Genzime reports MS drug effective, but with small chance of deadly side effect

BOSTON Genzyme Corp. said yesterday that results from its experimental multiple sclerosis drug alemtuzumab proved it to be very effective, but patients must be monitored to avoid a potentially deadly side effect.

Three-year data from a mid-stage trial, which tested the drug on 334 patients with multiple sclerosis, showed the drug significantly reduced the risk of relapse compared to Merck’s MS drug called Rebif. Patients had at least a 70 percent reduced risk of progression of disability after three years, compared to those taking Rebif, Cambridge-based Genzyme said.

The data, presented at the Congress of the European Committee for Treatment and Research in Multiple Sclerosis, showed patients who had not been treated and took Genzyme’s drug alemtuzumab had a 73 percent reduction in the risk of relapse.

“These results demonstrate the durability of the previously reported effect of alemtuzumab for the treatment of multiple sclerosis that, by our analysis, exceeds any marketed products and anything that we can see in development,” said Richard Moscicki, chief medical officer for Genzyme.

Still, there is concern among investors over its safety.

Six patients in the trial were diagnosed with idiopathic thrombocytopenic purpura, characterized by a decline in platelet counts that can lead to potentially catastrophic internal bleeding. One patient died, four were successfully treated, and one recovered without treatment.

To protect against this possible side effect, Genzyme’s monitoring program requires patients to have their blood drawn once a month.