United States securities and exchange commission logo March 8, 2021 Christopher Anzalone Chief Executive 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, 2020 Filed November 23, 2020 File No. 001-38042 Dear Mr. Anzalone: 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