Now Teva Pharmaceutical (NASDAQ:TEVA) knows what it feels like to be on the other side of a patent challenge. The generic-drug maker said last week that Momenta Pharmaceuticals (NASDAQ:MNTA) and Novartis (NYSE:NVS) are challenging the patents on its blockbuster multiple sclerosis drug Copaxone.

Launching a generic version of Copaxone could be a boon to the duo, who have also teamed up to make a generic version of Sanofi-Aventis' (NYSE:SNY) Lovenox, but it'll be a while before they can launch. Teva's lawsuit for patent infringement will trigger a 30-month stay before the Food and Drug Administration will approve the generic makers' marketing application. Of course, if Momenta and Novartis win the lawsuit first, that would also allow the FDA to approve the drug. But at the turtle's pace at which the courts move, I'd guess the 30 months will run out first.

Investors are usually in the dark about the chances of the patents getting overturned, and this case is no different. For competitive reasons, Momenta didn't want to give away its strategy for how it and Novartis plan to bypass Teva's seven patents, which will expire in May 2014. Novartis and Momenta may have company in the courtroom, though; Mylan (NYSE:MYL) recently announced that it had licensed the marketing rights in the U.S., among other places, for the generic version of Copaxone produced by India-based NATCO Pharma.

It's unclear whether Momenta and Novartis were the first to file an abbreviated new drug application (ANDA) for generic Copaxone, or whether Mylan or some other drugmaker could have snuck in ahead of them. They'll have to wait until the FDA updates its database before they'll know whether they're eligible for the 180 days of marketing exclusivity that usually accompanies the first application filed.

Even if Momenta and Novartis weren't the first to file (or don't get Teva's patents overturned), making a generic version of Copaxone should eventually produce big bucks for the drugmakers. Copaxone is a complex drug, which should ward off competition from other generic-drug makers and keep the price of the generics high.

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