Merck's ISENTRESS(R) (raltegravir) Tablets in Combination with other Anti-HIV Medicines Maintained Reductions in HIV-1 Viral Load and Increased CD4 Cell Counts Through 48 Weeks of Therapy in Treatment-Experienced Adults.

BOSTON -- ISENTRESS([R]) (raltegravir) tablets, Merck's HIV integrase inhibitor, in combination with other anti-HIV medicines, maintained significant HIV-1 viral load suppression and increased CD4 cell counts through 48 weeks of therapy compared to placebo in combination with anti-HIV medicines, in two Phase III studies of 699 treatment-experienced patients failing antiretroviral therapies (ARTs). Patients in the studies had HIV resistant to at least one drug in each of three classes [nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs) and protease inhibitors (PIs)] of oral antiretroviral medicines.

In October, the U.S. Food and Drug Administration (FDA) granted ISENTRESS accelerated approval for use in combination with other antiretroviral agents for the treatment of HIV-1 infection in treatment-experienced adult patients with evidence of viral replication with HIV-1 strains resistant to multiple antiretroviral agents. The approval was based on analyses of viral load reductions and CD4 cell count increases from baseline through 24 weeks in two phase III studies of ISENTRESS. This week, 48-week data from those same studies were presented at the 15th Conference on Retroviruses and Opportunistic Infections (CROI).

The use of other active agents with ISENTRESS is associated with a greater likelihood of treatment response. The safety and efficacy of ISENTRESS have not been established in treatment-naive adult patients or pediatric patients. There are no study results demonstrating the effect of ISENTRESS on clinical progression of HIV-1 infection.

"The 48-week efficacy results are consistent with what we observed at Week 24," said Roy Steigbigel M.D., professor of medicine, pathology, microbiology and pharmacology, State University of New York at Stony Brook and lead study investigator for one of the studies.

ISENTRESS studied in nearly 700 patients

The data presented this week are from Week 48 results from two identical ongoing multi-center, double-blind, randomized, placebo-controlled Phase III studies (BENCHMRK-1 and BENCHMRK-2) that compare ISENTRESS in combination with optimized background therapy (OBT) to placebo plus OBT. The primary endpoint of this ongoing study is the percentage of patients in each study arm that achieve HIV RNA viral levels less than 400 copies/mL at Week 16. Patients in BENCHMRK-1 were enrolled in Europe, Asia/Pacific and Peru. The mean baseline viral load was 4.6 log10 copies/mL for the regimen with ISENTRESS and 4.5 log10 copies/mL for the placebo regimen, respectively. The median baseline CD4 cell counts were 140 cells/mm3 for the regimen with ISENTRESS and 105 cells/mm3 for the placebo regimen, respectively. Patients in BENCHMRK-2 were enrolled in North and South America. The mean baselin...

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