New Preclinical Data Show Significant Anti-Tumor Activity Associated With Infinity's Hedgehog Antagonist IPI-926

Once-Daily Dose Administration Demonstrates Potential for Best-in-Class Properties

SAN DIEGO, Calif. and CAMBRIDGE, Mass., April 13, 2008 (GLOBE NEWSWIRE) -- Infinity Pharmaceuticals, Inc. (Nasdaq:INFI) today announced that preclinical studies evaluating IPI-926, Infinity's novel Hedgehog pathway inhibitor, demonstrated that the compound has excellent pharmaceutical properties in vivo, including oral bioavailability, potent inhibition of the Hedgehog pathway, and long plasma and tumor half-life. Notably, in a novel mouse model of medulloblastoma, once-daily dose administration of IPI-926 resulted in 100 percent survival during the treatment period. These data were reported in an oral presentation today by Melissa Pink, a research investigator at Infinity, during the Annual Meeting of the American Association of Cancer Research (AACR) in San Diego, California.

IPI-926 is a novel, proprietary derivative of the natural plant product cyclopamine that binds to the Smoothened receptor to inhibit the Hedgehog pathway. When abnormally activated in adults, the Hedgehog pathway is believed to play a central role in allowing the proliferation and survival of certain cancer-causing cells, including those implicated in certain deadly cancers such as pancreatic cancer, prostate cancer, small cell lung cancer, breast cancer, and certain brain cancers.

"These promising new data show that once-daily oral administration of IPI-926 achieves therapeutic levels in plasma and tumors in preclinical models," stated Vito Palombella, Ph.D., vice president of drug discovery at Infinity. "By leveraging our synthetic and medicinal chemistry expertise, we improved the potency and optimized the pharmaceutical properties of cyclopamine, an existing natural antagonist of the Hedgehog pathway, through the discovery of IPI-926. Based on the preclinical data we are sharing at AACR on the potency, half-life, and in vivo anti-tumor activity of IPI-926, we believe that it has the potential to be a best-in-class Hedgehog pathway antagonist."

IPI-926 is a potent and selective inhibitor of the Hedgehog pathway in preclinical models. Infinity used a novel mouse model of medulloblastoma developed in the laboratory of Neil Watkins, M.B.B.S., Ph.D., assistant professor of oncology at The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins University, to evaluate the activity of IPI-926 in vivo. Evaluation of the pharmacokinetics and pharmacodynamics of IPI-926 in this model demonstrated that the compound has excellent oral bioavailability, a long plasma half-life and duration of action, and good distribution to tumor tissue. In addition, daily oral administration of IPI-926 led to a dose-dependent inhibition of tumor growth, with tumor regression seen at higher doses. In a similar study, once-daily administration of oral IPI-926 resulted in a 100 percent survival while on treatment and median overall survival of 48 days, a four-fold increase over the 12 days seen in the vehicle-treated group.

Julian Adams, Ph.D., president of research and development and chief scientific officer at Infinity, added, "The Hedgehog pathway is implicated in medulloblastoma and many other very aggressive cancers. We believe that these and other data being presented this week at AACR provide a strong scientific rationale for clinical development of IPI-926 in several different types of cancer. We look forward to completing our investigational new drug-enabling studies and initiating human clinical trials later this year."

About IPI-926

IPI-926 is a novel, proprietary derivative of the natural plant product cyclopamine that binds to the Smoothened receptor to inhibit the Hedgehog pathway. In preclinical studies, IPI-926 has shown potent and selective inhibition of the Hedgehog pathway and attractive pharmacological properties, including oral bioavailability and extended half-life. IPI-926 has demonstrated biological activity in multiple preclinical animal models of cancer. Infinity anticipates commencing clinical trials of IPI-926 in the second half of 2008.

About the Hedgehog Signaling Pathway

The Hedgehog signaling pathway is normally active during embryonic development in regulating tissue and organ formation. When abnormally activated in adults, however, the Hedgehog pathway is believed to play a central role in allowing the proliferation and survival of certain cancer-causing cells, including in certain deadly cancers such as pancreatic cancer, prostate cancer, small cell lung cancer, breast cancer, and certain brain cancers. In addition, recent evidence also points to an important potential role for the Hedgehog pathway in cancer stem cells. Cancer stem cells are progenitor cells suspected to be primarily responsible for tumor growth, survival, and metastasis, despite treatment with conventional chemotherapeutic agents.

About Infinity Pharmaceuticals, Inc.

Infinity is an innovative cancer drug discovery and development company that is seeking to leverage its strength in small molecule drug technologies to discover, develop, and deliver to patients best-in-class medicines for the treatment of cancer and related conditions. For more information on Infinity, please refer to the company's website at http://www.infi.com.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. These statements involve risks and uncertainties that could cause actual results to be materially different from historical results or from any future results expressed or implied by such forward-looking statements. Such forward-looking statements include statements regarding the utility of Hedgehog pathway inhibition to treat various types of cancer and future clinical trial activity for IPI-926. Such statements are subject to numerous factors, risks, and uncertainties that may cause actual events or results to differ materially from Infinity's current expectations. For example, there can be no guarantee that IPI-926 will successfully complete necessary preclinical and clinical development phases. In particular, management's expectations could be affected by risks and uncertainties relating to: results of clinical trials and preclinical studies, including subsequent analysis of existing data and new data received from ongoing and future studies; the content and timing of decisions made by the U.S. Food and Drug Administration and other regulatory authorities and investigational review boards at clinical trial sites; Infinity's ability to obtain additional funding required to conduct its research, development, and commercialization activities; unplanned cash requirements and expenditures; and Infinity's ability to obtain, maintain, and enforce patent and other intellectual property protection for its Hedgehog pathway inhibitors, including IPI-926. These and other risks which may impact management's expectations are described in greater detail under the caption "Risk Factors" included in Infinity's annual report on Form 10-K for the year ended December 31, 2007, as filed with the Securities and Exchange Commission on March 14, 2008. Further, 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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CONTACT:  Infinity Pharmaceuticals, Inc. 
          Monique Allaire
          (617) 453-1105
          Monique.Allaire@infi.com

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