Pharmaprojects R&D Pipeline News Feed
First new kind of anti-HIV medicine for over four years gains approval
9 Aug 2007
Pfizer has received approval in the US for Selzentry (maraviroc), a first-in-class drug for use in HIV/AIDS. The product, a CCR5 antagonist, is the first new kind of anti-HIV medication to get the go-ahead since Trimeris/Roche’s Fuzeon (enfurvirtide) was green-lighted in March 2003.
For now, the US FDA has only approved the product for use in treatment-experienced patients who only have HIV which infects T-cells via the CCR5 co-receptor. This is owing to the drugs mechanism of action, in which it binds to this co-receptor, preventing viral entry. Some patients, however, particularly those with more advanced disease, have virus which uses the CXCR4 co-receptor. There have been concerns that use of CCR5 inhibitors might encourage the virus to switch to the CXCR4 tropic form, which is associated with more aggressive disease, and post-marketing studies will be watching closely for any sign of this. In any case, the US accelerated approval will only be followed by a traditional approval once longer-term data has been generated.
Getting the drug approved represents a major triumph for Pfizer, as at one point there were serious doubts as to whether the CCR5 inhibitors were a viable class of drugs at all. Indeed, Selzentry has seen both of its closest rivals flounder in clinical trials. GlaxoSmithKline/Ono’s aplaviroc hydrochloride was discontinued following reports of hepatotoxicity, and Schering-Plough’s vicriviroc maleate was held-up by cancers seen in Phase II. This gave Pfizer a clear run to the market.
If launch goes ahead as planned in September, Selzentry will bring the number of types of anti-HIV medications to five, joining the nucleoside reverse transcriptase inhibitors, the non-nucleoside transcriptase inhibitors, the protease inhibitors and the sole fusion inhibitor Fuzeon. But we might not have to wait so long for the next new type of weapon in the anti-HIV armoury. Merck & Co’s HIV integrase inhibitor, Isentress (raltegravir), is already awaiting approval in the US, with FDA action expected in October.
