Four IFN-β formulations are currently approved for the treatment of MS: IFN-β 1b (Betaseron®/Extavia®) injected every other day s.c., IFN-β 1a (Rebif®) injected three times a week s.c., IFN-β 1a (Avonex®) injected once a week i.m. and pegylated IFN-β 1a (Plegridy®) injected every two weeks s.c. This evidence concerns the gene IFNB1 and myeloid sarcoma.