Merck & Co. Inc., of Kenilworth, N.J., said 48 weeks of treatment with 1,200 mg of raltegravir, delivered as 2 x 600 mg once daily, was statistically noninferior (88.9 percent, 472/531) to the marketed formulation of the drug, branded Isentress, dosed at 400 mg twice-daily (88.3 percent, 235/266), in both cases as combination therapy with Truvada (emtricitabine/tenofovir disoproxil fumarate, Gilead Sciences Inc.) in previously untreated adults with HIV-1 infection.