OUR PURPOSE PIONEERING SCIENCE PATIENTS OUR PEOPLE ENVIRONMENT COMMUNITY REPORTING 9 CEO LETTER BIOGEN 2021 YEAR IN REVIEW And we did not stop there. We collaborated with global scientific leaders on a meta-analysis of air pollution and dementia and a groundbreaking survey of 450-plus health clinic staff from 47 U.S. states to garner real- world insights into the health impacts of the climate crisis. Additionally, we accelerated our ongoing work with MIT to create a state-of-the-art integrated model of how various climate actions impact public health. We also have advanced our Diversity, Equity and Inclusion (DE&I) strategy, with an ongoing focus on hiring and engaging a diverse workforce, promoting health equity, and making notable gains in supplier diversity. We shared the results of a global pay equity analysis with employees and publicly disclosed our EEO-1 data (Equal Employment Opportunity), which provides a demographic breakdown of our U.S. workforce by gender and race, and released our first stand-alone DE&I Report in October 2021. We strive to build on our priorities for health equity and access across our operations. For example, we continue to expand efforts globally in order to reach more patients, with a growing focus on low- and middle- income countries. Globally, we are taking further action to ensure that our research and clinical trials are inclusive and representative. We aim to remove barriers for treatment and overcome the stigma of dementia. Black or African American and Hispanic and Latino populations are respectively two and one-and-a-half times more likely than older White Americans to have Alzheimer’s disease, yet they are also more likely to be diagnosed later in the course of their disease 4 . To change this, we are working with advocates and organizations such as The Balm in Gilead, Inc., the National Association of Free and Charitable Clinics, Black Health Matters, the Global Alzheimer’s Platform, the National Minority Quality Forum and USAgainstAlzheimer’s to improve early detection and care. We also continue to invest significantly in building a diverse talent pipeline through STEM equity education. In 2021, we entered into a collaboration with Morehouse School of Medicine to launch a Health Equity Fellowship program, through which M.D. and/or Ph.D. students will advance projects at Biogen that support more equitable healthcare experiences for patients in underrepresented and underserved communities. As a result of our ESG commitments and progress, we were listed as the top biotech leader on the Dow Jones Sustainability World Index for a seventh time and won the 2021 U.S. Chamber of Commerce Foundation’s best sustainability program award. Potential for Growth and Value Creation We have entered 2022 with a robust and diversified pipeline, which includes approximately 30 clinical programs across a broad set of disease areas and multiple modalities, 10 of which are in Phase 3 or filed. We attribute this success to our own innovative research and to the more than 30 business development deals we have reached over the past five years, spanning a range of disease areas including MS, depression, stroke, and Parkinson’s disease. Our work going forward is based on four strategic pillars to drive growth and value creation over the medium to long term. The first of these pillars is Biogen’s continued leadership in neuroscience, which as of April 29, 2022, comprises over 20 of our approximately 30 programs in clinical development. We continue to believe in significant potential opportunities in Alzheimer’s disease and depression, two large therapeutic areas with great unmet need. For 2022, we expect two remaining data readouts in these areas, including additional Phase 3 data for zuranolone and pivotal data for lecanamab, with the potential to complete two new regulatory filings. In the long term, we have the opportunity to build upon our planned entry into neuropsychiatry with BIIB104 (AMPA PAM), an investigational drug which is currently being evaluated in a Phase 2 study for cognitive impairment associated with schizophrenia. A second pillar of potential growth is our specialized immunology portfolio with two promising Phase 3 programs in lupus, a disease that affects an estimated 1.5 million Americans and at least five million people worldwide 5 . We believe we have potential first-in- class molecules for both systemic lupus erythematosus (SLE), with dapirolizumab pegol (anti-CD40L) being developed in collaboration with UCB and BIIB059 (anti-BDCA2), and cutaneous lupus 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.”