Bear Stearns maintains buy on Serono (SRA

).

Analyst Tim Wilson says the approval is based on results of studies in patients with relapsing remitting multiple sclerosis (RRMS) PRISMS and EVIDENCE, with the latter being a head-to-head study against Biogen's Avonex. Rebif's approval breaks Avonex's U.S. Orphan Drug Status. Wilson says this is very good news for Serono. The company will will be aided by the strongest marketing argument any drug can have -- the FDA thinks Rebif is more efficacious than Avonex. To build his new model, Wilson says he must first hear what the company says about its rollout plan; he expects this will be detailed on a conference call on Mar. 11.