Expanded Access Program for MK-0518, an Investigational HIV Integrase Inhibitor, Established for Patients with Limited Available Treatment Options

Worldwide Access Program will be Conducted Along with Phase III Studies

Business Editors/Health/Medical Writers

TORONTO--(BUSINESS WIRE)--Aug. 17, 2006--A worldwide expanded access program for HIV/AIDS patients with limited or no treatment options was announced today by Merck & Co., Inc., Whitehouse Station, N.J., U.S.A., with respect to its investigational HIV integrase inhibitor, MK-0518, now in Phase III development. Program enrollment will begin in the next few months, pending regulatory review and approvals.

"Making MK-0518 available to those who would like access to this investigational drug but who are unable to participate in the clinical studies underscores our commitment to patients," said Dr. Peter S. Kim, president, Merck Research Laboratories (MRL)

MK-0518 belongs to a new class of investigational antiretroviral therapy (ART) agents called integrase inhibitors that inhibit the insertion of the HIV viral DNA into human DNA. Integrase is one of three HIV enzymes - reverse transcriptase, protease and integrase - required by the virus to reproduce. Drugs are available that inhibit the functions of the protease and reverse transcriptase enzymes but, to date, there are no approved drugs that target the integration stage of the HIV-1 lifecycle.

Expanded access

"The MK-0518 program is another example of Merck's dedication to people living with HIV/AIDS around the world," commented Dr. Randi Leavitt, senior director, Infectious Diseases - Clinical Research, MRL and lead coordinator of the expanded access program. "This makes the third expanded access program that Merck has initiated. In mid and late 1990, the Company implemented expanded access programs for two other investigational drugs for treatment of HIV," Dr. Leavitt explained.

Expanded access is a mechanism supported by many regulatory agencies for getting investigational treatment to patients who have a life threatening disease and who cannot be satisfactorily treated with an alternative therapy or available drug. Expanded access programs are not required by regulatory agencies. These programs are facilitated and supported by drug manufacturers in recognition of the promise an unapproved drug may hold for patients facing a life-threatening disease.

MK-0518 expanded access study design

The expanded access program with MK-0518 is a non-comparative, multi-center, open-label, voluntary treatment use study. Investigators will follow patients according to standard of care. The study will continue until approximately three months after MK-0518 has been launched in the local market.

To be eligible to participate, patients must have documented HIV-1 infection, be at least 16 years old, have limited or no treatment options available to them due to resistance or intolerance to multiple anti-retroviral regimens, are not achieving adequate virologic suppression on current regimen and be at risk of clinical or immunologic progression, and be clinically stable

Patients are excluded from the study if they have received MK-0518 in a clinical trial, require any medications prohibited by the protocol, have acute hepatitis due to any cause or clinically significant chronic liver disease, have a condition which the investigator deems will interfere with adherence and safety, or are pregnant. Patients will receive open-label MK-0518 400 mg twice daily, in addition to optimized background therapy (OBT). Investigators will select the OBT based on the patient's prior treatment history and anti-retroviral resistance testing. OBT will not be provided by Merck. Safety and tolerability of MK-0518 will be monitored.

The program will be managed by a clinical research organization (CRO). The CRO will collect all case report information including serious adverse events and drug-related adverse events that result in Grade 3 or above laboratory toxicity, leading to treatment interruption or discontinuation. No efficacy data will be collected.

About Merck's HIV/AIDS research program

Merck's HIV clinical research program began in 1985. Merck scientists were among the first to discover and develop medicines for the treatment of HIV/AIDS. In 1996, Merck introduced a protease inhibitor, which was followed by the introduction in 1999 of a non-nucleoside reverse transcriptase inhibitor (NNRTI).

In addition to MK-0518, Merck is focused on developing new treatments for millions of individuals who are already infected with HIV, as well as on preventing HIV transmission through the development of a vaccine. Merck also licensed a compound to the International Partnership for Microbicides (IPM) for development as a possible means of preventing HIV infection in women.

Merck's HIV/AIDS access commitment

Since Merck's first HIV products reached the market a decade ago, the Company has worked to expand access to these medicines - particularly in the world's poorest countries and those hardest hit by the pandemic. Today, Merck programs and partnerships round the world are helping to prevent and treat HIV/AIDS, expand health care capacity, foster greater disease awareness and acceptance and provide support for people living with HIV/AIDS, their families and communities. Through these and other pioneering efforts, Merck is making a substantial contribution toward meeting one of the most critical needs targeted by the United Nations Millennium Development Goals: halting and beginning to reverse the spread of HIV/AIDS.

About Merck

Merck & Co., Inc., which operates as Merck, Sharp & Dohme (MSD) outside the United States, is a global research-driven pharmaceutical company dedicated to putting patients first. Established in 1891, Merck currently discovers, develops, manufactures and markets vaccines and medicines to address unmet medical needs. The Company devotes extensive efforts to increase access to medicines through far-reaching programs that not only donate Merck medicines but help deliver them to the people who need them. Merck also publishes unbiased health information as a not-for-profit service. For more information, visit www.merck.com.

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, 2005, and in its periodic reports on Form 10-Q and Form 8-K, which the Company incorporates by reference. MK-0518 is an investigational oral HIV integrase inhibitor under development by Merck & Co., Inc.

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