In the news ... 2006 archive

Yet Another Setback for CCR5

February 1, 2006

Pfizer has announced that an independent Data Safety Monitoring Board (DSMB) has halted one arm of a study involving their experimental anti-HIV drug, maraviroc. This is the latest setback for a new class of anti-HIV drugs called CCR5 antagonists.

This study was comparing maraviroc, either once a day or twice a day, to Sustiva in people starting treatment for the first time (called treatment naive). One group of people took 300mg of maraviroc once a day along with Combivir. Another group took 300mg of maraviroc two times a day plus Combivir. The third group took 600mg of Sustiva plus Combivir. Combivir was used twice daily in all groups at the standard dosage.

The DSMB’s review of the first 206 people in the study for 16 weeks showed that the once-daily maraviroc group was less likely than the other two groups to achieve undetectable viral loads. The difference between the groups exceeded the pre-set limits, and required that the once-daily arm of the study be stopped. The other two arms of the study are continuing unchanged.

A year ago there were three CCR5 inhibitors entering large clinical trials. These new drugs seemed to hold tremendous promise. All have since run into problems. First, GlaxoSmithKlein’s drug, aplaviroc, was discontinued due to liver toxicities. Next, Shearing Plough halted a study that compared their CCR5 drug, vicriviroc, to Sustiva in people who had never taken anti-HIV drugs. The study was halted because more people taking vicriviroc were seeing increases in their viral loads than people taking Sustiva. Now maraviroc has run into similar problems, at least when it is given once a day.

Research is ongoing on both maraviroc and vicriviroc. While the results of these trials have been disappointing, the drugs may still prove to be useful for people with HIV.