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10-K primary document
BIIB · Annual Report (Form 10-K) · Filed February 6, 2026

Biogen Inc10-K exhibit

biib-20251231xex21.htm
Document

Exhibit 21

BIOGEN INC.

The following is a list of subsidiaries of Biogen Inc. as of December 31, 2025, omitting some subsidiaries which, considered in the aggregate, would not constitute a significant subsidiary.
SUBSIDIARYSTATE OR OTHER JURISDICTION OF
INCORPORATION OR ORGANIZATION
Biogen Foundation Inc.Massachusetts
Biogen MA Inc.Massachusetts
Biogen Realty CorporationMassachusetts
Biogen Realty Limited PartnershipMassachusetts
Biogen U.S. CorporationMassachusetts
Biogen U.S. Limited PartnershipMassachusetts
Alcyone Therapeutics, Inc.Delaware
Biogen (RTP) Realty LLCDelaware
Biogen Chesapeake LLCDelaware
Biogen Digital Health Inc.Delaware
Biogen Digital Health Global LLCDelaware
Biogen Holding I LLCDelaware
Biogen Holding II LLCDelaware
Biogen OUS Holding Inc.Delaware
Biogen Manufacturing Holding LLCDelaware
Biogen New Ventures Inc.Delaware
Biogen SRO Inc.Delaware
Biogen Therapeutics Inc.Delaware
Biogen U.S. Pacific LLCDelaware
Biogen U.S. West CorporationDelaware
Conforma Therapeutics CorporationDelaware
Human Immunology Biosciences, Inc.Delaware
Stromedix, LLCDelaware
Nightstar, Inc.Delaware
Reata Pharmaceuticals Global, Inc.Delaware
Reata Pharmaceuticals Holdings, LLC.Delaware
Reata Pharmaceuticals, Inc.Delaware
Biogen (Argentina) SRLArgentina
Biogen Australia PTY LtdAustralia
Biogen Austria GmbHAustria
Biogen Belgium N.V./S.A.Belgium
Biogen International Holding LimitedBermuda
Biogen (Bermuda) Technologies Ltd.Bermuda
Biogen Brasil Produtos Farmaceuticos LTDABrazil
Biogen Canada Inc.Canada
Biogen Chile SpAChile
Biogen Biotechnology (Shanghai) Co., LtdChina
BIIB Colombia S.A.S.Colombia
Biogen Pharma d.o.o.Croatia
Biogen (Czech Republic) s.r.o.Czech Republic
Biogen (Denmark) A/SDenmark



SUBSIDIARYSTATE OR OTHER JURISDICTION OF
INCORPORATION OR ORGANIZATION
Biogen Estonia OUEstonia
Biogen Finland OYFinland
Biogen France S.A.S.France
Biogen GmbHGermany
Reata Germany GmbHGermany
Biogen Hong Kong LimitedHong Kong
Biogen Hungary KFTHungary
Biogen Idec Biotech India Pvt. Ltd.India
Biogen Capability Center India Private LimitedIndia
Biogen Idec (Ireland) Ltd.Ireland
Nightstar Europa LimitedIreland
Biogen Distribution Services LimitedIreland
Biogen Italia S.R.L.Italy
Biogen Japan Ltd.Japan
Biogen Korea LLCKorea
Biogen Latvia SIALatvia
Biogen Lithuania UABLithuania
Biogen Luxembourg Holding S.a.r.l.Luxembourg
Biogen Mexico S. de R.L. de C.V.Mexico
Biogen NZ Biopharma Ltd.New Zealand
Biogen Norway ASNorway
Biogen Poland Sp. z.o.o.Poland
Biogen Portugal Sociedade Farmaceutica, Unipessoal Lda.Portugal
Biogen Arabia LimitedSaudi Arabia
Biogen Regional Headquarters LLCSaudi Arabia
Biogen Slovakia s.r.o.Slovak Republic
Biogen Pharma, farmacevtska in biotehnoloska druzba, d.o.o.Slovenia
Biogen Spain, S.L.Spain
Biogen Sweden ABSweden
Biogen Digital Health International GmbHSwitzerland
Biogen International GmbHSwitzerland
Biogen International Neuroscience GmbHSwitzerland
Biogen Management Services GmbHSwitzerland
Biogen Switzerland AGSwitzerland
Eidetica Biopharma GmbHSwitzerland
Biogen Taiwan LimitedTaiwan
Biogen Turkey Ilac Ticaret Limited SirketiTurkey
Biogen B.V.The Netherlands
Biogen Netherlands B.V.The Netherlands
Biogen Idec LimitedUnited Kingdom
Biogen Idec Research Ltd.United Kingdom
Convergence Pharmaceuticals LimitedUnited Kingdom
Convergence Pharmaceuticals Holdings Ltd.United Kingdom
Old Convergence Pharmaceuticals LimitedUnited Kingdom
Reata U.K. LimitedUnited Kingdom
SUBSIDIARYSTATE OR OTHER JURISDICTION OF
INCORPORATION OR ORGANIZATION
Silver Acquisition Co. Ltd.United Kingdom



Nightstar Therapeutics LimitedUnited Kingdom
NightstaRx LimitedUnited Kingdom
Tungsten Bidco LimitedUnited Kingdom
Biogen Idec Uruguay SAUruguay


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