An advisory panel for the U.S. Food and Drug Administration has announced that it's backing a new HIV drug from Merck Co. for rapid government approval. The drug's brand name is Isentress (active substance: raltegravir) and belongs to the antiretroviral integrase inhibitor class. Integrase is an enzyme that HIV uses to integrate its genetic material into human cells, and Isentress interferes with this process by inhibiting the enzyme. Raltegravir's chemical formula is C₂₀H₂₁FN₆O₅.

Like all antiretroviral drugs, Isentress' purpose is to lower the viral load in the bloodstream. Merck has showed that Isentress can indeed reduce viral load in patients whose infection is advancing despite taking combinations of other drugs. These patients are the primary target of the drug.

The U.S. Food and Drug Administration usually follows the recommendations of its advisory panels, although it isn't required to do so. However, the unanimous backing by its panel for Merck's drug means that by all odds the drug will soon be approved. It entered Phase III clinical trials in 2006 and it is available to certain patients with advanced HIV disease through an expanded access program.

Merck showed that after 16 weeks, more than 60% of the ~460 patients receiving Isentress had their HIV virus levels reduced to an undetectable level, compared with 33% to 36% of patients in the placebo group, which was made of 240 other patients.