Page 1

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , DC 20549 FORM 10 - K ( Mark One ) ANNUAL REPORT UNDER SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended September 30 , 2021 . TRANSITION REPORT UNDER SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from Commission file number 001-38042 ARROWHEAD PHARMACEUTICALS , INC . ( Exact name of registrant as specified in its charter ) Delaware ( State or other jurisdiction of incorporation or organization ) to Title of each class Common Stock , $ 0.001 par value 46-0408024 ( I.R.S. Employer Identification No. ) 177 E. Colorado Blvd , Suite 700 Pasadena , California 91105 ( 626 ) 304-3400 ( Address and telephone number of principal executive offices ) Securities registered pursuar to Section 12 ( b ) of the Exchange Act : Trading Symbol ( s ) ARWR Securities registered pursuant to Section 12 ( g ) of the Exchange Act : None Indicate by a check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes No Indicate by a check mark if the registrant is not required to file reports pursuant to Section 13 or 15 ( d ) of the Act . Yes No Indicate by check mark whether the registrant ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months ( or for such shorter period that the registrant was required to file such reports ) , and ( 2 ) has been subject to such filing requirements for the past 90 days . Yes > No Name of each exchange on which registered The Nasdaq Global Select Market Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T ( § 232.405 of this chapter ) during the preceding 12 months ( or for such shorter period that the registrant was required to submit such files ) . Yes No Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , a smaller reporting company , or an emerging growth company . See the definitions of " large accelerated filer , " " accelerated filer , " " smaller reporting company " and " emerging growth company " in Rule 12b - 2 of the Exchange Act . Large accelerated filer > Smaller reporting company Emerging growth company Accelerated filer Non - accelerated filer If an emerging growth company , indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13 ( a ) of the Exchange Act . Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404 ( b ) of the Sarbanes - Oxley Act ( 15 U.S.C. 7262 ( b ) ) by the registered public accounting firm that prepared or issued its audit report . Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Act ) . Yes No The aggregate market value of issuer's voting and non - voting outstanding Common Stock held by non - affiliates was approximately $ 5.9 billion based upon the closing stock price of issuer's Common Stock on March 31 , 2021. Shares of common stock held by each officer and director and by each person who is known to own 10 % or more of the outstanding Common Stock have been excluded in that such persons may be deemed to be affiliates of the Company . This determination of affiliate status is not necessarily a conclusive determination for other purposes . As of November 15 , 2021 , 104,525,708 shares of the issuer's Common Stock were issued and outstanding . DOCUMENTS INCORPORATED BY REFERENCE Portions of the Definitive Proxy Statement to be filed for Arrowhead Pharmaceuticals Inc.'s 2022 Annual Meeting of Stockholders are incorporated by reference into Part III hereof .