Amgen Inc said it had asked the U.S. Food and Drug Administration to approve a monthly single-dosing option for its recently approved cholesterol drug, Repatha. The FDA approved Repatha, one of two approved treatments in a new class of injectable "bad" cholesterol-lowering drugs called PCSK9 inhibitors, on Aug. 27. The drug is approved for patients with hereditary forms of high cholesterol - heterozygous familial hypercholesterolemia and a rarer homozygous form of the condition, in addition to those with cardiovascular disease.