UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

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THRESHOLD

PHARMACEUTICALS, INC.

(Name of the Registrant as Specified in its Charter)

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See the reverse side of this notice to obtainproxy materials and voting instructions.*** Exercise Your Right to Vote ***Important Notice Regarding the Availability of Proxy Materials for theStockholder Meeting to Be Held on <mtgdate>.You are receiving this communication because you holdshares in the above named company.This is not a ballot. You cannot use this notice to votethese shares. This communication presents only anoverview of the more complete proxy materials that areavailable to you on the Internet. You may view the proxymaterials online at www.proxyvote.com or easily request apaper copy (see reverse side).We encourage you to access and review all of the importantinformation contained in the proxy materials before voting.Meeting InformationMeeting Type: <mtgtype>For holders as of: <recdate>Date: Time: <mtgtime>Location:0000292490_1 R1.0.1.25THRESHOLD PHARMACEUTICALS, INCTHRESHOLD PHARMACEUTICALS, INC.170 Harbor Way, Suite 300South San Francisco, CA 94080Annual MeetingApril 25, 2016June 24, 2016June 24, 2016 3:00 PM PDTThreshold Pharmaceticals, Inc.170 Harbor Way, Suite 300South San Francisco, CA 94080

Please Choose One of the Following Voting MethodsVote In Person: Many stockholder meetings have attendance requirements including, but not limited to, the possessionof an attendance ticket issued by the entity holding the meeting. Please check the meeting materials for any specialrequirements for meeting attendance. At the meeting, you will need to request a ballot to vote these shares.Vote By Internet: To vote now by Internet, go to www.proxyvote.com. Have the information that is printed in the boxmarked by the arrow available and follow the instructions.Vote By Mail: You can vote by mail by requesting a paper copy of the materials, which will include a proxy card.How To Vote Before You VoteHow to Access the Proxy MaterialsProxy Materials Available to VIEW or RECEIVE:How to View Online:Have the information that is printed in the box marked by the arrow (located on thefollowing page) and visit: www.proxyvote.com.How to Request and Receive a PAPER or E-MAIL Copy:If you want to receive a paper or e-mail copy of these documents, you must request one. There is NO charge forrequesting a copy. Please choose one of the following methods to make your request:1) BY INTERNET: www.proxyvote.com2) BY TELEPHONE: 1-800-579-16393) BY E-MAIL*: sendmaterial@proxyvote.com* If requesting materials by e-mail, please send a blank e-mail with the information that is printed in the box markedby the arrow (located on the following page) in the subject line. 0000292490_2 R1.0.1.251. Notice and Proxy Statement 2. Annual Report on Form 10-KRequests, instructions and other inquiries sent to this e-mail address will NOT be forwarded to your investmentadvisor. Please make the request as instructed above on or before June 12, 2016 to facilitate timely delivery.

Voting items0000292490_3 R1.0.1.25The Board of Directors recommends you voteFOR the following:1. Election of DirectorsNominees01 Bruce C. Cozadd 02 David R. Hoffmann 03 George G.C. Parker, PhDThe Board of Directors recommends you vote FOR proposals 2 and 3.2 To ratify the appointment of Ernst & Young LLP as the Company’s independent registered public accountingfirm for the fiscal year ending December 31, 2016.3 To approve, on an advisory basis,the compensation of the Company’s Named Executive Officers as disclosed inthe proxy statement.NOTE: Such other business as may properly come before the meeting or any adjournment or postponement thereof.

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