Alnylam Pharmaceuticals Inc., of Cambridge, Mass., started the phase III ENVISION trial testing givosiran, an RNAi therapeutic targeting aminolevulinic acid synthase 1, in approximately 75 patients with acute hepatic porphyrias, with a primary endpoint of annualized rate of porphyria attacks requiring hospitalization, urgent health care visit or hemin administration at home over the six-month treatment period.