Subsequent Events	12 Months Ended
Sep. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	NOTE 13. SUBSEQUENT EVENTS San Diego Lease Agreement with ARE-SD Region No. 72 LLC On November 19, 2021, the Company entered into a new lease for a San Diego, California research facility. The 15-year lease is for approximately 144,000 square feet of office and research and development laboratory space to be constructed in San Diego, California. This lease will replace the Company’s current research facility sublease for property located in San Diego, California. The increased capacity of this new facility compared to the Company’s current research facility in San Diego will accommodate increased personnel for the Company’s expanding pipeline of current and future drug candidates. The estimated rent commencement date for the lease is in May 2023 after construction and leasehold improvements have been completed. The lease payments, which begin on the rent commencement date, will be approximately $119.0 million over the initial 15-year term. The Company also estimates payments for operating expenses to be approximately $3.0 million for the first year of the lease, and these payments will continue throughout the initial 15-year term. The Company expects to pay approximately $31.0 million for leasehold improvements, net of tenant improvement allowances. Pursuant to the lease, within twelve months of the expiration of the initial 15-year term, the Company has the option to extend the lease for up to one additional ten-year term, with certain annual increases in base rent. F-25 Exclusive License Agreement with Glaxosmithkline Intellectual Property (No. 3) Limited On November 22, 2021, the Company entered into an Exclusive License Agreement (the “GSK License Agreement”) with Glaxosmithkline Intellectual Property (No. 3) Limited (“GSK”). Under the GSK License Agreement, GSK has received an exclusive license for ARO-HSD, the Company’s investigational RNAi therapeutic being developed as a treatment for patients with alcohol-related and nonalcohol related liver diseases, such as nonalcoholic steatohepatitis (NASH). The exclusive license is worldwide with the exception of greater China, for which the Company will retain rights to develop and commercialize. Beyond the Company’s Phase 1/2 study of (ARO-HSD), which the Company is responsible for completing, GSK is wholly responsible for clinical development and commercialization of ARO-HSD in its territory. Under the terms of the agreement, Arrowhead will receive an upfront payment of $120 million and is eligible for additional payments of $30 million at the start of Phase 2 and $100 million upon achieving a successful Phase 2 trial readout and the first patient dosed in a Phase 3 trial. Furthermore, should the Phase 3 trial read out positively, and the potential new medicine receives regulatory approval in major markets, the deal provides for commercial milestone payments to Arrowhead of up to $190 million at first commercial sale, and up to $590 million in sales-related milestone payments. Arrowhead is further eligible to receive tiered royalties on net product sales in a range of mid-teens to twenty percent. The transactions contemplated under the GSK Agreement are subject to customary closing conditions, including clearance by the relevant competition authorities.

Subsequent Events

12 Months Ended

Sep. 30, 2021

NOTE 13. SUBSEQUENT EVENTS

San Diego Lease Agreement with ARE-SD Region No. 72 LLC

On November 19, 2021, the Company entered into a new lease for a San Diego, California research facility. The 15-year lease is for approximately 144,000 square feet of office and research and development laboratory space to be constructed in San Diego, California. This lease will replace the Company’s current research facility sublease for property located in San Diego, California. The increased capacity of this new facility compared to the Company’s current research facility in San Diego will accommodate increased personnel for the Company’s expanding pipeline of current and future drug candidates.

The estimated rent commencement date for the lease is in May 2023 after construction and leasehold improvements have been completed. The lease payments, which begin on the rent commencement date, will be approximately $119.0 million over the initial 15-year term. The Company also estimates payments for operating expenses to be approximately $3.0 million for the first year of the lease, and these payments will continue throughout the initial 15-year term. The Company expects to pay approximately $31.0 million for leasehold improvements, net of tenant improvement allowances. Pursuant to the lease, within twelve months of the expiration of the initial 15-year term, the Company has the option to extend the lease for up to one additional ten-year term, with certain annual increases in base rent.

F-25

Exclusive License Agreement with Glaxosmithkline Intellectual Property (No. 3) Limited

On November 22, 2021, the Company entered into an Exclusive License Agreement (the “GSK License Agreement”) with Glaxosmithkline Intellectual Property (No. 3) Limited (“GSK”). Under the GSK License Agreement, GSK has received an exclusive license for ARO-HSD, the Company’s investigational RNAi therapeutic being developed as a treatment for patients with alcohol-related and nonalcohol related liver diseases, such as nonalcoholic steatohepatitis (NASH). The exclusive license is worldwide with the exception of greater China, for which the Company will retain rights to develop and commercialize. Beyond the Company’s Phase 1/2 study of (ARO-HSD), which the Company is responsible for completing, GSK is wholly responsible for clinical development and commercialization of ARO-HSD in its territory. Under the terms of the agreement, Arrowhead will receive an upfront payment of $120 million and is eligible for additional payments of $30 million at the start of Phase 2 and $100 million upon achieving a successful Phase 2 trial readout and the first patient dosed in a Phase 3 trial. Furthermore, should the Phase 3 trial read out positively, and the potential new medicine receives regulatory approval in major markets, the deal provides for commercial milestone payments to Arrowhead of up to $190 million at first commercial sale, and up to $590 million in sales-related milestone payments. Arrowhead is further eligible to receive tiered royalties on net product sales in a range of mid-teens to twenty percent. The transactions contemplated under the GSK Agreement are subject to customary closing conditions, including clearance by the relevant competition authorities.