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Vertex Pharmaceuticals Announces Advancement to Phase Ib Clinical Trial for VX-950, an Investigational Oral Protease Inhibitor for the Treatment of Hepatitis C

Cambridge, MA, November 8, 2004 -- Vertex Pharmaceuticals Incorporated (Nasdaq: VRTX) announced today the initiation of a Phase Ib clinical trial for VX-950, an investigational oral protease inhibitor for the treatment of hepatitis C virus (HCV) infection. The double-blind, placebo-controlled study will evaluate the tolerability, pharmacokinetics and viral kinetics of multiple, ascending doses of VX-950 over a period of up to 14 days. Approximately 60 subjects will be enrolled in the study, which will include both healthy volunteers and patients with chronic hepatitis C infection. This is the first reported initiation of a study that involves 14 days of administration of an HCV protease inhibitor in patients with chronic hepatitis C infection.

"Vertex has been a pioneer in the discovery and development of direct antivirals for the treatment of HCV infection, which have the potential to transform HCV clinical care," said John Alam, M.D., Senior Vice President of Drug Evaluation and Approval at Vertex. "The Phase Ib study announced today is expected to provide us with important information on the ability of VX-950 to reduce viral load, which we expect will help to define the potential clinical impact of this new class of drugs."

Study Design
The clinical study will first assess healthy volunteers receiving multiple doses of VX-950 for a five-day period. Following this initial assessment, the study will evaluate three different doses of VX-950 in HCV patients, over 14 days of treatment in serially configured dose groups. Vertex plans to evaluate the data from the three dose groups in this double-blind, placebo-controlled study when the third dose is complete. The study, which will enroll subjects at two centers in Europe, may include patients with HCV who are either treatment-naive or treatment-experienced. Vertex anticipates that the Phase Ib study will be completed in the first half of 2005.

Preclinical studies have shown that VX-950 significantly reduces levels of HCV RNA in both an in vitro replicon system and infectious virus assays. In the Phase Ia clinical study, VX-950 was well-tolerated and demonstrated oral bioavailability. Furthermore, combined clinical and preclinical pharmacokinetic results indicate that VX-950 can be administered in a dose regimen that may achieve liver concentrations substantially greater than target concentrations (IC50 and IC90 in non-clinical studies).

Clinical Need and Market Opportunity in HCV Infection
Chronic hepatitis C virus (HCV) infection is a serious public health concern affecting approximately 2.7 million people in the United States. HCV causes inflammation of the liver, which may lead to fibrosis and cirrhosis, liver cancer and ultimately, liver failure. Cirrhosis of the liver resulting from chronic HCV infection is the leading indication for liver transplantation in the U.S. Due to the asymptomatic nature of HCV infection, it often goes undetected for up to 20 years following initial infection. Worldwide, the disease strikes as many as 185 million people. Each year, 8,000 to 10,000 people in the U.S. die from complications of HCV.

The current standard of care in HCV treatment is a combination of weekly injections of pegylated interferon alpha (peg-IFN) and daily oral dosing of ribavirin. This combination therapy provides a sustained viral response for only 40 to 50 percent of patients chronically infected with genotype 1 HCV, the most difficult viral strain to treat and the most common form in the U.S.

Vertex's drug development portfolio includes two different approaches for advancing the future standard of care in HCV. In addition to VX-950, Vertex is developing merimepodib, an IMPDH inhibitor in combination with peg-IFN and ribavirin. Addition of merimepodib to standard therapy has the potential to enhance antiviral activity and improve clinical outcomes for a larger percentage of patients. Vertex owns worldwide development and commercialization rights for merimepodib, and owns worldwide development and commercialization rights to VX-950 except for Japan and certain Far East markets.

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 partners. Vertex's product pipeline is principally focused on viral diseases, inflammation, autoimmune diseases and cancer. Vertex co-promotes the new HIV protease inhibitor, Lexiva(R), with GlaxoSmithKline.

This press release may contain forward-looking statements, including statements that (i) Vertex expects that the study will be conducted as described; (ii) the Phase Ib clinical trial will provide important information on the ability of VX-950 to reduce viral load and will help define the clinical impact of direct antiviral therapies; (iii) direct antivirals have the potential to transform HCV clinical care; (iv) the VX-950 Phase Ib study will be completed in the first half of 2005; and (v) addition of merimepodib to standard therapy has the potential to enhance antiviral activity and improve clinical outcomes for a larger percentage of patients. While management makes its best efforts to be accurate in making forward-looking statements, such statements are subject to risks and uncertainties that could cause Vertex's actual results to vary materially. These risks and uncertainties include, among other things, the risks that clinical trials for merimepodib or VX-950 may not proceed as planned due to technical, scientific, supply or patient enrollment issues, that actual clinical studies of VX-950 will not reflect the results obtained in earlier clinical and nonclinical testing, that clinical results may not demonstrate the value of direct antiviral and combination therapies for HCV patients generally, and other risks listed under Risk Factors in Vertex's Form 10-K filed with the Securities and Exchange Commission on March 15, 2004 and amended on September 8, 2004.

Lexiva(R) is a registered trademark of the GlaxoSmithKline group of companies.

Vertex Contacts:
Michael Partridge, Director, Corporate Communications, (617) 444-6108
Lora Pike, Manager, Investor Relations, (617) 444-6755
Zach Barber, Specialist, Media Relations, (617) 444-6470