Vertex Pharmaceuticals to Start Phase 3 'REALIZE' Trial with Telaprevir in Treatment-Failure HCV Patients

• First HCV protease inhibitor in pivotal trial for this difficult to treat patient population

• Trial to enroll all major treatment-failure patient groups, including null responders, partial responders and relapsers

• Two telaprevir registration programs to address significant unmet need in treatment-naive and treatment-failure patients

Cambridge, Mass., Aug 19, 2008 -- Vertex Pharmaceuticals Incorporated (Nasdaq: VRTX) today announced that the Company has reached agreement with U.S. and E.U. regulatory authorities to proceed with the REALIZE trial, a pivotal Phase 3 clinical trial with the hepatitis C virus (HCV) protease inhibitor telaprevir in combination therapy for patients with chronic HCV infection who failed to achieve a sustained viral response (SVR) with prior therapy.

The trial will be conducted in the U.S. and E.U. and will enroll approximately 650 genotype 1 HCV patients who failed prior treatment with pegylated interferon (peg-IFN) and ribavirin (RBV). The trial is designed to evaluate two 48-week telaprevir-based regimens in comparison with a 48-week control arm. Telaprevir will be dosed for 12 weeks. The primary endpoint of the trial is SVR, defined as undetectable HCV RNA (less than10 IU/mL) 24 weeks after the completion of treatment.

"In Phase 2 clinical trials, telaprevir-based regimens have demonstrated the potential to increase sustained viral response rates across a broad spectrum of patients infected with the hepatitis C virus, including patients who failed to achieve SVR with previous pegylated interferon and ribavirin therapy, many of whom are at high risk for life-threatening HCV-related complications," said Ira Jacobson, MD, Chief of the Division of Gastroenterology and Hepatology, Weill Medical College of Cornell University. "The REALIZE trial of telaprevir is a landmark Phase 3 trial of an investigational HCV protease inhibitor in null responder and other patients who failed prior treatment and will seek to generate additional data to demonstrate the benefit of telaprevir in this difficult to treat patient population."

"Approximately 6 million patients are chronically infected with hepatitis C in the U.S. and E.U. today, and approximately 650,000 of these patients have failed previous treatments of pegylated interferon and ribavirin therapy and are in need of a new therapeutic option to treat their disease," said Kurt C. Graves, Vertex's Executive Vice President, Chief Commercial Officer and Head, Strategic Development. "Data generated from this Phase 3 trial in treatment-failure patients, as well as data from the ongoing Phase 3 ADVANCE trial in treatment-naive patients, may further contribute to the emerging profile of telaprevir to address the significant medical need in both treatment-naive and treatment-failure patients."

Global Phase 3 Trial in Patients who Failed to Achieve SVR with Prior Therapy

The REALIZE Trial (Re-treatment of Patients with Telaprevir-based Regimen to Optimize Outcomes) will enroll approximately 650 genotype 1 HCV patients and will be conducted by Tibotec at more than 100 centers in the U.S. and E.U. Tibotec expects to complete enrollment of the REALIZE trial in the first quarter of 2009. The trial will include the following patient groups:

• Null responders (defined as patients who achieved less than 2 log reduction in HCV RNA at Week 12 of prior therapy);

• Partial responders (defined as patients who achieved at least a 2 log reduction at Week 12, but failed to achieve undetectable HCV RNA by Week 24 of prior therapy); and

• Relapsers (defined as patients who had undetectable HCV RNA at the completion of at least 42 weeks of prior treatment, but relapsed during follow-up).

The REALIZE trial will dose telaprevir in combination with pegylated interferon alfa-2a (PEGASYS) and ribavirin. The REALIZE trial will enroll three 48-week trial arms:

1. Telaprevir dosed at 750 mg every eight hours (q8h) for 12 weeks in combination with standard doses of peg-IFN and RBV, followed by 36 weeks of treatment with peg-IFN and RBV alone;

2. Delayed start arm, comprised of 4 weeks of treatment with peg-IFN and RBV, followed by telaprevir dosed at 750 mg q8h for 12 weeks in combination with standard doses of peg-IFN and RBV, followed by another 32 weeks of peg-IFN and RBV alone; and

3. A control arm with standard doses of peg-IFN and RBV dosed for 48 weeks.

Patients in all treatment arms will be followed for 24 weeks after completion of treatment to assess SVR.

Updates on the status of Vertex and Tibotec's clinical trials of telaprevir are available at www.clinicaltrials.gov.

Pivotal Trial in Treatment-Naive Patients

Vertex and Tibotec are also conducting the global 3-arm pivotal Phase 3 ADVANCE trial in treatment-naive genotype 1 HCV patients that is focused on 24-week telaprevir-based regimens for patients achieving rapid viral response (HCV RNA less than 10 IU/mL at 4 weeks). Vertex is on track to complete enrollment of the ADVANCE trial during the fourth quarter of 2008 and expects to have sustained viral response (SVR) data from the trial in the first half of 2010.

About Telaprevir

Telaprevir (VX-950) is an investigational oral inhibitor of HCV protease, an enzyme essential for viral replication, and is one of the most advanced investigational antiviral agents in development that specifically targets HCV. The types of adverse events that were seen across all treatment arms in Phase 2b trials of telaprevir are those that have been commonly observed with peg-IFN and RBV.

The most common adverse events, regardless of treatment assignment, were fatigue, rash, headache and nausea, with rash being the most common reason for treatment discontinuation in patients treated with telaprevir. There have been reports of severe rashes in clinical trials of telaprevir-based therapy. Gastrointestinal disorders, skin adverse events (rash, pruritus) and anemia were more common in the telaprevir arms compared to the control arm over the dosing period.

About Vertex

Vertex Pharmaceuticals Incorporated is a global biotechnology company committed to the discovery and development of breakthrough small molecule drugs for serious diseases. The Company's strategy is to commercialize its products both independently and in collaboration with major pharmaceutical companies. Vertex's product pipeline is focused on viral diseases, inflammation, autoimmune diseases, cancer, pain and cystic fibrosis. Vertex co-discovered the HIV protease inhibitor, Lexiva, with GlaxoSmithKline.

For further information, visit www.vpharm.com.