OUR PURPOSE PIONEERING SCIENCE PATIENTS OUR PEOPLE ENVIRONMENT COMMUNITY REPORTING 21 ENHANCING OUR STRATEGIC PORTFOLIO BIOGEN 2021 YEAR IN REVIEW Spinal muscular atrophy (SMA) SMA, an inherited disease that can have a devastating effect on voluntary muscle movement, affects approximately 1 in every 10,000 babies born in the U.S. Before the introduction of treatments, SMA was a leading cause of mortality in infants. Tragically, if left untreated, the majority of infants with the most severe form of SMA die within two years. With other forms of SMA, some sit but never walk and some walk but may lose that ability over time. Biogen introduced the first FDA-approved therapy to treat SMA, SPINRAZA® (nusinersen), in 2016. SPINRAZA® has demonstrated significant benefit in individuals with SMA, from pre-symptomatic infants to adults with later-onset SMA. In 2021, we celebrated five years of SPINRAZA being marketed, with more than 11,000 patients treated commercially and through our clinical studies and early access program as of Dec. 31, 2021. NURTURE, the industry’s longest-running study of pre-symptomatic patients with SMA, shows the potential and long-term benefit of early treatment before SMA symptom onset. During the 2022 Muscular Dystrophy Association (MDA) Clinical & Scientific Conference, we shared the latest results from NURTURE participants treated with SPINRAZA for up to 5.7 years (median 4.9 years). After 11 months of additional follow up since our 2020 interim analysis, all children who were able to walk alone maintained this ability and one child gained the ability to walk alone, increasing the total percentage to 92% (23/25). Importantly, most children achieved motor milestones within age-appropriate timelines and no motor milestones have been lost. Þ READ MORE ABOUT THE NURTURE STUDY We are working to address remaining unmet needs and answer critical questions for the SMA community through our new and ongoing research, as well as digital solutions to advance clinical care and patient empowerment. – DEVOTE: Building on the proven efficacy and well-established safety of SPINRAZA in a broad range of patients with SMA, the Phase 2/3 DEVOTE study is evaluating the safety, tolerability and potential for even greater efficacy of nusinersen when administered at a higher, earlier dose than currently approved. Initial findings from DEVOTE show no new safety concerns in study participants who were followed for up to 10 months, and support the continued development of investigational higher dose nusinersen. Þ READ MORE ABOUT OUR RESEARCH PRESENTED AT THE 2021 VIRTUAL CURE SMA RESEARCH & CLINICAL CARE MEETING – RESPOND: In 2021, the first patient was treated in the global Phase 4 clinical study RESPOND to examine the clinical benefit and assess the safety of SPINRAZA in infants and children with SMA who still have unmet clinical needs following treatment with gene therapy Zolgensma® (onasemnogene abeparvovec). RESPOND will be conducted at approximately 20 sites worldwide and aims to enroll up to 60 children with SMA. Þ READ MORE ABOUT THE RESPOND STUDY – ASCEND: Our ASCEND study enrolled the first patient in early 2022. The study will evaluate the potential benefit of an investigational higher dose of nusinersen in children, teens and adults who were previously treated with Evrysdi® (risdiplam). ASCEND is projected to enroll up to 135 later-onset, non-ambulatory individuals with SMA (aged 5 to 39). Þ READ MORE ABOUT THE ASCEND STUDY Biogen is also advancing research to evaluate biomarkers and digital tools that expand on traditional clinical assessments and incorporate more sensitive measures to help better predict and monitor the course of SMA. Þ READ MORE ABOUT OUR DATA PRESENTED AT THE AMERICAN ACADEMY OF NEUROLOGY (AAN) 2021 VIRTUAL ANNUAL MEETING