As expected, Merck & Co's Isentress, the firm’s new first-in-class AIDS drug, has received a recommendation for approval from a US regulatory advisory panel.

The Antiviral Drugs Advisory Committee of the US Food and Drug Administration has voted unanimously to recommend 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. If approved by the agency, and a decision is expected as early as the middle of October, Isentress would be the first in a new class of antiretroviral agents, called integrase inhibitors, to hit the market.

The committee’s positive recommendation came as no surprise, given that FDA staff had earlier posted documents on the agency’s website saying that Phase II and III data provide evidence that the antiviral activity of Isentress “is superior to optimised background therapy in treatment-experience patients with few or no remaining treatment options”.

The FDA says that Isentress appeared to be well-tolerated in studies with and the benefits of the drug outweighed the potential risks of cancer, liver and muscle problems. The agency said an analysis of rash and liver-related side effects "did not detect a specific safety signal” associated with Isentress and while there were more cases of cancers among patients in clinical studies receiving the drug, the FDA said the imbalance appeared to reflect the low rate of cancer seen in patients on placebo.

Merck has proposed a plan to manage the drug's risks, which would include a programme to monitor for drug resistance and cancers, a pregnancy registry and additional clinical trials. Peter Kim, president of Merck Research Laboratories, noted that despite the availability of various treatment options, ie protease and reverse transcriptase inhibitors, “the HIV epidemic continues, so there remains a need for new therapeutic approaches. This positive recommendation signals an important step forward".

The company noted that it is also moving forward with regulatory filings outside the USA and analysts are predicting that Isentress can become a $1 billion product. If approved, it will join Pfizer’s Selzentry (maraviroc), which was approved a month ago, 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.