The approval of Pfizer's maraviroc was dealt a blow Wednesday as the drug's maker received an approvable letter from the FDA requesting additional information on the investigational HIV compound.
The FDA had been expected to approve maraviroc this week.
Pfizer said in a statement, “We plan to continue discussions with the FDA to address any outstanding questions and finalize the product labeling as soon as possible.”
Pfizer did not elaborate on the approvable letter’s questions or issue a timetable for FDA action.
Maraviroc was granted priority review status in February. Priority review status, which trims time off the standard approval time period, is usually granted to compounds deemed an advance over existing therapies by the FDA.
In April, an FDA panel of outside experts recommended the agency approve maraviroc, citing a need for new HIV treatments. However, some panelists shared concerns about liver damage, heart problems and infection associated with the drug. GlaxoSmithKline stopped work on a similar CCR5 drug after it was found to cause liver problems.
Analysts have projected sales of maraviroc, if approved, to reach $500 million by 2011.