Wall Street Journal (06.21.07)::Jennifer Corbett Dooren; Avery Johnson

On Wednesday evening, the US Food and Drug Administration issued an “approvable” letter to Pfizer Inc. regarding its HIV drug maraviroc. An approvable letter means FDA believes a product is worth approving, but the agency needs more information. Pfizer’s hopes for an outright approval stemmed from an April endorsement of maraviroc by a panel of FDA reviewers.

Maraviroc aims to block HIV from entering human cells through the CCR5 pathway. Of candidates in this new class of HIV drugs, it is furthest along in development. Pfizer proposed maraviroc be used for patients with advanced HIV who were failing treatment on other HIV drugs, an estimated 40,000 patients in the United States. The drug would not work against HIV strains that use another pathway, CXCR4, to infect cells.

FDA is not asking for further clinical trials of maraviroc, so it could still reach the market in the third quarter of this year. But the agency said it remains concerned about potential liver damage, heart problems, and infection associated with maraviroc.

Pfizer said it will quickly work with FDA to address any questions and finalize product labeling. The company said its plan to make maraviroc available to patients in 30 countries would not be affected by FDA’s decision.