Pfizer Drops Development of Antiretroviral Capravirine, Citing Lack of Efficacy in Trials

Pharmaceutical company Pfizer announced on Friday that it is stopping the development of two drugs, including one to treat HIV infection, Reuters reports (Clarke, Reuters, 7/4). The company said it is dropping the development of the antiretroviral capravirine because the drug in two studies did not significantly boost the efficacy of already-approved antiretroviral combinations among HIV-positive people who had failed to respond to those regimens. Pfizer plans to return the rights to capravirine to Shionogi & Co., the Japanese company that developed the compound. Pfizer will continue its late-stage trials of another antiretroviral drug called maraviroc, which is designed to prevent HIV from entering cells (Vogt, AP/San Francisco Chronicle, 7/1). Barbara Ryan, an analyst with Deutsche Bank, said capravirine would have produced peak sales of about $200 million if it had been approved, according to Reuters (Reuters, 7/4).