Biogen Idec and Elan confirmed the death of the second patient suffering from a progressive multifocal leukoencephalopathy, caused by treatment with their drug Tysabri in combination with Avonex.

Analysts are confirmed that the second death will put more pressure on the companies’ market values.
Elan and Biogen Idec Shares lost more than half their value this week. Shares of Irish pharmaceuticals maker Elan Corp. dropped 17 % on Friday.

In London markets, shares of Elan were down 17 % at 4.70 euros, below the stock’s 52-week low reached on Tuesday at 5.31 euros.

Biogen shares were down 3.4 % in speculative trading ahead of the open in New York at $38. Elan’s New York shares were down 8.3 % at $6.10.

"Given that at present these are two isolated cases from a cohort of patients who have been on combination therapy, from a medical investigator’s point of view, a second case gives greater possibility of isolating common factors that may have triggered the disease," on of the analysts at Goodbody stock brokers in Dublin reported. "However, until that link is discovered and/or the on-going patient screening is successfully completed, there is little visibility on the future of Tysabri."