Biogen Idec ( BIIB) gathered investors together Wednesday to pitch the company's research pipeline and stifle concerns that its leading position in the multiple sclerosis treatment market was vulnerable to competition. A phase III study of a long-acting version of Avonex, the company's top-selling multiple sclerosis drug, will begin in the middle of the year, the company announced. The drug, called PEG-Avonex, aims to be more convenient than but equally effective as Avonex, Biogen Idec's most important drug with $2.2 billion in sales last year. Multiple sclerosis patients will take PEG-Avonex by injection every two weeks or every four weeks instead of the weekly injection required for Avonex. Biogen Idec also said that patient enrollment has completed in the first of two phase III studies of the company's oral multiple sclerosis drug known as BG-12. Both BG-12 and PEG-Avonex are important for Biogen Idec's future growth because of competition from Novartis ( NVS) and the German drug maker Merck KGaA, which are developing oral multiple sclerosis drugs of their own. Both the Novartis drug, known as FTY720, and the Merck drug, cladribine, have posted positive results in phase III studies, and both companies have already announced plans to seek regulatory approval later this year. All current multiple sclerosis drugs, including Biogen's Avonex and Tysabri, which it co-markets with Elan ( ELN), are administered by injections, which leaves them commercially vulnerable to an oral multiple sclerosis drug, if one can be approved that is equally or more effective with an acceptable safety profile.