-  Investigational New Drug Application Activated in the U.S. -

    CAMBRIDGE, Mass., Dec. 5 /PRNewswire-FirstCall/ -- Vertex Pharmaceuticals
Incorporated (Nasdaq: VRTX) announced today the initiation of a Phase II
clinical trial for VX-950, an investigational oral hepatitis C virus (HCV)
protease inhibitor for the treatment of HCV infection.  The 28-day study will
evaluate the safety, tolerability and pharmacodynamics of VX-950 when combined
with pegylated interferon and ribavirin.  Pegylated interferon and ribavirin
are two approved treatments for HCV infection.  Twelve treatment-naive
subjects will be enrolled in the study at two centers in the United States.
This is the first clinical study of VX-950 to be initiated under an open
investigational new drug (IND) application with the United States Food and
Drug Administration, and marks the beginning of a broad Phase II clinical
development program planned for VX-950 that will evaluate the compound in
multiple clinical studies in 2006, including a three-month study in more than
200 treatment-naive patients.
    "This first Phase II study for VX-950 will enable Vertex to evaluate the
safety, tolerability and pharmacodynamics of VX-950 over 28 days when combined
with pegylated interferon and ribavirin," said John Alam, M.D., Senior Vice
President of Drug Evaluation and Approval at Vertex.  "This initial Phase II
trial is anticipated to support the evaluation of VX-950 in a key three-month
Phase II study in more than 200 HCV patients that we expect to initiate in
early 2006."

    Phase II Development Plans
    The objectives of the 28-day Phase II study announced today are to
evaluate the safety, tolerability and pharmacodynamics of VX-950 dosed at
750 mg every eight hours with standard doses of pegylated interferon and
ribavirin.  Vertex expects to obtain 28-day results from this initial Phase II
study in the first quarter of 2006.  Following completion of 28 days of
treatment, patients will receive the standard of care.  In early 2006, Vertex
expects to initiate a three-month Phase II clinical study in more than 200
treatment-naive subjects.  A major objective of this three-month study, in
addition to an evaluation of safety, will be to measure HCV RNA at the end of
treatment and post-treatment as a measure for sustained viral response,
potentially enabling a decision to move to Phase III clinical development of
VX-950.  Vertex also plans to initiate multiple other clinical studies
throughout 2006.
    Vertex recently completed a healthy volunteer study with the new VX-950
tablet formulation.  Results from this study support the use of the VX-950
tablet formulation in Phase II studies.

    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 3.4 million individuals in the United States, 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.

    About VX-950
    VX-950 is an oral inhibitor of hepatitis C virus protease, an enzyme
essential for viral replication.  In a 14-day, Phase Ib study concluded
earlier in 2005, VX-950, administered as a single agent, produced a rapid and
dramatic reduction in HCV RNA in HCV patients.  In the Phase Ib study, 26 of
28 patients receiving any dose of VX-950 achieved more than a 3-log10
reduction in plasma HCV RNA within two days of treatment.  After 14 days,
patients in the best dose group (750 mg every 8 hours) achieved a mean
reduction in HCV RNA of 4.4-log10, a 25,000-fold reduction in viral levels.
Overall in the Phase Ib study, adverse events observed in patients receiving
VX-950 that were considered possibly related to the drug were mild, and
generally similar in frequency to events in the placebo group.  The most
common adverse events reported in both 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) results from an initial Phase II study will be available
in the first quarter of 2006; (ii) a three-month Phase II study in more than
200 patients will be initiated in early 2006, and will potentially enable a
decision to move into phase III evaluation of VX-950; and (iii) VX-950 will be
evaluated in multiple additional clinical studies in 2006. 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-950 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-950 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 the Company's
clinical trials commenced during 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, 2005.

    Vertex Contacts:
     Lynne Brum, VP, Corporate Communications and Financial Planning,
      (617) 444-6614
     Michael Partridge, Director, Corporate Communications, (617) 444-6108
     Lora Pike, Manager, Investor Relations, (617) 444-6755
     Zachry Barber, Specialist, Media Relations, (617) 444-6470

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