11.   Serono executives have argued that stronger doses of beta interferon work better for patients with more advanced multiple sclerosis.

12.   So proving that beta interferon achieves both outcomes will give Biogen a significant marketing advantage, analysts say.

13.   The current M.S. treatments, known as beta interferons, are made by Biogen Inc. and Chiron Corp.

14.   The first drug to do this was Betaseron, a genetically engineered form of the immune system hormone beta interferon.

15.   The patent related to a specific cell line and production method for a compound known as recombinant beta interferon.

16.   The Rentschler beta interferon is essentially identical to that of Biogen.