CAMBRIDGE, Mass. (AP) — Biogen Idec said Monday it will launch its new multiple sclerosis drug Tecfidera in Europe in the coming weeks following approval by the European Commission.

The European Union regulatory agency cleared the once-a-day pill for patients with relapsing multiple sclerosis, the most common form of the immune disease in which the body attacks the brain and spinal cord. Studies of Tecfidera show it can reduce relapses of the disease and slow disability. Multiple sclerosis can be difficult to treat because symptoms can come and go, often reappearing months later.

The U.S. Food and Drug Administration approved Tecfidera in late March and it has since become the country’s most prescribed pill for multiple sclerosis, according to Biogen. The Massachusetts-based biotech drugmaker also markets the multiple sclerosis drugs Avonex and Tysabri.

Shares of Biogen Idec Inc. fell $2.92 to $309.18 in morning trading.