Biogen Inc.

Biogen Inc. is an American biotechnology company that discovers, develops, and commercializes therapies for neurological, immunological, and rare diseases, generating $9.81 billion in revenue in fiscal 2025. Founded in 1978 by a group that included Nobel laureates Walter Gilbert and Phillip Sharp, Biogen was one of the first biotechnology companies and, until recently, built its entire economic identity around a single disease area: multiple sclerosis.

This is a story about a company trying to replace its legacy revenue before the legacy runs out. Biogen's MS franchise has been in steady decline since TECFIDERA's U.S. patent cliff, and a second wave of biosimilar competition for TYSABRI is gathering. The firm has responded with a three-part wager: that LEQEMBI will become the Alzheimer's standard of care, that its late-stage immunology pipeline — Litifilimab in lupus and Felzartamab in antibody-mediated rejection — will produce at least one meaningful franchise, and that the recently closed $5.6 billion Apellis acquisition will supply near-term commercial growth to bridge the gap before those pipeline readouts arrive. The file turns on a single question: whether the growth portfolio can outrun the MS erosion before the market loses patience with the transition.