Sanofi and Isis Pharmaceuticals have suffered a setback after advisors to the European Medicines Agency recommended against approving Kynamro for the treatment of a rare genetic form of high cholesterol.

The agency's Committee for Medicinal Products for Human Use (CHMP) has adopted a negative opinion for Kynamro (mipomersen) for the treatment of patients with homozygous familial hypercholesterolaemia (HoFH). The CHMP said the drug was effective at reducing LDL cholesterol levels in the aforementioned patients but it was concerned about the medicine’s safety.

Specifically, the Committee noted that a high proportion of patients stopped taking Kynamro within two years, mainly due to side effects such as flu-like symptoms, injections site reactions and liver toxicity. This was considered important "because Kynamro is intended for long-term treatment in order to maintain the cholesterol-lowering effect".

The CHMP was also concerned by tests showing a build-up of fat in the liver and increased enzyme levels, "and was not convinced that the company had proposed sufficient measures to prevent the risk of irreversible liver damage". Moreover, a greater proportion of patients taking Kynamro experienced serious cardiovascular events than those on placebo.

The negative opinion surprised some observers given that two months ago, the US Food and Drug Administration's Endocrinologic and Metabolic Drugs Advisory Committee voted 9 to 6 in favour of Kynamro. Sanofi's Genzyme unit said it plans to request a re-examination of the CHMP opinion and the division's chief executive David Meeker said "we are disappointed [as] patients with HoFH carry extreme, ongoing cardiovascular risk with significantly elevated LDL-C levels despite use of currently available therapies".

He added that "this is a rare disease patient population, with a life-threatening condition, in need of new therapies".