United States securities and exchange commission logo May 19, 2023 Kenneth Myszkowski Chief Financial Officer Arrowhead Pharmaceuticals, Inc. 177 E. Colorado Blvd, Suite 700 Pasadena, California 91105 Re: Arrowhead Pharmaceuticals, Inc. Form 10-K for the Fiscal Year Ended September 30, 2022 Filed November 28, 2022 File No. 001-38042 Dear Kenneth Myszkowski: We have completed our review of your filing. We remind you that the company and its management are responsible for the accuracy and adequacy of their disclosures, notwithstanding any review, comments, action or absence of action by the staff. Sincerely, Division of Corporation Finance Office of Life Sciences