Arrowhead Pharmaceuticals (ARWR) 10-Q 10 May 22 2022 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Mar. 31, 2022	May 05, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2
Trading Symbol	ARWR
Entity Registrant Name	ARROWHEAD PHARMACEUTICALS, INC.
Entity Central Index Key	0000879407
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--09-30
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		105,736,200
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity File Number	001-38042
Entity Tax Identification Number	46-0408024
Entity Address, Address Line One	177 E. Colorado Blvd
Entity Address, Address Line Two	Suite 700
Entity Address, City or Town	Pasadena
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	91105
City Area Code	626
Local Phone Number	304-3400
Document Quarterly Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Entity Interactive Data Current	Yes

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2022	Sep. 30, 2021
CURRENT ASSETS
Cash and cash equivalents	$ 86,408	$ 184,434
Accounts receivable	1,317	10,255
Prepaid expenses	6,622	4,362
Other current assets	7,796	2,191
Marketable securities	122,575	126,728
Short term investments	192,912	56,627
TOTAL CURRENT ASSETS	417,630	384,597
Property and equipment, net	54,888	48,675
Intangible assets, net	12,813	13,663
Long term investments	201,590	245,595
Right-of-use assets	16,379	17,346
Other assets	275	272
TOTAL ASSETS	703,575	710,148
CURRENT LIABILITIES
Accounts payable	10,603	9,457
Accrued expenses	23,710	14,001
Accrued payroll and benefits	3,765	9,773
Lease liabilities	2,910	2,250
Deferred revenue	97,869	111,055
TOTAL CURRENT LIABILITIES	138,857	146,536
LONG-TERM LIABILITIES
Lease liabilities, net of current portion	22,698	23,295
Deferred revenue, net of current portion	89,754	131,495
TOTAL LONG-TERM LIABILITIES	112,452	154,790
Commitments and contingencies (Note 7)
Arrowhead Pharmaceuticals, Inc. stockholders’ equity:
Common stock, $0.001 par value; 145,000 shares authorized; 105,702 and 104,327 shares issued and outstanding as of March 31, 2022 and September 30, 2021, respectively	198	197
Additional paid-in capital	1,115,373	1,053,386
Accumulated other comprehensive loss	(107)	(69)
Accumulated deficit	(663,198)	(644,692)
TOTAL STOCKHOLDERS’ EQUITY	452,266	408,822
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 703,575	$ 710,148

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2022	Sep. 30, 2021
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	145,000,000	145,000,000
Common stock, shares issued	105,702,000	104,327,000
Common stock, shares outstanding	105,702,499	104,327,000

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Income (Loss) (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Income Statement [Abstract]
REVENUE	$ 151,805	$ 32,811	$ 179,244	$ 54,113
OPERATING EXPENSES
Research and development	75,985	44,697	141,750	81,251
General and administrative expenses	34,267	16,346	59,262	25,147
TOTAL OPERATING EXPENSES	110,252	61,043	201,012	106,398
OPERATING INCOME (LOSS)	41,553	(28,232)	(21,768)	(52,285)
OTHER INCOME (EXPENSE)
Interest income, net	1,054	1,524	2,210	3,692
Other income (expense)	1,759	(110)	1,052	1,043
TOTAL OTHER INCOME (EXPENSE)	2,813	1,414	3,262	4,735
INCOME (LOSS) BEFORE INCOME TAXES	44,366	(26,818)	(18,506)	(47,550)
NET INCOME (LOSS)	$ 44,366	$ (26,818)	$ (18,506)	$ (47,550)
NET INCOME (LOSS) PER SHARE - BASIC	$ 0.42	$ (0.26)	$ (0.18)	$ (0.46)
NET INCOME (LOSS) PER SHARE - DILUTED	$ 0.41	$ (0.26)	$ (0.18)	$ (0.46)
Weighted average shares outstanding - basic	105,545	103,867	105,034	103,303
Weighted average shares outstanding - diluted	107,929	103,867	105,034	103,303
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX:
Foreign currency translation adjustments	$ 1	$ (96)	$ (38)	$ 84
COMPREHENSIVE INCOME (LOSS)	$ 44,367	$ (26,914)	$ (18,544)	$ (47,466)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity (unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning Balance, Amount at Sep. 30, 2020	$ 461,779	$ 195	$ 965,410	$ 18	$ (503,844)
Beginning Balance, Shares at Sep. 30, 2020		102,376,000
Stock-based compensation	23,502		23,502
Exercise of stock options, Amount	7,734		7,734
Exercise of stock options, Shares		820,000
Common stock - restricted stock units vesting, Amount		$ 1	(1)
Common stock - restricted stock units vesting, Shares		824,000
Foreign currency translation adjustments	84			84
Net income (loss)	(47,550)				(47,550)
Ending Balance, Amount at Mar. 31, 2021	445,549	$ 196	996,645	102	(551,394)
Ending Balance, Shares at Mar. 31, 2021		104,020,000
Beginning Balance, Amount at Dec. 31, 2020	454,472	$ 195	978,655	198	(524,576)
Beginning Balance, Shares at Dec. 31, 2020		103,194,000
Stock-based compensation	15,359		15,359
Exercise of stock options, Amount	2,632		2,632
Exercise of stock options, Shares		282,000
Common stock - restricted stock units vesting, Amount		$ 1	(1)
Common stock - restricted stock units vesting, Shares		544,000
Foreign currency translation adjustments	(96)			(96)
Net income (loss)	(26,818)				(26,818)
Ending Balance, Amount at Mar. 31, 2021	445,549	$ 196	996,645	102	(551,394)
Ending Balance, Shares at Mar. 31, 2021		104,020,000
Beginning Balance, Amount at Sep. 30, 2021	408,822	$ 197	1,053,386	(69)	(644,692)
Beginning Balance, Shares at Sep. 30, 2021		104,327,000
Stock-based compensation	58,306		58,306
Exercise of stock options, Amount	$ 3,682		3,682
Exercise of stock options, Shares	444,764	444,000
Common stock - restricted stock units vesting, Amount		$ 1	(1)
Common stock - restricted stock units vesting, Shares		931,000
Foreign currency translation adjustments	$ (38)			(38)
Net income (loss)	(18,506)				(18,506)
Ending Balance, Amount at Mar. 31, 2022	452,266	$ 198	1,115,373	(107)	(663,198)
Ending Balance, Shares at Mar. 31, 2022		105,702,000
Beginning Balance, Amount at Dec. 31, 2021	372,560	$ 197	1,080,035	(108)	(707,564)
Beginning Balance, Shares at Dec. 31, 2021		104,798,000
Stock-based compensation	33,802		33,802
Exercise of stock options, Amount	1,537		1,537
Exercise of stock options, Shares		237,000
Common stock - restricted stock units vesting, Amount		$ 1	(1)
Common stock - restricted stock units vesting, Shares		667,000
Foreign currency translation adjustments	1			1
Net income (loss)	44,366				44,366
Ending Balance, Amount at Mar. 31, 2022	$ 452,266	$ 198	$ 1,115,373	$ (107)	$ (663,198)
Ending Balance, Shares at Mar. 31, 2022		105,702,000

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ (18,506)	$ (47,550)
Stock-based compensation	58,307	23,502
Depreciation and amortization	5,167	3,766
Unrealized (gains) losses on marketable securities	4,153	(773)
Amortization/(accretion) of note premiums/discounts	329	193
Changes in operating assets and liabilities:
Accounts receivable	8,938	(109)
Prepaid expenses and other current assets	(7,914)	(2,213)
Deferred revenue	(54,926)	247,118
Accounts payable	1,146	(1,530)
Accrued expenses	3,699	2,271
Other	990	276
NET CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES	1,383	224,951
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(10,530)	(11,437)
Purchases of investments	(148,391)	(40,000)
Proceeds from sale of investments	55,781	47,545
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES	(103,140)	(3,892)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from the exercises of stock options	3,731	7,735
NET CASH PROVIDED BY FINANCING ACTIVITIES	3,731	7,735
NET INCREASE (DECREASE) IN CASH	(98,026)	228,794
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	184,434	143,583
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$ 86,408	$ 372,377

Organization and Significant Ac

Organization and Significant Accounting Policies	6 Months Ended
	Mar. 31, 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-ENaC2 for cystic fibrosis, ARO-DUX4 for facioscapulohumeral muscular dystrophy, ARO-COV for the coronavirus that causes COVID-19 and other possible future pulmonary-borne pathogens, ARO-C3 for complement mediated diseases and ARO-RAGE and ARO-MUC5AC for various muco-obstructive or inflammatory pulmonary conditions. ARO-HSD for liver disease was out-licensed to Glaxosmithkline (“GSK”) in November 2021. ARO-XDH is being developed for uncontrolled gout under a collaboration agreement with Horizon Therapeutics Ireland DAC (“Horizon”). JNJ-75220795 (ARO-JNJ1) is being developed by Janssen as a potential treatment for patients with non-alcoholic steatohepatitis (NASH). for chronic hepatitis B virus was out-licensed to Janssen in October 2018. 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 the first half of fiscal 2022, the Company continued to develop and advance its pipeline and partnered candidates and expanded its facilities to support the Company’s growing pipeline. Several key recent developments include: i) dosed the first patients in its PALISADE study, a phase 3 clinical study to evaluate the safety and efficacy of ARO-APOC3 in adults with familial chylomicronemia syndrome (FCS); ii) entered into an exclusive license agreement with GSK for ARO-HSD; iii) Janssen presented clinical data from REEF-1, a Phase 2b study of different combination regimens, including JNJ-73763989 (JNJ-3989), formerly called ARO-HBV, and/or JNJ-56136379 (JNJ-6379), and a nucleos(t)ide analog (NA) for the treatment of chronic hepatitis B virus infection (CHB); iv) filed for regulatory clearance to begin a Phase 1/2a study of ARO-C3 and subsequently dosed the first subjects in AROC3-1001, a Phase 1/2 clinical study of ARO-C3, the Company’s i nvestigational RNA interference (RNAi) therapeutic designed to reduce production of complement component 3 (C3) as a potential therapy for various complement mediated diseases; v) presented additional interim clinical data from AROHSD1001, AROAAT2002, and AROAPOC31001; vi) completed the purchase of 13 acres of land in the Verona Technology Park in Verona, Wisconsin, which is planned to be the site of an approximately 140,000 square foot drug manufacturing facility and an approximately 115,000 square foot laboratory and office facility and entered into a lease agreement for a new 144,000 square foot laboratory and office facility in San Diego, California. Both facilities will provide additional space to support the Company’s continued growth ; vii) completed enrollment in Phase 2b ARCHES-2 study of investigational ARO-ANG3 for patients with mixed dyslipidemia ; viii) filed for regulatory clearance to initiate Phase 1/2a study of ARO-RAGE for treatment of Asthma; ix) filed for regulatory clearance to initiate Phase 1/2a study of ARO-MUC5AC for treatment of muco-obstructive lung disease; x) initiated and dosed the first patients in the Phase 2 GATEWAY clinical study of investigational ARO-ANG3 for the treatment of patients with homozygous familial hypercholersterolemia; xi) decided not to pursue further clinical development of ARO-HIF2 based on a number of factors including the evolving competitive landscape for HIF2 inhibitors. The Company is actively monitoring the ongoing COVID-19 pandemic. The financial results for the three and six months ended March 31, 2022 were not significantly impacted by COVID-19. Operationally, the Company has experienced delays in its earlier stage programs due to a shortage in non-human primates, which are critical to the Company’s preclinical programs. Additionally, the Company has experienced delays in enrollment in its clinical trials. 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 with limited impact, other than for enhanced safety measures, including work from home policies and intermittent lab supply shortages. However, the Company cannot predict the impact the progression of COVID-19 will have on future financial and operational 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 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 licensing and collaboration agreements. Research and development activities have required significant capital investment since the Company’s inception and are expected to continue to require significant cash expenditure in the future, particularly as the Company’s pipeline of drug candidates and its headcount have both expanded significantly. Additionally, significant capital investment will be required as the Company’s pipeline matures into later stage clinical trials, as well as with the Company’s plans to increase its internal manufacturing capabilities, as well as expand its footprint in Verona, Wisconsin and San Diego, California. At March 31, 2022, the Company had $86.4 million in cash and cash equivalents (including $7.9 million in restricted cash), $192.9 million in short-term investments, $122.6 million in marketable securities and $201.6 million in long-term investments to fund operations. During the six months ended March 31, 2022, the Company’s cash and investments balance decreased by $9.9 million, which was primarily due to cash being used to fund the Company’s operations, partially offset by the $120.0 million upfront payment received from GSK. In total, the Company remains eligible for $ . 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 There have been no recent accounting pronouncements that have significantly impacted this Quarterly Report on Form 10-Q, beyond those disclosed in the Company’s most recent Annual Report on Form 10-K.

Collaboration and License Agree

Collaboration and License Agreements	6 Months Ended
	Mar. 31, 2022
Collaboration And License Agreements [Abstract]
Collaboration and License Agreements	NOTE 2. COLLABORATION AND LICENSE AGREEMENTS Amgen Inc. On September 28, 2016, the Company entered into two collaboration and license agreements and a common stock purchase agreement with Amgen. Under the Second Collaboration and License Agreement (the “Olpasiran Agreement”), Amgen has received a worldwide, exclusive license to Arrowhead’s novel RNAi Olpasiran (previously referred to as AMG 890 or ARO-LPA) program. These RNAi molecules are designed to reduce elevated lipoprotein(a), which is a genetically validated, independent risk factor for atherosclerotic cardiovascular disease. Under the prior collaboration and license agreement (the “First Collaboration and License Agreement” or the “ARO-AMG1 Agreement”), Amgen received an option to a worldwide, exclusive license for ARO-AMG1, an RNAi therapy for an undisclosed genetically validated cardiovascular target. Under both agreements, Amgen is wholly responsible for clinical development and commercialization. Under the terms of the agreements taken together, 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, and $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 further eligible to receive up to low double-digit royalties for sales of products under the Olpasiran Agreement. In July 2019, Amgen informed the Company that it would not be exercising its option for an exclusive license for ARO-AMG1, and as such, there will be no further milestone or royalty payments under the ARO-AMG1 Agreement. The Company has evaluated these agreements in accordance with FASB Topics 808 – Collaboration Arrangements and 606 - Revenue for Contracts from Customers. The Company has substantially completed its performance obligations under the Olpasiran Agreement and the ARO-AMG1 Agreement. Future milestones and royalties achieved will be recognized in their entirety when earned. In July 2020, Amgen initiated a Phase 2 clinical study of Olpasiran, which resulted in a $20.0 million milestone payment to the Company. During the three and six months ended March 31, 2022 and 2021, the Company recognized $0 and $0 of revenue associated with its agreement with Amgen, respectively. Janssen Pharmaceuticals, Inc. On October 3, 2018, the Company entered into a License Agreement (the “Janssen License Agreement”) and a Research Collaboration and Option Agreement (the “Janssen Collaboration Agreement”) with Janssen, part of the Janssen Pharmaceutical Companies of Johnson & Johnson. The Company also entered into a stock purchase agreement with JJDC (“JJDC Stock Purchase Agreement”). Under the Janssen License Agreement, Janssen has received a worldwide, exclusive license to the Company’s JNJ-3989 (ARO-HBV) program, the Company’s third-generation subcutaneously administered RNAi therapeutic candidate being developed as a potential therapy for patients with chronic hepatitis B virus infection. Beyond the Company’s Phase 1/2 study of JNJ-3989 (ARO-HBV), which the Company was responsible for completing, Janssen is wholly responsible for clinical development and commercialization of JNJ-3989. Under the Janssen Collaboration Agreement, Janssen was able to select three new targets against which Arrowhead would develop clinical candidates. These candidates were subject to certain restrictions and do not include candidates that already were in the Company’s pipeline. The Company was obligated to perform discovery, optimization and preclinical research and development, entirely funded by Janssen, which on its own or in combination with Janssen development work, would have been sufficient to allow the filing of a U.S. Investigational New Drug Application or equivalent, at which time Janssen would have the option to take an exclusive license. If the option was exercised, Janssen would have been wholly responsible for clinical development and commercialization of each optioned candidate. Under the terms of the 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 JJDC in Arrowhead Common Stock under the JJDC The Company has evaluated these agreements in accordance with FASB Topics 808 – Collaboration Arrangements and 606 - Revenue for Contracts from Customers. At the inception of these agreements, the Company identified one distinct performance obligation. Regarding the Janssen License Agreement, the Company determined that the key deliverables included the license and certain R&D services including the Company’s responsibility to complete the Phase 1/2 study of JNJ-3989 (ARO-HBV) and the Company’s responsibility to ensure certain manufacturing of JNJ-3989 (ARO-HBV) drug product is completed and delivered to Janssen (the “Janssen R&D Services”). Due to the specialized and unique nature of these Janssen R&D Services and their direct relationship with the license, the Company determined that these deliverables represent one distinct bundle and, thus, one performance obligation. The Company also determined that Janssen’s option to require the Company to develop up to three new targets is not a material right and, thus, not a performance obligation at the onset of the agreement. The consideration for this option is accounted for separately. The Company determined the transaction price totaled approximately $252.7 million, which includes the upfront payment, the premium paid by JJDC for its equity investment in the Company, two $25.0 million milestone payments related to JNJ-3989 (ARO-HBV), and estimated payments for reimbursable Janssen R&D Services to be performed. The Company has allocated the total $252.7 million initial transaction price to its one distinct performance obligation for the JNJ-3989 (ARO-HBV) license and the associated Janssen R&D Services. The Company has recognized this transaction price in its entirety as of September 30, 2021, as its performance obligations were substantially completed. Future milestones and royalties achieved will be recognized in their entirety when earned. During the three months ended March 31, 2022 and 2021, the Company recognized approximately $0 and $7.5 million of revenue associated with this performance obligation, respectively. During the six months ended March 31, 2022 and 2021, the Company recognized approximately $0 and $20.2 million of revenue associated with this performance obligation, respectively. As of March 31, 2022, there were $0 in contract assets recorded as accounts receivable, and $0 of contract liabilities recorded as current deferred revenue on the Company’s Consolidated Balance Sheets. The Company has conducted its discovery, optimization and preclinical research and development of JNJ-75220795 (ARO-JNJ1), ARO-JNJ2, and ARO-JNJ3 under the Janssen Collaboration Agreement. All costs and labor hours spent by the Company have been entirely funded by Janssen. During the three months ended March 31, 2022, Janssen’s option period expired unexercised for two of the three candidates (ARO-JNJ2 and ARO-JNJ3) under the Janssen Collaboration Agreement . During the three months ended , 2022 and 2021, the Company recognized $0.1 million and $0.1 million of revenue associated with these efforts, respectively. During the six months ended , 2022 and 2021, the Company recognized $0.1 million and $0.3 million of revenue associated with these efforts, respectively. As of , 2022, there were $ million of cont receivable and $ of contract liabilities recorded as curren Sheets. Takeda Pharmaceuticals U.S.A., Inc. On October 7, 2020, the Company entered into an Exclusive License and Co-funding agreement (the “Takeda License Agreement”) with Takeda. Under the Takeda License Agreement, Takeda and the Company will co-develop the Company’s ARO-AAT program, the Company’s second-generation subcutaneously administered RNAi therapeutic candidate being developed as a treatment for liver disease associated with alpha-1 antitrypsin deficiency. 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 will receive an exclusive license to commercialize ARO-AAT, while the Company will be 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. The Company has evaluated the Takeda License Agreement in accordance with FASB Topics 808 – Collaborative Arrangements and 606 - Revenue for Contracts from Customers. At the inception of the Takeda License Agreement, the Company identified one distinct performance obligation. The Company determined that the key deliverables included the license and certain R&D services including the Company’s responsibilities to complete the initial portion of the SEQUOIA study, to complete the ongoing Phase 2 AROAAT2002 study and to ensure certain manufacturing of ARO-AAT drug product is completed and delivered to Takeda (the “Takeda R&D Services”). Due to the specialized and unique nature of these Takeda R&D Services and their direct relationship with the license, the Company determined that these deliverables represent one distinct bundle and, thus, one performance obligation. Beyond the Takeda R&D Services, which are the responsibility of the Company, Takeda will be responsible for managing future clinical development and commercialization outside the United States. Within the United States, the Company will also participate in co-development and co-commercialization efforts and will co-fund these efforts with Takeda as part of the 50/50 profit sharing structure within the United States. The Company considers the collaborative activities, including the co-development and co-commercialization, to be a separate unit of account within Topic 808, and as such, these co-funding amounts will be recorded as Research and Development Expenses or General and Administrative Expenses, as appropriate. The Company determined the initial transaction price totaled $300.0 million, which includes the upfront payment. The Company has excluded any future milestones or royalties from this transaction price to date. The Company has allocated the total $300.0 million initial transaction price to its one distinct performance obligation for the ARO-AAT license and the associated Takeda R&D Services. Revenue will be recognized using a proportional performance method (based on actual patient visits completed versus total estimated visits completed for the ongoing SEQUOIA and AROAAT2002 clinical studies). Revenue for the three months ended March 31, 2022 and 2021 was $20.8 million and $25.4 million, respectively. Revenue for the six months ended March 31, 2022 and 2021 was $41.6 million and $33.6 million, respectively. As of March 31, 2022, there were $0 in contract assets recorded as accounts receivable, $77.9 million in contract liabilities recorded as deferred revenue and $89.8 million in contract liabilities recorded as deferred revenue, net of the current portion, and $5.0 million in contract liabilities recorded as accrued expenses. The $5.0 million in accrued expenses was primarily driven by co-development and co-commercialization activities. Horizon Therapeutics Ireland DAC On June 18, 2021, the Company entered into the Horizon License Agreement with Horizon. Under the Horizon License Agreement, Horizon 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 Company has evaluated the Horizon License Agreement in accordance with FASB Topics 808 – Collaborative Arrangements and 606 - Revenue for Contracts from Customers. At the inception of the Horizon License Agreement, the Company identified one distinct performance obligation. The Company determined that the key deliverables included the license and certain R&D services, including the Company’s responsibilities to conduct all activities through the preclinical stages of development of ARO-XDH (the “Horizon R&D Services”). Due to the specialized and unique nature of these Horizon R&D Services and their direct relationship with the license, the Company determined that these deliverables represented one distinct bundle and, thus, one performance obligation. Beyond the Horizon R&D Services, which are the responsibility of the Company, Horizon will be responsible for managing future clinical development and commercialization of ARO-XDH. The Company determined the initial transaction price totaled $40.0 million, including the upfront payment. The Company has excluded any future estimated milestones or royalties, from this transaction price to date. The Company will allocate the total $40.0 million initial transaction price to its one distinct performance obligation for the ARO-XDH license and the associated Horizon R&D Services. Revenue will be recognized on a straight-line basis over the estimated timeframe for completing the Horizon R&D Services. The Company determined that the straight-line basis was appropriate as its efforts will be expended evenly over the course of completing its performance obligation. Revenue for the three months ended March 31, 2022 and 2021 was $6.7 million and $0, respectively. Revenue for the six months ended March 31, 2022 and 2021 was $13.3 million and $0, respectively. As of March 31, 2022, there were $0 million in contract assets recorded as accounts receivable, $20.0 million in contract liabilities recorded as deferred revenue. As of , 2022, there were $1.3 million of cont receivable and $0 of contract liabilities recorded as curren Sheets. Glaxosmithkline Intellectual Property (No. 3) Limited On November 22, 2021, the Company entered into an Exclusive License Agreement (the “GSK License Agreement”) with 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 retained rights to develop and commercialize. itory. Under the terms of the agreement, the Company has received 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 the Company of up to $190 million at first commercial sale, and up to $590 million in sales-related milestone payments. The Company is further eligible to receive tiered royalties on net product sales in a range of mid-teens to twenty percent. The Company has evaluated the GSK License Agreement in accordance with FASB Topics 808 – Collaborative Arrangements and 606 - Revenue for Contracts from Customers. At the inception of the GSK License Agreement, the Company identified one distinct performance obligation. The Company determined that the key deliverables included the license and certain R&D services, including the Company’s responsibility to complete the Phase 1/2 study, (the “GSK R&D Services”). Due to the specialized and unique nature of these GSK R&D Services and their direct relationship with the license, the Company determined that these deliverables represented one distinct bundle and, thus, one performance obligation. Beyond the GSK R&D Services, which are the responsibility of the Company, GSK will be responsible for managing future clinical development and commercialization in its territory. The Company determined the initial transaction price totaled $120.0 million, including the upfront payment. The $120.0 million upfront payment was collected in January 2022. The Company has excluded any future estimated milestones or royalties from this transaction price to date. The Company has allocated the total $120.0 million initial transaction price to its one distinct performance obligation for the ARO-HSD license and the associated GSK R&D Services. As the Company has completed its performance obligation related to this agreement, the upfront payment of $120.0 million will be fully recognized as of the three and six months ended March 31, 2022. Revenue for the three and six months ended March 31, 2022 and 2021 was $120.0 million and $0, respectively. As of March 31, 2022, there were $0 in contract assets recorded as accounts receivable, $0 in contract liabilities recorded as deferred revenue.

Property and Equipment

Property and Equipment	6 Months Ended
	Mar. 31, 2022
Property Plant And Equipment [Abstract]
Property and Equipment	NOTE 3. PROPERTY AND EQUIPMENT The following table summarizes the Company’s major classes of property and equipment: March 31, 2022 September 30, 2021 (In thousands) Computers, software, office equipment and furniture $ 2,272 $ 2,170 Research equipment 28,370 27,500 Leasehold improvements 42,017 41,524 Construction in Progress 6,414 345 Land 2,996 - Total gross fixed assets 82,069 71,539 Less: Accumulated depreciation and amortization (27,181 ) (22,864 ) Property and equipment, net $ 54,888 $ 48,675 Depreciation and amortization expense for property and equipment for the three months ended March 31, 2022 and 2021 was $2.2 million and $1.5 million, respectively. Depreciation and amortization expense for property and equipment for the six months ended March 31, 2022 and 2021 was $4.3 million and $2.9 million, respectively. Construction in Progress relates to the Company’s Verona and San Diego research facilities. Land relates to the Company’s Verona, Wisconsin research facility.

Investments

Investments	3 Months Ended
	Dec. 31, 2021
Held To Maturity Securities Classified [Abstract]
Investments	NOTE 4. INVESTMENTS Investments at March 31, 2022 primarily consisted of corporate bonds that have maturities of less than 36 months, a certificate of deposit and marketable equity securities. The Company’s corporate bonds consist of both short-term and long-term bonds and are classified as “held-to-maturity” on the Company’s Consolidated Balance Sheets. The Company’s certificate of deposit matures in less than 12 months and is classified as “held-to-maturity” on the Company’s Consolidated Balance Sheet, or classified as cash and cash equivalents if the corporate bonds are purchased 90 days or less from maturity. The Company’s marketable equity securities consist of mutual funds that primarily invest in U.S. government bonds, U.S. government agency bonds, corporate bonds and other asset-backed debt securities. Dividends from these funds are automatically re-invested. The Company may also invest excess cash balances in money market accounts, government-sponsored enterprise securities, and/or commercial paper. These securities are classified as cash and cash equivalents on the Company’s Consolidated Balance Sheet. The Company accounts for its held to maturity investments in accordance with FASB ASC 320, Investments – Debt and Equity Securities and its marketable equity securities in accordance with ASC 321, Investments – Equity Securities. We did not record any impairment charges related to our marketable debt securities during the three and six months ended March 31, 2022. The following tables summarize the Company’s short-term and long-term investments and marketable securities as of March 31, 2022 and September 30, 2021 by measurement category: As of March 31, 2022 (In thousands) Cost Basis Gross Unrealized Gains Gross Unrealized Losses Fair Value Classified as Cash Equivalents Commercial notes (due within ninety days) $ 26,678 $ 1 $ (1 ) $ 26,678 Classified as Held to Maturity Commercial notes (due within one year) $ 142,912 $ 225 $ (307 ) $ 142,830 Commercial notes (due within one through three years) $ 201,590 $ - $ (5,864 ) $ 195,726 Certificate of deposit (due within one year) $ 50,000 $ - $ - $ 50,000 Classified as Marketable Securities Marketable securities $ 128,805 $ - $ (6,230 ) $ 122,575 Total $ 549,985 $ 226 $ (12,402 ) $ 537,809 As of September 30, 2021 (In thousands) Cost Basis Gross Unrealized Gains Gross Unrealized Losses Fair Value Classified as Held to Maturity Commercial notes (due within one year) $ 56,627 $ 803 $ - $ 57,430 Commercial notes (due within one through three years) $ 195,595 $ 1,151 $ (103 ) $ 196,643 Certificate of deposit (due within one through two years) $ 50,000 $ - $ - $ 50,000 Classified as Marketable Securities Marketable securities $ 127,481 $ - $ (753 ) $ 126,728 Total $ 429,703 $ 1,954 $ (856 ) $ 430,801

Intangible Assets

Intangible Assets	6 Months Ended
	Mar. 31, 2022
Goodwill And Intangible Assets Disclosure [Abstract]
Intangible Assets	NOTE 5. INTANGIBLE ASSETS Intangible assets subject to amortization include patents and a license agreement capitalized as part of the Novartis RNAi asset acquisition in March 2015. The license agreement associated with the Novartis RNAi asset acquisition is being amortized over the estimated life remaining at the time of acquisition, which was 21 years, and the accumulated amortization of the asset is $1.1 million. The patents associated with the Novartis RNAi asset acquisition are being amortized over the estimated life remaining at the time of acquisition, which was 14 years, and the accumulated amortization of the assets is $11.0 million. Amortization expense for the three months ended March 31, 2022 and 2021 was $0.4 million and $0.4 million, respectively. Amortization expense for the six months ended March 31, 2022 and 2021 was $0.9 million and $0.9 million, respectively. Amortization expense is expected to be $0.9 million for the remainder of fiscal The following table provides details on the Company’s intangible asset balances: Intangible Assets Subject to Amortization (in thousands) Balance at September 30, 2021 $ 13,663 Impairment - Amortization (850 ) Balance at March 31, 2022 $ 12,813

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Mar. 31, 2022
Equity [Abstract]
Stockholders' Equity	NOTE 6. STOCKHOLDERS’ EQUITY At March 31, 2022, the Company had a total of 150,000,000 shares of capital stock authorized for issuance, consisting of 145,000,000 shares of Common Stock, par value $0.001 per share, and 5,000,000 shares of Preferred Stock, par value $0.001 per share. At March 31, 2022, 105,702,499 In August 2020, the Company entered into an Open Market Sale Agreement (the “ATM Agreement”), pursuant to which the Company may, from time to time, sell up to $250,000,000 in shares of the Company’s Common Stock through Jefferies LLC, acting as the sales agent and/or principal, in an at-the-market offering. The Company is not required to sell shares under the ATM Agreement. The Company will pay Jefferies LLC a commission of up to 3.0% of the aggregate gross proceeds received from all sales of the common stock under the ATM Agreement. Unless otherwise terminated, the ATM Agreement continues until the earlier of selling all shares available under the ATM Agreement or December 2, 2022. At March 31, 2022, no shares have been sold under the ATM Agreement.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Mar. 31, 2022
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	NOTE 7. COMMITMENTS AND CONTINGENCIES Litigation From time to time, the Company may be subject to various claims and legal proceedings in the ordinary course of business. If the potential loss from any claim, asserted or unasserted, or legal proceeding is considered probable and the amount is reasonably estimable, the Company will accrue a liability for the estimated loss. There were no contingent liabilities recorded as of March 31, 2022. Commitments On December 20, 2021, the Company completed a purchase of 13 acres of land in the Verona Technology Park in Verona, WI, which is planned to be the site of an approximately 140,000 square foot drug manufacturing facility and an approximately 115,000 square foot laboratory and office facility to support process development and analytical activities. Arrowhead intends to invest between $200 million and $250 million into the buildout of the facilities. As part of this acquisition, the Company also entered into a development agreement with the City of Verona to construct certain infrastructure improvements within the TIF district, and will be reimbursed by the City of Verona by future tax increment revenue generated from the developed property. The total amount of funding that City of Verona will pay as reimbursements under the TIF program for these improvements is not guaranteed and will depend on future tax revenues generated from the developed property. Technology License Commitments The Company has licensed from third parties the rights to use certain technologies for its research and development activities, as well as in any products the Company may develop using these licensed technologies. These agreements and other similar agreements often require milestone and royalty payments. Milestone payments, for example, may be required as the research and development process progresses through various stages of development, such as when clinical candidates enter or progress through clinical trials, upon a new drug application and upon certain sales level milestones. These milestone payments could amount to the mid to upper double-digit millions of dollars. During the three and six months ended March 31, 2022 and 2021, the Company did not reach any milestones. Under certain agreements, the Company may be required to make mid to high single-digit percentage royalty payments based on a percentage of sales of the relevant products.

Leases

Leases	6 Months Ended
	Mar. 31, 2022
Leases [Abstract]
Leases	NOTE 8. LEASES Leases In April 2019, the Company entered into a lease for its corporate headquarters in Pasadena, California. The 91 month office building lease between the Company and 177 Colorado Owner, LLC is for approximately 24,000 square feet of office space located at 177 E. Colorado Blvd, Pasadena, California. The increased capacity of this new office space compared to the Company’s prior corporate headquarters will accommodate increased personnel as the Company’s pipeline of drug candidates expands and moves closer to market. Lease payments began on September 30, 2019 and are estimated to total approximately $8.7 million over the term. March 31 compared to the Company’s current corporate headquarters is intended to accommodate increased personnel as the Company’s pipeline of drug candidates continues to expand and move closer to ma In January 2016, the Company entered into a lease for its research facility in Madison, Wisconsin. The lease was for approximately 60,000 square feet of office and laboratory space and ha d an expiration date of September 30, 2026 . The lease was amended in January 2019 and May 2020 to expand the rentable square feet by an additional square feet and to extend the lease expiration date to September 30, 2031 . Lease payments are estimated to total approximately $ 26.2 million for the term. The Company incurred approximately $ 11.0 million of leasehold improvements for the additional 40,000 square feet, net of tenant improvement allowances. The lease contains two options to renew for two terms of five years . The exercise of these options were not determined to be reasonably certain and thus was not included in lease liabilities on the Company’s Consolidated Balance Sheet at March 31 , 202 2 . In November 2020 and December 2020, the Company entered into amendments to expand the rentable square space by an additional 10,743 square feet and these amendments added a total of approximately $ 1.2 million of lease payments for the remainder of the term. In March 2020, the Company entered into a sublease agreement for additional research and development facility space in San Diego, California. The Sublease provides additional space needed to accommodate the recent growth of the Company’s personnel and discovery efforts. The Sublease is for approximately 21,000 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 ten-year Operating lease cost during the three months ended March 31, 2022 and 2021 was $1.3 million and $1.1 million, respectively. Operating lease cost during the six months ended March 31, 2022 and 2021 was $2.6 million and $2.0 million, respectively. Variable lease costs for the three months ended March 31, 2022 and 2021 was $0.1 million and $0.2 million, respectively. Variable lease costs for the six months ended March 31, 2022 and 2021 was $0.3 million and $0.5 million, respectively. There was no short-term lease cost during the three and six months ended March 31, 2022 and 2021. The following table presents payments of operating lease liabilities on an undiscounted basis as of March 31, 2022: (in thousands) 2022 (remainder of fiscal year) $ 2,537 2023 4,786 2024 4,621 2025 4,749 2026 5,050 2027 and thereafter 13,200 Total $ 34,943 Less imputed interest $ (9,335 ) Total operating lease liabilities (includes current portion) $ 25,608 Cash paid for the amounts included in the measurement of the operating lease liabilities on the Company’s Consolidated Balance Sheet and included in Other changes in operating assets and liabilities within cash flows from operating activities on the Company’s Consolidated Statements of Cash Flows for the six months ended March 31 March 31 7.6 years

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Mar. 31, 2022
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	NOTE 9. STOCK-BASED COMPENSATION Arrowhead has three plans that provide for equity-based compensation. Under the 2004 Equity Incentive Plan and the 2013 Incentive Plan, as of March 31, 2022, 218,107 and 4,183,395 shares, respectively, of Arrowhead’s Common Stock are reserved for the grant of stock options, stock appreciation rights, and restricted stock unit awards to employees, consultants and others. No further grants may be made under the 2004 Equity Incentive Plan. As of March 31, 2022, there were options granted and outstanding to purchase 218,107 and 1,871,258 shares of Common Stock under the 2004 Equity Incentive Plan and the 2013 Incentive Plan, respectively, and there were 2,312,137 restricted stock units granted and outstanding under the 2013 Incentive Plan. As of March 31, 2022, there were 857,290 shares reserved for options and 691,750 shares reserved for restricted stock units issued as inducement grants to new employees outside of equity compensation plans. As of March 31, 2022, there were 3,000 shares of Common Stock reserved for options and 1,474,350 shares of Common Stock reserved for restricted stock units granted and outstanding under the 2021 Incentive Plan. As of March 31, 2022, the total number of shares available under the 2021 Incentive Plan was 6,635,816 shares, which includes 110,791 shares that were forfeited under the 2013 Incentive Plan. Stock Options The following table summarizes information about stock options: Number of Options Outstanding Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Term Aggregate Intrinsic Value Balance at September 30, 2021 3,456,239 $ 19.60 Granted - - Cancelled (61,820 ) 44.77 Exercised (444,764 ) 8.28 Balance at March 31, 2022 2,949,655 $ 20.78 5.4 years $ 83,259,543 Exercisable at March 31, 2022 2,342,356 $ 15.41 4.8 years $ 75,982,912 Stock-based compensation expense related to stock options for the three months ended March 31, 2022 and 2021 was $2.7 million and $3.3 million, respectively. Stock-based compensation expense related to stock options for the six months ended March 31, 2022 and 2021 was $5.7 million and $6.4 million, respectively. For non-qualified stock options, the expense creates a timing difference, resulting in a deferred tax asset, which is fully reserved by a valuation allowance. The grant date fair value of the options granted by the Company for the three months ended March 31, 2022 and 2021 was $0 and $1.4 million, respectively. The grant date fair value of the options granted by the Company for the six months ended March 31, 2022 and 2021 was $0 and $8.1 million, respectively. The intrinsic value of the options exercised during the three months ended March 31, 2022 and 2021 was $10.8 million and $20.9 million, respectively. The intrinsic value of the options exercised during the six months ended March 31, 2022 and 2021 was $23.3 million and $52.8 million, respectively. As of March 31, 2022, the pre-tax compensation expense for all outstanding unvested stock options in the amount of $18.6 million will be recognized in the Company’s results of operations over a weighted average period of 1.9 The fair value of each stock option award is estimated on the date of grant using the Black-Scholes option pricing model. The Black-Scholes option valuation model was developed for use in estimating the fair value of traded options, which do not have vesting restrictions and are fully transferable. The determination of the fair value of each stock option is affected by the Company’s stock price on the date of grant, as well as assumptions regarding a number of highly complex and subjective variables. Because the Company’s employee stock options have characteristics significantly different from those of traded options, and because changes in the subjective input assumptions can materially affect the fair value estimate, in management’s opinion, the existing models do not necessarily provide a reliable single measure of the fair value of its employee stock options. The assumptions used to value stock options are as follows: Six Months Ended March 31, 2022 2021 Dividend yield N/A - Risk-free interest rate N/A 0.4 – 0.6% Volatility N/A 86.6 – 90.4% Expected life (in years) N/A 6.25 Weighted average grant date fair value per share of options granted N/A $ 48.62 The dividend yield is zero as the Company currently does not pay a dividend. The risk-free interest rate is based on that of the U.S. Treasury bond. Volatility is estimated based on volatility average of the Company’s Common Stock price. Restricted Stock Units Restricted stock units (“RSUs”), including time-based, market condition-based, and performance condition-based awards, have been granted under the Company’s 2013 Incentive Plan, 2021 Incentive Plan, and as inducements grants granted outside of the Company’s equity-based compensation plans under Rule 5635(c)(4) of the Nasdaq Listing Rules. At vesting, each outstanding RSU will be exchanged for one share of the Company’s Common Stock. RSU awards generally vest subject to the satisfaction of service requirements or the satisfaction of both service requirements and achievement of certain performance targets. The following table summarizes the activity of the Company’s RSUs: Number of RSUs Weighted- Average Grant Date Fair Value Per Share Unvested at September 30, 2021 3,831,850 $ 61.24 Granted 1,605,450 56.73 Vested (931,063 ) 49.25 Forfeited (37,625 ) 63.42 Unvested at March 31, 2022 4,468,612 $ 62.10 During the three months ended March 31, 2022 and 2021, the Company recorded $28.2 million and $12.1 million of expense related to RSUs, respectively. During the six months ended March 31, 2022 and 2021, the Company recorded $49.7 million and $17.1 million of expense related to RSUs, respectively. Such expense is included in stock-based compensation expense in the Company’s Consolidated Statements of Operations and Comprehensive Income (Loss). For RSUs, the expense creates a timing difference, resulting in a deferred tax asset, which is fully reserved by a valuation allowance. For RSUs, the grant date fair value of the award is based on the Company’s closing stock price at the grant date, with consideration given to the probability of achieving performance conditions for performance-based awards. The grant date fair value of the RSUs granted by the Company for the three months ended March 31, 2022 and 2021 was $83.4 million and $101.6 million, respectively. The grant date fair value of the RSUs granted by the Company for the six months ended March 31, 2022 and 2021 was $91.1 million and $109.0 million, respectively. As of March 31, 2022, the pre-tax compensation expense for all unvested RSUs in the amount of $206.8 million will be recognized in the Company’s results of operations over a weighted average period of 2.7 years.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Mar. 31, 2022
Fair Value Disclosures [Abstract]
Fair Value Measurements	NOTE 10. FAIR VALUE MEASUREMENTS The Company measures its financial assets and liabilities at fair value. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (i.e., exit price) in an orderly transaction between market participants at the measurement date. Additionally, the Company is required to provide disclosure and categorize assets and liabilities measured at fair value into one of three different levels depending on the assumptions (i.e., inputs) used in the valuation. Level 1 provides the most reliable measure of fair value while Level 3 generally requires significant management judgment. Financial assets and liabilities are classified in their entirety based on the lowest level of input significant to the fair value measurement. The fair value hierarchy is defined as follows: Level 1—Valuations are based on unadjusted quoted prices in active markets for identical assets or liabilities. Level 2—Valuations are based on quoted prices for similar assets or liabilities in active markets, or quoted prices in markets that are not active for which significant inputs are observable, either directly or indirectly. Level 3—Valuations are based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. Inputs reflect management’s best estimate of what market participants would use in valuing the asset or liability at the measurement date. The following table summarizes fair value measurements at March 31, 2022 and September 30, 2021 for assets and liabilities measured at fair value on a recurring basis: March 31, 2022: Level 1 Level 2 Level 3 Total (in thousands) Classified as Cash and cash equivalents Commercial Notes $ - $ 26,678 $ - $ 26,678 Classified as Marketable Securities Marketable securities $ 122,575 $ - $ - $ 122,575 Classified as Held to Maturity Short-term investments $ - $ 142,830 $ - $ 142,830 Long-term investments $ - $ 195,726 $ - $ 195,726 Certificate of deposits $ 50,000 $ - $ - $ 50,000 Classified as Contingent Consideration Contingent consideration $ - $ - $ - $ - September 30, 2021 Level 1 Level 2 Level 3 Total (in thousands) Classified as Marketable Securities Marketable securities $ 126,728 $ - $ - $ 126,728 Classified as Held to Maturity Short-term investments $ - $ 57,430 $ - $ 57,430 Long-term investments $ - $ 196,643 $ - $ 196,643 Certificate of deposit $ 50,000 $ - $ - $ 50,000 Classified as Contingent Consideration Contingent consideration $ - $ - $ - $ -

Subsequent Events

Subsequent Events	6 Months Ended
	Mar. 31, 2022
Subsequent Events [Abstract]
Subsequent Events	NOTE 11. SUBSEQUENT EVENTS Visirna Therapeutics, Inc . On April 25, 2022, Arrowhead Pharmaceuticals, Inc., entered into definitive agreements to form a joint venture, Visirna Therapeutics, Inc. (“Visirna”) with Vivo Capital (“Vivo”) through which the Company and Vivo intend to expand the reach of innovative medicines in Greater China. The Company licensed to Visirna the exclusive rights to develop and commercialize four of Arrowhead’s investigational RNA interference (RNAi) therapeutic candidates for cardiometabolic diseases in mainland China, Hong Kong, Macau, and Taiwan. Vivo will provide initial funding of $60.0 million to Visirna. The Company has a majority stake in Visirna following this initial funding and is further eligible to receive potential royalties on commercial sales.

Organization and Significant _2

Organization and Significant Accounting Policies (Policies)	6 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements There have been no recent accounting pronouncements that have significantly impacted this Quarterly Report on Form 10-Q, beyond those disclosed in the Company’s most recent Annual Report on Form 10-K.

Property and Equipment (Tables)

Property and Equipment (Tables)	6 Months Ended
	Mar. 31, 2022
Property Plant And Equipment [Abstract]
Summary of Property and Equipment	The following table summarizes the Company’s major classes of property and equipment: March 31, 2022 September 30, 2021 (In thousands) Computers, software, office equipment and furniture $ 2,272 $ 2,170 Research equipment 28,370 27,500 Leasehold improvements 42,017 41,524 Construction in Progress 6,414 345 Land 2,996 - Total gross fixed assets 82,069 71,539 Less: Accumulated depreciation and amortization (27,181 ) (22,864 ) Property and equipment, net $ 54,888 $ 48,675

Investments (Tables)

Investments (Tables)	3 Months Ended	6 Months Ended
	Dec. 31, 2021	Mar. 31, 2022
Held To Maturity Securities Classified [Abstract]
Summary of Short-term and Long-term Investments and Marketable Securities	The following tables summarize the Company’s short-term and long-term investments and marketable securities as of March 31, 2022 and September 30, 2021 by measurement category:	As of March 31, 2022 (In thousands) Cost Basis Gross Unrealized Gains Gross Unrealized Losses Fair Value Classified as Cash Equivalents Commercial notes (due within ninety days) $ 26,678 $ 1 $ (1 ) $ 26,678 Classified as Held to Maturity Commercial notes (due within one year) $ 142,912 $ 225 $ (307 ) $ 142,830 Commercial notes (due within one through three years) $ 201,590 $ - $ (5,864 ) $ 195,726 Certificate of deposit (due within one year) $ 50,000 $ - $ - $ 50,000 Classified as Marketable Securities Marketable securities $ 128,805 $ - $ (6,230 ) $ 122,575 Total $ 549,985 $ 226 $ (12,402 ) $ 537,809 As of September 30, 2021 (In thousands) Cost Basis Gross Unrealized Gains Gross Unrealized Losses Fair Value Classified as Held to Maturity Commercial notes (due within one year) $ 56,627 $ 803 $ - $ 57,430 Commercial notes (due within one through three years) $ 195,595 $ 1,151 $ (103 ) $ 196,643 Certificate of deposit (due within one through two years) $ 50,000 $ - $ - $ 50,000 Classified as Marketable Securities Marketable securities $ 127,481 $ - $ (753 ) $ 126,728 Total $ 429,703 $ 1,954 $ (856 ) $ 430,801

Intangible Assets (Tables)

Intangible Assets (Tables)	6 Months Ended
	Mar. 31, 2022
Goodwill And Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets	The following table provides details on the Company’s intangible asset balances: Intangible Assets Subject to Amortization (in thousands) Balance at September 30, 2021 $ 13,663 Impairment - Amortization (850 ) Balance at March 31, 2022 $ 12,813

Leases (Tables)

Leases (Tables)	6 Months Ended
	Mar. 31, 2022
Leases [Abstract]
Summary of Maturities of Operating Lease Liabilities on an Undiscounted Basis	The following table presents payments of operating lease liabilities on an undiscounted basis as of March 31, 2022: (in thousands) 2022 (remainder of fiscal year) $ 2,537 2023 4,786 2024 4,621 2025 4,749 2026 5,050 2027 and thereafter 13,200 Total $ 34,943 Less imputed interest $ (9,335 ) Total operating lease liabilities (includes current portion) $ 25,608

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Mar. 31, 2022
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summarized Information about Stock Options	The following table summarizes information about stock options: Number of Options Outstanding Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Term Aggregate Intrinsic Value Balance at September 30, 2021 3,456,239 $ 19.60 Granted - - Cancelled (61,820 ) 44.77 Exercised (444,764 ) 8.28 Balance at March 31, 2022 2,949,655 $ 20.78 5.4 years $ 83,259,543 Exercisable at March 31, 2022 2,342,356 $ 15.41 4.8 years $ 75,982,912
Assumptions Used to Value Stock Options	The assumptions used to value stock options are as follows: Six Months Ended March 31, 2022 2021 Dividend yield N/A - Risk-free interest rate N/A 0.4 – 0.6% Volatility N/A 86.6 – 90.4% Expected life (in years) N/A 6.25 Weighted average grant date fair value per share of options granted N/A $ 48.62
Summary of Share Activity Related to RSUs	The following table summarizes the activity of the Company’s RSUs: Number of RSUs Weighted- Average Grant Date Fair Value Per Share Unvested at September 30, 2021 3,831,850 $ 61.24 Granted 1,605,450 56.73 Vested (931,063 ) 49.25 Forfeited (37,625 ) 63.42 Unvested at March 31, 2022 4,468,612 $ 62.10

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Mar. 31, 2022
Fair Value Disclosures [Abstract]
Fair Value Measurements for Assets and Liabilities Measured at Fair Value on Recurring Basis	The following table summarizes fair value measurements at March 31, 2022 and September 30, 2021 for assets and liabilities measured at fair value on a recurring basis: March 31, 2022: Level 1 Level 2 Level 3 Total (in thousands) Classified as Cash and cash equivalents Commercial Notes $ - $ 26,678 $ - $ 26,678 Classified as Marketable Securities Marketable securities $ 122,575 $ - $ - $ 122,575 Classified as Held to Maturity Short-term investments $ - $ 142,830 $ - $ 142,830 Long-term investments $ - $ 195,726 $ - $ 195,726 Certificate of deposits $ 50,000 $ - $ - $ 50,000 Classified as Contingent Consideration Contingent consideration $ - $ - $ - $ - September 30, 2021 Level 1 Level 2 Level 3 Total (in thousands) Classified as Marketable Securities Marketable securities $ 126,728 $ - $ - $ 126,728 Classified as Held to Maturity Short-term investments $ - $ 57,430 $ - $ 57,430 Long-term investments $ - $ 196,643 $ - $ 196,643 Certificate of deposit $ 50,000 $ - $ - $ 50,000 Classified as Contingent Consideration Contingent consideration $ - $ - $ - $ -

Organization and Significant _3

Organization and Significant Accounting Policies - Additional Information (Detail) $ in Thousands	Dec. 20, 2021ft²a	Mar. 31, 2022USD ($)	Nov. 19, 2021ft²	Sep. 30, 2021USD ($)
Organization And Significant Accounting Policies [Line Items]
Cash and cash equivalents		$ 86,408		$ 184,434
Restricted Cash		7,900
Short-term investments		192,912		56,627
Marketable securities		122,600
Long-term investments		201,590		$ 245,595
Net increase (decrease) in cash and investments		9,900
GSK
Organization And Significant Accounting Policies [Line Items]
Upfront milestone payment received		120,000
Janssen
Organization And Significant Accounting Policies [Line Items]
Development regulatory and sales milestones payments		$ 4,900,000
Wisconsin | Drug Manufacturing Facility
Organization And Significant Accounting Policies [Line Items]
Planned area of the site | ft²	140,000
Wisconsin | Laboratory and Office Facility
Organization And Significant Accounting Policies [Line Items]
Planned area of the site | ft²	115,000
Wisconsin | Verona Technology Park
Organization And Significant Accounting Policies [Line Items]
Land purchased, number of acres | a	13
California | Research Facility in San Diego
Organization And Significant Accounting Policies [Line Items]
Office space leases, in square feet | ft²			144,000

Collaboration and License Agr_2

Collaboration and License Agreements - Amgen, Inc - Additional Information (Detail) $ in Thousands	Sep. 28, 2016USD ($)Agreement	Mar. 31, 2022USD ($)	Mar. 31, 2021USD ($)	Mar. 31, 2022USD ($)	Mar. 31, 2021USD ($)	Sep. 30, 2021USD ($)	Jul. 31, 2020USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenues		$ 151,805	$ 32,811	$ 179,244	$ 54,113
Contract liabilities		97,869		97,869		$ 111,055
Collaboration and License agreements | Amgen
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Agreement date	Sep. 28, 2016
Number of agreements | Agreement	2
Cash received as due under collaboration agreement	$ 35,000
License Collaboration And Stock Purchase Agreement | Amgen
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Proceeds from the issuance of common stock	21,500
Olpasiran and ARO-AMG1 Agreement | Amgen
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments	$ 30,000						$ 20,000
Revenues		0	$ 0	0	$ 0
Contract liabilities		0		0
Contract assets		0		0
Olpasiran Agreement | Amgen | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional remaining development regulatory and sales milestones payments		$ 400,000		$ 400,000

Collaboration and License Agr_3

Collaboration and License Agreements - Janssen Pharmaceuticals, Inc - Additional Information (Detail)	Oct. 03, 2018USD ($)Obligation	Mar. 31, 2022USD ($)	Mar. 31, 2021USD ($)	Mar. 31, 2022USD ($)	Mar. 31, 2021USD ($)	Jan. 31, 2022USD ($)	Sep. 30, 2021USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenues		$ 151,805,000	$ 32,811,000	$ 179,244,000	$ 54,113,000
Deferred revenue		97,869,000		97,869,000			$ 111,055,000
Collaboration and License agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Initial transaction price	$ 252,700,000
JJDC | Common Stock Purchase Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Agreement date	Oct. 3, 2018
Proceeds from the issuance of common stock	$ 75,000,000
Janssen | Collaboration and License agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Cash received as due under collaboration agreement	175,000,000
Janssen
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development, regulatory and sales milestones payments		4,900,000,000		4,900,000,000
Milestone payment	$ 73,000,000
Janssen | License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Agreement date	Oct. 3, 2018
Janssen | License Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development, regulatory and sales milestones payments	$ 1,600,000,000
Janssen | Research Collaboration and Option Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Agreement date	Oct. 3, 2018
Janssen | Collaboration Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development, regulatory and sales milestones payments	$ 600,000,000
Janssen | JNJ-3989 (ARO-HBV) Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment	$ 25,000,000
Number of distinct performance obligations | Obligation	1
Revenues		0	7,500,000	0	20,200,000
Contract assets						$ 0
Deferred revenue						$ 0
Janssen | JNJ-75220795 (ARO-JNJ1)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenues		100,000	$ 100,000	100,000	$ 300,000
Contract assets		100,000		100,000
Deferred revenue		$ 0		$ 0

Collaboration and License Agr_4

Collaboration and License Agreements - Takeda Pharmaceuticals U.S.A., Inc - Additional Information (Detail) $ in Thousands	Oct. 07, 2020USD ($)ObligationBundle	Mar. 31, 2022USD ($)	Mar. 31, 2021USD ($)	Mar. 31, 2022USD ($)	Mar. 31, 2021USD ($)	Sep. 30, 2021USD ($)	Jan. 31, 2021USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenues		$ 151,805	$ 32,811	$ 179,244	$ 54,113
Contract liabilities, current		97,869		97,869		$ 111,055
Deferred revenue, net of current portion		89,754		89,754		$ 131,495
Takeda License Agreement | License and Co-Funding Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Agreement date	Oct. 7, 2020
Ratio of Profit Sharing Structure for United States Commercialization	50/50 profit sharing
Cash received as due under collaboration agreement							$ 300,000
Number of distinct bundle | Bundle	1
Number of distinct performance obligations | Obligation	1
Initial transaction price	$ 300,000
Revenues		20,800	$ 25,400	41,600	$ 33,600
Contract assets		0		0
Takeda License Agreement | License and Co-Funding Agreement | Deferred Revenue
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liabilities, current		77,900		77,900
Deferred revenue, net of current portion		89,800		89,800
Takeda License Agreement | License and Co-Funding Agreement | Accrued Expenses
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liabilities, current		$ 5,000		$ 5,000
Takeda License Agreement | Minimum [Member] | License and Co-Funding Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of eligible to receive tiered royalties on net sales	20.00%
Takeda License Agreement | Maximum | License and Co-Funding Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of eligible to receive tiered royalties on net sales	25.00%
Development regulatory and sales milestones payments							$ 740,000

Collaboration and License Agr_5

Collaboration and License Agreements - Horizon Therapeutics Ireland DAC - Additional Information (Detail) $ in Thousands	Jun. 18, 2021USD ($)ObligationBundle	Mar. 31, 2022USD ($)	Mar. 31, 2021USD ($)	Mar. 31, 2022USD ($)	Mar. 31, 2021USD ($)	Sep. 30, 2021USD ($)	Jul. 31, 2021USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenues		$ 151,805	$ 32,811	$ 179,244	$ 54,113
Contract liabilities		97,869		97,869		$ 111,055
Horizon Therapeutics Ireland DAC | ARO-XDH
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Agreement date	Jun. 18, 2021
Cash received as due under collaboration agreement							$ 40,000
Number of distinct performance obligations | Obligation	1
Initial transaction price	$ 40,000
Revenues		6,700	0	13,300	0
Contract assets		0		0
Contract liabilities		20,000		20,000
Horizon Therapeutics Ireland DAC | License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of distinct bundle | Bundle	1
Number of distinct performance obligations | Obligation	1
Horizon Therapeutics Ireland DAC | ARO-XDH Supply Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenues		1,300	$ 0	1,300	$ 0
Contract assets		1,300		1,300
Contract liabilities		$ 0		$ 0
Horizon Therapeutics Ireland DAC | Maximum | ARO-XDH
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development regulatory and sales milestones payments	$ 660,000

Collaboration and License Agr_6

Collaboration and License Agreements - Glaxosmithkline Intellectual Property (No. 3) Limited - Additional Information (Detail) $ in Thousands	Nov. 22, 2021USD ($)ObligationBundle	Oct. 03, 2018USD ($)	Jan. 31, 2022USD ($)	Mar. 31, 2022USD ($)	Mar. 31, 2021USD ($)	Mar. 31, 2022USD ($)	Mar. 31, 2021USD ($)	Sep. 30, 2021USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenues				$ 151,805	$ 32,811	$ 179,244	$ 54,113
Contract liabilities				$ 97,869		97,869		$ 111,055
Collaboration and License agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Initial transaction price		$ 252,700
Collaboration and License agreements | GSK
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment	$ 120
Milestone payment receivable at start of phase two	30
Milestone payment receivable upon achievement of phase two and first patient dosed in phase three	100
Tiered royalties on net product sales receive description				The Company is further eligible to receive tiered royalties on net product sales in a range of mid-teens to twenty percent.
Collaboration and License agreements | Maximum | GSK
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Commercial milestone payments at first commercial sale	190
Sales-related milestone payments	$ 590
ARO-HSD Agreement | GSK
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of distinct bundle | Bundle	1
Number of distinct performance obligations | Obligation	1
Initial transaction price	$ 120,000
Cash received as due under collaboration agreement			$ 120,000
Performance obligation related to agreement, upfront payment				$ 120,000		120,000
Revenues				120,000	$ 0	120,000	$ 0
Contract assets				0		0
Contract liabilities				$ 0		$ 0

Property and Equipment - Summar

Property and Equipment - Summary of Property and Equipment (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Sep. 30, 2021
Property Plant And Equipment [Abstract]
Computers, software, office equipment and furniture	$ 2,272	$ 2,170
Research equipment	28,370	27,500
Leasehold improvements	42,017	41,524
Construction in Progress	6,414	345
Land	2,996
Total gross fixed assets	82,069	71,539
Less: Accumulated depreciation and amortization	(27,181)	(22,864)
Property and equipment, net	$ 54,888	$ 48,675

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Property Plant And Equipment [Abstract]
Depreciation and amortization expense for property and equipment	$ 2.2	$ 1.5	$ 4.3	$ 2.9

Investments - Summary of Short-

Investments - Summary of Short-term and Long-term Investments and Marketable Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Sep. 30, 2021
Schedule Of Held To Maturity Securities And Marketable Securities [Line Items]
Short-term and Long-term Investments and Marketable Securities, Cost Basis	$ 549,985	$ 429,703
Short-term and Long-term Investments and Marketable Securities, Gross Unrealized Gains	226	1,954
Short-term and Long-term Investments and Marketable Securities, Gross Unrealized Losses	(12,402)	(856)
Short-term and Long-term Investments and Marketable Securities, Fair Value	537,809	430,801
Commercial Notes Due Within Ninety Days
Schedule Of Held To Maturity Securities And Marketable Securities [Line Items]
Cash Equivalents, Cost Basis	26,678
Cash Equivalents, Gross Unrealized Gains	1
Cash Equivalents, Gross Unrealized Losses	(1)
Cash Equivalents, Fair Value	26,678
Commercial Note Due Within One Year
Schedule Of Held To Maturity Securities And Marketable Securities [Line Items]
Held to Maturity, Cost Basis	142,912	56,627
Held to Maturity, Gross Unrealized Gains	225	803
Held to Maturity, Gross Unrealized Losses	(307)
Held to Maturity, Fair Value	142,830	57,430
Commercial Note Due Within One Through Three Years
Schedule Of Held To Maturity Securities And Marketable Securities [Line Items]
Held to Maturity, Cost Basis	201,590	195,595
Held to Maturity, Gross Unrealized Gains		1,151
Held to Maturity, Gross Unrealized Losses	(5,864)	(103)
Held to Maturity, Fair Value	195,726	196,643
Certificate of Deposit Due Within One Year
Schedule Of Held To Maturity Securities And Marketable Securities [Line Items]
Held to Maturity, Cost Basis	50,000
Held to Maturity, Fair Value	50,000
Certificate of Deposit Due Within One Through Two Years
Schedule Of Held To Maturity Securities And Marketable Securities [Line Items]
Held to Maturity, Cost Basis		50,000
Held to Maturity, Fair Value		50,000
Marketable Securities
Schedule Of Held To Maturity Securities And Marketable Securities [Line Items]
Marketable Securities, Cost Basis	128,805	127,481
Marketable Securities, Gross Unrealized Losses	(6,230)	(753)
Marketable Securities, Fair Value	$ 122,575	$ 126,728

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Finite Lived Intangible Assets [Line Items]
Amortization expense	$ 400	$ 400	$ 900	$ 850
Amortization of license agreements remainder of fiscal year 2022	900		900
Amortization of license agreements in 2023	1,700		1,700
Amortization of license agreements in 2024	1,700		1,700
Amortization of license agreements in 2025	1,700		1,700
Amortization of license agreements in 2026	1,700		1,700
Amortization of license agreements, thereafter	5,200		$ 5,200
Novartis | Licensing Agreement
Finite Lived Intangible Assets [Line Items]
Amortization period of intangible assets			21 years
Finite-lived intangible assets, accumulated amortization	1,100		$ 1,100
Novartis | Patents
Finite Lived Intangible Assets [Line Items]
Amortization period of intangible assets			14 years
Finite-lived intangible assets, accumulated amortization	$ 11,000		$ 11,000

Intangible Assets - Schedule of

Intangible Assets - Schedule of Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Intangible Assets Net Excluding Goodwill [Abstract]
Intangible assets subject to amortization, beginning balance			$ 13,663
Intangible assets subject to amortization, Amortization	$ (400)	$ (400)	(900)	$ (850)
Intangible assets subject to amortization, ending balance	$ 12,813		$ 12,813

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	1 Months Ended
	Aug. 31, 2020	Mar. 31, 2022	Sep. 30, 2021
Class Of Stock [Line Items]
Capital stock authorized for issuance		150,000,000
Common stock, shares authorized		145,000,000	145,000,000
Common stock, par value		$ 0.001	$ 0.001
Preferred stock, shares authorized		5,000,000
Preferred stock, par value		$ 0.001
Common stock, shares outstanding		105,702,499	104,327,000
At The Market Agreement
Class Of Stock [Line Items]
Shares issued to institutional investors		0
At The Market Agreement | Maximum
Class Of Stock [Line Items]
Common stock shares value reserved for future issuance	$ 250,000,000
Percentage of commission to sales agent	3.00%
2004 Equity Incentive Plan, 2013 Equity Incentive Plan, 2021 Equity Incentive Plan and Inducement Grants
Class Of Stock [Line Items]
Common Stock, Share reserve for issuance		14,054,083

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	Dec. 20, 2021USD ($)ft²a	Mar. 31, 2022USD ($)	Mar. 31, 2022USD ($)
Other Commitments [Line Items]
Contingent liabilities		$ 0	$ 0
Technology License Commitments
Other Commitments [Line Items]
Milestone payments		$ 0	$ 0
Verona Technology Park | Wisconsin
Other Commitments [Line Items]
Land purchased, number of acres | a	13
Drug Manufacturing Facility | Wisconsin
Other Commitments [Line Items]
Planned area of the site | ft²	140,000
Laboratory and Office Facility | Wisconsin
Other Commitments [Line Items]
Planned area of the site | ft²	115,000
Facilities | Minimum [Member]
Other Commitments [Line Items]
Amount intends to invest for buildout of the facilities	$ 200,000,000
Facilities | Maximum
Other Commitments [Line Items]
Amount intends to invest for buildout of the facilities	$ 250,000,000

Leases - Additional Information

Leases - Additional Information (Detail) $ in Thousands	Nov. 19, 2021USD ($)ft²Option	Oct. 23, 2020USD ($)ft²	Mar. 31, 2020USD ($)ft²	Apr. 30, 2019USD ($)ft²Option	Jan. 31, 2016ft²	Dec. 31, 2020USD ($)ft²Option	Mar. 31, 2022USD ($)	Mar. 31, 2021USD ($)	Mar. 31, 2022USD ($)	Mar. 31, 2021USD ($)	May 31, 2020USD ($)ft²
Lessee Lease Description [Line Items]
Estimated lease payments							$ 34,943		$ 34,943
Operating lease cost							1,300	$ 1,100	2,600	$ 2,000
Variable lease cost							100	200	300	500
Short-term lease cost							$ 0	$ 0	0	0
Operating lease cash payments									$ 2,200	$ 1,400
Weighted-average remaining lease term							7 years 7 months 6 days		7 years 7 months 6 days
Weighted-average discount rate							8.50%		8.50%
California | Halozyme, Inc. | Sublease Agreement
Lessee Lease Description [Line Items]
Office space leases, in square feet | ft²			21,000
Estimated lease payments			$ 2,000
Lease expiration date			Jan. 14, 2023
Sublease commencement date			Apr. 1, 2020
Corporate Headquarters In Pasadena | California
Lessee Lease Description [Line Items]
Office space leases, in square feet | ft²		24,000
Estimated lease payments		$ 6,900
Payments for leasehold improvements, net of tenant improvement allowances		$ 4,000
Lease expansion commencement period		2021-07
Lease expansion expiration month and year		2027-04
Corporate Headquarters In Pasadena | California | Colorado Owner, LLC
Lessee Lease Description [Line Items]
Lease term				91 months
Office space leases, in square feet | ft²				24,000
Lease payments, commencement date				Sep. 30, 2019
Estimated lease payments				$ 8,700
Lease expiration date				Apr. 30, 2027
Payments for leasehold improvements, net of tenant improvement allowances				$ 3,500
Operating lease renewal term				5 years
Number of options to renew | Option				1
Research Facility in Madison | Wisconsin
Lessee Lease Description [Line Items]
Office space leases, in square feet | ft²					60,000
Estimated lease payments						$ 1,200					$ 26,200
Lease expiration date					Sep. 30, 2026						Sep. 30, 2031
Operating lease renewal term						5 years
Number of options to renew | Option						2
Additional office space for lease | ft²						10,743					40,000
Expected leasehold improvements, net of tenant improvement allowances											$ 11,000
Research Facility in San Diego | California
Lessee Lease Description [Line Items]
Lease term	15 years
Office space leases, in square feet | ft²	144,000
Lease payments, commencement date	May 31, 2023
Estimated lease payments	$ 119,000
Payments for leasehold improvements, net of tenant improvement allowances	$ 31,000
Operating lease renewal term	10 years
Estimated payments for operating expenses	$ 3,000
Research Facility in San Diego | California | Maximum
Lessee Lease Description [Line Items]
Number of options to renew | Option	1

Leases - Summary of Maturities

Leases - Summary of Maturities of Operating Lease Liabilities on an Undiscounted Basis (Detail) $ in Thousands	Mar. 31, 2022USD ($)
Leases [Abstract]
2022 (remainder of fiscal year)	$ 2,537
2023	4,786
2024	4,621
2025	4,749
2026	5,050
2027 and thereafter	13,200
Total	34,943
Less imputed interest	(9,335)
Total operating lease liabilities (includes current portion)	$ 25,608

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options outstanding	2,949,655		2,949,655		3,456,239
RSU awards vesting, description			At vesting, each outstanding RSU will be exchanged for one share of the Company’s Common Stock. RSU awards generally vest subject to the satisfaction of service requirements or the satisfaction of both service requirements and achievement of certain performance targets.
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 2.7	$ 3.3	$ 5.7	$ 6.4
Grant date fair value of the options granted	0	1.4	0	8.1
Intrinsic value of options exercised	10.8	20.9	23.3	52.8
Unrecognized pre-tax compensation expense	18.6		$ 18.6
Weighted average period to recognize pre-tax compensation expense			1 year 10 months 24 days
Dividend yield			0.00%
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 28.2	12.1	$ 49.7	17.1
Weighted average period to recognize pre-tax compensation expense	2 years 8 months 12 days
Grant date fair value of other than options granted	$ 83.4	$ 101.6	91.1	$ 109
Unrecognized pre-tax compensation expense	$ 206.8		$ 206.8
2004 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance	218,107		218,107
2004 Equity Incentive Plan | Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options outstanding	218,107		218,107
2013 Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance	4,183,395		4,183,395
Number of shares forfeited			110,791
2013 Incentive Plan | Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options outstanding	1,871,258		1,871,258
2013 Incentive Plan | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of restricted stock units outstanding	2,312,137		2,312,137
Outside Of Equity Compensation Plans
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance	857,290		857,290
Outside Of Equity Compensation Plans | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance	691,750		691,750
2021 Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common Stock, Share reserve for issuance	6,635,816		6,635,816
2021 Incentive Plan | Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options outstanding	3,000		3,000
2021 Incentive Plan | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of restricted stock units outstanding	1,474,350		1,474,350

Stock-Based Compensation - Summ

Stock-Based Compensation - Summarize Information about Stock Options (Detail) - USD ($)	6 Months Ended
	Mar. 31, 2022
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Options Outstanding, beginning balance	3,456,239
Number of Options Outstanding, Cancelled	(61,820)
Number of Options Outstanding, Exercised	(444,764)
Number of Options Outstanding, ending balance	2,949,655
Number of Options Outstanding, Exercisable	2,342,356
Weighted-Average Exercise Price Per Share, beginning balance	$ 19.60
Weighted-Average Exercise Price Per Share, Cancelled	44.77
Weighted-Average Exercise Price Per Share, Exercised	8.28
Weighted-Average Exercise Price Per Share, ending balance	20.78
Weighted-Average Exercise Price Per Share, Exercisable	$ 15.41
Weighted-Average Remaining Contractual Term	5 years 4 months 24 days
Weighted-Average Remaining Contractual Term, Exercisable	4 years 9 months 18 days
Aggregate Intrinsic Value	$ 83,259,543
Aggregate Intrinsic Value, Exercisable	$ 75,982,912

Stock-Based Compensation - Assu

Stock-Based Compensation - Assumptions Used to Value Stock Options (Detail)	6 Months Ended
	Mar. 31, 2021$ / shares
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Abstract]
Risk-free interest rate, minimum	0.40%
Risk-free interest rate, maximum	0.60%
Volatility, minimum	86.60%
Volatility, maximum	90.40%
Expected life (in years)	6 years 3 months
Weighted average grant date fair value per share of options granted	$ 48.62

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of RSUs Activity (Detail) - Restricted Stock Units (RSUs)	6 Months Ended
	Mar. 31, 2022$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of RSUs, Unvested, beginning of period | shares	3,831,850
Number of RSUs, Granted | shares	1,605,450
Number of RSUs, Vested | shares	(931,063)
Number of RSUs, Forfeited | shares	(37,625)
Number of RSUs, Unvested, End of period | shares	4,468,612
Weighted-Average Grant Date Fair Value, beginning balance | $ / shares	$ 61.24
Weighted-Average Grant Date Fair Value, Granted | $ / shares	56.73
Weighted-Average Grant Date Fair Value, Vested | $ / shares	49.25
Weighted-Average Grant Date Fair Value, Forfeited | $ / shares	63.42
Weighted-Average Grant Date Fair Value, ending balance | $ / shares	$ 62.10

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value Measurements for Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Mar. 31, 2022	Sep. 30, 2021
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Commercial Notes	$ 26,678
Marketable securities	122,575	$ 126,728
Held to Maturity, Fair Value	142,830	57,430
Long-term investments	195,726	196,643
Certificate of deposits	50,000	50,000
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	122,575	126,728
Certificate of deposits	50,000	50,000
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Commercial Notes	26,678
Held to Maturity, Fair Value	142,830	57,430
Long-term investments	$ 195,726	$ 196,643

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) $ in Millions	Apr. 25, 2022USD ($)
Subsequent Event
Subsequent Event [Line Items]
Initial funding	$ 60