As expected, Merck & Co's Isentress, the New Jersey-based drugs giant’s first-in-class AIDS drug, has been approved by US regulators.

The US Food and Drug Administration has granted accelerated approval of Isentress (raltegravir) in combination with other antiretroviral therapy for the treatment of HIV infection in treatment-experienced patients who have developed resistance to other AIDS drugs. The agency’s go-ahead means that Isentress is the first in a new class of antiretroviral agents, called integrase inhibitors, to hit the market.

The FDA's decision was based on a 24-week analysis of clinical trials in which Isentress, in combination with optimised background therapy in treatment-experienced patients, provided significant reductions in HIV RNA viral load and increases in CD4 cell counts. The company also noted the comments of Joseph Eron, from the University of North Carolina Chapel Hill School of Medicine, who said that development of the treatment “is a significant milestone in the history of HIV/AIDS therapy because we now have a drug that's potent against another key enzyme essential for viral replication".

The company also noted that it has “worked closely with the HIV community regarding the price of Isentress” and the wholesale cost will be $27 per day, or around $10,000 a year, which is comparable to the price of several available ritonavir-boosted protease inhibitors. Martin Delaney of the Fair Pricing Coalition, a network of activists and organisations that works with pharmaceutical companies, said that Merck “has acted responsibly in its pricing of the drug”. He added that while “we still believe that lower prices are always possible, Merck has avoided the temptation to set ever higher prices for each new HIV drug".

Analysts believe that Isentress could well achieve blockbuster status in a couple of years’ time and the treatment joins Pfizer’s Selzentry (maraviroc), which was approved in August, onto the market. Selzentry is another first-in-class HIV treatment, which works by blocking entry of the virus through the CCR5 co-receptor into white blood cells.