UNITED STATES

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 (Earliest Event Reported): July 21, 2015

CYTRX CORPORATION

(Exact Name of Registrant as Specified in its Charter)

Delaware

(State or Other Jurisdiction of Incorporation)

(310) 826-5648

(Registrant’s Telephone Number, Including Area Code)

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:

On July 21, 2015, CytRx Corporation (“we,” “us,” “our” or the “Company”) entered into an underwriting agreement with Jefferies LLC, as representative of the several underwriters, relating to our public offering of 9,100,000 shares of common stock for total gross proceeds of $25,025,000. The public offering price is $2.75 per share of common stock. In addition, the underwriting agreement provides the underwriters a 30-day option to purchase from us up to an additional 1,365,000 shares of our common stock.

We expect the offering to close on July 24, 2015, subject to the satisfaction of customary closing conditions. The net proceeds to us from the offering are expected to be approximately $23,223,500, after deducting underwriting discounts and commissions and estimated offering expenses payable by us. The offering is being made pursuant to our existing shelf registration statement on Form S-3 (File No. 333-192597), which was filed with the Securities and Exchange Commission on November 27, 2013 and declared effective on December 23, 2013, and a prospectus supplement thereunder.

The underwriting agreement contains customary representations, warranties and covenants by us, customary conditions to closing, indemnification obligations of the Company and the underwriters, including with respect to liabilities under the Securities Act of 1933, as amended, as well as customary termination provisions.

Pursuant to the underwriting agreement, we and our directors and officers have agreed not to sell or otherwise dispose of any common stock held by them for a period ending 90 days after the date of the underwriting agreement without first obtaining the written consent of Jefferies LLC, subject to certain exceptions.

The underwriting agreement is attached hereto as an exhibit to provide interested persons with information regarding its terms, but is not intended to provide any other factual information about us. The representations, warranties and covenants contained in the underwriting agreement were made only for purposes of the underwriting agreement as of specific dates indicated therein, were solely for the benefit of the parties to the agreement, and may be subject to limitations agreed upon by the parties, including being qualified by confidential disclosures exchanged between the parties in connection with the execution of the underwriting agreement.

A copy of the opinion of TroyGould PC relating to the legality of common stock offered by us is attached as Exhibit 5.1 hereto.

The foregoing description of the underwriting agreement is not complete and is qualified in its entirety by reference to the full text of the underwriting agreement, a copy of which is filed as Exhibit 1.1 to this Current Report on Form 8-K and is incorporated by reference herein.

On July 20, 2015, we issued a press release announcing the proposed offering and on July 21, 2015, we issued a press release announcing the pricing of the offering. Copies of the press releases are attached hereto as Exhibits 99.1 and 99.2, respectively, and incorporated herein by reference.

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(d) Exhibits

There are filed as part of this report the exhibits listed on the accompanying Index to Exhibits, which information is incorporated herein by reference.

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SIGNATURES

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

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EXHIBIT INDEX

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