Merck's AIDS drug backed by FDA

Merck & Co.'s Isentress, the company's new first-in-class AIDS drug, has received a recommendation for approval from FDA. The Antiviral Drugs Advisory Committee of FDA voted unanimously to recommend accelerated approval of Isentress (raltegravir) in combination with other antiretroviral therapy (ART) for the treatment of HIV infection in treatment-experienced patients with ongoing viral replication, despite existing therapy. If approved, the drug would be the first in a new class of antiretroviral agents called integrase inhibitors available for the treatment of HIV.

The agency granted Isentress priority review status. Under the priority review designation, FDA is expected to review and act on the New Drug Application for Isentress within 6 months of submission, which the company anticipates will be by mid-October.

The positive recommendation came as no surprise, as 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 optimized background therapy in treatment-experience patients with few or no remaining treatment options".

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. Although there were more cases of cancers among patients in clinical studies receiving the drug, the agency argued that the imbalance appeared to reflect the low rate of cancer witnessed in patients on placebo.

Merck has proposed a plan to manage the drug's risks, including 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, the HIV epidemic continues, so there remains a need for new therapeutic approaches. This positive recommendation signals an important step forward for the treatment of patients living with HIV."

The company noted that it is also moving forward with regulatory filings outside the US and analysts are predicting that Isentress can become a $1 billion product.

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