On February 11, 2023, Marianne De Backer, a director of Arrowhead Pharmaceuticals, Inc. (the “Company”), notified the Company of her decision to resign as a director, effective as of April 2, 2023. Dr. De Backeris an independent director who also serves as a member of the Company's Audit Committee, Compensation Committee, and as Chair of its Nomination Committee. Dr. De Backer's decision to resign was based on her recent appointment as Chief Executive Officer and director of Vir Biotechnology, Inc., and did not result from any disagreement with the Company.