The treatment was launched in Europe in 1998. In March 2002 FDA approved Rebif, overriding Avonex's orphan drug status, the first time the agency has done so based on efficacy. The head-to-head data from its comparison study with Avonex were compelling enough that FDA decided patients needed the new option. (See "Head to Head,")

"We changed the mindset of consumers," says Paul Lammers, the US unit's chief medical officer. "They used to have the idea that, 'Well, let's try this for a while, and if it doesn't work, let's go up a bit.' Now the concept of treating early and with higher doses has really been established with Re-bif. For patients, this means long-term efficacy now and less disability later."

The franchise also includes Novantrone (mitoxantrone), indicated for reducing neurological disability in patients with worsening MS. Pusey sums up the franchise this way: "Our overarching goal is to make a profound difference in the daily lives of people with MS. In 2004 we made great strides toward this goal with the launch of Rebif product enhancements, including the Rebiject II and 29-gauge needle, and the addition of MS LifeLines Nurse Educators, a program that provides education and in-home training."

MS Market Shakeup So far the buzz for Tysabri (previously know as Antegren) is based on data from clinical trials that compare the drug with placebo. In those studies, Tysabri reduced the rate of relapses (temporary worsening of symptoms) by 66 percent compared with no treatment. Biogen/Elan researchers also tested the drug in combination with Avonex against placebo, and together they reduced relapse rates by 54 percent.

What the research did not do was to test Tysabri in head-to-head studies against other products. MS experts point out that each control group is unique and that the only way to determine a product's superiority is by direct comparison.

When asked about Tysabri, Serono's US executives are quick to note several things: 1) Biogen's Amevive (alefacept) failed to live up to its claims, 2) Biogen and Elan only released partial data for Tysabri, and 3) prevention of relapses is not the only measure of how well a MS drug—and its patients—are doing; a drug must also slow the progression of the disease.

"We welcome any new product for MS patients because there is still unmet medical need out there," Firouz says. "But are we afraid of the competition? No. We entered the market here two years ago as the number-four player, and we now have nearly 20 percent of new-prescription share. We had three competitors to go after, and we're going to deal with natalizumab in the same way—step by step, with the right resources at the right time. I am confident that we will achieve market leadership with Rebif by 2006."

The multiple sclerosis market has been a hard-fought battle among four competitors: Serono's Rebif, Biogen's Avonex, and Schering AG's Betaseron (all a form of recombinant interferon beta 1a) and Teva's Copaxone (glatiramer). After Rebif was approved in Europe, it quickly gained market leadership there. Serono muscled its way into the US market in 2002 by overcoming the orphan drug status of Avonex, and it soon partnered with Pfizer to sell Rebif in the United States. In its first year here, sales grew 165 percent, quickly earning it a 17 percent share in the MS arena.

Putting Rebif up against Avonex—two biologics based on the same protein—was another bold move for Serono. Says Lammers: "The company felt really confident about what we had seen so far in terms of profiles. Therefore we were willing to take this calculated risk, and it paid off." In another confident move, Serono has head-to-head studies under way comparing Rebif with Copaxone.