Health Canada Approves ISENTRESS(TM) (raltegravir)

    Only drug to inhibit Integrase Enzyme

    TORONTO, Nov. 30 /CNW/ - Merck Frosst announced today that Health Canada
granted a Notice of Compliance with Conditions (NOC/c) to ISENTRESS(TM)
(raltegravir) for use in combination with other antiretroviral agents for the
treatment of HIV-1 infection in treatment-experienced adult patients who have
evidence of viral replication and HIV-1 strains resistant to multiple
antiretroviral agents.(1) It has been issued marketing authorization with
conditions, pending the results of studies to verify its clinical benefit.
Patients should be advised of the nature of this authorization.
    A Notice of Compliance with Conditions reflects the promising nature of
the clinical evidence in patients with this serious disease and the need for
further follow up to verify the clinical benefits. The NOC/c is based on an
analysis of clinical trials in which raltegravir, in combination with other
antiretroviral agents, was shown to be effective at reducing viral load and
increasing CD4 cell counts, the two most widely recognized measures of
efficacy against HIV/AIDS infection.(1),(5)
    Now available in Canada, raltegravir is the first medicine to be approved
in a new class of antiretroviral drugs called integrase inhibitors.(1),(2)
Raltegravir works by inhibiting the insertion of HIV DNA into human DNA by the
integrase enzyme.(1) Inhibiting integrase from performing this essential
function limits the ability of the virus to replicate and infect new cells.(3)
There are drugs in use that inhibit two other enzymes critical to the HIV
replication process - protease and reverse transcriptase - but raltegravir is
the only drug approved that inhibits the integrase enzyme.(4),(2) Raltegravir
is administered as a single 400 mg tablet taken twice daily with or without
food with other HIV medications. Raltegravir does not require boosting with
ritonavir, which can be associated with adverse side effects.
    Resistance to current therapies is one of the leading challenges to
treating HIV. "ISENTRESS(TM) will definitively play an important role in the
management of patients who have developed resistance against first line
therapies and furthermore will be welcomed by physicians and patients because
it is effective, well tolerated and has few side effects," said Dr. Mark
Wainberg, Director, McGill AIDS Centre and Professor of Medicine and
Microbiology at McGill University. "ISENTRESS(TM) can make a difference in the
lives of many patients who can no longer be adequately treated by traditional

    Clinical Data support

    Data from two Phase III multi-centre, double-blind, randomized,
placebo-controlled studies (BENCHMRK-1 and BENCHMRK-2) in 699
treatment-experienced adult patients with documented resistance to at least
one drug in each of three classes (NRTIs, NNRTIs and PIs) of antiretroviral
therapies showed that raltegravir 400 mg dosed twice daily in combination with
optimized background therapy (OBT) was significantly (p(less than)0.001) more
effective at both reducing levels of HIV viral RNA and increasing CD4 cell
counts in these patients living with HIV, when compared to a regimen of
placebo plus OBT.(1)
    Pooled analyses from the two Phase III studies showed that after 24 weeks
of therapy, 75.5 percent of patients (216 out of 286) receiving raltegravir in
combination with OBT achieved HIV viral RNA load reduction to below 400
copies/mL compared to 39.3 percent of patients (59 out of 150) receiving
placebo plus OBT.(1) In addition, after 24 weeks of therapy, 62.6 percent of
patients (179 out of 286) receiving raltegravir plus OBT achieved viral load
reduction to below 50 copies/mL compared to 33.3 percent of patients (50 out
of 150) receiving placebo plus OBT. After 24 weeks of therapy, increases in
CD4 cell counts from baseline were 89 and 35 cells/mm(3) for patients
receiving raltegravir plus OBT and for those receiving placebo plus OBT,
respectively.(1) These efficacy results were supported by the 48 week analysis
of a randomized, double-blind, controlled, dose-ranging trial in
antiretroviral treatment-experienced HIV-1 infected patients.(1)
    "Raltegravir is an important new advance in the treatment of HIV/AIDS,
because it is the first therapy in a new class of drugs that attacks the virus
in a completely different way, said Dr. François Bertrand, Executive Director,
Medical at Merck Frosst. "This approval builds on our long standing commitment
to research in HIV/AIDS, with the goal of making truly differentiated
therapies available to patients in need. This is another tangible example of
Merck's overall commitment to discover and market new medications which
address truly unmet medical needs."

    Tolerability profile of raltegravir

    The safety assessment of raltegravir in treatment-experienced patients is
based on the pooled safety data from three randomized clinical studies in
treatment-experienced patients taking 400 mg of raltegravir dosed twice daily
plus OBT or placebo plus OBT. The most commonly reported adverse experiences
((greater than)10% in either group) of all intensities and regardless of
causality were diarrhea in 16.6% and 19.5% , nausea in 9.9% and 14.2%,
headache in 9.7% and 11.7%, pyrexia in 4.9% and 10.3% of patients,

    Access program

    ISENTRESS(TM) was provided to more than 400 Canadians through a special
access program by Health Canada.

    Our Commitment to HIV research

    We are committed to developing innovative therapies that offer advances
in the treatment of infectious diseases - including HIV. The Company's efforts
to develop investigational treatments for HIV/AIDS have been under way for
more than 20 years and continue today. We began our HIV integrase inhibitor
research in 1993 and were the first to demonstrate inhibition of HIV integrase
in vitro and in vivo.
    Raltegravir is one part of our history in HIV research, which includes
the development of CRIXIVAN(R) (indinavir sulfate), a PI; STOCRIN(R)(+)
(efavirenz), an NNRTI; and research currently underway on additional treatment

    About Merck Frosst

    At Merck Frosst, patients come first. Merck Frosst Canada Ltd. is a
research-driven pharmaceutical company discovering, developing and marketing a
broad range of innovative medicines and vaccines to improve human health.
Merck Frosst is one of the top 20 R&D investors in Canada, with an investment
of $114 million in 2006. More information about Merck Frosst is available at

    Forward-looking statement

    This press release contains "forward-looking statements" as that term is
defined in the Private Securities Litigation Reform Act of 1995. These
statements are based on management's current expectations and involve risks
and uncertainties, which may cause results to differ materially from those set
forth in the statements. The forward-looking statements may include statements
regarding product development, product potential or financial performance. No
forward-looking statement can be guaranteed, and actual results may differ
materially from those projected. Merck undertakes no obligation to publicly
update any forward-looking statement, whether as a result of new information,
future events, or otherwise. Forward-looking statements in this press release
should be evaluated together with the many uncertainties that affect Merck's
business, particularly those mentioned in the cautionary statements in Item 1
of Merck's Form 10-K for the year ended Dec. 31, 2006, and in its periodic
reports on Form 10-Q and Form 8-K, which the Company incorporates by

    ISENTRESS(TM) Trademark Merck & Co., Inc. Used under license
    CRIXIVAN(R) Trademark of Merck & Co., Inc. Used under license.
    (+) In Canada STOCRIN(R) is marketed as SUSTIVA by BMS

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    1.  Raltegravir product monograph.
    2.  National Electronic Library of Medicines. Phase III data on
        investigational integrase inhibitor raltegravir (Raltegravir) for
        treatment experienced HIV patients. Available at:
        Accessed on June 21, 2007.
    3.  Grinsztejn B, Nguyen BY, Katlama C, et al. Safety and Efficacy of the
        HIV-1 Integrase Inhibitor Raltegravir (MK-0518) in Treatment-
        Experienced Patients with Multidrug-Resistant Virus: A Phase II
        Randomised Controlled Trial. Lancet. 2007;369:1261-1269.
    4.  Hazuda DJ, Felock P, Witmer M, et al. Inhibitors of strand transfer
        that prevent integration and inhibit HIV-1 replication in cells.
        Science 2000; 287: 646-50. U.S.
    5.  U.S. Department of Health and Human Services, AidsInfo. Is My
        Treatment Regimen Working? Available at

For further information:

For further information: Fiona Robinson, Hill & Knowlton Canada, Tel:
(416) 413-4737,; Martine Drolet, Merck
Frosst Canada Ltd., Tel: (514) 428-3037,

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