he HIV drugs made by Gilead Sciences ( GILD ) have long been the rock upon which the drug maker has built its other franchises. And for the last five years, it has dominated the market, despite recovery from long-time rival GlaxoSmithKline ( GSK ). But Leerink analyst Geoffrey Porges notes that Gilead may find itself "stuck between a rock and a hard place" as it labors to develop new HIV drugs amid a changing treatment landscape and contends with new and cheaper drugs from the likes of Glaxo and Merck ( MRK ).