock are entitled to one vote for each share held of record on all matters submitted to a vote of the stockholders and do not have cumulative voting rights with respect to the election of directors. Generally, all matters to be voted on by stockholders must be approved by the holders of a majority of the common stock and preferred stock (voting together as a single class on an as-if converted basis), or, in the case of the election of directors, a plurality, represented at a meeting at which a quorum is present. Subject to preferences that may be applicable to the outstanding shares of preferred stock, the holders of common stock are entitled to receive ratably such dividends as may be declared by the board of directors out of funds legally available therefor. Upon the liquidation, dissolution or winding up of Sunesis, holders of our common stock are entitled to share ratably in all assets legally available for distribution to stockholders remaining after payment of liabilities and the liquidation preferences of outstanding shares of preferred stock. Holders of common stock have no preemptive rights and no right to convert their common stock into any other securities. There are no redemption or sinking fund provisions applicable to our common stock. All outstanding shares of common stock are, and all shares of common stock to be outstanding upon the completion of any offering pursuant to this registration statement of which this prospectus is a part, will be fully paid and non-assessable.

Preferred Stock. We will establish the designations, voting powers, preferences and rights of the preferred stock of each series, as well as the qualifications, limitations or restrictions thereof, in a certificate of designation relating to that series. We will file as an exhibit to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the form of any certificate of designation that describes the terms of the series of preferred stock we are offering before the issuance of that series of preferred stock. This description will include:

When we issue shares of preferred stock under this prospectus, the shares will be fully paid and non-assessable and will not have, or be subject to, any preemptive or similar rights.

The General Corporation Law of the State of Delaware, the state of our incorporation, provides that the holders of preferred stock will have the right to vote separately as a class on any proposal involving fundamental changes in the rights of holders of that preferred stock. This right is in addition to any voting rights that may be provided for in the applicable certificate of designation.

Charter Documents. In accordance with our amended and restated certificate of incorporation, our board of directors is divided into three classes, with staggered three-year terms. Only one class of directors is elected at each annual meeting of our stockholders, with the other classes continuing for the remainder of their respective three-year terms. Because our stockholders do not have cumulative voting rights, in the case of the election of directors, holders of a plurality of the common stock represented at a meeting at which a quorum is present will be able to elect all of our directors. Our amended and restated certificate of incorporation and amended and restated bylaws provide that all actions taken by the holders of common stock must be effected at a duly called meeting of stockholders and not by a consent in writing, and that only our board of directors, chairman of the board, chief executive officer, or president (in the absence of a chief executive officer) or holder of greater than 10% of our common stock may call a special meeting of stockholders. Our amended and restated certificate of incorporation requires a 66- 2/3% stockholder vote for the amendment, repeal or modification of certain provisions of our amended and restated certificate of incorporation and amended and restated bylaws relating to the absence of cumulative voting, the classification of our board of directors, the requirement that stockholder actions be effected at a duly called meeting, and the designated parties entitled to call a special meeting of the stockholders.

The classification of our board of directors, the lack of cumulative voting and the 66- 2/3% stockholder voting requirements make it more difficult for our existing common stockholders to replace our board of directors as well as for another party to obtain control of us by replacing our board of directors. Since our board of directors has the power to retain and discharge our officers, these provisions could also make it more difficult for existing common stockholders or another party to effect a change in management. In addition, the authorization of undesignated preferred stock makes it possible for our board of directors to issue shares of preferred stock with voting or other rights or preferences that could impede the success of any attempt to change our control.

These provisions may have the effect of deterring hostile takeovers or delaying changes in our control or management. These provisions are intended to enhance the likelihood of continued stability in the composition of our board of directors and its policies and to discourage certain types of transactions that may involve an actual or threatened change in control. These provisions are designed to reduce our vulnerability to an unsolicited acquisition proposal. The provisions also are intended to discourage certain tactics that may be used in proxy fights. However, such provisions could have the effect of discouraging others from making tender offers for our shares and, as a consequence, they also may inhibit fluctuations in the market price of our shares that could result from actual or rumored takeover attempts. Such provisions also may have the effect of preventing changes in our management.

Delaware Takeover Statute. We are subject to Section 203 of the DGCL which regulates acquisitions of some Delaware corporations. In general, Section 203 prohibits, with some exceptions, a publicly held Delaware corporation such as us from engaging in a “business combination” with an “interested stockholder” for a period of three years following the time that the stockholder became an interested stockholder, unless:

Section 203 of the DGCL generally defines a “business combination” to include any of the following:

In general, Section 203 defines an “interested stockholder” as any entity or person beneficially owning 15% or more of the outstanding voting stock of the corporation and any entity or person that is an affiliate or associate of such entity or person.

Section 203 of the DGCL could depress our stock price and delay, discourage or prohibit transactions not approved in advance by our board of directors, such as takeover attempts that might otherwise involve the payment to our stockholders of a premium over the market price of our common stock.

The transfer agent and registrar for our common stock is American Stock Transfer & Trust Company. Its address is 6201 15th Avenue, Brooklyn, New York 11219. Its phone number is (718) 921-8124. The transfer agent for any preferred stock that we may offer under this prospectus will be named and described in the prospectus supplement for that series.

Our common stock is listed on The NASDAQ Stock Market under the symbol “SNSS.”

We may issue debt securities from time to time, 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 debt securities that 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. The terms of any debt securities offered under a prospectus supplement may differ from the terms described below. Unless the context requires otherwise, whenever we refer to the indenture, we also are referring to any supplemental indentures that specify the terms of a particular series of debt securities.

We will issue the debt securities under the indenture that we will enter into with the trustee named in the indenture. The indenture will be qualified under the Trust Indenture Act of 1939, as amended, or the Trust Indenture Act. We have filed the form of indenture as an exhibit 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 following summary of material provisions of the debt securities and the indenture is subject to, and qualified in its entirety by reference to, all of the provisions of the indenture 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 indenture that contains the terms of the debt securities.

The indenture does not limit the amount of debt securities that we may issue. It provides that we may issue debt securities up to the principal amount that we may authorize and may be in any currency or currency unit that we may designate. Except for the limitations on consolidation, merger and sale of all or substantially all of our assets contained in the indenture, the terms of the indenture do not contain any covenants or other provisions designed to give holders of any debt securities protection against changes in our operations, financial condition or transactions involving us.

We may issue the debt securities issued under the indenture as “discount securities,” which means they may be sold at a discount below their stated principal amount. These debt securities, as well as other debt securities that are not issued at a discount, may be issued with “original issue discount,” or OID, for U.S. federal income tax purposes because of interest payment and other characteristics or terms of the debt securities. Material U.S. federal income tax considerations applicable to debt securities issued with OID will be described in more detail in any applicable prospectus supplement.

We will describe in the applicable prospectus supplement the terms of the series of debt securities being offered, including:

We will set forth in the applicable prospectus supplement the terms on which a series of debt securities may be convertible into or exchangeable for our common stock or our other securities. We will include provisions as to settlement upon conversion or exchange and 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 or our other securities that the holders of the series of debt securities receive would be subject to adjustment.

Unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, the indenture will not contain any covenant that restricts our ability to merge or consolidate, or sell, convey, transfer or otherwise dispose of our assets as an entirety or substantially as an entirety. However, any successor to or acquirer of such assets (other than a subsidiary of ours) must assume all of our obligations under the indenture or the debt securities, as appropriate.

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

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 of, premium, if any, and accrued interest, if any, due and payable immediately. If an event of default specified in the last bullet point above occurs with respect to us, the principal amount of 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 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 indenture, 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. 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:

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

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.

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

We and the trustee may change an indenture without the consent of any holders with respect to specific matters:

In addition, under the indenture, 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, unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, we and the trustee may make the following changes only with the consent of each holder of any outstanding debt securities affected:

Each indenture provides that we can elect to be discharged from our obligations with respect to one or more series of debt securities, except for specified obligations, including obligations to:

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

We will issue the debt securities of each series only in fully registered form without coupons and, unless we provide otherwise in the applicable prospectus supplement, in denominations of $1,000 and any integral multiple thereof. The indenture provides 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, 55 Water Street, New York, New York 10041, or DTC, or another depositary named by us and identified in the applicable prospectus supplement with respect to that series. To the extent the debt securities of a series are issued in global form and as book-entry, a description of terms relating to any book entry securities will be set forth in the applicable prospectus supplement.

At the option of the holder, subject to the terms of the indenture 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 indenture 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 impose 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:

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. 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. Subject to this provision, the trustee is under no obligation to exercise any of the powers given it by the indenture 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.

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.

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 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.

The indenture 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 of 1939 is applicable.

The following description, together with the additional information we may include in any applicable prospectus supplement and free writing prospectus, 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 in combination with common stock, preferred stock or debt securities offered by any prospectus supplement. 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 in more detail in the applicable prospectus supplement. The following description of warrants will apply to the warrants offered by this prospectus unless we provide otherwise in the applicable prospectus supplement. The applicable prospectus supplement for a particular series of warrants may specify different or additional terms.

We have filed forms of the warrant agreements and forms of warrant certificates containing the terms of the warrants that may be offered as exhibits to the registration statement of which this prospectus is a part. We

will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the form of warrant and/or the warrant agreement and warrant certificate, as applicable, that describe the terms of the particular series of warrants we are offering, and any supplemental agreements, before the issuance of such warrants. The following summaries of material terms and provisions of the warrants are subject to, and qualified in their entirety by reference to, all the provisions of the form of warrant and/or the warrant agreement and warrant certificate, as applicable, and any supplemental agreements applicable to a particular series of warrants that we may offer under this prospectus. We urge you to read the applicable prospectus supplement related to the particular series of warrants that we may offer under this prospectus, as well as any related free writing prospectus, and the complete form of warrant and/or the warrant agreement and warrant certificate, as applicable, and any supplemental agreements, that contain the terms of the warrants.

We will describe in the applicable prospectus supplement the terms of the series of warrants being offered, including:

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

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. The warrants may be exercised as set forth in the prospectus supplement relating to the warrants offered. Unless we otherwise specify in the applicable prospectus supplement, warrants may be exercised at any time up to the close of business on the expiration date set forth in the prospectus supplement relating to the warrants offered thereby. After the close of business on the expiration date, unexercised warrants will become void.

Upon receipt of payment and the warrant or warrant certificate, as applicable, properly completed and duly executed at the corporate trust office of the warrant agent, if any, or any other office, including ours, indicated in the prospectus supplement, we will, as soon as practicable, issue and deliver the securities purchasable upon such exercise. If less than all of the warrants (or the warrants represented by such warrant certificate) are exercised, a new warrant or a new warrant certificate, as applicable, will be issued for the remaining warrants.

Unless we provide otherwise in the applicable prospectus supplement, the warrants and any warrant agreements will be governed by and construed in accordance with the laws of the State of New York.

Each warrant agent, if any, 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.

As of March 31, 2014, there were warrants to purchase a total of 19,171,205 shares of common stock outstanding. Of the warrants that were outstanding, 9,871,205 are to purchase shares of common stock are exercisable at a weighted average exercise price of $2.36, and may be exercised for cash or, under certain circumstances, on a cashless basis, in which case we will deliver, upon exercise, the number of shares with respect to which the warrant is being exercised reduced by a number of shares having a value (as determined in accordance with the terms of the applicable warrant) equal to the aggregate exercise price of the shares with respect to which the warrant is being exercised. Warrants to purchase 4,650,000 shares of common stock were outstanding at an exercise price of $8.50 and warrants to purchase 4,650,000 shares of common stock were outstanding at an exercise price of $12.00, all of which will become exercisable after unblinding of our VALOR trial and may only be exercised for cash.

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, 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.

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. Securities issued in global form will be registered in the name of the depositary or its participants. Consequently, for securities issued in global form, 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 book-entry 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 holders, of the securities.

We may terminate a global security or issue securities in non-global form. In these cases, investors may choose to hold their securities in their own names or in “street name.” Securities held by an 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 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 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 holders, of those securities.

Our obligations, as well as the obligations of any applicable trustee and of any third parties 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 depositary 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 the indenture or for other purposes. In such an event, we would seek approval only from the holders, and not the indirect holders, of the securities. Whether and how the holders contact the indirect holders is up to the holders.

If you hold securities through a bank, broker or other financial institution, either in book-entry form or in street name, you should check with your own institution to find out:

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 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 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 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 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 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 in global form only, 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.

The rights of an indirect holder 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 in the form of a global security, an investor should be aware of the following:

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.

In a few special situations described below, the 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 name, so that they will be direct holders. We have described the rights of holders and street name investors above.

Unless we provide otherwise in the applicable prospectus supplement, the global security will terminate when the following special situations occur:

The applicable prospectus supplement also may list additional situations for terminating a global security that would apply only to the particular series of securities covered by the applicable prospectus supplement. When a global security terminates, the depositary, and not we or any applicable trustee, is responsible for deciding the names of the institutions that will be the initial direct holders.

We may sell the securities from time to time pursuant to underwritten public offerings, “at the market” offerings, negotiated transactions, block trades or a combination of these methods. We may sell the securities to or through underwriters or dealers, through agents, or directly to one or more purchasers. We may distribute securities from time to time in one or more transactions:

A prospectus supplement or supplements (and any related free writing prospectus that we may authorize to be provided to you) will describe the terms of the offering of the securities, including, to the extent applicable:

Only underwriters named in the prospectus supplement will be underwriters of the securities offered by the prospectus supplement.

If underwriters are used in the sale, they will acquire the securities for their own account and may resell the securities from time to time in one or more transactions at a fixed public offering price or at varying prices determined at the time of sale. The obligations of the underwriters to purchase the securities will be subject to the conditions set forth in the applicable underwriting agreement. We may offer the securities to the public through underwriting syndicates represented by managing underwriters or by underwriters without a syndicate. Subject to certain conditions, the underwriters will be obligated to purchase all of the securities offered by the prospectus supplement, other than securities covered by any over-allotment option. Any public offering price and any discounts or concessions allowed or reallowed or paid to dealers may change from time to time. We may use underwriters with whom we have a material relationship. We will describe in the prospectus supplement, naming the underwriter, the nature of any such relationship.

We may sell 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, our agent will act on a best-efforts basis for the period of its appointment.

We may authorize agents or underwriters to solicit offers by certain types of 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.

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

All securities we may offer, other than common stock, will be new issues of securities with no established trading market. Any underwriters may make a market in these securities, but will not be obligated to do so and may discontinue any market making at any time without notice. We cannot guarantee the liquidity of the trading markets for any securities.

Any underwriter may engage in over-allotment, stabilizing transactions, short-covering transactions and penalty bids in accordance with Regulation M under the Exchange Act. Over-allotment 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 price. Syndicate-covering or other short-covering transactions involve purchases of the securities, either through exercise of the over-allotment option or 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 stabilizing or 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 the activities at any time.

Any underwriters that are qualified market makers on The NASDAQ Stock Market may engage in passive market making transactions in the common stock on The NASDAQ Stock Market in accordance with Regulation M under the Exchange Act, during the business day prior to the pricing of the offering, before the commencement of offers or sales of the common stock. 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. Passive market making may stabilize the market price of the securities at a level above that which might otherwise prevail in the open market and, if commenced, may be discontinued at any time.

In compliance with guidelines of the Financial Industry Regulatory Authority, or FINRA, the maximum consideration or discount to be received by any FINRA member or independent broker dealer may not exceed 8% of the aggregate amount of the securities offered pursuant to this prospectus and the applicable prospectus supplement.

Unless otherwise indicated in the applicable prospectus supplement, certain legal matters in connection with the offering and the validity of the securities being offered by this prospectus, and any supplement thereto, will be passed upon by Cooley LLP, Palo Alto, 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, 2013, and the effectiveness of our internal control over financial reporting as of December 31, 2013, as set forth in their reports, which are incorporated by reference in this prospectus and elsewhere in the registration statement. Our financial statements as of December 31, 2013 are incorporated by reference in reliance on Ernst & Young LLP’s reports, given on their authority as experts in accounting and auditing.

This prospectus is part of the registration statement on Form S-3 we filed with the SEC under the Securities Act and does not contain all of the information set forth in the registration statement. Whenever a reference is made in this prospectus to any of our contracts, agreements or other documents, the reference may not be complete and you should refer to the exhibits that are a part of the registration statement or the exhibits to the reports or other documents incorporated by reference into this prospectus for a copy of such contract, agreement or other document. Because we are subject to the information and reporting requirements of the Exchange Act, we file annual, quarterly and current reports, proxy statements and other information with the SEC. Our SEC filings are available to the public over the Internet at the SEC’s website at http://www.sec.gov. You also may read and copy any document we file 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 further information on the operation of the Public Reference Room. We maintain a website at http://www.sunesis.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 the information we file with it, which means that we can disclose important information to you by referring you to another document that we have filed separately with the SEC. You should read the information incorporated by reference because it is an important part of this prospectus. Information in this prospectus supersedes information incorporated by reference that we filed with the SEC prior to the date of this prospectus, while information that we file later with the SEC will automatically update and supersede the information in this prospectus. We incorporate by reference into this registration statement of which this prospectus is a part the information or documents listed below that we have filed with the SEC (Commission File No. 000-51531):

We also incorporate by reference any future filings (other than Current Reports or portions thereof 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 unless such Form 8-K expressly provides to the contrary) made with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, including those made after the date of the initial filing of the registration statement of which this prospectus is a part and prior to effectiveness of such registration statement, until we file a post-effective amendment that indicates the termination of the offering of the securities made by this prospectus and will become a part of this prospectus from the date that such documents are filed with the SEC. Information in such future filings updates and supplements the information provided in this prospectus. Any statements in any such future filings will automatically be deemed to modify and supersede any information in any document we previously filed with the SEC that is incorporated or deemed to be incorporated herein by reference to the extent that statements in the later filed document modify or replace such earlier statements.

You may request a copy of these filings, at no cost, by writing to or telephoning us at the following address:


	*Per Share* *and* *Accompanying* *Warrants*		*Total*
Public offering price	$	2,000	$	5,000,000
Underwriting discount(1)	$	100	$	250,000
Proceeds, before expenses, to us	$	1,900	$	4,750,000


Underwriter	Number of Shares		Number of Warrants
Cowen and Company, LLC		1,050		525,000
Wells Fargo Securities, LLC		950		475,000
Oppenheimer & Co. Inc.		500		250,000

Total		2,500		1,250,000


	Per Share and Accompanying Warrant		Total
Public offering price	$	2,000	$	5,000,000
Underwriting discount	$	100	$	250,000
Proceeds, before expenses, to us	$	1,900	$	4,750,000


	Page
ABOUT THIS PROSPECTUS		ii
PROSPECTUS SUMMARY		1
RISK FACTORS		5
FORWARD-LOOKING STATEMENTS		5
FINANCIAL RATIOS		7
USE OF PROCEEDS		7
DESCRIPTION OF CAPITAL STOCK		7
DESCRIPTION OF DEBT SECURITIES		11
DESCRIPTION OF WARRANTS		17
LEGAL OWNERSHIP OF SECURITIES		19
PLAN OF DISTRIBUTION		23
LEGAL MATTERS		24
EXPERTS		24
WHERE YOU CAN FIND MORE INFORMATION		25
INCORPORATION OF CERTAIN INFORMATION BY REFERENCE		25


	Year Ended December 31,
	2009			2010			2011			2012			2013
Ratio of earnings to fixed charges(1)(2)		—			—			—			—			—
Deficiency of earnings available to cover fixed charges	$	(40,226	)	$	(24,587	)	$	(20,141	)	$	(43,951	)	$	(34,598	)


	Page
About This Prospectus Supplement		S-ii
Prospectus Supplement Summary		S-1
Risk Factors		S-7
Special Note Regarding Forward-Looking Statements		S-9
Use of Proceeds		S-11
Dilution		S-12
Concurrent Offering of Common Stock and Warrants to Purchase Common Stock		S-14
Description of Securities We Are Offering		S-15
Underwriting		S-19
Legal Matters		S-23
Experts		S-23
Where You Can Find More Information		S-23
Incorporation of Certain Information By Reference		S-24


Public offering price per share of Series D Preferred Stock and accompanying warrants			$	2,000
Historical net tangible book value per share as of June 30, 2017	$	0.53
Increase per share attributable to investors purchasing Series D Preferred Stock and warrants in this offering		0.13

As adjusted net tangible book value per share after this offering				0.66

Dilution per share to investors purchasing Series D Preferred Stock and warrants in this offering			$	1.34


Cowen		Wells Fargo Securities