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Raltegravir as Effective as Efavirenz at Suppressing HIV Viral Load and Increasing CD4 Cell Counts in Treatment-Naive Patients Up to 144 Weeks When Used in Combination Therapy

MONTREAL, July 20 /CNW Telbec/ - Merck Frosst Canada Ltd's integrase inhibitor, Raltegravir (ISENTRESS(TM)), was as effective as efavirenz at maintaining viral load suppression to undetectable levels (less than 50 copies/mL) and at improving CD4 counts in previously untreated (treatment-naive) patients through 144 weeks in a Phase II study still underway. Both medicines were administered in combination with two other anti-HIV medicines, tenofovir and lamivudine. These results were presented today at the 5th International AIDS Society's (IAS) Conference on HIV Pathogenesis, Treatment & Prevention in Cape Town, South Africa.

"We are encouraged that this data clearly demonstrates the efficacy of raltegravir in a treatment naive population for up to 144 weeks. In addition, raltegravir was associated with a superior tolerability profile as evidenced by more favourable lipid levels and less neuropsychiatric adverse events, said Dr. David Fletcher, MD FRCPC and HIV specialist at the Maple Leaf Medical Clinic in Toronto. It is important for patients at any stage of HIV to have access to different treatment options like raltegravir that are effective and have a demonstrated tolerability profile in order to help them manage their disease." 

Raltegravir studied for 144 weeks in nearly 200 previously untreated

adult patients 

These 144-week findings are from an ongoing multi-center, dose-ranging, double-blind, randomised trial of previously untreated HIV-infected adult patients. In this study, 198 treatment-naive, HIV-infected patients received either raltegravir administered orally twice daily in combination with tenofovir and lamivudine or 600 mg efavirenz dosed orally once daily in combination with the same agents. During the first 48 weeks of the study, patients were randomised to one of four dose regimens (100, 200, 400 and 600 mg twice daily). After 48 weeks, all groups receiving raltegravir received 400 mg dosed twice daily. 

Viral load reductions and increase in CD4 cell counts maintained through

144 weeks 

After 144 weeks of therapy, 78 percent of the 160 patients on the regimen containing raltegravir maintained HIV viral load suppression to below 50 copies/mL. Results were comparable for patients taking the efavirenz-based regimen, with 76 percent of the 38 patients maintaining suppression to below 50 copies/mL (95 percent CI). Eighty percent of patients receiving the regimen containing raltegravir maintained suppression in viral load to less than 400 copies/mL compared to 76 percent of patients taking the regimen containing efavirenz (95 percent CI). Patients on both treatment regimens experienced increases in CD4 cell counts. At 144 weeks of treatment, the mean increase from baseline in CD4 cell count was 252 cells/mm3 for patients receiving the regimen containing raltegravir and 233 cells/mm3 or patients receiving the regimen containing efavirenz. 

Demonstrated tolerability profile and less effect on lipid levels demonstrated 

Both treatment regimens were generally well tolerated, with cumulative rates of drug-related clinical adverse experiences (AEs) less frequent in the regimen containing raltegravir versus the regimen containing efavirenz (54 percent versus 76 percent, respectively). Raltegravir had less effect on total or LDL cholesterol, or triglycerides.

In the study, the most commonly reported AEs in the regimens containing raltegravir and efavirenz, respectively, were diarrhea (6.9 versus 10.5 percent), nausea (12.5 versus 10.5 percent), dizziness (8.8 versus 26.3 percent), headache (8.8 versus 23.7 percent), abnormal dreams (6.3 versus 18.4 percent), insomnia (8.1 versus 10.5 percent) and nightmares (0.0 versus 10.5 percent). Neuropsychiatric AEs overall (of these, abnormal dreams and nightmares in particular) were reported less frequently in the regimen containing raltegravir versus the regimen containing efavirenz, (35 percent versus 61 percent, respectively) through Week 144. 

About raltegravir 

Raltegravir is a first-in-class integrase inhibitor. Raltegravir is the only integrase inhibitor approved in more than 80 countries worldwide for treatment-experienced adult patients. Raltegravir works by inhibiting the insertion of HIV-1 DNA into human DNA by the integrase enzyme and has demonstrated rapid antiviral activity. Inhibiting integrase from performing this essential function limits 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-1 replication process - protease and reverse transcriptase - but raltegravir is the only drug approved that inhibits the integrase enzyme.

Raltegravir is a single 400 mg tablet taken twice daily without regard to food. Raltegravir does not require boosting with ritonavir. 

About Merck Frosst Canada Ltd. 

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 close to $110 million in 2007.

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, 2008, 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. 

ISENTRESS(TM) is a Trademark of Merck & Co., Inc. Used under license      -30-  /For further information: or to arrange an interview: Geneviève Déry, HKDP, Communications & public affairs, (514) 395-0375, ext. 232, Mobile: (514) 219-2764,; Natacha Raphael, Merck Frosst Canada Ltd, (514) 428-3280, Mobile: (514) 910-3280, 

Posted: July 2009