Amgen’s newest cholesterol-lowering drug has only been approved for three days, with plans to launch this coming week. But already, Alnylam Pharmaceuticals in Cambridge is coming out with early-stage trial data suggesting it has a drug that can achieve similar results with far less frequent injections. Cambridge-based Alnylam (Nasdaq: ALNY) presented results of an early-stage trial today at a conference in London for a drug that lowers levels of a protein made in the liver called PCSK9, which…