Pfizer announced today that it has restricted use of its investigational drug capravirine for some patients in
clinical trials based on results of a 12-month animal
toxicology study, which demonstrated an unexpected finding of vasculitis. This decision was reached in discussions with the
FDA late Wednesday.
Vasculitis, an
inflammation of the blood vessels, was observed in animals that received very high doses of capravirine in the 12-month toxicology study; this finding was not seen in previously conducted animal
safety studies. Pfizer is working closely with the FDA to conduct additional animal toxicology studies to further evaluate the safety profile of capravirine. To date, no cases of vasculitis have been detected in
patients receiving capravirine in the Pfizer trials.
Capravirine, a non-nucleoside reverse transcriptase inhibitor (NNRTI) is presently the subject of phase II and III clinical trials to determine the drug’s safety and efficacy in people living with HIV. 650 patients are
currently enrolled in six separate studies. The FDA is permitting treatment-experienced patients, who previously have failed NNRTIs but are responding well to capravirine, to continue their current capravirine drug
regimens. The remaining patients will discontinue use of capravirine but will remain on study protocols.
"Patient safety is always paramount in our clinical studies," said Dr. Barry Quart, Senior Vice President, Pfizer Global Research & Development and Site Director, La Jolla
laboratories. "We remain committed to
the capravirine program and expect to resume clinical trials once these safety issues have been resolved."
Capravirine is being developed by the La Jolla Laboratories of Pfizer Global Research and Development and will be marketed by Agouron Pharmaceuticals, a Pfizer company (NYSE:PFE).
Agouron is committed to the discovery, development, and marketing of innovative therapeutic products engineered to inactivate
proteins that play key roles in cancer,
AIDS, and other serious
diseases. Agouron
employs more than 1400 people of whom approximately 850 are engaged in research and development.