Details were thin on the ground yesterday from Genzyme and Isis Pharmaceuticals regarding another significant delay to mipomersen, a novel antisense product that is being developed to treat patients with inherited, hard-to-treat and very high cholesterol. Regulatory filings, which were due in mid-2010, have been pushed back by 12 months, the companies casually announced yesterday, without really explaining why.

Unfortunately, this is not the first set back for the project, and fears about the drug’s potential beyond ultra-niche patient populations have been mounting for some time; a foggy route to market is not helping. Despite being the subject of an eye-watering licensing deal, struck between Isis and Genzyme at the dawn of 2008 worth up to $1.9bn, confidence in mipomersen could continue to sag considerably in the coming months, ahead of pivotal trial data and further clarity.