Dr. Booth has served as a member of our board of directors since September 2015 and served as Chairman of the board of directors from September 2025 to June 2026. Dr. Booth was our co-founder, President and Chief Executive Officer from September 2015 to August 2017. Dr. Booth joined Atlas Venture in 2005 and currently serves as a partner of Atlas Venture. Previously, from 2004 to 2005, Dr. Booth was a principal at Caxton Health Holdings L.L.C., a healthcare-focused investment firm, where he focused on the firm’s venture capital activities. From June 2020 until its acquisition by Sanofi in August 2025, Dr. Booth served as Chair of the board of directors of Vigil Neuroscience, Inc. He currently serves as a member of the board of Sionna Therapeutics, Inc. a publicly traded biotechnology company. He also serves as either Chair or member of the board of directors of multiple privately held companies. Dr. Booth holds a D.Phil. in molecular immunology from Oxford University’s Nuffield Department of Medicine and a B.S. in biochemistry from Pennsylvania State University.