Three may be company, but when competitors are threatening to steal patients away from your first two, three's a welcome addition.

Biogen Idec (Nasdaq: BIIB) jumped 7% yesterday after the company said its oral multiple sclerosis drug, BG-12, passed its first phase 3 trial. The company didn't say how well it worked, except to say that the drug demonstrated a "highly statistically significant" reduction in patients who relapsed at two years compared with placebo.

Biogen currently sells Avonex and co-markets Tysabri with Elan (NYSE: ELN). The drugs, especially Avonex, are under threat from multiple angles. While revenue from Avonex in the U.S. was up in the fourth quarter, the increase was entirely due to price boost; volume of sales actually slipped 4%.

There's plenty of competition from other injectable multiple sclerosis drugs, but the real threat comes from Novartis (NYSE: NVS), which recently launched Gilenya, an oral drug. Teva Pharmaceuticals (Nasdaq: TEVA) is also working on an oral medication called laquinimod.

From the other end, sanofi-aventis (NYSE: SNY) has a multiple sclerosis drug Campath, which it inherited in the acquisition of Genzyme. The drug is infused, but if it demonstrates exceptional efficacy, Avonex and Tysabri could lose patients.

Can BG-12 rescue Biogen? Maybe.

The fact that it's taken orally should help, but we'll need to see the full data before we can see how it compares to Gilenya and laquinimod. Even then, it'll be somewhat difficult to declare a winner since the patients in the trial are different.

The true test will come later this year in a head-to-head trial against Teva's Copaxone, the top-selling multiple sclerosis drug in the world. If BG-12 can beat Copaxone, or work as well with fewer side effects, Biogen could have a third multiple sclerosis blockbuster on its hands.

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