Vertex's Collaborator Merck Suspends Patient Enrollment in Clinical Trials of MK-0457 (VX-680) Pending Full Analysis of Clinical Data

Vertex Pharmaceuticals Incorporated (Nasdaq: VRTX) and Merck & Co., Inc. today provided an update to their collaborative Aurora kinase research and development program, which is targeting the treatment of cancer. Merck has suspended enrollment in clinical trials of the lead investigational Aurora kinase inhibitor in the collaboration, MK-0457 (VX-680), pending a full analysis of all efficacy and safety data for MK-0457. The decision was based on preliminary safety data, in which a clinical safety finding of QTc prolongation was observed in one patient. Merck and Vertex have a broad research and development program underway to evaluate Aurora kinase inhibitors as novel approaches to targeted cancer treatment. As part of Merck’s strategy to develop multiple drug candidates in different tumor types and treatment combinations, Merck plans to initiate in early 2008 a Phase 1 trial of VX-689 in patients with advanced and/or refractory solid tumors. MK-0457 is being investigated in a Phase 2 trial in patients with treatment-refractory chronic myelogenous leukemia (CML) or Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ALL) containing the T315I mutation, as well as an ongoing Phase 1 clinical trial in patients with advanced leukemias. Patients currently enrolled in these trials may continue to be treated with MK-0457, with additional monitoring for QTc prolongation. A recently initiated Phase 1 trial of MK-0457 in combination with dasatinib in patients with CML or Ph+ALL has also been suspended. In addition, development of the Aurora kinase inhibitor MK-6592 (VX-667) has been discontinued after the compound did not meet pharmacokinetic objectives in a Phase 1 clinical study. About Merck Oncology Merck Oncology focuses on all aspects of cancer care -- prevention, treatment, and supportive care. Through strong internal research capabilities, selective alliances and acquisitions, and enabling technologies such as the Molecular Profiling platform of Rosetta, Merck Oncology is looking to lead in the discovery, development and delivery of targeted anticancer therapies customized for patient subpopulations. Merck Oncology conducts research at sites in Boston, Seattle, West Point, Japan and Italy. 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 bacterial infection. Vertex co-discovered the HIV protease inhibitor, Lexiva, with GlaxoSmithKline. Vertex's press releases are available at www.vrtx.com. 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) Merck and Vertex expect to continue to evaluate the clinical potential of Aurora kinase inhibitors, with the goal of developing multiple drug candidates in different tumor types and treatment combinations, and (ii) Merck expects to initiate a Phase 1 clinical trial of VX-689 in early 2008. 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 the actual results of studies to vary materially. Those risks and uncertainties include, among other things, the risk that planned studies will not be commenced due to unanticipated scientific developments or business constraints, that observed outcomes in clinical investigations of smaller numbers of patients will not be reflected in clinical trials involving larger numbers of patients, that unexpected and adverse outcomes in ongoing clinical and nonclinical studies will occur, and other risks listed under Risk Factors in Vertex's Form 10-K filed with the Securities and Exchange Commission on March 1, 2007. Vertex disclaims any obligation to update the information contained in this press release as new data become available. (VRTX-GEN)