Isis says cholesterol drug works, but safety weighs

Isis Pharmaceuticals Inc said on Wednesday its cholesterol-lowering drug mipomersen was effective in a late-stage clinical trial, but safety concerns pushed the company's shares down as much as 20 per cent. Mipomersen, which Isis is developing with partner Genzyme Corp, is designed to lower "bad" LDL cholesterol in patients with severe, inherited high cholesterol, known as familial hypercholesterolemia. The trial tested 124 patients with pre-existing coronary artery disease who were taking the maximum tolerated dose of a statin such as Lipitor. Those taking mipomersen experienced an average reduction in LDL cholesterol of 28 per cent after 26 weeks of treatment. That compared with an average reduction of 5 per cent for patients treated with a placebo. The results mirror those of a previous trial - and though the drug proved effective, some patients developed elevated liver enzymes, a possible sign of liver damage. Isis said there was nothing in other laboratory tests to indicate that the patients had any liver dysfunction, but analysts are concerned that the marker itself, even without liver damage, would lead to restricted sales.