Pfizer’s week has started brightly with the news that European regulators have given the green light to the firm’s new HIV treatment Celsentri.

The European Commission has approved Celsentri (maraviroc) as a combination treatment in adults who have CCR5-tropic detectable virus and who have become resistant to other available therapies. The drug, which was approved by the Food and Drug Administration last month in the USA (where it is being marketed as Selzentry) 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.

Celsentri was developed by scientists at Pfizer's research centre in Sandwich, UK, and this latest approval is based on 48-week data from two MOTIVATE studies which showed that maraviroc substantially cut viral load when compared to “optimised background therapy” alone.

Gerd Faetkenheuer, of the department of internal medicine at the University of Cologne in Germany, said that “although other treatments are currently available, maraviroc targets the fight against the HIV virus in a new way.” Filippo von Schloesser, president of the Italian HIV patient organization Fondazione Nadir Onlus, stated that the disease “is a significant health concern in Europe and infection rates are still increasing. Without new medicines, resistance to current treatments is one of the biggest challenges facing HIV care today.” He added that the approval of maraviroc “will offer a new option”.

Analysts believe that Celsentri could generate annual sales of $500 million by 2011.