Early yesterday evening, Biogen IDEC (NASDAQ:BIIB) and Elan (NYSE:ELN) announced that Tysabri had been approved by the FDA for the treatment of multiple sclerosis (MS). It's a great drug, but what a terrible name. Tysabri sounds more like the name of some obscure race in Star Trek or perhaps like some budget car produced in southeastern Europe. This drug was formerly called Antegren, so it's going to take time for some of us to get used to the new name.

Tysabri will compete with Biogen IDEC's own Avonex, Betaseron from Chiron (NASDAQ:CHIR), Copaxone from Teva (NASDAQ:TEVA), and Rebif from Serono (NYSE:SRA). Though it is hardly a competition on equal footing. It's more like the Boston Red Sox playing the Bad News Bears. Just imagine Curt Schilling taking the hill against Tatum O'Neal.

Since head to head trials of Tysabri against any of these other products have not been conducted, no scientific claims of superiority can be made. That said, most people, including myself, think that Tysabri is automatically the new market leader. At the one-year mark in the phase 3 study AFFIRM, the rate of relapses was reduced by 66% compared to placebo. That result trounces all of the other products, which tend to reduce relapses by only one-third. This outcome represents a major advance in the treatment of MS.

Tysabri has long been regarded as a drug that will generate a whopping level of sales. That's a fairly reasonable assumption given the large size of this market. Now that the drug has been approved, I am fine-tuning my own numbers to come up with a peak sales estimate in the MS market. I will have that article up on the main page on December 7th. Be sure to check back then.

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Fool contributor Charly Travers does not own shares of any company mentioned in this article. Charly is also an analyst for Motley Fool Rule Breakers. If you'd like to see what David Gardner and his team of analysts have cooking, we invite you to take a risk-free trial with no obligation.