FDA Advisers Urge Approval of First CCR5 Blocker for AIDS

SILVER SPRING, Md., April 27 -- An FDA advisory panel has unanimously recommended accelerated approval of a novel oral antiretroviral drug as an add-on treatment for adults infected with CCR5-tropic HIV-1.

Maraviroc, which is being developed by Pfizer and would be marketed as Celsentri, is the first in a new class of antiretroviral drugs called CCR5-receptor antagonists.

The FDA is expected to make a final decision on the drug within weeks. Although the FDA generally follows the recommendations of its advisory panels, it is not obligated to do so.

In clinical trials about 45% of patients randomized to maraviroc on top of standard antiretroviral therapy had undetectable HIV viral loads after 24 weeks, versus 23% of placebo patients.

The drug was given twice daily in 150- or 300-mg tablets. Unlike available AIDS drugs that attack HIV-infected cells, maraviroc blocks the virus from entering healthy immune cells.

An FDA briefing document noted that a "concern during clinical development has been the possibility of an increase in infection or malignancy with its use." Development of a second drug in the same class, aplaviroc, was halted when it was linked to hepatotoxicity in trials and a possible association with lymphoma has been reported for a third investigational agent-vicriviroc , which targets a different CCR5 co-receptor antagonist.

But the FDA's maraviroc review-team members reported that they saw no evidence of an increase in lymphoma or other cancers in the Pfizer data. They did, however, note a possible increase in cardiovascular events, but said it was not clear whether this was a true cardiovascular signal.

Likewise, there was no evidence of hepatoxicity, but there was a small increase in herpes and some other infections.

Although the FDA's Antiretroviral Products' Advisory Committee unanimously recommended approval, the committee said that since there are no long-term safety or efficacy data, the FDA should require close post-marketing surveillance.