Genentech and Biogen Idec will continue to analyze the study results and will submit the data for presentation at an upcoming medical meeting.

"We are disappointed in the outcome of the primary endpoint, but not surprised given the significant clinical challenges presented by PPMS," said Hal Barron, M.D., Genentech senior vice president, development and chief medical officer. "There was some evidence of biologic activity, and we will continue to review all the data to better understand the role of B cells in MS."

"While the primary results are not what we had hoped, we continue to believe in the potential of B cell therapy for patients living with MS," said Michael Panzara, M.D., MPH, Vice President and Chief Medical Officer, Neurology Strategic Business Unit, Biogen Idec. "PPMS is widely considered a difficult form of MS to treat and historically no therapy has proven efficacy in this disease state."

About the Study

This Phase II/III randomized, double-blind, placebo-controlled, multi-center study was designed to evaluate the efficacy, safety and tolerability of four courses of Rituxan in patients with PPMS. A total of 439 patients from approximately 60 sites in the U.S. and Canada were randomized 2:1 to receive either four treatment courses of Rituxan six months apart or placebo. MRI evaluations were conducted at baseline, weeks 6, 48, 96 and 122.

Detailed safety data from the study is currently being evaluated. The incidence of overall adverse events was comparable between Rituxan and placebo treatment groups. Serious adverse events were 16.4 percent in the Rituxan arm versus 13.6 percent in the placebo arm, with an incidence of serious infections of 4.5 percent compared with <1.0 percent respectively. Infectious events reported in at least 10 percent of patients in either group included upper respiratory and urinary tract infections. Most infectious events in the Rituxan arm were reported as mild to moderate in severity, though events of greater severity were reported more frequently in patients receiving Rituxan. There were more infusion-related reactions with Rituxan, the majority of which were mild to moderate in severity. The companies continue to monitor the long-term safety of Rituxan treatment.

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