PRESS RELEASE: FDA Advisory Committee Unanimously Recommends Accelerated Approval of ISENTRESS

FDA Advisory Committee Unanimously Recommends Accelerated Approval of ISENTRESSâ„¢ (raltegravir), Merck's Investigational Oral Integrase Inhibitor, for Treatment of HIV

WHITEHOUSE STATION, N.J., Sept.  5, 2007 - Merck & Co., Inc. announced today that the Antiviral Drugs Advisory Committee of the U.S. Food and Drug Administration (FDA) voted unanimously to recommend accelerated FDA approval of ISENTRESS™ (raltegravir) in combination with other antiretroviral therapy (ART) for the treatment of HIV infection in treatment-experienced patients with ongoing viral replication despite existing therapy.

If approved, ISENTRESS would be the first in a new class of antiretroviral agents called integrase inhibitors available for the treatment of HIV. The FDA is not bound by the committee's recommendation but takes its advice into consideration when reviewing investigational medicines.

The FDA granted ISENTRESS priority review status, a designation for investigational products that address unmet medical needs. Under the priority review designation, the FDA is expected to review and act on the New Drug Application for ISENTRESS within six months of submission. Merck anticipates FDA action by mid-October.

"ISENTRESS is an important example of our ongoing commitment to HIV research," said Peter S. Kim, Ph.D., president, Merck Research Laboratories. "Despite the availability of various treatment options, the HIV epidemic continues, so there remains a need for new therapeutic approaches. This positive recommendation signals an important step forward for the treatment of patients living with HIV."

In addition to the FDA regulatory application, Merck is also moving forward with regulatory filings in countries outside of the United States.

The advisory committee's recommendation was based on review of efficacy and safety results from studies with ISENTRESS used in combination with optimized background therapy in treatment-experienced HIV-infected patients who had failed antiretroviral therapies, and who had HIV resistant to at least one drug in each of three classes of oral ARTs.

About ISENTRESS
ISENTRESS works to inhibit the insertion of HIV DNA into human DNA by the viral integrase enzyme. Inhibiting integrase from performing this essential function blocks the ability of the virus to replicate and infect new cells. There are drugs in use that inhibit two other enzymes critical to the HIV replication process - protease and reverse transcriptase - but currently no approved drugs that inhibit integrase.

Prevalence of HIV/AIDS
In 2003, over one million Americans were living with HIV and it is estimated that approximately 40,000 new cases of HIV/AIDS are diagnosed each year in the U.S.i Worldwide, an estimated 40 million people are infected with HIV/AIDS, and more than four million new infections occurred in 2006.ii AIDS is one of the top causes of infectious disease-related mortality worldwide, responsible for nearly three million deaths last year alone.iii

Merck HIV research
Merck's efforts to develop investigational treatments and a vaccine against HIV/AIDS have been under way for more than 20 years and continues today. Merck began its HIV integrase inhibitor research in 1993, and Merck was the first to demonstrate inhibition of HIV integrase in vitro and in vivo.

About Merck
Merck & Co., Inc. 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 [1].

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 risk factors and cautionary statements in Item 1A 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 reference.