UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

(Rule 14a-101)

INFORMATION REQUIRED IN PROXY STATEMENT

SCHEDULE 14A INFORMATION

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Securities Exchange Act of 1934

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ARROWHEAD PHARMACEUTICALS, INC.

(Name of Registrant as Specified in Its Charter)

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*** Exercise Your Right to Vote *** Important Notice Regarding the Availability of Proxy Materials for the Stockholder Meeting to Be Held on March 16, 2018. ARROWHEAD PHARMACEUTICALS, INC. ARROWHEAD PHARMACEUTICALS, INC. 225 SOUTH LAKE AVENUE, SUITE 1050 PASADENA, CA 91101 E35948-P00586 Meeting Information Meeting Type: Annual Meeting For holders as of: January 23, 2018 Date: March 16, 2018 Time: 10:00 AM PT Location: Meeting live via the Internet-please visit www.virtualshareholdermeeting.com/ARWR2018. The company will be hosting the meeting live via the Internet this year. To attend the meeting via the Internet please visit www.virtualshareholdermeeting.com/ARWR2018 and be sure to have the information that is printed in the box marked by the arrow XXXX XXXX XXXX XXXX (located on the following page). You are receiving this communication because you hold shares in the company named above. This is not a ballot. You cannot use this notice to vote these shares. This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. You may view the proxy materials online at www.proxyvote.com or easily request a paper copy (see reverse side). We encourage you to access and review all of the important information contained in the proxy materials before voting. proxy See the materials reverse and side voting of this instructions. notice to obtain

Before You Vote How to Access the Proxy Materials Proxy Materials Available to VIEW or RECEIVE: NOTICE AND PROXY STATEMENT FORM 10-K How to View Online: Have the information that is printed in the box marked by the arrow XXXX XXXX XXXX XXXX (located on the following page) and visit: www.proxyvote.com. How to Request and Receive a PAPER or E-MAIL Copy: If you want to receive a paper or e-mail copy of these documents, you must request one. There is NO charge for requesting a copy. Please choose one of the following methods to make your request: 1) BY INTERNET: www.proxyvote.com 2) BY TELEPHONE: 1-800-579-1639 3) BY E-MAIL*: sendmaterial@proxyvote.com * If requesting materials by e-mail, please send a blank e-mail with the information that is printed in the box marked by the arrow XXXX XXXX XXXX XXXX (located on the following page) in the subject line. Requests, instructions and other inquiries sent to this e-mail address will NOT be forwarded to your investment advisor. Please make the request as instructed above on or before March 1, 2018 to facilitate timely delivery. How To Vote Please Choose One of the Following Voting Methods Vote By Internet: Before The Meeting: Go to www.proxyvote.com. Have the information that is printed in the box marked by the arrow XXXX XXXX XXXX XXXX (located on the following page) available and follow the instructions. During The Meeting: Go to www.virtualshareholdermeeting.com/ARWR2018. Have the information that is printed in the box marked by the arrow XXXX XXXX XXXX XXXX (located on the following page) available and follow the instructions. Vote By Mail: You can vote by mail by requesting a paper copy of the materials, which will include a proxy card. E35949-P00586

Voting Items The the following: Board of Directors recommends you vote FOR 1. Election of Directors Nominees: 01) Christopher Anzalone 04) Douglass Given 02) Mauro Ferrari 05) Michael S. Perry 03) Edward W. Frykman 06) William Waddill The Board of Directors recommends you vote FOR the following proposals: 2. To approve the compensation paid to the Company’s named executive officers, as disclosed pursuant to Item 402 of Regulation S-K, including the compensation tables and narrative discussion. 3. To ratify the selection of Rose, Snyder & Jacobs LLP as independent auditors of the Company for the fiscal year ending September 30, 2018. NOTE: Such other business as may properly come before the meeting or any adjournment thereof. E35950-P00586

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