Lipid Levels were not Increased in Patients Taking MK-0518, an Investigational HIV Integrase Inhibitor, in Combination Therapy after 24 Weeks of Therapy

Lipid Levels were not Increased in Patients Taking MK-0518, an Investigational HIV Integrase Inhibitor, in Combination Therapy after 24 Weeks of Therapy

Business Wire - September 27, 2006

SAN FRANCISCO -- Levels of total cholesterol and triglycerides were not increased in HIV-infected patients taking MK-0518, an investigational integrase inhibitor being developed by Merck & Co., Inc., with tenofovir (Viread(R)) and lamivudine (Epivir(R)). In contrast, increased levels of both lipid parameters were observed in patients taking efavirenz (Sustiva(R)) combined with the same drugs.

The interim 24 week results are from an ongoing 48 week study in 198 treatment-naive HIV-infected patients, and were presented by Merck as a late breaker today at the American Society for Microbiology's 46th Annual International Conference on Antimicrobial Agents and Chemotherapy (ICAAC).

"This study provides important preliminary data on this investigational compound in regard to lipid parameters in patients with HIV disease," said Hedy Teppler, M.D., director of Infectious Diseases and Clinical Research, Merck Research Laboratories, Merck & Co., Inc. "Longer term follow-up of these patients is planned to confirm these findings."

About MK-0518

MK-0518 belongs to a new class of investigational antiretroviral therapy agents called integrase inhibitors that inhibit the insertion of the HIV viral DNA into human DNA. 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 the other two enzymes involved in viral replication - protease and reverse transcriptase - but there are no approved drugs that inhibit integrase.

Study results

These new results are from week 24 of an ongoing, two-part 48 week, multi-center, double-blind, randomized trial of treatment-naive HIV-infected patients receiving MK-0518 at doses of 100 mg, 200 mg, 400 mg or 600 mg orally twice daily versus efavirenz, all in combination with tenofovir and lamivudine. The study showed that patients taking MK-0518 had a mean baseline cholesterol of 161 mg/dL to 168 mg/dL and a mean decrease from baseline of 2 mg/dL to 7 mg/dL across the dosing range (n=160). Patients taking efavirenz 600 mg had a mean baseline cholesterol of 170 mg/dL and a mean increase from baseline of 19 mg/dL (n=38). The difference observed between MK-0518 groups versus efavirenz was statistically significant (p less than 0.05).

As for triglycerides, patients taking MK-0518 had a mean baseline of 110 mg/dL to 155 mg/dL and a mean change from baseline of an increase of 2 mg/dL to a decrease of 43 mg/dL across the dosing range (100 mg, 200 mg, 400 mg, 600 mg). Patients taking efavirenz 600 mg had baseline triglycerides of 129 mg/dL and a mean increase from baseline of 47 mg/dL.

At enrollment, patients had less than seven days of prior exposure to antiretroviral therapy, HIV RNA of at least 5000 copies/mL and CD4 counts of at least 100 cells/uL. The majority of patients were male, non-white, and were between 34 to 37 years old. Patients undergoing immunosuppressive therapy or with diagnosed acute hepatitis, chronic liver disease or renal disease were excluded from the study.

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.

Merck's efforts to develop investigational treatments and a vaccine against HIV/AIDS have been underway for almost 20 years and continue today. Merck began its HIV integrase inhibitor research in the early 1990's, and Merck was the first to demonstrate integrase strand transfer inhibition and to define the mechanism of action. Merck was also the first to demonstrate antiviral efficacy in vitro and in vivo.

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. All other brands are trademarks of their respective owners and are not trademarks of Merck & Co., Inc.

CONTACT: Merck & Co., Inc.

Media: Janet Skidmore, 267-305-7715

Skip Irvine, 267-305-5397 | Cell: 215-806-6757

Investor: Graeme Bell, 908-423-5185

SOURCE: Merck & Co., Inc.
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