SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

Date of report (Date of earliest event reported): November 12, 2012 (November 9, 2012)

GENSPERA, INC.

(Exact name of registrant as specified in Charter)

2511 N Loop 1604 W, Suite 204

San Antonio, TX 78258

(Address of Principal Executive Offices)

210-479-8112

(Issuer Telephone number)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

¨ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

¨ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

¨ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

¨ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Item 8.01 Other Events.

On November 9, 2012, GenSpera, Inc. (the “Company”) announced that interim data from its ongoing Phase I trial of G-202 were presented at the EORTC-NCI-AACR Symposium on Molecular Targets and Cancer Therapeutics in Dublin, Ireland. A copy of the press release is attached to this report as Exhibit 99.01.

A copy of the poster presented at the symposium will be made available for a limited time at www.genspera.com (in the section entitled Technology subsection Publications). The reference to our web address is not intended to incorporate by reference the information contained at our site into this report.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this Report on Form 8-K to be signed on its behalf by the undersigned hereunto duly authorized.

Dated: November 12, 2012

INDEX OF EXHIBITS