The superiority of raltegravir, the first integrase inhibitor to reach phase 3 clinical trials, was seen in virtually every primary, secondary and subgroup category, said Roy Steigbigel, MD, professor of medicine, State University of New York Stony Brook Health Sciences Center, Stony Brook, New York, New York, United States.

Dr. Steigbigel presented the results of the second Blocking integrase in treatment Experienced patients with a Novel Compound against HIV: MeRcK: MK-0518 (BENCHMRK-II) in a presentation on February 28^th.

"We had patients whose virus showed genotypic resistance to all available drugs. They essentially had no drugs that were active against HIV," Dr. Steigbigel said. "Yet when these patients were given raltegravir, 61% of them were able to reduce viral levels in the blood to undetectable levels. That compared to 5% of patients with the same background of drug who did not receive raltegravir."

Raltegravir is an investigative integrase inhibitor being developed by Merck. In earlier studies the drug was known as MK-0518.

In the 2 BENCHMRK studies, raltegravir was clearly superior to the best optimised treatment without raltegravir, said researcher David Cooper, MD, director, National Centre in HIV Epidemiology and Clinical Research, Sydney, Australia.

Overall, Dr. Cooper said, 77% of the 232 patients in the first BENCHMRK study achieved an undetectable viral load after 16 weeks of treatment compared with 41% of 118 patients who did not receive the experimental drug (P < .001).

In BENCHMRK-II, Dr. Steigbigel said the results mirrored Dr. Cooper's. Among 230 patients on raltegravir, 77% achieved undetectable viral loads compared with 43% of 119 patients on the best available care without raltegravir.

Dr. Steigbigel said that when raltegravir was combined with 2 newly approved agents -- the injectable fusion inhibitor enfuvirtide (Fuzeon, also known as T-20) and darunavir (Prezista), "about 98% of patients were able to reach undetectable virus levels."

Integrase is one of three enzymes that are required for viral replication. Drugs to inhibit the other two enzymes -- protease and reverse transcriptase -- have already been developed and are basic backbones of multidrug combinations.


[Presentation title: Results of BENCHMRK-1 (-2), a Phase III Study Evaluating the Efficacy and Safety of Raltegravir (MK-0518), a Novel HIV-1 Integrase Inhibitor, in Patients With Triple-Class Resistant Virus. Abstract 105a&b]

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