Subsequent Events

12 Months Ended

Sep. 30, 2025

Subsequent Events [Abstract]

Subsequent Events

SUBSEQUENT EVENTS

Novartis

On August 29, 2025, the Company entered into an Exclusive License and Collaboration Agreement (the “Novartis Collaboration Agreement”) with Novartis Pharma AG (“Novartis”) for the co-development and commercialization of multiple preclinical programs in rare, genetic diseases. Under the Novartis Collaboration Agreement, Novartis has received an exclusive worldwide license to the Company's ARO-SNCA preclinical stage program. The Novartis Collaboration Agreement closed on October 17, 2025 subsequent to clearance under the Hart-Scott-Rodino Antitrust Improvement Act. Under the terms of the Novartis Collaboration Agreement, the Company received $200.0 million as an upfront payment. The Company is also eligible to receive $30.0 million associated with certain target nominations. Further, for each of the 4 programs, the Company is eligible to receive development milestone payments between $175.0 million and $245.0 million per program and sales milestone payments between $285.0 million and $370.0 million per program. The Company is also eligible to receive tiered royalties on net sales of licensed products of up to the low double digits.

Sarepta DM1 Milestone

On November 20, 2025, the Company earned a $200.0 million milestone payment from Sarepta. The milestone was earned when Arrowhead achieved the second development milestone event in a Phase 1/2 clinical study of ARO-DM1, also called SRP-1003, an investigational RNAi therapeutic for the treatment of type 1 myotonic dystrophy (DM1), the most common adult-onset muscular dystrophy. The second milestone event included the achievement of a patient enrollment target, drug safety committee review and subsequent authorization to dose escalate and proceed, and completion of day 105 study visit by at least one patient in the clinical trial.

REDEMPLO Commercial Launch

The FDA approved the Company's New Drug Application (NDA) for REDEMPLO (plozasiran) injection for Familial Chylomicronemia Syndrome (FCS), on November 18, 2025. This approval, which was based on the results of the Phase 3 PALISADE clinical trial, was completed within the Prescription Drug User Fee Act (PDUFA) VI timeframe. This approval is a significant milestone for the Company, and the commercial launch of REDEMPLO is in progress. We expect to begin generating revenue from sales of REDEMPLO in the upcoming fiscal year.