PRESS RELEASE: Sirtris Pharmaceuticals Initiates Phase 2a Clinical Trial in Patients with Type 2 Diabetes

Sirtris Pharmaceuticals Initiates Phase 2a Clinical Trial in Patients with Type 2 Diabetes

CAMBRIDGE, Mass. -- Aug 21, 2007 - Sirtris Pharmaceuticals, a biopharmaceutical company focused on discovering and developing small molecule drugs to treat diseases of aging, announced today the initiation of a Phase 2a clinical trial in India to evaluate its SRT501 product candidate in patients with Type 2 Diabetes whose glucose levels are not adequately controlled by their metformin treatment, a current first-line therapy for such patients.

Patients on metformin alone that have an HbA1c level greater than 7.5 percent, which suggests that their glucose levels are not adequately controlled by current treatment, will be allowed to enter this randomized, double-blind, placebo-controlled Phase 2a trial. Such patients will continue on their current metformin therapy together with either SRT501 or placebo, which will be administered once daily for three months. The trial endpoints will focus on measurements of diabetic status including fed and fasting glucose, insulin, and HbA1c levels. The trial is expected to enroll 130 patients; 65 patients in each of the SRT501 and placebo cohorts. This trial will also further assess the safety and pharmacokinetics of SRT501 in the diabetic population. Results from this trial are expected at the end of 2008.

Peter Elliott, Ph.D., Senior Vice President of Development said, "Metformin is a first-line therapy for Type 2 Diabetes in the United States, and this trial will provide us with insights into the safety and activity of SRT501 as well as the potential for synergy of SIRT1 activators with metformin."

"We are pleased to continue to advance the clinical development of SRT501 to treat diseases of aging such as Type 2 Diabetes. We also have a pipeline of SIRT1 activators, which are chemically distinct from and one thousand times more potent than SRT501," said Christoph Westphal, M.D., Ph.D., Chief Executive Officer of Sirtris.

The Company also has two additional trials of SRT501 in progress in patients with Type 2 Diabetes. These trials are evaluating SRT501, administered at 2 different doses, for 28 days in patients naive to other diabetes drug treatment. SRT501 is also being evaluated in patients with MELAS Syndrome (Mitochondrial Encephalopathy Lactic Acidosis and Stroke-like episodes), a rare mitochondrial disorder. SRT501 represents the first clinical-stage drug candidate in a portfolio of proprietary compounds based on Sirtris' sirtuin drug discovery platform.

About SRT501

SRT501, Sirtris' proprietary version of resveratrol and initial clinical candidate, activates the sirtuin, SIRT1. SIRT1 is a member of the human sirtuin family of enzymes. Specifically, SRT501 acts by increasing mitochondrial activity in pre-clinical models of disease, and we believe it may be therapeutic for metabolic diseases like Type 2 Diabetes as well as mitochondrial disorders such as MELAS Syndrome. Novel chemical entities, SIRT1 activators which are structurally unrelated to and one thousand times more potent than SRT501, expand the pipeline of drug candidates for Sirtris.

Sirtuins are a recently-discovered family of enzymes that appear to regulate certain beneficial effects of calorie restriction. There are seven human sirtuins (SIRT1-7), each having a different sub-cellular localization. Sirtris believes that sirtuins are attractive drug targets since some have a specialized function in mitochondrial activity which may be therapeutically beneficial for metabolic and other diseases. By harnessing a natural process, Sirtris believes sirtuin therapeutics offer the potential for a novel class of drugs that can treat significant diseases of aging in a new way.

About Sirtris Pharmaceuticals

Sirtris Pharmaceuticals is a biopharmaceutical company focused on discovering and developing proprietary, orally available, small molecule drugs with the potential to treat diseases associated with aging, including metabolic diseases such as Type 2 Diabetes. Our drug candidates are designed to mimic certain beneficial health effects of calorie restriction, without requiring a change in eating habits, by activation of sirtuins, a recently discovered class of enzymes that control the aging process. The company's headquarters are in Cambridge, Massachusetts.

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Such statements include, but are not limited to, the potential therapeutic effects of SIRT1 activators for multiple neurodegenerative diseases and other types of disorders, the progress and results of pre-clinical studies of SIRT1 activators, and the potential of sirtuin modulators to receive regulatory approval. These forward-looking statements about future expectations, plans and prospects of Sirtris Pharmaceuticals involve significant risks, uncertainties and assumptions, including risks related to the lack of results that would provide a basis for predicting whether any of the Company's product candidates will be safe or effective, or receive regulatory approval, the possibility that results of pre-clinical studies are not necessarily predictive of clinical trial results, the Company's potential inability to initiate and complete pre-clinical studies and clinical trials for its product candidates, the fact that none of the Company's product candidates has received regulatory approvals, the potential inability of the Company to gain market acceptance of the Company's product candidates, and those other risks factors that can be found in the Company's filings with the Securities and Exchange Commission. Actual results may differ materially from those Sirtris Pharmaceuticals contemplated by these forward-looking statements. Sirtris Pharmaceuticals does not undertake to update any of these forward-looking statements to reflect a change in its views or events or circumstances that occur after the date of this release.