Shares in Teva Pharmaceuticals slid to their lowest level since 2008 on the back of exceptional results for rival drug-maker Biogen Idec’s multiple sclerosis pill, BG-12.

The shares of the world’s largest maker of generic drugs lost 5.4% to 156.60 shekels, while US-traded shares have slid 7% since the report was published on 21 April.

Teva has reacted to the results by saying that clinical trials on multiple sclerosis treatments are not valid without a head- to-head trial.

Deutsche Bank has rallied to Teva’s aid, however, saying that the news over BG-12, was overdone and has reiterated its “buy” recommendation until more tests and safety information have been provided.