Pfizer Inc is developing maraviroc, a CCR5 receptor antagonist for the treatment of HIV-1 infection and rheumatoid arthritis. In April 2007, the FDA advisory committee voted to approve maraviroc for HIV-1 infection. Phase II and III clinical trials, and post-approval studies are ongoing in both treatment-experienced and -naive HIV patients. Phase II trials have also been initiated in patients with rheumatoid arthritis.