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

June 12, 2013

Date of Report (Date of earliest event reported)

AGENUS INC.

(Exact name of registrant as specified in its charter)

781-674-4400

(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 (see General Instruction A.2. below):

(e) At our Annual Meeting of Stockholders held on June 12, 2013 (the “Annual Meeting”), our stockholders approved Amendment No. 2 to our 2009 Stock Incentive Plan, as amended (the “2009 Plan”), which amendment had previously been adopted by our Board of Directors, subject to shareholder approval, to (i) increase the number of shares of our common stock that may be issued pursuant to awards granted under the 2009 Plan by an additional 2,000,000 shares, (ii) clarify that no more than 1,000,000 shares of our common stock may be issuable under the 2009 Plan pursuant to the exercise of incentive stock options and that no single participant may receive stock options or stock appreciation rights for more than 1,000,000 shares of our common stock in any calendar year, and (iii) include a prohibition against the repricing of outstanding stock options without stockholder approval . The description of Amendment No. 2 to the 2009 Plan set forth herein does not purport to be complete and is qualified in its entirety by reference to the full text of the such amendment, which is attached hereto as Exhibit 10.1 and is incorporated herein by reference.

In addition, on June 13, 2013, the Compensation Committee of our Board of Directors (the “Compensation Committee”) approved the following with respect to the compensation of our executive officers:

A total of 21,831,933 shares of our common stock, representing 78.4% of the shares outstanding and eligible to vote, were represented in person or by valid proxies at the Annual Meeting, constituting a quorum. The final results for each of the matters submitted to a vote of stockholders at the Annual Meeting are as follows:

(1) To elect the following nominees to the Board of Directors for a three year term expiring at our 2016 annual meeting of stockholders:

(2) To approve Amendment No. 2 to the 2009 Plan:

(3) To ratify the appointment of KPMG LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2013:

According to a preliminary list of additions and deletions made publicly available by Russell Investments, we expect our common stock to be excluded from the broad-market Russell 3000^® Index, Russell Global Index, and Russell Microcap^® Index when Russell Investments reconstitutes its comprehensive set of U.S. and global equity indices on June 28, 2013.

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.