News & Events

Vienna Austria, April 26, 2006- Vertex Pharmaceuticals Incorporated (Nasdaq: VRTX) today announced that researchers will present new data supporting clinical development of VX-950, an investigational oral hepatitis C virus (HCV) protease inhibitor being developed for the treatment of hepatitis C, at the 41st Annual Meeting of the European Association for the Study of the Liver (EASL) in Vienna. Two abstracts will be presented on Thursday, April 27 based on a clinical trial originally conducted in 2005. In the first presentation, researchers will review long-term viral sequencing follow-up data that showed that in patients previously dosed with VX-950 as a single agent for 14 days, a sub-optimal treatment period, wild-type virus supplanted treatment-emergent variants and that sensitivity to future treatment regimens that include VX-950 or other HCV protease inhibitors may be regained. In a second presentation, researchers will describe results of a whole genome analysis that suggests that the expression level of interferon-sensitive genes may be restored with VX-950 treatment. An additional late-breaker oral presentation will be delivered on Saturday, April 29. Taken together, these results strongly support further investigation of VX-950 for the treatment of hepatitis C.

"Data from early clinical studies have consistently shown a rapid and dramatic reduction in viral load in patients treated with VX-950, with good tolerability," said John Alam, M.D., EVP, Medicines Development, and Chief Medical Officer of Vertex. "We are pleased to share the results of these extensive viral sequencing and gene expression analyses with the HCV medical community and discuss the implications of our findings for future clinical studies."

Viral Sequencing Analysis
In a previously presented analysis from a clinical study of VX-950 dosed as a single agent that was completed in 2005, viral variants were detected after 14 days of dosing with VX-950 alone. These viral variants displayed varying degrees of sensitivity to VX-950, depending on VX-950 plasma exposure observed during 14 days of dosing. In an oral presentation at EASL titled "Wild-type HCV NS3 Protease Re-emerges During Follow-up After 14 days of Dosing with VX-950 in Patients with Genotype 1 HCV," researchers describe HCV RNA sequencing results that showed that following 14 days of dosing as a single agent, the viral population in patients returned within three to seven months as predominantly wild-type, the virus phenotype present before treatment. The findings from this study suggest that viral variants associated with decreased susceptibility to VX-950 may have reduced replicative fitness in patients. The study further suggests that some HCV-infected patients who have been treated with VX-950 monotherapy for 14 days, a sub-optimal treatment period, may regain sensitivity to VX-950, and that treatment failure may not compromise future therapeutic options.

Gene Expression Analysis
In a poster presentation titled "Antiviral Activity of VX-950 Resolves Expression of an HCV-Associated Gene Signature," Vertex researchers describe data suggesting a normalization of gene expression in peripheral blood cells in hepatitis C patients responding to VX-950 treatment to levels similar to those of healthy, uninfected patients. In the gene expression analysis, researchers identified 258 genes that are differentially expressed in the setting of chronic HCV infection, including a large number of genes associated with viral response, cellular defense and immune response. In patients who achieved the greatest reduction in plasma HCV RNA following 14 days of dosing, sustained levels of interferon-sensitive gene expression were observed in peripheral blood cells.

Late-breaker: Phase Ib Combination Study
A late-breaker oral presentation titled "Initial Results of a 14-Day Study of the Hepatitis C Virus Protease Inhibitor VX-950, In Combination with Peginterferon-alfa-2a" will be presented on Saturday, April 29, by Henk W. Reesink, M.D., Associate Professor of Medicine at Academic Medical Center in Amsterdam. In accordance with embargo rules for the EASL conference, these data will first be disclosed publicly in conjunction with the presentation at 5:30p.m. Central European Summer Time (11:30 a.m. Eastern Daylight Time) on Saturday, April 29.

About Hepatitis C
Hepatitis C is a liver disease caused by the hepatitis C virus, which is found in the blood of people with the disease. HCV, a serious public health concern affecting more than 3 million individuals in the United States and 170 worldwide, is spread through direct contact with the blood of infected people. Though many people with hepatitis C may not experience symptoms, others may have symptoms such as jaundice, abdominal pain, fatigue and fever. Hepatitis C significantly increases a person's risk for developing long-term infection, chronic liver disease, cirrhosis or death. The burden of liver disease associated with HCV infection is increasing, and current therapies only provide sustained benefit in about 50% of patients with genotype 1 HCV, the most common strain of the virus. Novel HCV-specific compounds in clinical development have the potential to increase the proportion of patients who can eradicate the virus.

About VX-950
VX-950 is an investigational oral inhibitor of hepatitis C virus protease, an enzyme essential for viral replication. In early 2006, Vertex reported results from a 28-day, Phase II study of VX-950 dosed in combination with peg-IFN and ribavirin. In this study, 12 of 12 patients had plasma HCV RNA levels below the limit of detection (10 IU/mL) at 28 days. There were no treatment discontinuations and no serious adverse events reported. In previous studies, the most common adverse events reported in both the placebo and VX-950 patients were headache, frequent urination and gastrointestinal symptoms.

Vertex researchers were the first to solve the three-dimensional crystal structure of HCV protease, and have used structural insights to enable the design of small molecule HCV protease inhibitors, including VX-950.

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 principally focused on viral diseases, inflammation, autoimmune diseases and cancer. Vertex co-promotes the HIV protease inhibitor, Lexiva, with GlaxoSmithKline.

Lexiva is a registered trademark of the GlaxoSmithKline group of companies.

Safe Harbor Statement
This press release may contain forward-looking statements, including statements that (i) HCV-infected patients who have been treated with VX-950 monotherapy for 14 days may regain sensitivity to VX-950; and (ii) the expression level of interferon-sensitive genes may be restored with VX-950 treatment. 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 future studies will not confirm expectations based on the previous studies referenced in this release, and other risks listed under Risk Factors in Vertex's form 10-K filed with the Securities and Exchange Commission on March 16, 2006.

Vertex Contacts:
Lynne H. Brum, Vice President, Strategic Communications, (617) 444-6614
Michael Partridge, Director, Corporate Communications, (617) 444-6108
Lora Pike, Manager, Investor Relations, (617) 444-6755
Zachry Barber, Senior Media Relations Specialist, (617) 444-6470