Biogen and Genentech shares fall after Rituxan deaths

Stock shares of drug makers Biogen Idec Inc. of Cambridge and Genentech Inc. fell after it was disclosed that two lupus patients using a drug called Rituxan had died of a rare brain infection.

In mid-morning trading on the Nasdaq Stock Market, Biogen shares were off $1.05, or 2 percent, to $49.18, and on the New York Stock Exchange, shares of Genentech of California were down 50 cents, or 0.6 percent, to $80.46.

Biogen and Genentech market Rituxan, which has been approved as a treatment for rheumatoid arthritis and non-Hodgkin's lymphoma, a form of blood cancer.

Rituxan's use in treating patients with lupus is still in the experimental stages.
(By Chris Reidy, Globe staff)