Researchers to Evaluate a Once-Daily Investigational Dose of Raltegravir, Merck’s Integrase Inhibitor, in an Investigational Population, Patients Previously Untreated for HIV-1

QDMRK Once-Daily Raltegravir Study to be Conducted in 21 Countries Worldwide

WHITEHOUSE STATION, N.J. - Merck & Co., Inc. today announced that researchers will conduct a clinical trial to evaluate the use of raltegravir tablets at a once-daily investigational dose in an investigational population, previously untreated (treatment-naïve) HIV patients. The once-a-day dose will be compared to a twice-daily regimen, and both will be studied in combination with Truvada® (emtricitabine and tenofovir disoproxil fumarate), in treatment-naïve HIV patients. The trial, called QDMRK, is a double-blind, randomized, active comparator-controlled clinical trial that aims to enroll 750 patients at 94 centers in 21 countries.

The study will measure the proportion of patients achieving HIV RNA less than 50 copies/mL at weeks 48 and 96 to determine the antiretroviral activity of raltegravir once daily (raltegravir given 800 mg QD) compared to twice daily (raltegravir 400 mg BID). The study will also evaluate the proportion of patients achieving HIV RNA less than 400 copies/mL and the change from baseline in CD4 cell counts.

Patients interested in taking part in the QDMRK clinical trial are encouraged to speak with their physician. For more information, please visit www.benchmrk.com and click on QDMRK.

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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, 2007, and in any risk factors or cautionary statements contained in the Company’s periodic reports on Form 10-Q or current reports on Form 8-K, which the Company incorporates by reference.
Truvada® is a registered trademark of it’s respective owner and is not a trademark of Merck & Co., Inc.