OUR PURPOSE PIONEERING SCIENCE PATIENTS OUR PEOPLE ENVIRONMENT COMMUNITY REPORTING 8 CEO LETTER BIOGEN 2021 YEAR IN REVIEW Scale (ALSFRS-R) did not reach statistical significance; however, signs of reduced disease progression across multiple secondary and exploratory endpoints were observed. Furthermore, the totality of evidence from the Phase 3 and its ongoing open-label extension showed that participants who started tofersen earlier experienced better outcomes, further suggesting a positive clinical effect. Advancing Digital Health Recent advances in the understanding of disease biology, along with an exponential acceleration in technologies, are paving the way for a shift in how diseases of the central nervous system (CNS) are diagnosed, measured and treated. This is why in 2021 we formed Biogen Digital Health, a global unit dedicated to pioneering personalized and digital medicine in neuroscience. We believe that now, more than ever, biology and technology should go hand in hand to better meet patient needs while enabling a shift toward more prevention-focused, affordable and equitable care. Building complementary digital solutions that predict, measure and prevent disease is of particular importance in neuroscience due to the heterogeneity and complexity of measuring neurological disease progression. For example, developing validated digital biomarkers may enable us to accelerate clinical development and increase the probability of success of our pipeline assets, and also create opportunities for clinicians to better monitor disease progression with more sensitive and predictive measures than those currently available. As pioneers in neuroscience, we will explore synergistic opportunities for digital therapeutics to further address the unmet needs of patients. 2021 Financial Performance Our financial results for full-year 2021 underscored Biogen’s ability to execute in the face of challenges. The company generated GAAP diluted earnings per share of $10.40 and Non-GAAP diluted earnings per share of $19.13 on $11.0 billion in revenue. Notwithstanding generic competition to TECFIDERA (dimethyl fumarate) in the U.S., which materially impacted our revenue base in 2021, we maintained global leadership in MS, including the significant progress of VUMERITY (diroximel fumarate) to treat relapsing MS. In SMA, the global expansion of SPINRAZA contributed to incremental revenue growth year over year outside the U.S. Our work in biosimilars has accelerated over the past few years as we strive to bring greater value to healthcare systems and access to patients while enhancing our own cash flow generation opportunities. During the year, we generated approximately $3.6 billion in net cash flow from operations. We spent approximately $250 million on capital expenditures, resulting in free cash flow of approximately $3.4 billion 3 . We ended 2021 with $4.7 billion in cash, cash equivalents and marketable securities, and a healthy balance sheet. We expect that we will continue to generate significant cash flow in 2022, providing us with multiple options for capital allocation. Late in 2021, we announced a series of cost reduction measures to lower the company’s expenses and bring them in line with our revised revenue expectations. The plan, which we began implementing in early 2022, is expected to yield approximately $500 million in annualized savings, a significant portion of which will be realized this year. Some of these savings will be offset by investments in Biogen’s pipeline and strategic initiatives. Contributing to a Better World Our Environmental, Social and Governance (ESG) efforts prioritize climate, health and equity, with a focus on vulnerable populations, as well as ongoing leadership in governance, transparency and disclosure. Reflecting our broader commitment to these priorities, we continued to tie a portion of our employees’ and executive officers’ compensation to advancing our ESG efforts. ESG oversight is formally embedded into our Board’s Governance Principles. One hallmark of our ESG efforts is Healthy Climate, Healthy Lives™, a $250 million initiative to eliminate fossil fuel emissions across our operations by 2040 to contribute to improved public health. In 2021, we grew our electric vehicle program to 12 countries and expanded our environmental impact assessment for key facilities and products. We joined with nine other industry leaders to launch Energize, a bold effort to decarbonize the pharmaceutical value chain. We believe that now, more than ever, biology and technology should go hand in hand to better meet patient needs while enabling a shift toward more prevention- focused, affordable and equitable care.”