Pfizer has finally been given the go-ahead by US regulators to market its new HIV treatment maraviroc, which will be called Selzentry on home soil.

The US Food and Drug Administration has approved Selzentry, as a combination treatment in adults who have CCR5-tropic detectable virus and who have become resistant to other available therapies. This is the first new HIV medicine in more than a decade, says Pfizer, and works by blocking entry of the virus through the CCR5 co-receptor into white blood cells.

Selzentry is expected to be available in the USA by the middle of September, which will be a relief for Pfizer which many observers thought would get the go-ahead quite a bit earlier. The FDA’s Antiviral Drugs Advisory Committee gave a unanimous recommendation for approval of the drug in April but the agency only granted an approvable letter in June.

The reasons for the FDA’s hesitance a couple of months have now become clear, however. It has granted accelerated approval to Selzentry, a process which allows for an earlier-than-normal green light for drugs that provide a “meaningful therapeutic advantage” over existing treatment for serious or life-threatening diseases.

48-week data needed for full approval

This approval is based on 24-week data from the MOTIVATE study, which showed that maraviroc substantially cut viral load when compared to “optimised background therapy” alone but longer-term data, after 48 weeks, will be required before the FDA can consider traditional approval. The product has a boxed warning about liver damage and a statement about the possibility of heart attacks, the FDA noted.

The agency’s announcement comes a couple of weeks after EU regulators issued a positive opinion recommending approval of the compound which will be marketed outside the USA as Celsentri. Interestingly, the FDA approval comes just a few days after three senior HIV marketing managers have left Pfizer, which has been conducting an internal investigation into allegations that maraviroc was improperly promoted to doctors before the agency have it the green light. The probe was also looking at claims that unapproved materials and funds were used to promote the older AIDS drug Viracept (nelfinavir).

Late-stage pipeline looking a lot healthier

Pfizer shares climbed higher than they have all year on the news, up 2.2%, though the increase was also helped by a statement from the firm which said that growth in its Phase II portfolio supports the goal of tripling its late-stage portfolio by 2009.

Pfizer has 47 programmes in Phase II, the largest in its history, compared with 32 around the end of last year, while the number of Phase III projects has risen to 11, up from eight. John LaMattina, Pfizer’s outgoing president of global R&D, said that in the last eight months, the firm has advanced 27 programmes, with the loss of just 13, which is “especially gratifying since we are continuing to make major structural and organisational changes”.

He added that Pfizer is “revising the allocation of our capital so that we target the areas of greatest medical and commercial promise” and concluded that “this performance is remarkable in a period of profound change”.