CAMBRIDGE, Mass. (AP) — Biogen Idec Inc. said Thursday it will be able to roughly quadruple production of its drug Tysabri after the Food and Drug Administration approved a new process for making the Crohn’s disease and multiple sclerosis treatment. Biogen Idec, which is based in Cambridge, Mass., markets Tysabri with Elan Corp. PLC of Ireland. European Union regulators approved the sale of Tysabri made with the “high titer” process in December. The process will be used to make Tysabri at Biogen’s plant in Research Triangle Park, N.C.