Isis Falls on Drug Concerns - Analyst Blog

Shares of Isis Pharmaceuticals Inc. (ISIS) slipped more than 2% despite the company reporting positive results on its lead pipeline candidate, mipomersen. Isis and partner, Genzyme Corp. (GENZ) recently announced positive results from a phase III study. 

Data showed that patients suffering from heterozygous familial hypercholesterolemia (heFH) experienced a 28% reduction in low density lipoprotein (LDL) or “bad" cholesterol after 26 weeks of treatment with mipomersen. In contrast, patients receiving placebo experienced a 5% increase in cholesterol levels. 

Although these results were encouraging and statistically significant, concerns regarding the candidate’s safety profile surfaced with the company reporting elevations in liver transaminases, which is a sign of possible liver damage. 

While the company stated that the elevations were similar to that observed in earlier studies, we remain concerned that concerns regarding the safety profile of the drug could limit its commercial potential once it is launched. 

Genzyme intends to file for approval in the U.S. and E.U. in the first half of 2011 for the treatment of patients with homozygous FH (hoFH), which represents a much smaller patient population. hoFH is a very rare condition that is estimated to affect about 1 in a million people. The heFH indication represents larger commercial potential as it affects about 1 in every 500 persons. 

The companies stated that the filing could also include patients with severe hypercholesterolemia. Results from an ongoing phase III study in patients with severe hypercholesterolemia are expected in mid-2010. 

Data from another phase III study involving hypercholesterolemic patients at high risk for coronary heart disease are expected in the same time-frame. 

While we remain positive on the company’s antisense technology, we are concerned about Isis’ dependence on mipomersen for future growth. A delay in the development and commercialization of the candidate would be a major setback for the company.

We currently have a Neutral recommendation on Isis.
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