OUR PURPOSE PIONEERING SCIENCE PATIENTS OUR PEOPLE ENVIRONMENT COMMUNITY REPORTING 26 ENHANCING OUR STRATEGIC PORTFOLIO BIOGEN 2021 YEAR IN REVIEW Specialized immunology Decades of study by Biogen at the intersection of neurological and immunological pathways provide the company with expertise in immunology. Leveraging this expertise, we’re continuing to build our specialized immunology portfolio, with two potentially compelling Phase 3 programs in lupus – a chronic long-term disease that can cause inflammation and pain in any part of the body. It is estimated that 1.5 million U.S. residents and at least 5 million people worldwide have a form of lupus. In 2021, the first patient was dosed in TOPAZ-1, a global Phase 3 study evaluating the clinical efficacy and assessing the safety of BIIB059, which was discovered and developed exclusively by Biogen. It is a first-in-class, humanized IgG1 monoclonal antibody (mAb) Parkinson’s disease / Movement disorders Genetic neurodevelopmental Pre – 2016 2022 – 2025 2016 – 2021 2026 – 2030 Spinal muscular atrophy Biosimilars Neuromuscular Biosimilar launches Neuropsychiatry Lupus Stroke Alzheimer’s Multiple sclerosis Multiple sclerosis Multiple sclerosis Depression Alzheimer’s Biosimilar launches Neuromuscular Multiple sclerosis DIGITAL HEALTH BUSINESS DEVELOPMENT SPOTLIGHT Building a multi-franchise portfolio in areas of high unmet need During Biogen’s 2021 virtual Investor R&D Day, we provided a comprehensive review of the company’s robust and diversified neuroscience pipeline. We highlighted key advancements among our clinical programs, including programs in Phase 3 or filed, and highlights of our work on Alzheimer’s disease, neuropsychiatry, ALS, stroke, lupus and Parkinson’s disease. Our management and scientific leaders were joined by executives from Eisai, Sage Therapeutics and Denali Therapeutics. Þ ACCESS THE INVESTOR R&D DAY PRESENTATION In advance of the live webcast, nine video presentations were made available on movement disorders; MS portfolio; Alzheimer’s disease research portfolio; building the pipeline of the future; human genetics; biotherapeutics and medicinal sciences; gene therapy; biomarkers; and our new global unit, Biogen Digital Health. Þ VIEW PRE-EVENT PRESENTATIONS Expected 2022 Milestone   POTENTIAL FOR RENEWED GROWTH AND VALUE CREATION OVER TIME targeting blood dendritic cell antigen 2 (BDCA2), as compared to placebo, in participants with active systemic lupus erythematosus (SLE). TOPAZ-1 is a 52-week study that is expected to be conducted at approximately 135 sites worldwide and aims to enroll 540 adults with active SLE. Þ READ MORE ABOUT THE TOPAZ-1 STUDY With the TOPAZ-1 study, we are reinforcing Biogen’s commitment to the inclusion of underrepresented groups in our clinical trials. We have set enrollment targets that reflect the prevalence of SLE in Black or African American and Hispanic and Latino communities with the aim to achieve appropriate representation. Þ READ MORE ABOUT BIOGEN EFFORTS TO INCREASE REPRESENTATION IN CLINICAL TRIALS We plan to initiate a pivotal study for BIIB059 in cutaneous lupus erythematosus in 2022.        