As filed with the Securities and Exchange Commission on June 10, 2011

Registration No. 333-            

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form S-3

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

THRESHOLD PHARMACEUTICALS, INC.

(Exact Name of Registrant as Specified in Its Charter)

Delaware	94-3409596
(State or other jurisdiction of incorporation or organization)	(I.R.S. Employer Identification Number)

1300 Seaport Boulevard, Suite 500

Redwood City, California 94063

(650) 474-8200

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

Harold E. Selick, Ph.D.

Chief Executive Officer

1300 Seaport Boulevard

Redwood City, California 94063

Telephone: (650) 474-8200

Facsimile: (650) 474-2529

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

Copy to:

Stephen B. Thau

Morrison & Foerster LLP

755 Page Mill Road

Palo Alto, CA 94304

Telephone: (650) 813-5640

Facsimile: (650) 251-3745

Approximate date of commencement of proposed sale to the public: From time to time after this Registration Statement becomes effective.

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

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box. þ

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act of 1933, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ¨

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act of 1933, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ¨

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

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

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer,” and “smaller reporting company” in Rule 12b-2 of the Securities Exchange Act of 1934.

Large accelerated filer	¨	Accelerated filer	¨
Non-accelerated filer	¨  (Do not check if a smaller reporting company)	Smaller reporting company	þ

CALCULATION OF REGISTRATION FEE

Title of each class of securities to be registered	Amount to be registered (1)(2)(3)	Proposed maximum offering price per unit (3)	Aggregate maximum offering price (3)(4)(5)	Amount of registration fee (3)
Common stock, par value $.001 per share (6)
Preferred stock, par value $.001 per share
Debt securities
Warrants
Rights
Units (7)
Total			$50,000,000	$5,805

(1) Also includes an indeterminate aggregate principal amount and number of securities of each identified class of securities up to a proposed aggregate offering price of $50,000,000, which may be offered by the registrant from time to time in unspecified numbers and at indeterminate prices, and as may be issued upon conversion, redemption, repurchase, exchange or exercise of any securities registered hereunder, including under any applicable anti-dilution provisions. Except as provided in Rule 462(b) under Securities Act of 1933, in no event will the aggregate offering price of all types of securities issued by the Registrant pursuant to this registration statement exceed $50,000,000.

(2) Pursuant to Rule 416 under the Securities Act of 1933, this registration statement also covers any additional securities that may be offered or issued in connection with any stock split, stock dividend or similar transaction.

(3) Pursuant to General Instruction II.D. of Form S-3, the table lists each of the classes of securities being registered and the aggregate proceeds to be raised, but does not specify by each class information as to the amount to be registered, proposed maximum offering price per unit, and proposed maximum aggregate offering price.

(4) The proposed maximum aggregate offering price has been estimated solely to calculate the registration fee in accordance with Rule 457(o) under the Securities Act of 1933.

(5) Includes consideration to be received by the registrant, if applicable, for registered securities that are issuable upon exercise, conversion or exchange of other registered securities.

(6) Each share of common stock registered hereunder includes an associated Series A participating preferred stock purchase right. Until the occurrence of certain prescribed events, none of which has occurred, the Series A participating preferred stock purchase rights are not exercisable, are evidenced by certificates representing the common stock, and may be transferred only with the common stock. No separate consideration is payable for the Series A participating preferred stock purchase rights.

(7) Consisting of some or all of the securities listed above, in any combination, including common stock, preferred stock, debt securities and warrants.

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

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

SUBJECT TO COMPLETION, DATED JUNE 10, 2011

PROSPECTUS

$50,000,000

Common Stock

Preferred Stock

Debt Securities

Warrants

Rights

Units

From time to time, we may offer up to $50,000,000 of our common stock; preferred stock; debt securities; warrants or rights to purchase common stock, preferred stock or debt securities or any combination of these securities; and units consisting of common stock, preferred stock, debt securities or warrants or any combination of these securities, in one or more transactions. We may also offer common stock or preferred stock upon conversion of debt securities; and common stock upon conversion of preferred stock.

We will provide 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 documents incorporated by reference, may also add, update or change information contained in this prospectus. You should read this prospectus, the applicable prospectus supplement, any documents incorporated by reference and any related free writing prospectus carefully before buying any of the securities being offered.

We may offer and sell these securities to or through one or more underwriters, dealers and agents, or directly to purchasers, on a continuous or delayed basis.

Our common stock trades on the NASDAQ Capital Market under the symbol “THLD.” The applicable prospectus supplement will contain information, where applicable, as to any other listing, if any, of the securities covered by the applicable prospectus supplement.

INVESTING IN OUR SECURITIES INVOLVES RISKS. YOU SHOULD REVIEW CAREFULLY THE RISKS AND UNCERTAINTIES DESCRIBED 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.

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

The date of this prospectus is                     , 2011

TABLE OF CONTENTS

	Page
About this Prospectus		1
About Threshold Pharmaceuticals		2
Incorporation of Information by Reference		2
Where You Can Find Additional Information		3
Cautionary Note Regarding Forward-Looking Statements		3
Risk Factors		4
Description of Securities We May Offer		4
Description of Capital Stock		4
Description of Debt Securities		8
Description of Warrants		14
Description of Rights		16
Description of Units		17
Use of Proceeds		18
Plan of Distribution		18
Legal Matters		19
Experts		20
EXHIBIT 4.1
EXHIBIT 5.1
EXHIBIT 23.2

ABOUT THIS PROSPECTUS

This document is called a prospectus and is part of a registration statement that we have filed with the Securities and Exchange Commission (“SEC”), using a “shelf” registration process. Under this shelf registration process, we may, from time to time, offer shares of our common stock and preferred stock, various series of debt securities or warrants or rights to purchase any of such securities, either individually or in units, in one or more offerings, in amounts we will determine from time to time, up to a total dollar amount of $50,000,000.

This prospectus provides you with a general description of the securities we may offer. Each time we offer a type or series of securities described in this prospectus, we will provide a prospectus supplement, or information that is incorporated by reference into this prospectus, containing more specific information about the terms of the securities that we are 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 and securities. This prospectus, together with applicable prospectus supplements, any information incorporated by reference and any related free writing prospectuses, includes all material information relating to these offerings and securities. We may also add, update or change in the prospectus supplement any of the information contained in this prospectus or in the documents that we have incorporated by reference into this prospectus, including without limitation, a discussion of any risk factors or other special considerations that apply to these offerings or securities or the specific plan of distribution. If there is any inconsistency between the information in this prospectus and a prospectus supplement or information incorporated by reference having a later date, you should rely on the information in that prospectus supplement or incorporated information having a later date. We urge you to read carefully this prospectus, any applicable prospectus supplement and any related free writing prospectus, together with the information incorporated herein by reference as described under the heading “Where You Can Find More Information,” before buying any of the securities being offered.

You should rely only on the information we have provided or incorporated by reference in this prospectus, any applicable prospectus supplement and any related free writing prospectus. We have not authorized anyone to provide you with different information. No dealer, salesperson or other person is authorized to give any information or to represent anything not contained in this prospectus, any applicable prospectus supplement or any related free writing prospectus.

Neither the delivery of this prospectus nor any sale made under it implies that there has been no change in our affairs or that the information in this prospectus is correct as of any date after the date of this prospectus. You should assume that the information 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 that any information we have incorporated by reference is accurate only as of the date of the document incorporated by reference, regardless of the time of delivery of this prospectus, any applicable prospectus supplement or any related free writing prospectus, or any sale of a security.

This prospectus 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 is a part, and you may obtain copies of those documents as described below under “Where You Can Find More Information.”

Market data and certain industry forecasts used in this prospectus and the documents included in this prospectus were obtained from market research, publicly available information and industry publications. We believe that these sources are generally reliable, but the accuracy and completeness of such information is not guaranteed. We have not independently verified this information, and we do not make any representation as to the accuracy of such information.

In this prospectus, unless the context otherwise requires, references to “we,” “us,” “our” or similar terms, as well as references to “Threshold Pharmaceuticals” or the “Company,” refer to Threshold Pharmaceuticals, Inc., either alone or together with our subsidiaries.

The name Threshold Pharmaceuticals, Inc. is our trademark. Other trademarks, product names and company names appearing in this prospectus and documents included in this prospectus or incorporated by reference in this prospectus are the property of their respective owners.

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ABOUT THRESHOLD PHARMACEUTICALS

We are a biotechnology company focused on the discovery and development of drugs targeting the microenvironment of solid tumors as novel treatments for patients living with cancer. The microenvironment of solid tumors is characterized by, among other things, hypoxia or lack of oxygen as a consequence of disordered blood vessel growth. This hypoxic environment is known to be resistant to standard chemotherapy and radiation. It is thought to be responsible for the poor prognosis of patients with solid tumors and hematological malignancies (blood cancers) and treating the hypoxic environment is currently believed to be a significant unmet medical need. Our hypoxia activated prodrug (“HAP”) product candidates, including TH-302, are designed to specifically target the hypoxic microenvironment of tumors by selective activation of the prodrug to release a potent cytotoxin. Our focus is on product candidates for the treatment of patients with cancer. Our clinical development efforts are currently focused on TH-302, for which we have exclusive worldwide marketing rights. TH-302, which we discovered, is a novel drug candidate that is activated under severe hypoxic conditions and was designed to specifically target the severe hypoxic regions that are believed to be present in all solid tumors. TH-302 is currently in Phase 1, Phase 1/2 and Phase 2 clinical trials. We are working to broaden the applicability of TH-302 to other cancers as well as to discover additional hypoxia activated prodrugs that will selectively target cancer cells.

We were incorporated in Delaware on October 17, 2001. Our principal executive offices are located at 1300 Seaport Boulevard, Suite 500 Redwood City, California, 94063. Our telephone number is (650) 474-8200. Our website is located at www.thresholdpharm.com. Information contained on, or that can be accessed through, our website is not part of this prospectus.

INCORPORATION OF INFORMATION BY REFERENCE

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 those documents. The information we incorporate by reference is an important part of this prospectus, and certain information that we will later file with the SEC will automatically update and supersede this information. We incorporate by reference the documents listed below as well as any future filings made with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act from the date of the initial registration statement and prior to the effectiveness of this registration statement, and any filings made after the date of this prospectus until we sell all of the securities under this prospectus, except that we do not incorporate any document or portion of a document that was furnished and deemed by the rules of the SEC not to have been filed:

• Our Annual Report on Form 10-K for the fiscal year ended December 31, 2010, filed with the SEC on March 24, 2011;

• The portions of our definitive Proxy Statement on Schedule 14A for our 2011 Annual Meeting of Stockholders, filed with the SEC on April 28, 2011, that are incorporated by reference into our Annual Report on Form 10-K for the fiscal year ended December 31, 2010;

• Our Quarterly Report on Form 10-Q for the quarter ended March 31, 2011, filed with the SEC on May 12, 2011;

• Our Current Reports on Form 8-K filed with the SEC on January 25, 2011, February 25, 2011, March 11, 2011, April 14, 2011, April 21, 2011, April 25, 2011, May 27, 2011, June 1, 2011 and June 6, 2011;

• The description of our capital stock contained in our Registration Statement on Form 8-A, as amended, filed with the SEC on January 28, 2005, including any amendment or report filed for the purpose of updating such description (including an amendment thereto dated as of February 4, 2005); and

• The description of our Series A participating preferred stock contained in our Registration Statement on Form 8-A filed with the SEC on August 9, 2006, including any amendment or report filed for the purpose of updating such description.

Additionally, all reports and other documents subsequently filed by us pursuant to Sections 13(a), 13(c), 14, and 15(d) of the Exchange Act after (i) the date of the initial registration statement and prior to effectiveness of the registration statement; and (ii) the date of this prospectus and prior to the termination or completion of this offering, shall be deemed to be incorporated by reference in this prospectus and to be part hereof from the date of filing of such reports and other documents. Any information that we subsequently file with the SEC that is incorporated by reference as described above will automatically update and supersede any previous information that is part of this prospectus.

We hereby undertake to provide without charge to each person, including any beneficial owner, to whom a copy of this prospectus is delivered, upon written or oral request of any such person, a copy of any and all of the information that has been or may be incorporated by reference in this prospectus, other than exhibits to such documents. Requests for such copies should be directed to our Investor Relations Department at 1300 Seaport Boulevard, Suite 500, Redwood City, California 94063, Telephone (650) 474-8200.

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WHERE YOU CAN FIND ADDITIONAL INFORMATION

We have filed with the SEC a registration statement on Form S-3 under the Securities Act of 1933, as amended (“Securities Act”), with respect to the securities covered by this prospectus. This prospectus, which is a part of the registration statement, does not contain all of the information set forth in the registration statement or the exhibits and schedules filed therewith. For further information with respect to us and the securities covered by this prospectus, please see the registration statement and the exhibits filed with the registration statement. A copy of the registration statement and the exhibits filed with the registration statement may be inspected without charge at the Public Reference Room maintained by the SEC, located 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 also maintains an Internet website that contains reports, proxy and information statements and other information regarding registrants that file electronically with the SEC. The address of the website is http://www.sec.gov.

We are subject to the information and periodic reporting requirements of the Securities Exchange Act of 1934, as amended (“Exchange Act”), and, in accordance therewith, we file periodic reports, proxy statements and other information with the SEC. Such periodic reports, proxy statements and other information are available for inspection and copying at the Public Reference Room and website of the SEC referred to above. We maintain a website at http://www.thresholdpharm.com. You may access our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and amendments to those reports filed pursuant to Sections 13(a) or 15(d) of the Exchange Act with the SEC free of charge at our website as soon as reasonably practicable after such material is electronically filed with, or furnished to, the SEC. Our website and the information contained on that site, or connected to that site, are not incorporated into and are not a part of this prospectus.

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus and the documents we incorporate by reference in this prospectus contains forward-looking statements within the meaning of Section 27A of the Securities Act and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act. We may, in some cases, use words such as “project,” “believe,” “anticipate,” “plan,” “expect,” “estimate,” “intend,” “should,” “would,” “could,” “potentially,” “will,” or “may,” or other words that convey uncertainty of future events or outcomes to identify these forward-looking statements. Forward-looking statements may include statements about:

• our ability to enroll and complete clinical trials for our TH-302 development program;

• the success of any clinical trials that we commence;

• the timing of results of our clinical trials;

• whether our product candidates, including TH-302, produce unwanted or unanticipated side effects;

• the costs and timing of obtaining drug supply for our pre-clinical and clinical activities;

• our receipt of regulatory approvals;

• our ability to establish and maintain intellectual property rights in our product candidates;

• uncertainties associated with obtaining and enforcing patents and other intellectual property rights;

• whether any product candidates that we are able to commercialize are safer or more effective than other marketed products, treatments or therapies;

• our research and development activities, including development of new product candidates, and projected expenditures;

• our ability to complete preclinical and clinical testing successfully for new product candidates that we may develop or license;

• our ability to have manufactured sufficient supplies of active pharmaceutical ingredient, or API, and drug product for clinical testing and commercialization;

• our ability to retain and hire necessary employees and appropriately staff our development programs;

• our cash needs; and

• our financial performance.

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There are a number of important factors that could cause actual results to differ materially from the results anticipated by these forward-looking statements. These important factors include those that we discuss under the heading “Risk Factors” and in other sections of our Quarterly Report on Form 10-Q for the quarter ended March 31, 2011, as well as in our other reports filed from time to time with the SEC that are incorporated by reference into this prospectus. You should read these factors and the other cautionary statements made in this prospectus and in the documents we incorporate by reference into this prospectus as being applicable to all related forward-looking statements wherever they appear in this prospectus or the documents we incorporate by reference into this prospectus. If one or more of these factors materialize, or if any underlying assumptions prove incorrect, our actual results, performance or achievements may vary materially from any future results, performance or achievements expressed or implied by these forward-looking statements. We undertake no obligation to publicly update any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law.

RISK FACTORS

Investing in our securities involves significant risks. You should review carefully the risks and uncertainties described under the heading “Risk Factors” contained in, or incorporated into, the applicable prospectus supplement and any related free writing prospectus, and under similar headings in the other documents that are incorporated by reference herein or therein. Each of the referenced risks and uncertainties could adversely affect our business, operating results and financial condition, as well as adversely affect the value of an investment in our securities. Additional risks not known to us or that we believe are immaterial may also adversely affect our business, operating results and financial condition and the value of an investment in our securities.

DESCRIPTION OF SECURITIES WE MAY OFFER

We may offer, from time to time, shares of our common stock and preferred stock, various series of debt securities or warrants or rights to purchase any of such securities, either individually or in units, in amounts we will determine from time to time, under this prospectus at prices and on terms to be determined by market conditions at the time of offering. This prospectus provides you with a general description of the securities we may offer. See “Description of Capital Stock,” “Description of Debt Securities,” Description of Warrants,” “Description of Rights,” and “Description of Units” below. Each time we offer a type or series of securities, 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, if applicable;

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

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

• voting or other rights, if any;

• conversion prices, if any; and

• important federal income tax considerations.

The prospectus supplement and any related free writing prospectus also may supplement, or, as applicable, 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.

The terms of any particular offering, the initial offering price and the net proceeds to us will be contained in the prospectus supplement, information incorporated by reference or free writing prospectus relating to such offering.

DESCRIPTION OF CAPITAL STOCK

The description below of our capital stock and provisions of our amended and restated certificate of incorporation and amended and restated bylaws are summaries and are qualified by reference to the amended and restated certificate of incorporation and the amended and restated bylaws. These documents are filed as exhibits to the registration statement of which this prospectus is a part.

Our amended and restated certificate of incorporation authorizes the issuance of up to 150,000,000 shares of common stock, par value $0.001 per share, and 2,000,000 shares of preferred stock, par value $0.001 per share. The rights and preferences of the preferred stock may be established from time to time by our board of directors.

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Common Stock

Each holder of common stock is entitled to one vote for each share on all matters submitted to a vote of the stockholders, except matters that relate only to one or more of the series of preferred stock, and each holder does not have cumulative voting rights. Accordingly, the holders of a majority of the shares of common stock entitled to vote in any election of directors can elect all of the directors standing for election, if they so choose.

Subject to preferences that may be applicable to any then outstanding preferred stock, holders of common stock are entitled to receive ratably those dividends, if any, as may be declared from time to time by the board of directors out of legally available funds. In the event of our liquidation, dissolution or winding up, holders of common stock will be entitled to share ratably in the net assets legally available for distribution to stockholders after the payment of all of our debts and other liabilities and the satisfaction of any liquidation preference granted to the holders of any outstanding shares of preferred stock.

Holders of common stock have no preemptive or conversion rights or other subscription rights, and there are no redemption or sinking fund provisions applicable to the common stock. All outstanding shares of common stock are, and the shares of common stock offered by us in this offering, when issued and paid for, will be fully paid and nonassessable. 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.

Preferred Stock

Our board of directors is authorized, subject to any limitations prescribed by law, without stockholder approval, to issue up to an aggregate of 2,000,000 shares of preferred stock in one or more series and to fix the rights, preferences, privileges and restrictions granted to or imposed upon the preferred stock, including voting rights, dividend rights, conversion rights, redemption privileges and liquidation preferences. The rights of the holders of common stock will be subject to, and may be adversely affected by, the rights of holders of any preferred stock that may be issued in the future. Issuance of preferred stock, while providing flexibility in connection with possible acquisitions and other corporate purposes, could have the effect of delaying, deferring or preventing a change in control of us. We have no present plans to issue any shares of preferred stock, but 200,000 shares of preferred stock have been designated as “Series A Participating Preferred Stock” to satisfy our obligations with respect to the Rights described below.

Warrants

As of June 9, 2011, we had outstanding warrants to purchase an aggregate of 3,588,221 shares of our common stock with an exercise price of $1.86 per share, warrants to purchase an aggregate of 7,329,819 shares of our common stock with an exercise price of $2.05 per share, and warrants to purchase an aggregate of 5,725,227 shares of our common stock with an exercise price of $2.46 per share. The exercise price and/or the number of shares of common stock issuable upon exercise of the warrants may be adjusted in certain circumstances, including certain issuances of securities at a price equal to less than the then current exercise price, subdivisions and stock splits, stock dividends, combinations, reorganizations, reclassifications, consolidations, mergers or sales of properties and assets and upon the issuance of certain assets or securities to holders of our common stock, as applicable.

Rights Agreement

In August 2006, our board of directors declared a dividend of one preferred stock purchase right, a Right, for each share of common stock outstanding as of the close of business on August 23, 2006. The Rights currently trade with, and are inseparable from, the common stock. The Rights will become exercisable only if a person or group (i) acquires beneficial ownership of 15% or more of our outstanding common stock or (ii) commences a tender or exchange offer that would result in that person or group becoming a beneficial owner of 15% or more of our outstanding common stock. Each Right allows its holder to purchase from us one one-thousandth of a share of Series A Participating Preferred Stock at a purchase price of $25.00 per one-thousandth of a preferred share, subject to adjustment. The Rights expire on August 8, 2016, unless we extend the expiration date, redeem or exchange the Rights on an earlier date or the Rights expire upon consummation of certain mergers, consolidations or sales of assets. Effective July 10, 2008, September 29, 2009, and March 11, 2011 we amended the terms of the Rights to ensure that they would not become exercisable solely by virtue of our sales of securities completed on August 29, 2008, October 5, 2009, and March 11, 2011 respectively.

Effect of Certain Provisions of our Amended and Restated Certificate of Incorporation and Bylaws and the Delaware Anti-Takeover Statute

Amended and Restated Certificate of Incorporation and Bylaws

Some provisions of Delaware law and our amended and restated certificate of incorporation and bylaws contain provisions that could make the following transactions more difficult:

• acquisition of us by means of a tender offer;

• acquisition of us by means of a proxy contest or otherwise; or

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• removal of our incumbent officers and directors.

These provisions, summarized below, are expected to discourage coercive takeover practices and inadequate takeover bids and to promote stability in our management. These provisions are also designed to encourage persons seeking to acquire control of us to first negotiate with our board of directors.

• Undesignated Preferred Stock. The ability to authorize undesignated preferred stock makes it possible for our board of directors to issue one or more series of preferred stock with voting or other rights or preferences that could impede the success of any attempt to change control of us. These and other provisions may have the effect of deferring hostile takeovers or delaying changes in control or management of our company.

• Stockholder Meetings. Our charter documents provide that a special meeting of stockholders may be called only by the chairman of our board of directors or by our president, or by a resolution adopted by a majority of our board of directors.

• Requirements for Advance Notification of Stockholder Nominations and Proposals. Our bylaws establish advance notice procedures with respect to stockholder proposals and the nomination of candidates for election as directors, other than nominations made by or at the direction of our board of directors or a committee of the board of directors.

• Elimination of Stockholder Action by Written Consent. Our amended and restated certificate of incorporation eliminates the right of stockholders to act by written consent without a meeting.

• Amendment of Bylaws. Any amendment of our bylaws by our stockholders requires approval by holders of at least 66 ²/3% of our then outstanding common stock, voting together as a single class.

• Staggered Board of Directors. Our amended and restated certificate of incorporation provide for the division of our board of directors into three classes, as nearly equal in size as possible, with staggered three-year terms. Under our amended and restated certificate of incorporation and amended and restated bylaws, any vacancy on the board of directors, including a vacancy resulting from an enlargement of the board of directors, may only be filled by vote of a majority of the directors then in office. The classification of the board of directors and the limitations on the removal of directors and filling of vacancies would have the effect of making it more difficult for a third party to acquire control of us, or of discouraging a third party from acquiring control of us.

Delaware Anti-Takeover Statute

We are subject to Section 203 of the General Corporation Law of the State of Delaware. This law prohibits a publicly held Delaware corporation from engaging in any business combination with any interested stockholder for a period of three years following the date that the stockholder became an interested stockholder unless:

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

• upon consummation of the transaction which resulted in the stockholder becoming an interested stockholder, the interested stockholder owned at least 85% of the voting stock of the corporation outstanding at the time the transaction commenced, excluding for purposes of determining the number of shares outstanding those shares owned by persons who are directors and also officers and by employee stock plans in which employee participants do not have the right to determine confidentially whether shares held subject to the plan will be tendered in a tender or exchange offer; or

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

Section 203 defines “business combination” to include:

• any merger or consolidation involving the corporation and the interested stockholder;

• any sale, transfer, pledge or other disposition of 10% or more of our assets involving the interested stockholder;

• in general, any transaction that results in the issuance or transfer by us of any of our stock to the interested stockholder; or

• the receipt by the interested stockholder of the benefit of any loans, advances, guarantees, pledges or other financial benefits provided by or through the corporation.

In general, Section 203 defines an “interested stockholder” as an entity or person beneficially owning 15% or more of the outstanding voting stock of the corporation and any entity or person affiliated with or controlling or controlled by the entity or person.

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Limitation of Liability

The Delaware General Corporation Law (“DGCL”) permits Delaware corporations to eliminate or limit the monetary liability of directors for breach of their fiduciary duty of care, subject to limitations. Our certificate of incorporation provides that our directors are not liable to us or our stockholders for monetary damages for breach of fiduciary duty as a director, except for liability for: (i) any breach of the director’s duty of loyalty to us or our stockholders; (ii) acts or omissions not in good faith or which involve intentional misconduct or a knowing violation of law; (iii) under Section 174 of the DGCL; or (iv) any transaction from which a director derived an improper personal benefit.

The DGCL provides for indemnification of directors, officers, employees and agents, subject to limitations. Our bylaws and the appendix thereto provide for the indemnification of our directors, officers, employees and agents to the extent permitted by Delaware law. Our directors and officers also are insured against certain liabilities for actions taken in such capacities, including liabilities under the Securities Act.

Section 145(a) of the DGCL provides that a Delaware corporation may indemnify any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action, suit or proceeding, whether civil, criminal, administrative or investigative (other than an action by or in the right of the corporation) by reason of the fact that such person is or was a director, officer, employee or agent of the corporation or is or was serving at the request of the corporation as a director, officer, employee or agent of another corporation or enterprise, against expenses, judgments, fines and amounts paid in settlement actually and reasonably incurred by such person in connection with such action, suit or proceeding if such person acted in good faith and in a manner such person reasonably believed to be in or not opposed to the best interests of the corporation, and, with respect to any criminal action or proceeding, if such person had no cause to believe the conduct was unlawful.

Section 145(b) of the DGCL provides that a Delaware corporation may indemnify any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action or suit by or in the right of the corporation to procure a judgment in its favor by reason of the fact that such person acted in any of the capacities set forth above, against expenses actually and reasonably incurred by such person in connection with the defense or settlement of such action or suit if such person acted under similar standards to those set forth above, except that no indemnification may be made in respect to any claim, issue or matter as to which such person shall have been adjudged to be liable to the corporation unless and only to the extent that the court in which such action or suit was brought shall determine that despite the adjudication of liability, but in view of all the circumstances of the case, such person is fairly and reasonably entitled to be indemnified for such expenses which the court shall deem proper.

Section 145 of the DGCL further provides that to the extent a director or officer of a corporation has been successful in the defense of any action, suit or proceeding referred to in subsection (a) and (b) or in the defense of any claim, issue or matter therein, such person shall be indemnified against expenses actually and reasonably incurred by such person in connection therewith; that indemnification provided for by Section 145 shall not be deemed exclusive of any other rights to which the indemnified party may be entitled; and that the corporation may purchase and maintain insurance on behalf of a director or officer of the corporation against any liability asserted against such officer or director and incurred by such person in any such capacity or arising out of such person’s status as such, whether or not the corporation would have the power to indemnify such person against such liabilities under Section 145.

As permitted by Section 102(b)(7) of the DGCL, our certificate of incorporation provides that none or our directors shall be liable to us or our stockholders for monetary damages for breach of fiduciary duty as a director. However, this provision does not eliminate or limit the liability of a director for acts or omissions not in good faith or for breaching such person’s duty of loyalty, engaging in intentional misconduct or knowingly violating the law, paying a dividend or approving a stock repurchase which was illegal, or obtaining an improper personal benefit. A provision of this type has no effect on the availability of equitable remedies, such as injunction or rescission, for breach of fiduciary duty.

We have a policy of directors’ liability insurance that insures the directors and officers against the cost of defense, settlement or payment of a judgment under certain circumstances.

We believe that the foregoing policies and provisions of our certificate of incorporation and bylaws are necessary to attract and retain qualified officers and directors. Insofar as indemnification for liabilities arising under the Securities Act may be permitted with respect to our directors, officers or persons controlling the registrant pursuant to the foregoing provisions, the registrant has been informed that in the opinion of the SEC such indemnification is against public policy as expressed in the Securities Act and is therefore unenforceable.

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Listing

Our common stock trades on the NASDAQ Capital Market under the symbol “THLD.”

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is BNY Mellon Shareowner Services, P.O Box 358016, Pittsburgh, PA 15252-8016.

DESCRIPTION OF DEBT SECURITIES

The following sets forth certain general terms and provisions of the base indenture, to be entered into between us and an entity, identified in the applicable prospectus supplement, as trustee, under which the debt securities are to be issued from time to time. We have filed a form of the base indenture as an exhibit to the registration statement of which this prospectus is a part. When the debt securities are offered in the future, the applicable offering material will explain the particular terms of those securities and the extent to which the general provisions may apply. The base indenture, as it may be supplemented, amended or modified from time to time, is referred to in this prospectus as the “indenture.” Wherever particular sections or defined terms of the indenture are referred to, it is intended that such sections or defined terms shall be incorporated herein by reference. In this section of this prospectus, the term “the Company” refers only to Threshold Pharmaceuticals, Inc. and not to any of its subsidiaries.

This summary and any description of the indenture and any debt securities in the applicable prospectus supplement, information incorporated by reference or free writing prospectus is subject to and is qualified in its entirety by reference to all the provisions of the indenture, any indenture supplement and the terms of the debt securities, including, in each case, the definitions therein of certain terms. We will file each of these documents, as applicable, with the SEC and incorporate them by reference as an exhibit to the registration statement of which this prospectus is a part on or before the time we issue a series of debt securities. See “Where You Can Find More Information” and “Incorporation of Certain Documents by Reference” above for information on how to obtain a copy of a document when it is filed. The specific terms of the debt securities as described in a prospectus supplement, information incorporated by reference, or free writing prospectus will supplement and, if applicable, may modify or replace the general terms described in this section.

The debt securities will represent unsecured general obligations of the Company, unless otherwise provided in the applicable offering material. As indicated in the applicable offering material, the debt securities will either be senior debt or subordinated debt.

General

The indenture does not limit the amount of debt securities that may be issued thereunder. The applicable prospectus supplement, documents incorporated by reference, or free writing prospectus with respect to any debt securities will set forth the following terms of the debt securities offered pursuant thereto:

• the title and series of such debt securities;

• any limit upon the aggregate principal amount of such debt securities of such series;

• whether such debt securities will be in global or other form;

• the date or dates and method or methods by which principal and any premium on such debt securities is payable;

• the interest rate or rates (or method by which such rate will be determined), if any;

• the dates on which any such interest will be payable and the method of payment;

• whether and under what circumstances any additional amounts are payable with respect to such debt securities;

• the notice, if any, to holders of such debt securities regarding the determination of interest on a floating rate debt security;

• the basis upon which interest on such debt securities shall be calculated, if other than that of a 360 day year of twelve 30-day months;

• the place or places where the principal of and interest or additional amounts, if any, on such debt securities will be payable;

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• any redemption or sinking fund provisions, or the terms of any repurchase at the option of the holder of the debt securities;

• the denominations of such debt securities, if other than $1,000 and integral multiples thereof;

• any rights of the holders of such debt securities to convert the debt securities into, or exchange the debt securities for, other securities or property;

• the terms, if any, on which payment of principal or any premium, interest or additional amounts on such debt securities will be payable in a currency other than U.S. dollars;

• the terms, if any, by which the amount of payments of principal or any premium, interest or additional amounts on such debt securities may be determined by reference to an index, formula, financial or economic measure or other methods;

• if other than the principal amount hereof, the portion of the principal amount of such debt securities that will be payable upon declaration of acceleration of the maturity thereof or provable in bankruptcy;

• any events of default or covenants in addition to or in lieu of those described herein and remedies therefor;

• whether such debt securities will be subject to defeasance or covenant defeasance;

• the terms, if any, upon which such debt securities are to be issuable upon the exercise of warrants, units or rights;

• any trustees and any authenticating or paying agents, transfer agents or registrars or any other agents with respect to such debt securities;

• the terms, if any, on which such debt securities will be subordinate to other debt of the Company;

• whether such debt securities will be guaranteed and the terms thereof;

• whether such debt securities will be secured by collateral and the terms of such security; and

• any other specific terms of such debt securities and any other deletions from or additions to or modifications of the indenture with respect to such debt securities.

Debt securities may be presented for exchange, conversion or transfer in the manner, at the places and subject to the restrictions set forth in the debt securities and the applicable offering material. Such services will be provided without charge, other than any tax or other governmental charge payable in connection therewith, but subject to the limitations provided in the indenture.

The indenture does not contain any covenant or other specific provision affording protection to holders of the debt securities in the event of a highly leveraged transaction or a change in control of the Company, except to the limited extent described below under “— Consolidation, Merger and Sale of Assets.”

Modification and Waiver

The indenture provides that supplements to the indenture and the applicable supplemental indentures may be made by the Company and the trustee for the purpose of adding any provisions to or changing in any manner or eliminating any of the provisions of the indenture or of modifying in any manner the rights of the holders of debt securities of a series under the indenture or the debt securities of such series, with the consent of the holders of a majority (or such greater amount as is provided for any series of debt securities) in principal amount of the outstanding debt securities issued under such indenture that are affected by the supplemental indenture, voting as a single class; provided that no such supplemental indenture may, without the consent of the holder of each such debt security affected thereby, among other things:

(a) change the stated maturity of the principal of, or any premium, interest or additional amounts on, such debt securities, or reduce the principal amount thereof, or reduce the rate or extend the time of payment of interest or any additional amounts thereon, or reduce any premium payable on redemption thereof or otherwise, or reduce the amount of the principal of debt securities issued with original issue discount that would be due and payable upon an acceleration of the maturity thereof or the amount thereof provable in bankruptcy, or change the redemption provisions or adversely affect the right of repayment at the option of the holder, or change the place of payment or currency in which the principal of, or any premium, interest or additional amounts with respect to any debt security is payable, or impair or affect the right of any holder of debt securities to institute suit for the payment after such payment is due (except a rescission and annulment of acceleration with respect to a series of debt securities by the holders of at least a majority in aggregate principal amount of the then outstanding debt securities of such series and a waiver of the payment default that resulted from such acceleration);

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(b) reduce the percentage of outstanding debt securities of any series, the consent of the holders of which is required for any such supplemental indenture, or the consent of whose holders is required for any waiver or reduce the quorum required for voting;

(c) modify any of the provisions of the sections of such indenture relating to supplemental indentures with the consent of the holders, waivers of past defaults or securities redeemed in part, except to increase any such percentage or to provide that certain other provisions of such indenture cannot be modified or waived without the consent of each holder affected thereby; or

(d) make any change that adversely affects the right to convert or exchange any security into or for common stock or other securities, cash or other property in accordance with the terms of the applicable debt security.

The indenture provides that a supplemental indenture that changes or eliminates any covenant or other provision of the indenture that has expressly been included solely for the benefit of one or more series of debt securities, or that modifies the rights of the holders of such series with respect to such covenant or other provision, shall be deemed not to affect the rights under the indenture of the holders of debt securities of any other series.

The indenture provides that the Company and the trustee may, without the consent of the holders of any series of debt securities issued thereunder, enter into additional supplemental indentures for one of the following purposes:

(a) to evidence the succession of another corporation to the Company and the assumption by any such successor of the covenants of the Company in such indenture and in the debt securities issued thereunder;

(b) to add to the covenants of the Company or to surrender any right or power conferred on the Company pursuant to the indenture;

(c) to establish the form and terms of debt securities issued thereunder;

(d) to evidence and provide for a successor trustee under such indenture with respect to one or more series of debt securities issued thereunder or to provide for or facilitate the administration of the trusts under such indenture by more than one trustee;

(e) to cure any ambiguity, to correct or supplement any provision in the indenture that may be defective or inconsistent with any other provision of the indenture or to make any other provisions with respect to matters or questions arising under such indenture; provided that no such action pursuant to this clause (e) shall adversely affect the interests of the holders of any series of debt securities issued thereunder in any material respect;

(f) to add to, delete from or revise the conditions, limitations and restrictions on the authorized amount, terms or purposes of issue, authentication and delivery of securities under the indenture;

(g) to add any additional events of default with respect to all or any series of debt securities;

(h) to supplement any of the provisions of the indenture as may be necessary to permit or facilitate the defeasance and discharge of any series of debt securities, provided that such action does not adversely affect the interests of any holder of an outstanding debt security of such series or any other security in any material respect;

(i) to make provisions with respect to the conversion or exchange rights of holders of debt securities of any series;

(j) to pledge to the trustee as security for the debt securities of any series any property or assets;

(k) to add guarantees in respect of the debt securities of one or more series;

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(l) to change or eliminate any of the provisions of the indenture, provided that any such change or elimination become effective only when there is no security of any series outstanding created prior to the execution of such supplemental indenture which is entitled to the benefit of such provision;

(m) to provide for certificated securities in addition to or in place of global securities;

(n) to qualify such indenture under the Trust Indenture Act of 1939, as amended;

(o) with respect to the debt securities of any series, to conform the text of the indenture or the debt securities of such series to any provision of the description thereof in the Company’s offering memorandum or prospectus relating to the initial offering of such debt securities, to the extent that such provision, in the good faith judgment of the Company, was intended to be a verbatim recitation of a provision of the indenture or such securities; or

(p) to make any other change that does not adversely affect the rights of holders of any series of debt securities issued thereunder in any material respect.

Unless otherwise provided in any applicable prospectus supplement, documents incorporated by reference or free writing prospectus, the following will be events of default under the indenture with respect to each series of debt securities issued thereunder:

(a) default for 30 days in the payment when due of interest on, or any additional amount in respect of, any series of debt securities;

(b) default in the payment of principal or any premium on any series of the debt securities outstanding under the indenture when due;

(c) default in the payment, if any, of any sinking fund installment when and as due by the terms of any debt security of such series, subject to any cure period that may be specified in any debt security of such series;

(d) failure by the Company for 60 days after receipt by registered or certified mail of written notice from the trustee upon instruction from holders of at least 25% in principal amount of the then outstanding debt securities of such series to comply with any of the other agreements in the indenture and stating that such notice is a “Notice of Default” under the indenture; provided, that if such failure cannot be remedied within such 60-day period, such period shall be automatically extended by another 60 days so long as: (i) such failure is subject to cure; and (ii) the Company is using commercially reasonable efforts to cure such failure; and provided, further, that a failure to comply with any such other agreement in the indenture that results from a change in generally accepted accounting principles shall not be deemed to be an event of default;

(e) certain events of bankruptcy, insolvency or reorganization of the Company; and

(f) any other event of default provided in a supplemental indenture with respect to a particular series of debt securities, provided that any event of default that results from a change in generally accepted accounting principles shall not be deemed to be an event of default.

In case an event of default specified in clause (a) or (b) above shall occur and be continuing with respect to any series of debt securities, holders of at least 25% in aggregate principal amount of the debt securities of such series then outstanding may declare the principal (or, in the case of discounted debt securities, the amount specified in the terms thereof) of such series to be due and payable. In case an event of default specified in clause (c), (d) (other than as it relates to an event of default with respect to the Company’s covenant to file reports with the SEC (see “— Certain Covenants — Reports” below)) or (f) above shall occur and be continuing with respect to any series of debt securities, holders of at least a majority in aggregate principal amount of the debt securities of such series then outstanding may declare the principal (or, in the case of discounted debt securities, the amount specified in the terms thereof) of such series to be due and payable. If an event of default described in (d) above shall occur with respect to the Company’s covenant to file reports with the SEC (see “— Certain Covenants — Reports” below), then the sole remedy of holders in such case shall be to receive additional interest, if and to the extent required, by the terms of the particular series of debt securities. If an event of default described in (e) above shall occur and be continuing then the principal amount (or, in the case of discounted debt securities, the amount specified in the terms thereof) of all the debt securities outstanding shall be and become due and payable immediately, without notice or other action by any holder or the trustee, to the full extent permitted by law. Any past or existing default or event of default with respect to any series of debt securities under such indenture may be waived by the holders of a majority in aggregate principal amount of the outstanding debt securities of such series, except in each case a continuing default: (i) in the payment of the principal of, any premium or interest on, or any additional amounts with respect to, any debt security of such series; or (ii) in respect of a covenant or provision which cannot be modified or amended without the consent of each holder affected thereby.

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The indenture provides that the trustee may withhold notice to the holders of any default with respect to any series of debt securities (except in payment of principal of or interest or premium on, or sinking fund payment in respect of, the debt securities) if the trustee considers it in the interest of holders to do so.

The indenture contains a provision entitling the trustee to be indemnified by the holders before proceeding to exercise any trust or power under the indenture at the request of such holders. The indenture provides that the holders of a majority in aggregate principal amount of the then outstanding debt securities of any series may direct the time, method and place of conducting any proceedings for any remedy available to the trustee or of exercising any trust or power conferred upon the trustee with respect to the debt securities of such series; provided, however, that the trustee may decline to follow any such direction if, among other reasons, the trustee determines in good faith that the actions or proceedings as directed may not lawfully be taken or would be unduly prejudicial to the holders of the debt securities of such series not joining in such direction. The right of a holder to institute a proceeding with respect to a series of debt securities will be subject to certain conditions precedent including, without limitation, that in case of an event of default specified in clause (a), (b) or (e) of the first paragraph above under “— Events of Default,” holders of at least 25%, or in case of an event of default other than specified in clause (a), (b) or (e) of the first paragraph above under “— Events of Default”, holders of at least a majority, in aggregate principal amount of the debt securities of such series then outstanding make a written request upon the trustee to exercise its powers under such indenture, indemnify the trustee and afford the trustee reasonable opportunity to act. Notwithstanding the foregoing, the holder has an absolute right to receipt of the principal of, premium, if any, and interest when due on the debt securities, to require conversion of debt securities if such indenture provides for convertibility at the option of the holder and to institute suit for the enforcement thereof.

Consolidation, Merger and Sale of Assets

The indenture provides that the Company may not directly or indirectly consolidate with or merge with or into, or sell, assign, transfer, lease, convey or otherwise dispose of all or substantially all of its assets and properties and the assets and properties of its subsidiaries (taken as a whole) to another person in one or more related transactions unless the successor person is a person organized under the laws of any domestic jurisdiction and assumes the Company’s obligations on the debt securities issued thereunder, and under the indenture, and after giving effect thereto no event of default, and no event that, after notice or lapse of time or both, would become an event of default, shall have occurred and be continuing, and that certain other conditions are met.

Certain Covenants

Payment of Principal, any Premium, Interest or Additional Amounts. The Company will duly and punctually pay the principal of, and premium and interest on or any additional amounts payable with respect to, any debt securities of any series in accordance with their terms.

Maintenance of Office or Agency. The Company will be required to maintain an office or agency in each place of payment for each series of debt securities for notice and demand purposes and for the purposes of presenting or surrendering debt securities for payment, registration of transfer, or exchange.

Reports. So long as any debt securities of a particular series are outstanding under the indenture, the Company will file with the trustee, within 30 days after the Company has filed the same with the SEC, unless such reports are available on the SEC’s EDGAR filing system (or any successor thereto), copies of the annual reports and of the information, documents and other reports (or copies of such portions of any of the foregoing as the SEC may from time to time by rules and regulations prescribe), which the Company may be required to file with the SEC pursuant to Section 13 or Section 15(d) of the Exchange Act; or, if the Company is not required to file information, documents or reports pursuant to either of said Sections, then it shall file with the trustee and the SEC, in accordance with rules and regulations prescribed from time to time by the SEC, such of the supplementary and periodic information, documents and reports which may be required pursuant to Section 13 of the Exchange Act in respect of a security listed and registered on a national securities exchange as may be prescribed from time to time in such rules and regulations.

Additional Covenants. Any additional covenants of the Company with respect to any series of debt securities will be set forth in the applicable prospectus supplement, documents incorporated by reference or free writing prospectus relating thereto.

Conversion Rights

The terms and conditions, if any, upon which the debt securities are convertible into common stock or preferred stock will be set forth in the applicable prospectus supplement, documents incorporated by reference or free writing prospectus relating thereto. Such terms will include the conversion price (or manner of calculation thereof), the conversion period, provisions as to whether conversion will be at the option of the holders or the Company, the events requiring an adjustment of the conversion price and provisions affecting conversion in the event of redemption of such debt securities and any restrictions on conversion.

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Redemption; Repurchase at the Option of the Holder; Sinking Fund

The terms and conditions, if any, upon which: (i) the debt securities are redeemable at the option of the Company; (ii) the holder of debt securities may cause the Company to repurchase such debt securities; or (iii) the debt securities are subject to any sinking fund will be set forth in the applicable prospectus supplement, documents incorporated by reference or free writing prospectus relating thereto.

Repurchases on the Open Market

The Company or any affiliate of the Company may at any time or from time to time repurchase any debt security in the open market or otherwise. Such debt securities may, at the option of the Company or the relevant affiliate of the Company, be held, resold or surrendered to the trustee for cancellation.

Discharge, Defeasance and Covenant Defeasance

The indenture provides, with respect to each series of debt securities issued thereunder, that the Company may satisfy and discharge its obligations under such debt securities of a series and such indenture with respect to debt securities of such series if:

(a) all debt securities of such series previously authenticated and delivered, with certain exceptions, have been accepted by the trustee for cancellation; or

(b) (i) the debt securities of such series have become due and payable, or mature within one year, or all of them are to be called for redemption within one year under arrangements satisfactory to the trustee for giving the notice of redemption and the Company irrevocably deposits in trust with the trustee, as trust funds solely for the benefit of the holders of such debt securities, for that purpose, money or governmental obligations or a combination thereof sufficient (in the opinion of a nationally recognized independent registered public accounting firm expressed in a written certification thereof delivered to the trustee) to pay the entire indebtedness on the debt securities of such series to maturity or redemption, as the case may be, and pays all other sums payable by it under such indenture; and

(ii) the Company delivers to the trustee an officers’ certificate and an opinion of counsel, in each case stating that all conditions precedent provided for in such indenture relating to the satisfaction and discharge of such indenture with respect to the debt securities of such series have been complied with.

Notwithstanding such satisfaction and discharge, the obligations of the Company to compensate and indemnify the trustee, to pay additional amounts, if any, in respect of debt securities in certain circumstances and to convert or exchange debt securities pursuant to the terms thereof and the obligations of the Company and the trustee to hold funds in trust and to apply such funds pursuant to the terms of the indenture, with respect to issuing temporary debt securities, with respect to the registration, transfer and exchange of debt securities, with respect to the replacement of mutilated, destroyed, lost or stolen debt securities and with respect to the maintenance of an office or agency for payment, shall in each case survive such satisfaction and discharge.

Unless inapplicable to debt securities of a series pursuant to the terms thereof, the indenture provides that: (i) the Company will be deemed to have paid and will be discharged from any and all obligations in respect of the debt securities issued thereunder of any series, and the provisions of such indenture will, except as noted below, no longer be in effect with respect to the debt securities of such series (“defeasance”); and (ii) (1) the Company may omit to comply with the covenant described above under “— Consolidation, Merger and Sale of Assets” and any other additional covenants established pursuant to the terms of such series, and such omission shall be deemed not to be an event of default under clause (d) or (f) of the first paragraph of “— Events of Default” above and (2) the occurrence of any event described in clause (f) of the first paragraph of “— Events of Default” above shall not be deemed to be an event of default, in each case with respect to the outstanding debt securities of such series ((1) and (2) of this clause (ii), “covenant defeasance”); provided that the following conditions shall have been satisfied with respect to such series:

(a) the Company has irrevocably deposited in trust with the trustee as trust funds solely for the benefit of the holders of the debt securities of such series, for payment of the principal of and interest of the debt securities of such series, money or government obligations or a combination thereof sufficient (in the opinion of a nationally recognized independent registered public accounting firm expressed in a written certification thereof delivered to the trustee) without consideration of any reinvestment to pay and discharge the principal of and accrued interest on the outstanding debt securities of such series to maturity or earlier redemption (irrevocably provided for under arrangements satisfactory to the trustee), as the case may be;

(b) such defeasance or covenant defeasance will not result in a breach or violation of, or constitute a default under, such indenture or any other material agreement or instrument to which the Company is a party or by which it is bound;

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(c) no event of default or event which with notice or lapse of time would become an event of default with respect to such debt securities of such series shall have occurred and be continuing on the date of such deposit;

(d) the Company shall have delivered to the trustee an opinion of counsel as described in the indenture to the effect that the holders of the debt securities of such series will not recognize income, gain or loss for Federal income tax purposes as a result of the Company’s exercise of its option under this provision of such indenture and will be subject to federal income tax on the same amount and in the same manner and at the same times as would have been the case if such deposit and defeasance or covenant defeasance had not occurred;

(e) the Company has delivered to the trustee an officers’ certificate and an opinion of counsel, in each case stating that all conditions precedent provided for in such indenture relating to the defeasance contemplated have been complied with;

(f) if the debt securities are to be redeemed prior to their maturity, notice of such redemption shall have been duly given or in another manner satisfactory to the trustee; and

(g) any such defeasance or covenant defeasance shall comply with any additional or substitute terms provided for by the terms of such debt securities of such series.

Notwithstanding a defeasance or covenant defeasance, the Company’s obligations with respect to the following in respect of debt securities of such series will survive with respect to such securities until otherwise terminated or discharged under the terms of the indenture or no debt securities of such series are outstanding:

(a) the rights of holders of outstanding debt securities of such series to receive payments in respect of the principal of, interest on or premium or additional amounts, if any, payable in respect of, such debt securities when such payments are due from the trust referred in clause (a) in the preceding paragraph;

(b) the issuance of temporary debt securities, the registration, transfer and exchange of debt securities, the replacement of mutilated, destroyed, lost or stolen debt securities and the maintenance of an office or agency for payment and holding payments in trust;

(c) the rights, powers, trusts, duties and immunities of the trustee, and the Company’s obligations in connection therewith; and

(d) the defeasance or covenant defeasance provisions of the indenture.

Applicable Law

The indenture provides that the debt securities and the indenture will be governed by and construed in accordance with the laws of the State of New York.

DESCRIPTION OF WARRANTS

General

We may issue warrants to purchase debt securities, common stock, preferred stock or any combination of these securities. We may issue the warrants independently or together with any underlying securities, and the warrants may be attached or separate from the underlying securities. We may also issue a series of warrants under a separate warrant agreement to be entered into between us and a warrant agent. The warrant agent will act solely as our agent in connection with the warrants of such series and will not assume any obligation or relationship of agency for or with holders or beneficial owners of warrants.

The following description is a summary of selected provisions relating to the warrants that we may issue. The summary is not complete. When warrants are offered in the future, a prospectus supplement, information incorporated by reference or a free writing prospectus, as applicable, will explain the particular terms of those securities and the extent to which these general provisions may apply. The specific terms of the warrants as described in a prospectus supplement, information incorporated by reference, or free writing prospectus will supplement and, if applicable, may modify or replace the general terms described in this section.

This summary and any description of warrants in the applicable prospectus supplement, information incorporated by reference or free writing prospectus is subject to and is qualified in its entirety by reference to all the provisions of any specific warrant document or agreement. We will file each of these documents, as applicable, with the SEC and incorporate them by reference as an exhibit to the registration statement of which this prospectus is a part on or before the time we issue a series of warrants. See “Where You Can Find Additional Information” and “Incorporation of Information by Reference” above for information on how to obtain a copy of a warrant document when it is filed.

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When we refer to a series of warrants, we mean all warrants issued as part of the same series under the applicable warrant agreement.

Terms

The applicable prospectus supplement, information incorporated by reference or free writing prospectus, may describe the terms of any warrants that we may offer, including but not limited to the following:

• the title of the warrants;

• the total number of warrants;

• the price or prices at which the warrants will be issued;

• the price or prices at which the warrants may be exercised;

• the currency or currencies that investors may use to pay for the warrants;

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

• whether the warrants will be issued in registered form or bearer form;

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

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

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

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

• if applicable, a discussion of material United States federal income tax considerations;

• if applicable, the terms of redemption of the warrants;

• the identity of the warrant agent, if any;

• the procedures and conditions relating to the exercise of the warrants; and

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

Warrant Agreements

We may issue the warrants in one or more series under one or more warrant agreements, each to be entered into between us and a bank, trust company, or other financial institution as warrant agent. We may add, replace, or terminate warrant agents from time to time. We may also choose to act as our own warrant agent or may choose one of our subsidiaries to do so.

The warrant agent under a warrant agreement will act solely as our agent in connection with the warrants issued under that agreement. Any holder of warrants may, without the consent of any other person, enforce by appropriate legal action, on its own behalf, its right to exercise those warrants in accordance with their terms.

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Form, Exchange and Transfer

We may issue the warrants in registered form or bearer form. Warrants issued in registered form, i.e., book-entry form, will be represented by a global security registered in the name of a depository, which will be the holder of all the warrants represented by the global security. Those investors who own beneficial interests in a global warrant will do so through participants in the depository’s system, and the rights of these indirect owners will be governed solely by the applicable procedures of the depository and its participants. In addition, we may issue warrants in non-global form, i.e., bearer form. If any warrants are issued in non-global form, warrant certificates may be exchanged for new warrant certificates of different denominations, and holders may exchange, transfer, or exercise their warrants at the warrant agent’s office or any other office indicated in the applicable prospectus supplement, information incorporated by reference or free writing prospectus.

Prior to the exercise of their warrants, holders of warrants exercisable for debt securities will not have any of the rights of holders of the debt securities purchasable upon such exercise and will not be entitled to payments of principal (or premium, if any) or interest, if any, on the debt securities purchasable upon such exercise. Prior to the exercise of their warrants, holders of warrants exercisable for shares of preferred stock or common stock will not have any rights of holders of the preferred stock or common stock purchasable upon such exercise and will not be entitled to dividend payments, if any, or voting rights of the preferred stock or common stock purchasable upon such exercise.

Exercise of Warrants

A warrant will entitle the holder to purchase for cash an amount of securities at an exercise price that will be stated in, or that will be determinable as described in, the applicable prospectus supplement, information incorporated by reference or free writing prospectus. Warrants may be exercised at any time up to the close of business on the expiration date set forth in the applicable offering material. After the close of business on the expiration date, unexercised warrants will become void. Warrants may be redeemed as set forth in the applicable offering material.

Warrants may be exercised as set forth in the applicable offering material. Upon receipt of payment and the warrant certificate properly completed and duly executed at the corporate trust office of the warrant agent or any other office indicated in the applicable offering material, we will forward, as soon as practicable, the securities purchasable upon such exercise. If less than all of the warrants represented by such warrant certificate are exercised, a new warrant certificate will be issued for the remaining warrants.

DESCRIPTION OF RIGHTS

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

Each series of rights will be issued under a separate rights agreement which we will enter into with a bank or trust company, as rights agent, all which will be set forth in the relevant offering material. The rights agent will act solely as our agent in connection with the certificates relating to the rights and will not assume any obligation or relationship of agency or trust with any holders of rights certificates or beneficial owners of rights.

The following description is a summary of selected provisions relating to rights that we may offer. The summary is not complete. When rights are offered in the future, a prospectus supplement, information incorporated by reference or a free writing prospectus, as applicable, will explain the particular terms of those securities and the extent to which these general provisions may apply. The specific terms of the rights as described in a prospectus supplement, information incorporated by reference, or free writing prospectus will supplement and, if applicable, may modify or replace the general terms described in this section.

This summary and any description of rights in the applicable prospectus supplement, information incorporated by reference or free writing prospectus is subject to and is qualified in its entirety by reference to the rights agreement and the rights certificates. We will file each of these documents, as applicable, with the SEC and incorporate them by reference as an exhibit to the registration statement of which this prospectus is a part on or before the time we issue a series of rights. See “Where You Can Find Additional Information” and “Incorporation of Information by Reference” above for information on how to obtain a copy of a document when it is filed.

The applicable prospectus supplement, information incorporated by reference or free writing prospectus may describe:

• In the case of a distribution of rights to our stockholders, the date of determining the stockholders entitled to the rights distribution;

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• In the case of a distribution of rights to our stockholders, the number of rights issued or to be issued to each stockholder;

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

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

• the extent to which the rights are transferable;

• the date on which the holder’s ability to exercise the rights shall commence, and the date on which the rights shall expire;

• the extent to which the rights may include an over-subscription privilege with respect to unsubscribed securities;

• if applicable, the material terms of any standby underwriting or purchase arrangement entered into by us in connection with the offering of such rights; and

• any other terms of the rights, including, but not limited to, the terms, procedures, conditions and limitations relating to the exchange and exercise of the rights.

The provisions described in this section, as well as those described under “— Description of Debt Securities” and “— Description of Capital Stock” above, will apply, as applicable, to any rights we offer.

DESCRIPTION OF UNITS

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

The following description is a summary of selected provisions relating to units that we may offer. The summary is not complete. When units are offered in the future, a prospectus supplement, information incorporated by reference or a free writing prospectus, as applicable, will explain the particular terms of those securities and the extent to which these general provisions may apply. The specific terms of the units as described in a prospectus supplement, information incorporated by reference, or free writing prospectus will supplement and, if applicable, may modify or replace the general terms described in this section.

This summary and any description of units in the applicable prospectus supplement, information incorporated by reference or free writing prospectus is subject to and is qualified in its entirety by reference to the unit agreement, collateral arrangements and depositary arrangements, if applicable. We will file each of these documents, as applicable, with the SEC and incorporate them by reference as an exhibit to the registration statement of which this prospectus is a part on or before the time we issue a series of units. See “Where You Can Find Additional Information” and “Incorporation of Information by Reference” above for information on how to obtain a copy of a document when it is filed.

The applicable prospectus supplement, information incorporated by reference or free writing prospectus may describe:

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

• any provisions for the issuance, payment, settlement, transfer, or exchange of the units or of the securities composing the units;

• whether the units will be issued in fully registered or global form; and

• any other terms of the units.

The applicable provisions described in this section, as well as those described under “— Description of Debt Securities,” “— Description of Capital Stock” and “— Description of Warrants” above, will apply to each unit and to each security included in each unit, respectively.

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USE OF PROCEEDS

Unless otherwise indicated in the applicable prospectus supplement, information incorporated by reference or free writing prospectus, we intend to use the net proceeds from the sale of securities for general corporate purposes.

PLAN OF DISTRIBUTION

We may sell the securities offered by this prospectus from time to time in one or more transactions, including without limitation:

• through agents;

• to or through underwriters;

• through broker-dealers (acting as agent or principal);

• directly by us to purchasers (including our affiliates and stockholders), through a specific bidding or auction process, a rights offering, or otherwise;

• through a combination of any such methods of sale; or

• through any other methods described in a prospectus supplement.

The distribution of securities may be effected, from time to time, in one or more transactions, including:

• block transactions (which may involve crosses) and transactions on the Nasdaq Capital Market or any other organized market where the securities may be traded;

• purchases by a broker-dealer as principal and resale by the broker-dealer for its own account pursuant to a prospectus supplement;

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

• sales “at the market” to or through a market maker or into an existing trading market, on an exchange or otherwise; and

• sales in other ways not involving market makers or established trading markets, including direct sales to purchasers.

The securities may be sold at a fixed price or prices, which may be changed, or at market prices prevailing at the time of sale, at prices relating to the prevailing market prices or at negotiated prices. The consideration may be cash or another form negotiated by the parties. Agents, underwriters or broker-dealers may be paid compensation for offering and selling the securities. That compensation may be in the form of discounts, concessions or commissions to be received from us or from the purchasers of the securities. Dealers and agents participating in the distribution of the securities may be deemed to be underwriters, and compensation received by them on resale of the securities may be deemed to be underwriting discounts and commissions under the Securities Act. If such dealers or agents were deemed to be underwriters, they may be subject to statutory liabilities under the Securities Act.

We may also make direct sales through subscription rights distributed to our existing stockholders on a pro rata basis, which may or may not be transferable. In any distribution of subscription rights to our stockholders, if all of the underlying securities are not subscribed for, we may then sell the unsubscribed securities directly to third parties or may engage the services of one or more underwriters, dealers or agents, including standby underwriters, to sell the unsubscribed securities to third parties.

Some or all of the securities that we offer through this prospectus may be new issues of securities with no established trading market. Any underwriters to whom we sell our securities for public offering and sale may make a market in those securities, but they will not be obligated to do so and they may discontinue any market making at any time without notice. Accordingly, we cannot assure you of the liquidity of, or continued trading markets for, any securities that we offer.

Agents may, from time to time, solicit offers to purchase the securities. If required, we will name in the applicable prospectus supplement, document incorporated by reference or free writing prospectus, as applicable, any agent involved in the offer or sale of the securities and set forth any compensation payable to the agent. Unless otherwise indicated, any agent will be acting on a best efforts basis for the period of its appointment. Any agent selling the securities covered by this prospectus may be deemed to be an underwriter of the securities.

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If underwriters are used in an offering, securities will be acquired by the underwriters for their own account and may be resold, from time to time, in one or more transactions, including negotiated transactions, at a fixed public offering price or at varying prices determined at the time of sale, or under delayed delivery contracts or other contractual commitments. Securities may be offered to the public either through underwriting syndicates represented by one or more managing underwriters or directly by one or more firms acting as underwriters. If an underwriter or underwriters are used in the sale of securities, an underwriting agreement will be executed with the underwriter or underwriters at the time an agreement for the sale is reached. The applicable prospectus supplement will set forth the managing underwriter or underwriters, as well as any other underwriter or underwriters, with respect to a particular underwritten offering of securities, and will set forth the terms of the transactions, including compensation of the underwriters and dealers and the public offering price, if applicable. This prospectus, the applicable prospectus supplement and any applicable free writing prospectus will be used by the underwriters to resell the securities.

If a dealer is used in the sale of the securities, we, or an underwriter, will sell the securities to the dealer, as principal. The dealer may then resell the securities to the public at varying prices to be determined by the dealer at the time of resale. To the extent required, we will set forth in the prospectus supplement, document incorporated by reference or free writing prospectus, as applicable, the name of the dealer and the terms of the transactions.

We may directly solicit offers to purchase the securities and may make sales of securities directly to institutional investors or others. These persons may be deemed to be underwriters with respect to any resale of the securities. To the extent required, the prospectus supplement, document incorporated by reference or free writing prospectus, as applicable, will describe the terms of any such sales, including the terms of any bidding or auction process, if used.

Agents, underwriters and dealers may be entitled under agreements which may be entered into with us to indemnification by us against specified liabilities, including liabilities incurred under the Securities Act, or to contribution by us to payments they may be required to make in respect of such liabilities. If required, the prospectus supplement, document incorporated by reference or free writing prospectus, as applicable, will describe the terms and conditions of such indemnification or contribution. Some of the agents, underwriters or dealers, or their affiliates may be customers of, engage in transactions with or perform services for us or our subsidiaries or affiliates in the ordinary course of business.

Under the securities laws of some states, the securities offered by this prospectus may be sold in those states only through registered or licensed brokers or dealers.

Any person participating in the distribution of common stock registered under the registration statement that includes this prospectus will be subject to applicable provisions of the Exchange Act, and the applicable SEC rules and regulations, including, among others, Regulation M, which may limit the timing of purchases and sales of any of our common stock by any such person. Furthermore, Regulation M may restrict the ability of any person engaged in the distribution of our common stock to engage in market-making activities with respect to our common stock. These restrictions may affect the marketability of our common stock and the ability of any person or entity to engage in market-making activities with respect to our common stock.

Certain persons participating in an offering may engage in over-allotment, stabilizing transactions, short-covering transactions and penalty bids in accordance with Regulation M under the Exchange Act that stabilize, maintain or otherwise affect the price of the offered securities. If any such activities will occur, they will be described in the applicable prospectus supplement.

In compliance with the guidelines of the Financial Industry Regulatory Authority (“FINRA”), the aggregate maximum discount, commission or agency fees or other items constituting underwriting compensation to be received by any FINRA member or independent broker-dealer will not exceed 8% of any offering pursuant to this prospectus and any applicable prospectus supplement, as the case may be.

If more than 10% of the net proceeds of any offering of securities made under this prospectus will be received by FINRA members participating in the offering or affiliates or associated persons of such FINRA members, the offering will be conducted in accordance with FINRA Conduct Rule 5110(h).

To the extent required, this prospectus may be amended or supplemented from time to time to describe a specific plan of distribution.

LEGAL MATTERS

Our counsel, Morrison & Foerster LLP, Palo Alto, California, will pass upon the validity of the securities offered hereby.

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EXPERTS

The consolidated financial statements incorporated into this prospectus by reference to the Annual Report on Form 10-K for the year ended December 31, 2010 have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in accounting and auditing.

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PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

Item  14. Other Expenses of Issuance and Distribution

The estimated expenses payable by the Registrant in connection with the issuance and distribution of the securities being registered are as follows:

SEC Registration Fee	$	5,805
FINRA Filing Fee*	$	5,500
Printing Expenses*	$	50,000
Legal Fees and Expenses*	$	50,000
Listing Fees	$	**
Accounting Fees and Expenses*	$	50,000
Trustee Fees and Expenses*	$	30,000
Miscellaneous Fees and Expenses*	$	10,000
Total	$	201,305

* Estimated solely for the purposes of this Item. Actual expenses may vary.

** The listing fee is based upon the principal amount of securities listed, if any, and is therefore not currently determinable.

Item  15. Indemnification of Directors and Officers

We are incorporated under the laws of the State of Delaware. Section 145 (“Section 145”) of the General Corporation Law of the State of Delaware, as the same exists or may hereafter be amended (the “DGCL”), inter alia, provides that a Delaware corporation may indemnify directors and officers as well as other employees and individuals against expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by such person in connection with any threatened, pending or completed actions, suits or proceedings in which such person is made a party by reason of such person being or having been a director, officer, employee or agent to the Company. The DGCL provides that Section 145 is not exclusive of other rights to which those seeking indemnification may be entitled under any bylaw, agreement, vote of stockholders or disinterested directors or otherwise. Article VII of our Amended and Restated Bylaws provides for indemnification by us of our directors and officers, as well as persons serving at our request as a director, officer, employee or other agent of another corporation or of a partnership, joint venture, trust or other enterprise, including service with respect to an employee benefit plan, to the fullest extent permitted by the DGCL.

Section 102(b)(7) of the DGCL permits a corporation to provide in its certificate of incorporation that a director of the corporation shall not be personally liable to the corporation or its stockholders for monetary damages for breach of fiduciary duty as a director, except for liability (i) for any breach of the director’s duty of loyalty to the corporation or its stockholders, (ii) for acts or omissions not in good faith or which involve intentional misconduct or a knowing violation of law, (iii) pursuant to Section 174 of the DGCL (providing for liability of directors for unlawful payments of dividends or unlawful stock repurchases or redemptions), or (iv) for any transaction from which the director derived an improper personal benefit. Our Amended and Restated Certificate of Incorporation provides for such limitation of liability to the fullest extent permitted by DGCL.

As permitted by Delaware law, we have entered into indemnification agreements with each of our directors and officers. These indemnification agreements require us, among other things, to indemnify our directors and officers for certain expenses related to their service to us, including attorney’s fees and other costs and expenses, judgments, fines, penalties and settlement amounts reasonably incurred by or on behalf of such persons, subject to certain limitations.

In addition, our directors and officers are covered under directors’ and officers’ liability insurance policies maintained by us, subject to the limits of the policies, insuring such persons against various liabilities.

Item  16. Exhibits and Financial Statement Schedules.

(a) Exhibits. The following exhibits are included herein or incorporated herein by reference:

EXHIBIT NUMBER	DESCRIPTION
1.1*	Form of Underwriting Agreement with respect to Debt Securities
1.2*	Form of Underwriting Agreement with respect to Common Stock
1.3*	Form of Underwriting Agreement with respect to Preferred Stock

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1.4*	Form of Underwriting Agreement with respect to Warrants
1.5*	Form of Underwriting Agreement with respect to Units
3.1(1)	Amended and Restated Certificate of Incorporation of the Registrant
3.2(2)	Amended and Restated Bylaws of the Registration
3.3(3)	Certificate of Amendment of the Amended and Restated Certificate of Incorporation of the Registrant
4.1	Form of Indenture (including Form of Debt Securities)
4.2(4)	Form of Specimen Common Stock Certificate
4.3*	Form of Specimen Preferred Stock Certificate
4.4*	Form of Certificate of Designation of Preferred Stock
4.5*	Form of Warrant Agreement (including Form of Warrant Certificate) with respect to Warrants to purchase Debt Securities
4.6*	Form of Warrant Agreement (including Form of Warrant Certificate) with respect to Warrants to purchase Common Stock
4.7*	Form of Warrant Agreement (including Form of Warrant Certificate) with respect to Warrants to purchase Preferred Stock
4.8*	Form of Warrant Agreement (including Form of Warrant Certificate) with respect to Warrants to purchase Units
4.9*	Form of Unit Agreement (including Form of Unit Certificate)
4.10*	Form of Rights Agreement (including Form of Rights Certificate)
4.11(5)	Preferred Shares Rights Agreement, dated as of August 8, 2006, by and between Registrant and Mellon Investor Services LLC
4.12(6)	Amendment to Preferred Shares Rights Agreement dated as of July 10, 2008 among the Registrant and Mellon Investor Services LLC
4.13(7)	Second Amendment to Preferred Shares Rights Agreement dated as of September 29, 2009 among the Registrant and Mellon Investor Services LLC
4.13(8)	Third Amendment to Preferred Shares Rights Agreement dated as of March 11, 2011 among the Registrant and Mellon Investor Services LLC
5.1	Opinion of Morrison & Foerster LLP
23.1	Consent of Morrison & Foerster LLP (included in Exhibit 5.1)
23.2	Consent of PricewaterhouseCoopers LLP
24.1	Power of Attorney (included in the signature page to this registration statement)
25.1(9)	Form T-1 Statement of Eligibility under Trust Indenture Act of 1939 of Debt Trustee (to be filed prior to any issuance of Debt Securities)

* To be filed as an amendment or as an exhibit to a document filed under the Exchange Act and incorporated by reference into this registration statement.

(1) Filed as Exhibit 3.2 to our Registration Statement on Form S-1, as amended (File No. 333-114376), filed on April 9, 2004, and incorporated herein by reference.

(2) Filed as Exhibit 3.4 to our Registration Statement on Form S-1, as amended (File No. 333-114376), filed on April 9, 2004, and incorporated herein by reference.

(3) Filed as Exhibit 3.4 to our Annual Report on Form 10-K filed on March 13, 2009, and incorporated herein by reference.

(4) Filed as Exhibit 4.1 to our Registration Statement on Form S-1, as amended (File No. 333-114376), filed on April 9, 2004, and incorporated herein by reference.

(5) Filed as Exhibit 4.5 to our Current Report on Form 8-K filed on August 9, 2006, and incorporated herein by reference.

(6) Filed as Exhibit 4.2 to our Current Report on Form 8-K filed on July 14, 2008, and incorporated herein by reference.

(7) Filed as Exhibit 4.2 to our Current Report on Form 8-K filed on September 30, 2009, and incorporated herein by reference.

(8) Filed as Exhibit 4.2 to our Current Report on Form 8-K filed on March 11, 2011, and incorporated herein by reference.

(9) To be filed in accordance with the requirements of Section 305(b)(2) of the Trust Indenture Act of 1939.

Item  17. Undertakings

(a) The undersigned registrant hereby undertakes:

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

(i) To include any prospectus required by Section 10(a)(3) of the Securities Act;

(ii) To reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement. Notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the SEC pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than a 20% change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective registration statement; and

(iii) To include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement,

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

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

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

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

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

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

(5) That, for the purpose of determining liability of the Registrant under the Securities Act of 1933 to any purchaser in the initial distribution of the securities, the undersigned Registrant undertakes that in a primary offering of securities of the undersigned Registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned Registrant will be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser:

(i) Any preliminary prospectus or prospectus of the undersigned Registrant relating to the offering required to be filed pursuant to Rule 424;

(ii) Any free writing prospectus relating to the offering prepared by or on behalf of the undersigned Registrant or used or referred to by the undersigned Registrant;

(iii) The portion of any other free writing prospectus relating to the offering containing material information about the undersigned Registrant or its securities provided by or on behalf of the undersigned Registrant; and

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(iv) Any other communication that is an offer in the offering made by the undersigned Registrant to the purchaser.

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

(7) To supplement the prospectus, after the expiration of the subscription period to set forth the results of the subscription offer, the transactions by the underwriters during the subscription period, the amount of unsubscribed securities to be purchased by the underwriters, and the terms of any subsequent reoffering thereof. If any public offering by the underwriters is to be made on terms differing from those set forth on the cover page of the prospectus, a post-effective amendment will be filed to set forth the terms of such offering.

(8) To use its best efforts to distribute prior to the opening of bids, to prospective bidders, underwriters, and dealers, a reasonable number of copies of a prospectus which at that time meets the requirements of Section 10(a) of the Act, and relating to the securities offered at competitive bidding, as contained in the registration statement, together with any supplements thereto, and (2) to file an amendment to the registration statement reflecting the results of bidding, the terms of the reoffering and related matters to the extent required by the applicable form, not later than the first use, authorized by the issuer after the opening of bids, of a prospectus relating to the securities offered at competitive bidding, unless no further public offering of such securities by the issuer and no reoffering of such securities by the purchasers is proposed to be made.

(9) To file an application for the purpose of determining the eligibility of the trustee to act under subsection (a) of Section 310 of the Trust Indenture Act in accordance with the rules and regulations prescribed by the Commission under Section 305(b)(2) of the Trust Indenture Act.

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

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended, the Registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the Redwood City, State of California, on the 10th day of June, 2011.

	THRESHOLD PHARMACEUTICALS, INC.
June 10, 2011	By:	/s/    HAROLD E. SELICK
		Harold E. Selick, Ph.D.
		Chief Executive Officer

POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below constitutes and appoints, jointly and severally, Harold E. Selick, Ph.D. and Joel A. Fernandes, and each them severally, his true and lawful attorneys-in-fact and agents, each with full power of substitution, for him and in his name, place and stead, in any and all capacities, to sign any and all amendments (including post-effective amendments) to this registration statement, and to sign any registration statement for the same offering covered by this registration statement that is to be effective upon filing pursuant to Rule 462(b) promulgated under the Securities Act of 1933, as amended, and all post-effective amendments thereto, and to file the same, with all exhibits thereto and all documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact and agents, and each of them full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as he might or could do in person, hereby ratifying and confirming that each of said attorneys-in-fact and agents or any of them, or his or their substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed below by the following persons in the capacities and on the dates indicated.

Signature	Title	Date
/s/    HAROLD E. SELICK         Harold E. Selick, Ph.D.	Chief Executive Officer (principal executive officer)	June 10, 2011
/s/     JOEL A. FERNANDES         Joel A. Fernandes	Vice President, Finance and Controller (principal financial and accounting officer)	June 10, 2011
/s/    JEFFREY W. BIRD         Jeffrey W. Bird, M.D., Ph.D.	Director	June 10, 2011
/s/    BRUCE C. COZADD         Bruce C. Cozadd	Director	June 10, 2011
/s/    DAVID R. HOFFMANN         David R. Hoffmann	Director	June 10, 2011
/s/    WILFRED E. JAEGER         Wilfred E. Jaeger, M.D.	Director	June 10, 2011
/s/    GEORGE G. C. PARKER         George G. C. Parker, Ph.D.	Director	June 10, 2011
/s/    DAVID R. PARKSINSON         David R. Parkinson, M.D.	Director	June 10, 2011

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