It seemed like such a great marketing strategy for Teva Pharmaceutical (NASDAQ:TEVA) -- a way to potentially double the sales of its top drug just by running a post-marketing clinical trial. But alas, it wasn't meant to be.

Teva announced Monday that a double dose of its multiple sclerosis drug Copaxone didn't work any better than the currently available dose. The company only presented top-line results of the trial -- dubbed Forte -- but Teva isn't likely to get anything useful from the full results.

Post-marketing trials to expand Copaxone's market haven't exactly been Teva's forte, although it did have some success in a trial supporting the use of the drug early in the disease progression.

Still, I'm not sure the bad news warranted the more than 8% hit that Teva's stock took Monday. The results shouldn't change how well Copaxone competes against other multiple sclerosis drugs like Biogen Idec's (NASDAQ:BIIB) Avonex or Rebif from EMD Serono and Pfizer (NYSE:PFE). Granted, an extra $1.8 billion in yearly sales (if all patients suddenly started taking twice as much and Teva didn't discount the price) would have been nice, but even if the double dose was statistically better than the current dose, I doubt Teva could get away with charging twice as much for a supply.

Also, Teva isn't sitting back and blindly waiting for newcomers like Elan's (NYSE:ELN) and Biogen's Tysabri to catch it. In addition to expanding the market for Copaxone, it's also working on new multiple sclerosis drugs like its ATL/TV1102. The antisense drug, which was licensed from Antisense Therapeutics, which licensed it from Isis Pharmaceuticals (NASDAQ:ISIS), recently demonstrated some promising activity in a phase 2 trial.

While disappointing, the Forte results shouldn't be a major issue for Teva. Perhaps the biggest take-home message for investors is that getting a drug on the market doesn't eliminate the clinical trial risks.

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