Subsequent Events

3 Months Ended

Dec. 31, 2025

Subsequent Events [Abstract]

Subsequent Events

SUBSEQUENT EVENTSConvertible Senior Notes, Common Stock and Pre-Funded Warrants

On January 7, 2026, Arrowhead Pharmaceuticals entered into separate underwriting agreements for concurrent offerings of equity and convertible notes: first, with Jefferies and J.P. Morgan to sell 3,100,776 shares of common stock, $0.001 par value per share, at a public offering price of $64.50 per share, or alternatively in lieu of shares of common stock to certain investors, pre‑funded warrants to purchase up to 1,550,387 shares of common stock, at a public offering price of $64.499, which represents the per share public offering price for the common stock less the $0.001 per share exercise price for each pre-funded warrant. In addition, the Company granted the equity underwriters a 30-day option to purchase up to an additional 456,116 shares of common stock, on the same terms and conditions, which the equity underwriters exercised in full on January 8, 2026. The net proceeds from this equity offering was approximately $216.6 million after deducting customary underwriting discounts and offering expenses. These securities were issued under the Company’s automatic shelf registration statement, which closed on January 9, 2026.

Also on January 7, 2026, Arrowhead agreed with J.P. Morgan and Jefferies to issue $625.0 million of 0.00% convertible senior notes due 2032, with an additional $75.0 million overallotment option exercised in full on January 8, 2026. The net proceeds from the convertible notes offering are to be approximately $681.3 million, after deducting customary underwriting discounts and offering expenses. These securities were issued under the Company’s automatic shelf registration statement, which closed on January 12, 2026.

In connection with the convertible notes, Arrowhead entered into privately negotiated capped call transactions with one or more of the underwriters of the note offering or their affiliates or one or more other financial institutions. The capped call transactions will cover, subject to anti-dilution adjustments substantially similar to those applicable to the notes, the number of shares of Arrowhead’s common stock underlying the notes and are expected generally to reduce potential dilution to the Company’s common stock upon any conversion of Notes and/or offset any cash payments the Company is required to make in excess of the principal amount of converted Notes, as the case may be, with such reduction

and/or offset subject to a cap, based on the cap price of the capped call transaction. The cap price of the capped call transaction is approximately $119.33 per share (which represents a premium of approximately 85.0% over the public offering price per share of the Company’s common stock in the equity offering). The cost of the capped call transaction was approximately $47.9 million.

Asset Transfer Agreement with Bisirna Therapeutics, Inc (“Bisirna”)

On January 15, 2026, the consolidated variable interest entity, Visirna, closed on an Asset Transfer Agreement with Bisirna to sell and transfer certain assets and rights associated with R&D technology. The purchase price was $19.0 million, payable as (i) $9.0 million in paid-in-full warrants (exercise price of $0.18 per share) issued by Bisirna at the closing of the asset transfer, and (ii) $10.0 million of Bisirna Series A preferred shares, which were issued upon the closing of Bisirna’s Series A equity financing on January 15, 2026.

The Company is currently evaluating the financial statement impact of the transaction, including the accounting for the consideration received and any contingent consideration.

China NMPA NDA Approval and FCS Milestone

On January 5, 2026, the consolidated variable interest entity, Visirna, received NDA approval from the National Medical Products Administration (“NMPA”) in China for REDEMPLO. This approval triggered a $10.0 million regulatory milestone under the Sanofi License Agreement. The milestone payment is expected to be recognized as revenue in the second quarter of fiscal year 2026. The impact of this event was not reflected in the consolidated financial statements as of December 31, 2025.