A next-generation HIV drug from Gilead Sciences Inc. , which could be more effective and have fewer side effects with a lower dosage, will go to federal regulators for a decision on whether it should be approved. The drug - a combination of Gilead's emtricitabine and tenofovir alafenamide, or TAF - is the second so-called F/TAF drug submitted by the Foster City-based company to the Food and Drug Administration.