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 (Date of earliest event reported): May 18, 2011

Infinity Pharmaceuticals, Inc.

(Exact name of registrant as specified in charter)

Registrant’s telephone number, including area code: (617) 453-1000

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:

At the Annual Meeting of Stockholders of Infinity Pharmaceuticals, Inc. (the “Company”) held on May 18, 2011, our stockholders voted on four matters as follows:

1. The following eleven nominees were elected to the Company’s Board of Directors to serve for a one-year term expiring at the 2012 annual meeting of stockholders:

2. A non-binding, advisory proposal on the compensation of the Company’s named executive officers was approved.

3. The shareholders recommended, in a non-binding, advisory vote, that future advisory votes on the compensation of the Company’s named executive officers be held every three years.

After taking into consideration the foregoing voting results and the Board’s prior recommendation in favor of an advisory shareholder vote on the compensation of the Company’s named executive officers every three years, the Board intends to hold future advisory votes on the compensation of the Company’s named executive officers every three years.

4. The selection of Ernst & Young LLP as our independent registered public accounting firm for the current fiscal year was ratified.

On May 19, 2011, we issued a press release announcing clinical development plans for our Hsp90 chaperone inhibitor program including the initiation of a Phase 2 clinical trial of retaspimycin HCl, also known as IPI-504, in combination with docetaxel in patients with non-small cell lung cancer (NSCLC). In addition, we announced top-line results from our Phase 1b clinical trial of retaspimycin HCl in combination with docetaxel in patients with NSCLC. The full text of this press release is filed as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference.

SIGNATURE

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.