Organization and Significant Accounting Policies	9 Months Ended
Jun. 30, 2021
Accounting Policies [Abstract]
Organization and Significant Accounting Policies	NOTE 1. ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES Nature of Business and Recent Developments Arrowhead Pharmaceuticals, Inc. develops medicines that treat intractable diseases by silencing the genes that cause them. Using a broad portfolio of RNA chemistries and efficient modes of delivery, Arrowhead therapies trigger the RNA interference mechanism to induce rapid, deep and durable knockdown of target genes. RNA interference (“RNAi”) is a mechanism present in living cells that inhibits the expression of a specific gene, thereby affecting the production of a specific protein. Arrowhead’s RNAi-based therapeutics leverage this natural pathway of gene silencing. The Company’s pipeline includes ARO-APOC3 for hypertriglyceridemia, ARO-ANG3 for dyslipidemia, ARO-HSD for liver disease, ARO-ENaC for cystic fibrosis, ARO-HIF2 for renal cell carcinoma, ARO-DUX4 for facioscapulohumeral muscular dystrophy, ARO-LUNG2 for chronic obstructive pulmonary disorder, and ARO-COV for the coronavirus that causes COVID-19 and other possible future pulmonary-borne pathogens. ARO-XDH is being developed for uncontrolled gout under a collaboration agreement with Horizon Therapeutics Ireland DAC (“Horizon”). ARO-JNJ1, ARO-JNJ2 and ARO-JNJ3 are being developed for undisclosed liver-expressed targets under a collaboration agreement with Janssen Pharmaceuticals, Inc. (“Janssen”). ARO-AAT for liver disease associated with alpha-1 antitrypsin deficiency (“AATD”) was out-licensed to Takeda Pharmaceuticals U.S.A., Inc. (“Takeda”) in October 2020. JNJ3989 (formerly referred to as ARO-HBV) for chronic hepatitis B virus was out-licensed to Janssen in October 2018. Olpasiran (formerly referred to as AMG 890 or ARO-LPA) for cardiovascular disease was out-licensed to Amgen Inc. (“Amgen”) in 2016. Arrowhead operates lab facilities in Madison, Wisconsin and San Diego, California, where the Company’s research and development activities, including the development of RNAi therapeutics, take place. The Company’s principal executive offices are located in Pasadena, California. During fiscal year 2021, the Company continued to develop its pipeline and partnered candidates. The Company announced positive interim clinical data on (i) AROAAT2002, an open-label Phase 2 clinical study of ARO-AAT, the Company’s second-generation investigational RNAi therapeutic being co-developed with Takeda as a treatment for the rare genetic liver disease associated with AATD, (ii) AROHSD1001, a Phase 1/2 clinical study of 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), and (iii) AROHIF21001, a Phase 1b dose-finding clinical study of ARO-HIF2, the Company’s investigational RNAi therapeutic being developed as a treatment for patients with clear cell renal cell carcinoma. The Company also presented preclinical data on the development of ARO-DUX4, the Company’s investigational RNAi therapeutic being developed as a treatment for patients with facioscapulohumeral muscular dystrophy (FSHD), at the 28th Annual FSHD Society International Research Congress. The Company hosted a key opinion leader webinar on its cardiometabolic candidates, ARO-APOC3 and ARO-ANG3, and presented positive clinical data from the Phase 1/2 clinical studies of ARO-APOC3 and ARO-ANG3 at the American Heart Association Scientific Sessions 2020. The Company filed two Investigational New Drug Applications with the United States Food and Drug Administration (the “FDA”) to begin a Phase 2b clinical study of ARO-APOC3 in patients with severe hypertriglyceridemia and a Phase 2b clinical study of ARO-ANG3 in patients with mixed dyslipidemia, and initiated these two Phase 2b clinical studies in the third quarter of fiscal year 2021. In July 2021, the Company voluntarily paused AROENaC1001, a Phase 1/2 clinical study of ARO-ENaC, the Company’s investigational RNAi therapeutic being developed as a treatment for patients with cystic fibrosis, after receiving a preliminary update from an ongoing chronic toxicology study in rats that contained unexpected signals of local lung inflammation. New screening, enrollment and any further dosing of investigational ARO-ENaC have been paused pending additional data from ongoing nonclinical toxicology studies. The Company announced two collaborations during the first three quarters of fiscal year 2021: a collaboration with Takeda to co-develop and co-commercialize ARO-AAT for alpha-1 antitrypsin-associated liver disease and a collaboration with Horizon to develop ARO-XDH, an investigational RNAi therapeutic for uncontrolled gout. In July 2021, the Company received Breakthrough Therapy designation from the FDA for ARO-AAT, which is a process designed to expedite the development and review of drugs that are intended to treat a serious life-threatening disease or condition and preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints. The Company also earned a $10 million payment in connection with Janssen’s exercise of its option right for ARO-JNJ1 in May 2021, which option grants Janssen all rights, including licenses, and obligations to develop and commercialize ARO-JNJ1. See Note 2 for more information regarding the Company’s collaboration and license agreements. The Company’s partnered candidates under its collaboration agreements also continued to progress. Janssen began dosing patients in a Phase 2b triple combination study called REEF-1, designed to enroll up to 450 patients with chronic hepatitis B infection. The Company is currently performing discovery, optimization and preclinical research and development for ARO-JNJ1, ARO-JNJ2 and ARO-JNJ3 for Janssen as part of the Company’s Research Collaboration and Option Agreement with Janssen (“Janssen Collaboration Agreement”). Under the terms of the Janssen agreements taken together, the Company has received $175.0 million as an upfront payment, $75.0 million in the form of an equity investment by Johnson & Johnson Innovation-JJDC, Inc. (“JJDC”) in Arrowhead Common Stock, and three milestone payments totaling $60.0 million, which include a $10 million payment for Janssen’s exercise of its option right for ARO-JNJ1 in May 2021. The Company may receive up to $1.6 billion in additional development and sales milestones payments for the Janssen License Agreement, and up to $1.9 billion in additional development and sales milestone payments for the three additional targets covered under the Janssen Collaboration Agreement. The Company is further eligible to receive tiered royalties on product sales up to mid-teens under the Janssen License Agreement and up to low teens under the Janssen Collaboration Agreement. The Company’s collaboration agreement with Amgen for Olpasiran (previously referred to as AMG 890 or ARO-LPA) (the “Second Collaboration and License Agreement” or “Olpasiran Agreement”) continues to progress. In July 2020, Amgen initiated a Phase 2 clinical study, which resulted in a $20.0 million milestone payment to the Company. The Company has received $35.0 million in upfront payments, $21.5 million in the form of an equity investment by Amgen in the Company’s Common Stock, $30.0 million in milestone payments, and may receive up to an additional $400.0 million in remaining development, regulatory and sales milestone payments. The Company is eligible to receive up to low double-digit royalties for sales of products under the Olpasiran Agreement. On October 7, 2020, the Company entered into an Exclusive License and Co-Funding Agreement with Takeda (the “Takeda License Agreement”). Under the Takeda License Agreement, Takeda and the Company will co-develop the Company’s ARO-AAT program. Within the United States, ARO-AAT, if approved, will be co-commercialized under a 50/50 profit sharing structure. Outside the United States, Takeda will lead the global commercialization strategy and receive an exclusive license to commercialize ARO-AAT with the Company eligible to receive tiered royalties of 20% to 25% on net sales. In January 2021, the Company received $300.0 million as an upfront payment and is eligible to receive potential development, regulatory and commercial milestones of up to $740.0 million. On June 18, 2021, the Company entered into a Collaboration and License Agreement (the “Horizon License Agreement”) with Horizon Therapeutics Ireland DAC (“Horizon”). Under the Horizon License Agreement, Horizon has received a worldwide exclusive license for ARO-XDH, a previously undisclosed discovery-stage investigational RNAi therapeutic being developed by the Company as a potential treatment for people with uncontrolled gout. The Company will conduct all activities through the preclinical stages of development of ARO-XDH, and Horizon will be wholly responsible for clinical development and commercialization of ARO-XDH. In July 2021, the Company received $40 million as an upfront payment and is eligible to receive up to $660 million in potential development, regulatory and sales milestones. The Company is also eligible to receive royalties in the low- to mid-teens range on net product sales. The revenue recognition for these collaboration agreements is discussed further in Note 2 below. The Company is actively monitoring the ongoing COVID-19 pandemic. The financial results for the three and nine months ended June 30, 2021 were not significantly impacted by COVID-19. During fiscal year 2020, the Company had temporarily paused enrollment in its two ARO-AAT studies, SEQUOIA and the ARO-AAT 2002 study, but resumed the process of screening and enrolling patients. During the pause in enrollment, patients already enrolled in these studies continued to be dosed per protocol and continued to come in for their follow up visits. Additional delays have occurred in the Company’s earlier stage programs. Additionally, the Company’s operations at its research and development facilities in Madison, Wisconsin and San Diego, California, and its corporate headquarters in Pasadena, California have continued to operate with limited impact, other than for enhanced safety measures, including work from home policies. However, the Company cannot predict the impact the progression of COVID-19 will have on future financial results due to a variety of factors including the ability of the Company’s clinical sites to continue to enroll subjects, the ability of the Company’s suppliers to continue to operate, the continued good health and safety of the Company’s employees, and ultimately the length and severity of the COVID-19 pandemic. Liquidity The Consolidated Financial Statements have been prepared in conformity with the accounting principles generally accepted in the United States of America (“GAAP”), which contemplate the continuation of the Company as a going concern. Historically, the Company’s primary sources of financing have been through the sale of its securities and revenue from its collaboration agreements. Research and development activities have required significant capital investment since the Company’s inception. The Company expects its operations to continue to require cash investment to pursue its research and development goals, including clinical trials and related drug manufacturing. At June 30, 2021, the Company had $326.0 million in cash and cash equivalents (including $2.4 million in restricted cash), $63.9 million in short-term investments, $126.4 million in marketable securities and $128.4 million in long-term investments to fund operations. During the nine months ended June 30, 2021, the Company’s cash and investments balance increased by $191.7 million, which was primarily the result of the $300.0 million upfront payment from the Takeda License Agreement, partially offset by cash used to fund the Company’s research and development operations and general and administrative expenses. Summary of Significant Accounting Policies There have been no changes to the significant accounting policies disclosed in the Company’s most recent Annual Report on Form 10-K. Recent Accounting Pronouncements In November 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2018-18 Collaborative Arrangements (Topic 808). This update provides clarification on the interaction between Revenue Recognition (Topic 606) and Collaborative Arrangements (Topic 808) including the alignment of unit of account guidance between the two topics. ASU 2018-18 became effective for the Company on October 1, 2020 and did not have a material impact on its Consolidated Financial Statements. In August 2018, the FASB issued ASU No. 2018-15 Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. The new standard requires that certain implementation costs for cloud computing arrangements are capitalized and amortized over the term of the associated hosted cloud computing arrangement service. Capitalized implementation costs are classified in prepaid expenses and other assets. The amortization of the capitalized asset is presented in the same line on the statement of operations and comprehensive loss as the fees for the associated hosted cloud computing arrangement service and not included with depreciation or amortization expense related to property and equipment or intangible assets. Cash flows related to capitalized implementation costs are presented in cash flows used in operating activities. ASU 2018-15 became effective for the Company on October 1, 2020 and did not have a material impact on its Consolidated Financial Statements.

Organization and Significant Accounting Policies

9 Months Ended

Jun. 30, 2021

Organization and Significant Accounting Policies

NOTE 1. ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES

Nature of Business and Recent Developments

Arrowhead Pharmaceuticals, Inc. develops medicines that treat intractable diseases by silencing the genes that cause them. Using a broad portfolio of RNA chemistries and efficient modes of delivery, Arrowhead therapies trigger the RNA interference mechanism to induce rapid, deep and durable knockdown of target genes. RNA interference (“RNAi”) is a mechanism present in living cells that inhibits the expression of a specific gene, thereby affecting the production of a specific protein. Arrowhead’s RNAi-based therapeutics leverage this natural pathway of gene silencing. The Company’s pipeline includes ARO-APOC3 for hypertriglyceridemia, ARO-ANG3 for dyslipidemia, ARO-HSD for liver disease, ARO-ENaC for cystic fibrosis, ARO-HIF2 for renal cell carcinoma, ARO-DUX4 for facioscapulohumeral muscular dystrophy, ARO-LUNG2 for chronic obstructive pulmonary disorder, and ARO-COV for the coronavirus that causes COVID-19 and other possible future pulmonary-borne pathogens. ARO-XDH is being developed for uncontrolled gout under a collaboration agreement with Horizon Therapeutics Ireland DAC (“Horizon”). ARO-JNJ1, ARO-JNJ2 and ARO-JNJ3 are being developed for undisclosed liver-expressed targets under a collaboration agreement with Janssen Pharmaceuticals, Inc. (“Janssen”). ARO-AAT for liver disease associated with alpha-1 antitrypsin deficiency (“AATD”) was out-licensed to Takeda Pharmaceuticals U.S.A., Inc. (“Takeda”) in October 2020. JNJ3989 (formerly referred to as ARO-HBV) for chronic hepatitis B virus was out-licensed to Janssen in October 2018. Olpasiran (formerly referred to as AMG 890 or ARO-LPA) for cardiovascular disease was out-licensed to Amgen Inc. (“Amgen”) in 2016.

Arrowhead operates lab facilities in Madison, Wisconsin and San Diego, California, where the Company’s research and development activities, including the development of RNAi therapeutics, take place. The Company’s principal executive offices are located in Pasadena, California.

During fiscal year 2021, the Company continued to develop its pipeline and partnered candidates. The Company announced positive interim clinical data on (i) AROAAT2002, an open-label Phase 2 clinical study of ARO-AAT, the Company’s second-generation investigational RNAi therapeutic being co-developed with Takeda as a treatment for the rare genetic liver disease associated with AATD, (ii) AROHSD1001, a Phase 1/2 clinical study of 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), and (iii) AROHIF21001, a Phase 1b dose-finding clinical study of ARO-HIF2, the Company’s investigational RNAi therapeutic being developed as a treatment for patients with clear cell renal cell carcinoma. The Company also presented preclinical data on the development of ARO-DUX4, the Company’s investigational RNAi therapeutic being developed as a treatment for patients with facioscapulohumeral muscular dystrophy (FSHD), at the 28th Annual FSHD Society International Research Congress. The Company hosted a key opinion leader webinar on its cardiometabolic candidates, ARO-APOC3 and ARO-ANG3, and presented positive clinical data from the Phase 1/2 clinical studies of ARO-APOC3 and ARO-ANG3 at the American Heart Association Scientific Sessions 2020. The Company filed two Investigational New Drug Applications with the United States Food and Drug Administration (the “FDA”) to begin a Phase 2b clinical study of ARO-APOC3 in patients with severe hypertriglyceridemia and a Phase 2b clinical study of ARO-ANG3 in patients with mixed dyslipidemia, and initiated these two Phase 2b clinical studies in the third quarter of fiscal year 2021. In July 2021, the Company voluntarily paused AROENaC1001, a Phase 1/2 clinical study of ARO-ENaC, the Company’s investigational RNAi therapeutic being developed as a treatment for patients with cystic fibrosis, after receiving a preliminary update from an ongoing chronic toxicology study in rats that contained unexpected signals of local lung inflammation. New screening, enrollment and any further dosing of investigational ARO-ENaC have been paused pending additional data from ongoing nonclinical toxicology studies. The Company announced two collaborations during the first three quarters of fiscal year 2021: a collaboration with Takeda to co-develop and co-commercialize ARO-AAT for alpha-1 antitrypsin-associated liver disease and a collaboration with Horizon to develop ARO-XDH, an investigational RNAi therapeutic for uncontrolled gout. In July 2021, the Company received Breakthrough Therapy designation from the FDA for ARO-AAT, which is a process designed to expedite the development and review of drugs that are intended to treat a serious life-threatening disease or condition and preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints. The Company also earned a $10 million payment in connection with Janssen’s exercise of its option right for ARO-JNJ1 in May 2021, which option grants Janssen all rights, including licenses, and obligations to develop and commercialize ARO-JNJ1. See Note 2 for more information regarding the Company’s collaboration and license agreements.

The Company’s partnered candidates under its collaboration agreements also continued to progress. Janssen began dosing patients in a Phase 2b triple combination study called REEF-1, designed to enroll up to 450 patients with chronic hepatitis B infection. The Company is currently performing discovery, optimization and preclinical research and development for ARO-JNJ1, ARO-JNJ2 and ARO-JNJ3 for Janssen as part of the Company’s Research Collaboration and Option Agreement with Janssen (“Janssen Collaboration Agreement”). Under the terms of the Janssen agreements taken together, the Company has received $175.0 million as an upfront payment, $75.0 million in the form of an equity investment by Johnson & Johnson Innovation-JJDC, Inc. (“JJDC”) in Arrowhead Common Stock, and three milestone payments totaling $60.0 million, which include a $10 million payment for Janssen’s exercise of its option right for ARO-JNJ1 in May 2021. The Company may receive up to $1.6 billion in additional development and sales milestones payments for the Janssen License Agreement, and up to $1.9 billion in additional development and sales milestone payments for the three additional targets covered under the Janssen Collaboration Agreement. The Company is further eligible to receive tiered royalties on product sales up to mid-teens under the Janssen License Agreement and up to low teens under the Janssen Collaboration Agreement.

The Company’s collaboration agreement with Amgen for Olpasiran (previously referred to as AMG 890 or ARO-LPA) (the “Second Collaboration and License Agreement” or “Olpasiran Agreement”) continues to progress. In July 2020, Amgen initiated a Phase 2 clinical study, which resulted in a $20.0 million milestone payment to the Company. The Company has received $35.0 million in upfront payments, $21.5 million in the form of an equity investment by Amgen in the Company’s Common Stock, $30.0 million in milestone payments, and may receive up to an additional $400.0 million in remaining development, regulatory and sales milestone payments. The Company is eligible to receive up to low double-digit royalties for sales of products under the Olpasiran Agreement.

On October 7, 2020, the Company entered into an Exclusive License and Co-Funding Agreement with Takeda (the “Takeda License Agreement”). Under the Takeda License Agreement, Takeda and the Company will co-develop the Company’s ARO-AAT program. Within the United States, ARO-AAT, if approved, will be co-commercialized under a 50/50 profit sharing structure. Outside the United States, Takeda will lead the global commercialization strategy and receive an exclusive license to commercialize ARO-AAT with the Company eligible to receive tiered royalties of 20% to 25% on net sales. In January 2021, the Company received $300.0 million as an upfront payment and is eligible to receive potential development, regulatory and commercial milestones of up to $740.0 million.

On June 18, 2021, the Company entered into a Collaboration and License Agreement (the “Horizon License Agreement”) with Horizon Therapeutics Ireland DAC (“Horizon”). Under the Horizon License Agreement, Horizon has received a worldwide exclusive license for ARO-XDH, a previously undisclosed discovery-stage investigational RNAi therapeutic being developed by the Company as a potential treatment for people with uncontrolled gout. The Company will conduct all activities through the preclinical stages of development of ARO-XDH, and Horizon will be wholly responsible for clinical development and commercialization of ARO-XDH. In July 2021, the Company received $40 million as an upfront payment and is eligible to receive up to $660 million in potential development, regulatory and sales milestones. The Company is also eligible to receive royalties in the low- to mid-teens range on net product sales.

The revenue recognition for these collaboration agreements is discussed further in Note 2 below.

The Company is actively monitoring the ongoing COVID-19 pandemic. The financial results for the three and nine months ended June 30, 2021 were not significantly impacted by COVID-19. During fiscal year 2020, the Company had temporarily paused enrollment in its two ARO-AAT studies, SEQUOIA and the ARO-AAT 2002 study, but resumed the process of screening and enrolling patients. During the pause in enrollment, patients already enrolled in these studies continued to be dosed per protocol and continued to come in for their follow up visits. Additional delays have occurred in the Company’s earlier stage programs. Additionally, the Company’s operations at its research and development facilities in Madison, Wisconsin and San Diego, California, and its corporate headquarters in Pasadena, California have continued to operate with limited impact, other than for enhanced safety measures, including work from home policies. However, the Company cannot predict the impact the progression of COVID-19 will have on future financial results due to a variety of factors including the ability of the Company’s clinical sites to continue to enroll subjects, the ability of the Company’s suppliers to continue to operate, the continued good health and safety of the Company’s employees, and ultimately the length and severity of the COVID-19 pandemic.

Liquidity

The Consolidated Financial Statements have been prepared in conformity with the accounting principles generally accepted in the United States of America (“GAAP”), which contemplate the continuation of the Company as a going concern. Historically, the Company’s primary sources of financing have been through the sale of its securities and revenue from its collaboration agreements. Research and development activities have required significant capital investment since the Company’s inception. The Company expects its operations to continue to require cash investment to pursue its research and development goals, including clinical trials and related drug manufacturing.

At June 30, 2021, the Company had $326.0 million in cash and cash equivalents (including $2.4 million in restricted cash), $63.9 million in short-term investments, $126.4 million in marketable securities and $128.4 million in long-term investments to fund operations. During the nine months ended June 30, 2021, the Company’s cash and investments balance increased by $191.7 million, which was primarily the result of the $300.0 million upfront payment from the Takeda License Agreement, partially offset by cash used to fund the Company’s research and development operations and general and administrative expenses.

Summary of Significant Accounting Policies

There have been no changes to the significant accounting policies disclosed in the Company’s most recent Annual Report on Form 10-K.

Recent Accounting Pronouncements

In November 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2018-18 Collaborative Arrangements (Topic 808). This update provides clarification on the interaction between Revenue Recognition (Topic 606) and Collaborative Arrangements (Topic 808) including the alignment of unit of account guidance between the two topics. ASU 2018-18 became effective for the Company on October 1, 2020 and did not have a material impact on its Consolidated Financial Statements.

In August 2018, the FASB issued ASU No. 2018-15 Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. The new standard requires that certain implementation costs for cloud computing arrangements are capitalized and amortized over the term of the associated hosted cloud computing arrangement service. Capitalized implementation costs are classified in prepaid expenses and other assets. The amortization of the capitalized asset is presented in the same line on the statement of operations and comprehensive loss as the fees for the associated hosted cloud computing arrangement service and not included with depreciation or amortization expense related to property and equipment or intangible assets. Cash flows related to capitalized implementation costs are presented in cash flows used in operating activities. ASU 2018-15 became effective for the Company on October 1, 2020 and did not have a material impact on its Consolidated Financial Statements.