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): July 6, 2015 (July 5, 2015)

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):

On July 5, 2015, GenSpera, Inc. (“Company”) entered into securities purchase agreements (“Securities Purchase Agreement”) with certain institutional accredited investors (the “Investors”). Pursuant to the Securities Purchase Agreement, the Company sold an aggregate of $2,500,000, or 3,571,430 units, to the Investors in a private placement. The price per unit is $0.70 with each unit consisting of (i) one share of the Company’s common stock (“Shares”) (ii) one Series D common stock purchase warrant and (iii) one Series E common stock purchase warrant (collectively, the “Warrants”) (the “Offering”). Each Series D warrant has an exercise price of $0.80 per share, is immediately exercisable and separately transferable from the Shares and expires on the five year anniversary of the date of issuance. Each Series E warrant has an exercise price of $0.70 per share, is immediately exercisable and separately transferable from the Shares and expires on the eighteen month anniversary of the date of issuance. In the event that the shares underlying the Warrants are not subject to a registration statement at the time of exercise, the Warrants may be exercised on a cashless basis after 6 months from the issuance date. The Warrants also contain provisions providing for an adjustment in the underlying number of shares and exercise price in the event of stock splits or dividends and fundamental transactions. The closing of the Offering is anticipated to occur on or about July 9, 2015, subject to customary closing conditions.

In connection with the Offering, all Investors received registration rights through a registration rights agreement (“Registration Rights Agreement”) entered into on July 5, 2015. Pursuant to the Registration Rights Agreement, the Company agreed to file a registration statement with the Securities and Exchange Commission (“the Commission”) within 30 days from the date of the Registration Rights Agreement to register the resale of the Shares and shares of common stock underlying the Warrants and to maintain the effectiveness thereunder. The Company also agreed to have the registration statement declared effective within 60 days from the date of the Registration Rights Agreement. The Company agreed to keep the registration statement continuously effective until the earlier to occur of (i) the date after which all of the securities to be registered thereunder have been sold, or (ii) the date on which all the securities to be registered thereunder may be sold without volume or manner-of-sale restrictions and without current public information pursuant to Rule 144 under the Securities Act of 1933, as amended. We are also obligated to pay the Investors, as partial liquidated damages, a fee of 2.0% of each Investor’s subscription amount per month in cash upon the occurrence of certain events, including our failure to file and / or have the registration statement declared effective within the time provided.

H.C. Wainwright & Co., LLC (the “Placement Agent”) is acting as the sole placement agent for the Offering. The Placement Agent will receive a commission equal to 8% of gross proceeds, for an aggregate commission of $200,000, and a non-accountable expense allowance equal to 0.5% of the gross proceeds, or $12,500. The Placement Agent shall also receive common stock purchase warrants to purchase such number of shares equal to 8% of the Shares sold in the Offering to Investors, or 285,715 placement agent warrants with substantially the same terms as the Series D warrants (“PA Warrants”). Additionally, Placement Agent will be reimbursed for its legal and due diligence costs in an amount equal to $35,000. The Placement Agent will also receive a cash fee of 8% of gross proceeds received from the exercise of the Warrants and additional transaction fees equal to 8% of gross proceeds for any future investment by one of the Investors or a party introduced by Placement Agent, in the Company for a period of 18 months following the closing of the Offering. The Placement Agent shall further have a right of first refusal to act as lead underwriter, placement agent or manager with respect to a debt or equity transaction of the Company’s securities.

The Investors were additionally given a right of participation to invest in future offerings for up to 18 months from the date in which the Shares and Warrants are registered as contemplated in the Registration Rights Agreement. The Securities Purchase Agreement also prohibits the Company from issuing any common stock for 120 days after the effectiveness of the registration statement as contemplated in the Registration Rights Agreement. Additionally, until the 24 month anniversary of such effectiveness, the Company shall be prohibited from entering into any agreement to effect any issuance of common stock in a variable rate transaction.

The securities offered have not been registered under the Securities Act of 1933, as amended, and may not be offered or sold in the United States absent registration or an applicable exemption from registration requirements. This current report shall not constitute an offer to sell or the solicitation of an offer to buy, nor shall there be any sale of these securities in any state in which such offer, solicitation or sale would be unlawful prior to the registration or qualification under the securities laws of any such state.

The foregoing summaries of each of the Securities Purchase Agreement, Registration Rights Agreement and Warrant are qualified in their entirety by reference to the full text of each such document, a copy of the form of each is attached hereto as Exhibits 10.01, 10.02, and 10.03 respectively, and each of which is incorporated herein in its entirety by reference.

The information set forth above in Item 1.01 of this current report on Form 8-K is incorporated herein by reference in its entirety.

On July 6, 2015, we announced the Offering in a press release. A copy of the press release is attached to this report as Exhibit 99.01.

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: July 6, 2015

INDEX OF EXHIBITS