Press Release

Cambridge, MA, April 5, 2006- Vertex Pharmaceuticals Incorporated (Nasdaq: VRTX) today announced the initiation of a Phase II clinical development program for VX-680, an investigational drug candidate targeting Aurora kinase. In connection with the initiation of Phase II development, Vertex earned a $10 million milestone payment in March 2006 from Merck & Co., Inc. Vertex and Merck have a global collaboration to develop and commercialize VX-680.

The initiation of Phase II development for VX-680 is based on the enrollment of patients with advanced colorectal cancer in a Phase II extension of a previous Phase I clinical study. In addition, Merck expects to initiate a Phase II clinical study for VX-680 in patients with advanced lung cancer this year.

"We continue to make progress in the development of VX-680 as marked by the initiation of the Phase II clinical development program," said Stephen H. Friend, M.D., Ph.D., Executive Vice President, Oncology at Merck Research Laboratories. "This Phase II study represents a continuation of our efforts to broadly assess the activity of VX-680 in a range of solid tumors and hematologic cancers."

"VX-680's advancement to Phase II clinical development underscores the rapid progress that we and Merck have made to characterize the activity of this novel, potential cancer treatment," said Joshua Boger, Ph.D., Chairman, President and CEO of Vertex.

Phase II Study in Colorectal Cancer
The initiation of Phase II development for VX-680 is based on the enrollment of patients with advanced colorectal cancer who may have received up to three prior cancer treatments. The open-label, non-randomized study will enroll approximately 20 patients and is being conducted at major cancer treatment centers in the U.S.

Additional information on clinical trials for VX-680 is available at the National Institutes of Health clinical trial database at www.ClinicalTrials.gov (a service of the U.S. National Institutes of Health developed by the National Library of Medicine).

AACR Presentation
On Tuesday, April 4, 2006 at the 97th Annual Meeting for the American Association for Cancer Research (AACR) in Washington, DC, Vertex scientists presented a poster titled "Structural Basis for Potent Inhibition of the Aurora Kinases, Wild Type Abl Kinase and a T315I Multi-Drug Resistant Mutant Form of ABL Kinase by VX-680." In vitro, VX-680 is a potent inhibitor of wild type and drug resistant mutants of Abl kinase and Aurora kinases. Studies performed by Vertex scientists provide a structural interpretation for this potent inhibition and support the clinical investigation of VX-680 in patients with treatment-resistant forms of chronic myelogenous leukemia (CML). Merck is currently conducting a Phase I study with VX-680 in patients with hematologic cancers, including CML patients who have failed prior treatment.

VX-680 Clinical Studies
In addition to the Phase II clinical development program for VX-680 in colorectal cancer announced today, and the ongoing Phase I study in hematologic cancers, Merck is also completing a Phase I study of VX-680 administered in patients with solid tumors refractory to prior chemotherapy treatment.

Background: Aurora Kinases and the VX-680 Collaboration
Cancer cells typically contain mutations in a number of genes, which ultimately result in uncontrolled cell growth and tumor metastasis. As enzymes specific for and essential to cell growth and division, Aurora kinases hold the potential to be important control points for slowing the growth and spread of tumors. Aurora kinases (A, B and C) comprise a family of serine-threonine kinases that are believed to play multiple roles in the development and progression of cancer by acting as regulators of cell proliferation, by transforming normal cells into cancer cells and by down-regulating p53, one of the body's natural tumor suppressors. Aurora kinases are known to be over-expressed in many tumor types, including colon cancer, breast cancer, ovarian cancer and other cancers as well as in lymphoma and leukemias. Amplification of Aurora genes is associated with progression of colorectal cancer and poor prognosis in certain types of breast cancer.

In June 2004, Vertex entered into a global collaboration with Merck to develop and commercialize VX-680. Along with clinical development, Vertex and Merck are conducting a joint research program to characterize VX-680's activity across a broad range of cancer types and have identified an additional drug candidate targeting the Aurora kinases.

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.

Vertex Safe Harbor Statement
This press release may contain forward-looking statements, including statements that (i) Merck expects to initiate a Phase II clinical study for VX-680 in patients with advanced lung cancer this year; and (ii) Vertex and Merck will continue to assess the activity of VX-680 in a range of solid tumors and hematologic cancers. 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 VX-680 may not proceed as planned due to technical, scientific, or patient enrollment issues, or disagreements with regulatory authorities over trial design or other matters, that the scale and scope of future clinical and nonclinical studies may change and will be determined in significant part by data collected in ongoing and future trials, that further clinical studies of VX-680 may not reflect the results obtained in early clinical and nonclinical studies, that ongoing nonclinical studies, including toxicology studies, will yield currently unanticipated negative outcomes, that results from clinical trials commenced during 2005 and 2006 will be insufficient to support a Phase III program without additional trials and consequent delay in the timetable for potential approval, 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 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