Watch out, Novartis (NYSE: NVS). In addition to Merck KGaA's slightly delayed cladribine, it looks like your oral multiple sclerosis drug Gilenya might have more competition headed its way.

Teva Pharmaceutical (Nasdaq: TEVA) announced today that its oral multiple sclerosis drug, laquinimod, passed its phase 3 trial. The drug reduced the relapse rate compared to placebo and also helped slow the disability progression.

Is it better than Gilenya, Teva's Copaxone, or any of the other injected or infused multiple sclerosis drugs currently available from Biogen Idec (Nasdaq: BIIB), Elan (NYSE: ELN) and others? It's impossible to tell.

Teva didn't release any numbers -- expect them at a scientific meeting early next year. Even then, the drug was compared to placebo, so it might be hard to tell how well it works compared to the drugs currently on the market. Different clinical trials enroll different types of patients, so comparing among them is difficult.

No matter how the data look, Novartis has some time to prepare for the potential competition. Teva is running a second phase 3 trial that isn't scheduled to read out until the third quarter of next year. The earliest laquinimod could be on the market is 2012.

Whether that's enough time for Novartis to entrench Gilenya as the leader in oral multiple sclerosis competition will depend on the data. If laquinimod doesn't offer a substantially better efficacy and safety profile compared to Gilenya, doctors may not be interested in trying out another new multiple sclerosis drug. Doctors tend to stick with what they have experience with unless the clinical data are enough to overcome that inertia.

If Teva can show that laquinimod is substantially better, which might require a direct head-to-head trial to prove, the drugmaker could easily have a multibillion-dollar drug on its hands.

Stay tuned, Fools. This battle is just getting started.

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Elan is a Motley Fool Rule Breakers pick. Novartis is a Motley Fool Global Gains selection. The Fool owns shares of Teva Pharmaceutical. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.

Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool has a disclosure policy.