Company: ARWR
Filing Date: 2025-12-11
Form Type: S-3ASR
Source: 0001193125-25-314755
Chunk: 47

Company: ARROWHEAD PHARMACEUTICALS, INC.
Filing Date: 2025-12-11
Form: S-3ASR
Chunk 47
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 and will be governed by the final adjudication of such issue. Item 512(i) of Regulation S-K. The undersigned registrant hereby undertakes that:

| (i) | for purposes of determining any liability under the Securities Act, the information omitted from the form of                                                                                                                                         
 prospectus filed as part of this registration statement in reliance upon Rule 430A and contained in a form of prospectus filed by the registrant pursuant to Rule 424(b) (1) or (4) or 497(h) under the Securities Act shall be deemed to be part of 
 this registration statement as of the time it was declared effective.                                                                                                                                                                                |

| (ii) | for the purpose of determining any liability under the Securities Act, each post-effective amendment that                                                                                                                                   
 contains a form of prospectus shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof. |

Item 512(j) of Regulation S-K. The undersigned registrant hereby undertakes to file an application for the purpose of determining the eligibility of the trustee to act under subsection (a) of section 310 of the Trust Indenture Act (“Act”) in accordance with the rules and regulations prescribed by the Commission under section 305(b)(2) of the Act. II-4

SIGNATURES Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the city of Pasadena, State of California, on December 10, 2025.

| ARROWHEAD PHARMACEUTICALS, INC. |     |                          |
| By:                             |     | /s/ Christopher Anzalone |
|                                 |     | Christopher Anzalone     |
|                                 |     | Chief Executive Officer  |

POWER OF ATTORNEY Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed by the following persons in the capacities and on the dates indicated, each of whom also constitutes and appoints Christopher Anzalone and Daniel Apel, and each of them singly, his or her true and lawful attorney-in-factand agent, for him or her, with full power of substitution and resubstitution, for