Updated from 2:25 p.m. EST
The sudden suspension of multiple sclerosis drug Tysabri brought shock to doctors and patients -- but it brought relief to investors in companies whose products faced a challenge from the high-profile drug marketed byand
Analysts on both sides of the Atlantic recalculated their estimates for the biggest players in the MS market after Biogen and Elan pulled Tysabri, which had just entered the U.S. market in November.
After falling 43% Monday, Biogen shares closed up $2.61, or 6.8%, to $41.26 Tuesday. Elan, which tanked 70% Monday, lost 3 cents, or 0.4%, to $7.97 Tuesday.
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The drugof one confirmed death and one suspected case of a rare, often fatal disorder among patients in clinical trials who took both Tysabri and Biogen Idec's popular Avonex, the world's bestselling MS drug, which produced $1.4 billion in sales last year. Both patients received combination therapy for more than two years.
Although Elan predicted a quick return to the market for Tysabri -- perhaps in the third quarter -- analysts said the circumstances for the drug's suspension provided opportunities for many existing drugs, including Biogen Idec's Avonex.
Most major players in the MS drug market have some form of licensing, royalty and/or marketing agreements with partners. For example,, the Swiss developer of Rebif, has an alliance with. The German companysells its drug Betaseron through its U.S. subsidiary Berlex and it also has a marketing agreement with
Finally, Israel's, which sells Copaxone in the U.S., has an arrangement with France's. All of the foreign companies trade on U.S. markets via American Depositary Receipts, or ADRs.
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Many analysts believe Teva will be the most immediate beneficiary of Tysabri's misfortune. Copaxone, which acts differently than the older MS drugs, has forged into second place in the U.S. market with a 32.9% market share, less than one percentage point behind Avonex, according to IMS Health. These data represent an eight-week average through the week ended Feb. 18.
Élan, the largest Irish pharmaceutical company, and its US partner Biogen have withdrawn the multiple sclerosis drug ''Tysabri'' from clinical trials after the death of a patient. The drug was seen by many as a possible blockbuster drug with the potential to alleviate much of the suffering of the millions of multiple sclerosis suffers worldwide. However it is now quite unlikely that it will ever make it to market.

The news has seen the shares of both companies fall steeply, with Élan having lost almost 70% of its value after Monday's announcement. Two years ago Élan was the largest Irish PLC, with a value in excess of $20bn, but an accountancy scandal saw its shares fall from over €73 to €1.50 within a few weeks. Since then the stock had risen back to trade between €16 and €18 a share on the back of good restructuring news. However the withdrawal of ''Tysabri'' leaves Elan with almost no potential future revenue streams.

Biogen shares which had hit a 52 week high of $70 just two weeks before the announcement have since fallen to just $41.26. Combined equity losses on Monday for the two firms was over $17.8 billion.

The paitent who died had been taken in combination with another drug - ''Avonex'' - for the last two years. If it emerges that the death was as a result of taking ''Avonex'', then it is possible ''Tysabri'' could be re-introduced to the market. However for the moment rivals will be seeking to steal a lead in the potentially lucrative MS drug market.