Updated with analyst reaction.

WESTON, Mass. ( TheStreet) -- Efficacy of Biogen Idec's ( BIIB) experimental multiple sclerosis pill BG-12 was confirmed and demonstrated superiority over Teva's ( TEVA) currently marketed Copaxone, according to a second, successful late-stage study released Wednesday.

Biogen Idec plans to seek regulatory approval for BG-12 based on the positive data from the two, phase III studies, the first of which was announced in April. If approved, BG-12 will be Biogen's first oral MS drug therapy and another potential blockbuster, grabbing market share from both existing injectable drugs as well as competing oral therapies, analysts predict.

Biogen shares were up $10.83, or 10%, to $117.70 in early Wednesday trading.

"Overall, on a scale of 1-10, with '10' being absolute best case, we would put these data at, perhaps 8 or 9," said ISI Group biotech analyst Mark Schoenebaum, in an email to clients Wednesday morning.

"Our take is that BG-12 clearly showed a numerical difference against Copaxone (both were compared against placebo)... We see this as a major positive for the stock," said Deutsche Bank biotech analyst Robyn Karnauskas in an email to clients. BG-12's peak sales could reach $3-4 billion, making Biogen shares worth $129-$136, she said.

In the phase III study known as "Confirm" released Wednesday, treatment with BG-12 twice daily reduced the annualized relapse rate by 44% compared to placebo after two years. A three-times daily dose of BG-12 reduced the annualized relapse rate by 51% compared to placebo after two years. Both results were statistically significant, achieving the primary endpoint of the study.

The "Confirm" study also enrolled MS patients treated with Teva's injectable Copaxone as a comparator. The reduction in the annualized relapse rate for these patients was 29% compared to placebo after two years.

BG-12 reduced disability progression by 21% at the twice-daily dose and 24% at the three-times daily dose compared to placebo, while Teva's Copaxone reduced disability progression by 7% versus placebo. These results were not statistically significant, however, owing to an unexpectedly low rate of disease progression among patients treated with a placebo, Biogen said.

Biogen currently sells two injectable drugs for multiple sclerosis -- Avonex and Tysabri, the latter of which is co-marketed by Elan ( ELN).

--Written by Adam Feuerstein in Boston.

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