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): September 2, 2014

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:

Collaboration and License Agreement

On September 2, 2014, Infinity Pharmaceuticals, Inc. (“we”, “us” or “our”) entered into a collaboration and license agreement with AbbVie Inc., or AbbVie, which we refer to as the AbbVie agreement. Under the AbbVie agreement, we will collaborate with AbbVie to develop and commercialize products containing the compound known as duvelisib (also known as IPI-145), or duvelisib products, in oncology indications. We licensed rights to duvelisib, an oral inhibitor of phosphoinositide-3-kinase, or PI3K, delta,gamma, from Intellikine LLC.

Licensed Rights

Under the terms of the AbbVie agreement, we have granted to AbbVie licenses under applicable patents, patent applications, know-how and trademarks to develop, commercialize and manufacture duvelisib products in oncology indications. These licenses are generally co-exclusive with rights we retain, except that we have granted AbbVie exclusive licenses to commercialize duvelisib products outside the United States. We and AbbVie retain the rights to perform our respective obligations and exercise our respective rights under the AbbVie agreement, and we and AbbVie may each grant sublicenses to affiliates or third parties.

Development, Commercialization and Manufacturing Responsibilities

Under the AbbVie agreement, we and AbbVie have created a governance structure, including committees and working groups to manage the development, manufacturing and commercialization responsibilities for the duvelisib products. Generally, we and AbbVie must mutually agree on decisions, although in specified circumstances either we or AbbVie would be able to break a deadlock.

We have primary responsibility for the conduct of development of duvelisib products, except that AbbVie has responsibility for the conduct of certain contemplated combination clinical studies, which we refer to as the AbbVie studies. Excluding the AbbVie studies, to the extent they occur, the costs of which would be shared equally, we are responsible for all costs to develop duvelisib products up to a maximum amount of $667,000,000, after which we will share duvelisib product development costs equally with AbbVie. We and AbbVie share oversight of development and have each agreed to use diligent efforts, as defined in the AbbVie agreement, to carry out our development activities under an agreed upon development plan.

We and AbbVie share operational responsibility and decision making authority for commercialization of duvelisib products in the United States. Specifically, we have the primary responsibility for advertising, distribution, and booking sales, and we share certain other commercialization functions with AbbVie. We and AbbVie will each provide half of the sales representative effort to promote duvelisib products in the United States. Outside the United States, AbbVie has, with limited exceptions, operational responsibility and decision making authority to commercialize duvelisib products.

We have the responsibility to manufacture products containing duvelisib under the AbbVie agreement until we transition the manufacturing to AbbVie, which we expect to occur as promptly as practicable while ensuring continuity of supply. We and AbbVie will equally share the manufacturing or supply costs for duvelisib products for clinical studies and for commercialization in the United States. AbbVie will bear the cost of manufacturing duvelisib products for commercialization outside of the United States.

Financial Terms

AbbVie has agreed to pay us a non-creditable $275,000,000 upfront payment within 45 days. AbbVie has also agreed to pay us milestone payments associated with specified development, regulatory and commercialization events, up to an aggregate of $530,000,000 if all the milestones are achieved. Under the terms of the AbbVie agreement, we and AbbVie will equally share commercial profits or losses of duvelisib products in the United States.

Outside the United States, AbbVie has agreed to pay us a tiered royalty on net sales ranging from 23.5% to 30.5%, depending on annual net sales by AbbVie, its affiliates and its sublicensees. This tiered royalty can be reduced based on specified factors, including patent expiry, generic entry, reduction in our

royalties to Mundipharma International Corporation Limited and Purdue Pharmaceuticals Products L.P. and royalties paid to third parties with blocking intellectual property. These royalties are payable on a product-by-product and country-by-country basis until AbbVie ceases selling the product in the country.

Exclusivity

Subject to limited exceptions, we have agreed that we and our affiliates will not commercialize, or assist others in commercializing, in oncology indications any product that is a PI3K delta,gamma dual inhibitor that meets certain agreed-to criteria, other than the duvelisib products, and AbbVie has agreed to similar restrictions. Registration directed clinical trials and commercialization of duvelisib products for uses outside of oncology indications would require our and AbbVie’s mutual consent.

Term and Termination

The AbbVie agreement will remain in effect until all development, manufacturing and commercialization of duvelisib products cease, unless terminated earlier. Either we or AbbVie may terminate the AbbVie agreement if the other party is subject to certain insolvency proceedings or if the other party materially breaches the AbbVie agreement and the breach remains uncured for a specified period, which may be extended in certain circumstances. However, we may terminate the AbbVie agreement only on a country by country basis in the event AbbVie is not using diligent efforts to obtain regulatory approval or to commercialize duvelisib products in a country outside the United States. AbbVie may also terminate the AbbVie agreement for convenience after a specified notice period. In the event there is a material uncured breach by either us or AbbVie of development or commercialization obligations, the non-breaching party may also have the right to assume and conduct such applicable development or commercialization obligations. If AbbVie or any of its affiliates or sublicensees challenges the patents we have licensed to AbbVie, we can terminate the AbbVie agreement if the challenge is not withdrawn after a specified notice period.

If the AbbVie agreement is terminated, we would receive all rights to the regulatory filings related to duvelisib upon our request, our license to AbbVie terminates, and AbbVie grants us a perpetual, irrevocable license to develop, manufacture and commercialize products containing duvelisib, excluding any compound which is covered by patent rights controlled by AbbVie or its affiliates. This license would be royalty free, unless the AbbVie agreement is terminated for material breach, in which case, depending on the breaching party and the timing of the material breach, a royalty rate may be payable by us ranging from a low single-digit percentage to a low double-digit percentage of net sales, and, in some cases, subject to a payment cap.

If the AbbVie agreement is terminated, there are certain wind down obligations to ensure a smooth transition of the responsibilities of the parties.

The foregoing description of the collaboration and license agreement does not purport to be complete and is qualified in its entirety by reference to the complete text of the AbbVie agreement, which we intend to file with the Securities and Exchange Commission as an exhibit to our Quarterly Report on Form 10-Q for the period ending September 30, 2014.

On September 3, 2014, we issued a press release announcing the entry into a collaboration and license agreement with AbbVie Inc. A copy of this press release is attached 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.

Exhibit 99.1

Contacts:

Infinity Pharmaceuticals, Inc.

Jaren Irene Madden, 617-453-1336

Jaren.Madden@infi.com

http://www.infi.com

INFINITY AND ABBVIE ANNOUNCE GLOBAL STRATEGIC COLLABORATION TO DEVELOP AND COMMERCIALIZE DUVELISIB (IPI-145) IN ONCOLOGY

– Infinity to Receive $275 Million Up-Front Payment and $530 Million in Potential Milestones –

– Companies to Jointly Develop and Commercialize Duvelisib in U.S., with Equal Profit Share; Infinity to Receive Royalties on Sales Outside the U.S. –

– Infinity to Host Conference Call Today at 8:30 A.M. ET/7:30 A.M. CT –

Cambridge, MA and North Chicago, Ill – September 3, 2014 – Infinity Pharmaceuticals, Inc. (NASDAQ: INFI) and AbbVie Inc. (NYSE: ABBV) today announced that they have entered into a global collaboration to develop and commercialize duvelisib (IPI-145), Infinity’s oral inhibitor of phosphoinositide-3-kinase (PI3K)-delta and PI3K-gamma, for the treatment of patients with cancer. Duvelisib has shown clinical activity across a broad range of blood cancers, including indolent non-Hodgkin lymphoma (iNHL) and chronic lymphocytic leukemia (CLL). Infinity is conducting registration-focused trials evaluating the safety and efficacy of duvelisib, including DYNAMO^TM, a Phase 2 study in patients with iNHL, and DUO^TM, a Phase 3 study in patients with CLL.

Under the terms of the agreement, Infinity will receive an upfront payment of $275 million and is eligible to receive up to $530 million in additional payments for the achievement of

development, regulatory and commercial milestones, including up to $405 million for the achievement of milestones through the first commercial sale of duvelisib. In the U.S., the companies will jointly commercialize duvelisib and will share equally in any potential profits. Outside the U.S., AbbVie will be responsible for the conduct and funding of commercialization of duvelisib, and Infinity is eligible to receive tiered double-digit royalties on net product sales.

“We believe that duvelisib is a very promising investigational treatment based on clinical data showing activity in a broad range of blood cancers,” said Michael Severino, M.D., AbbVie executive vice president and chief scientific officer. “The addition of duvelisib will complement AbbVie’s emerging oncology pipeline and expand our research into combination therapies to generate improved outcomes for cancer patients. We look forward to working with Infinity to bring duvelisib to patients worldwide.”

“This collaboration is an important step toward fulfilling Infinity’s objective of bringing better treatments to patients and further advances our goal of building a sustainable, fully integrated biotechnology company,” stated Adelene Q. Perkins, chair, president and chief executive officer at Infinity. “AbbVie will be a wonderful partner for Infinity, bringing all of the expertise and scale of a successful, well established company, together with the energy, drive, innovation, and nimbleness of a young organization. We look forward to advancing duvelisib through monotherapy studies designed to enable registration and in furthering our shared longer-term vision of combining duvelisib with both current standards of care and novel, targeted therapies.”

Additional Details About the Collaboration

Development and commercialization activities under the collaboration will be managed through a shared governance structure. In the U.S., Infinity and AbbVie will jointly commercialize duvelisib, assuming regulatory approval, with Infinity booking sales, and will share equally in any potential profits or losses. Outside the U.S., AbbVie will be responsible for conducting and funding of any commercialization of duvelisib, and Infinity is eligible to receive tiered royalties on net product sales, with percentages ranging from 23.5 percent to 30.5 percent.

For sales of duvelisib in the U.S., AbbVie and Infinity will share equally the existing royalty obligations to Mundipharma International Corporation Limited/Purdue Pharmaceutical Products L.P., and Infinity will be responsible for these royalty obligations outside of the U.S. Infinity will also be responsible for the existing royalty obligations to Millennium: The Takeda Oncology Company for sales of duvelisib worldwide.

As part of the strategic collaboration, the companies will share responsibility for the conduct of specific trials specified within an agreed-upon global development plan, with each company leading the development of certain trials within the plan. For the initial global development plan agreed to by the companies, Infinity will fund the trials it conducts and the companies will share

equally the funding of trials conducted by AbbVie. The agreement includes plans to launch multiple Phase 2 and Phase 3 studies of duvelisib in hematologic malignancies over the next several years.

Conference Call Today at 8:30 a.m. ET/7:30 a.m. CT

Infinity will hold a conference call at 8:30 a.m. to discuss the strategic collaboration announced today. A live webcast of the conference call can be accessed in the Investors/Media section of Infinity’s website at www.infi.com. To participate in the conference call, please dial (877) 316-5293 (domestic) and (631) 291-4526 (international) five minutes prior to start time. The conference ID number is 97402440. An archived version of the webcast will be available on Infinity’s website for 30 days.

About the Development of Duvelisib for the Treatment of Blood Cancers

Infinity and AbbVie are developing duvelisib, an oral inhibitor of Class I PI3K-delta,gamma. The PI3Ks are a family of enzymes involved in multiple cellular functions, including cell proliferation and survival, cell differentiation, cell migration and immunity. The PI3K-delta,gamma isoforms are preferentially expressed in leukocytes (white blood cells), where they have distinct and mostly non-overlapping roles in immune cell development and function. Targeting PI3K-delta and PI3K-gamma may provide multiple opportunities to develop differentiated therapies for the treatment of hematologic malignancies.

In 2013, Infinity launched the DUETTS^TM (Duvelisib Trials in Hematologic Malignancies) program, a worldwide investigation of duvelisib in blood cancers. As part of the DUETTS program, patient enrollment is ongoing in DYNAMO^TM, a Phase 2 monotherapy study designed to evaluate the safety and efficacy of duvelisib in patients with refractory indolent non-Hodgkin lymphoma (iNHL) (ClinicalTrials.gov Identifier NCT01882803), and DUO^TM, a Phase 3 monotherapy study designed to evaluate the safety and efficacy of duvelisib in patients with relapsed/refractory chronic lymphocytic leukemia (CLL) (NCT02004522). DYNAMO+R^TM, a Phase 3 study of duvelisib in combination with rituximab in patients with previously treated follicular lymphoma (NCT02204982), is expected to start in 2014.

Additionally, a Phase 1 study of duvelisib in patients with advanced blood cancers is ongoing (NCT01476657).

About Infinity Pharmaceuticals, Inc.

Infinity is an innovative biopharmaceutical company dedicated to discovering, developing and delivering best-in-class medicines to people with difficult-to-treat diseases. Infinity combines proven scientific expertise with a passion for developing novel small molecule drugs that target emerging disease pathways. For more information on Infinity, please refer to the company’s website at www.infi.com.

About AbbVie Inc.

AbbVie is a global, research-based biopharmaceutical company formed in 2013 following separation from Abbott Laboratories. The company’s mission is to use its expertise, dedicated people and unique approach to innovation to develop and market advanced therapies that address some of the world’s most complex and serious diseases. AbbVie employs approximately 25,000 people worldwide and markets medicines in more than 170 countries. For further information on the company and its people, portfolio and commitments, please visit www.abbvie.com. Follow @abbvie on Twitter or view careers on AbbVie’s Facebook or LinkedIn page.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. Such forward-looking statements include those regarding the Company’s expectations about: the receipt of upfront, milestone, royalty and other payments under the agreement with AbbVie; the therapeutic and commercial potential of duvelisib; the expected benefits of the collaboration with AbbVie; the advancement of duvelisib through clinical trials; plans to conduct additional clinical trials of duvelisib; and its ability to execute on its strategic plans. Such statements are subject to numerous important factors, risks and uncertainties that may cause actual events or results to differ materially from the company’s current expectations. For example, there can be no guarantee that Infinity will report data in the time frames it has estimated, that any product candidate Infinity is developing will successfully complete necessary preclinical and clinical development phases, or that development of any of Infinity’s product candidates will continue. Further, there can be no guarantee that Infinity’s strategic collaboration with AbbVie will continue or that any positive developments in Infinity’s product portfolio will result in stock price appreciation. Management’s expectations and, therefore, any forward-looking statements in this press release could also be affected by risks and uncertainties relating to a number of other factors, including the following: Infinity’s results of clinical trials and preclinical studies, including subsequent analysis of existing data and new data received from ongoing and future studies; a failure of Infinity and/or AbbVie to fully perform under the strategic collaboration and/or an early termination of the collaboration and license agreement; the content and timing of decisions made by the U.S. FDA and other regulatory authorities, investigational review boards at clinical trial sites and publication review bodies; Infinity’s ability to obtain and maintain requisite regulatory approvals and to enroll patients in its clinical trials; unplanned cash requirements and expenditures; development of agents by Infinity’s competitors for diseases in which Infinity is currently developing or intends to develop its product candidates; and Infinity’s ability to obtain, maintain and enforce patent and other intellectual property protection for any product candidates it is developing. These and other risks which may impact management’s expectations are described in greater detail under the caption “Risk Factors” included in Infinity’s quarterly report on Form 10-Q filed with the Securities and Exchange Commission (SEC) on August 11, 2014, and other filings filed by Infinity with the SEC. Any forward-looking statements contained in this press release speak only as of the date hereof, and Infinity expressly disclaims any obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise.

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