Arrowhead Pharmaceuticals (ARWR) 10-Q 7 Aug 23 2023 Q3 Quarterly report Financial data

Cover

Cover - shares	9 Months Ended
	Jun. 30, 2023	Jul. 31, 2023
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2023
Document Transition Report	false
Entity File Number	001-38042
Entity Registrant Name	ARROWHEAD PHARMACEUTICALS, INC.
Entity Incorporation, State or Country Code	DE
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
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	ARWR
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		107,192,901
Entity Central Index Key	0000879407
Current Fiscal Year End Date	--09-30
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3
Amendment Flag	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2023	Sep. 30, 2022
Current assets:
Cash, cash equivalents and restricted cash	$ 105,334	$ 108,005
Accounts receivable	1,247	1,410
Short term investments	346,369	268,391
Prepaid expenses	10,053	7,289
Other current assets	7,162	20,204
Total current assets	470,165	405,299
Property and equipment, net	231,369	110,297
Intangible assets, net	10,687	11,962
Long-term investments	42,758	105,872
Right-of-use assets	40,667	58,291
Other assets	210	218
Total Assets	795,856	691,939
Current liabilities:
Accounts payable	7,874	2,868
Accrued expenses	38,191	46,856
Accrued payroll and benefits	4,434	12,251
Lease liabilities	2,823	2,776
Deferred revenue	16,905	74,099
Total current liabilities	70,227	138,850
Long-term liabilities:
Lease liabilities, net of current portion	79,911	78,800
Deferred revenue, net of current portion	0	55,950
Liability related to the sale of future royalties	263,064	0
Other liabilities	669	0
Total long-term liabilities	343,644	134,750
Commitments and contingencies (Note 7)
Noncontrolling interest and stockholders’ equity:
Common stock, $0.001 par value: Authorized 290,000 and 145,000 shares; issued and outstanding 107,102 and 105,960 shares	199	198
Additional paid-in capital	1,281,393	1,219,213
Accumulated other comprehensive loss	(411)	(136)
Accumulated deficit	(916,351)	(820,755)
Total Arrowhead Pharmaceuticals, Inc. stockholders’ equity	364,830	398,520
Noncontrolling interest	17,155	19,819
Total noncontrolling interest and stockholders’ equity	381,985	418,339
Total Liabilities, Noncontrolling Interest and Stockholders’ Equity	$ 795,856	$ 691,939

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2023	Apr. 27, 2023	Apr. 26, 2023	Mar. 16, 2023	Sep. 30, 2022
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.001			$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	290,000,000	290,000,000	145,000,000		145,000,000
Common stock, shares issued (in shares)	107,102,000				105,960,000
Common stock, shares outstanding (in shares)	107,102,000				105,960,000

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Income Statement [Abstract]
Revenue	$ 15,825	$ 32,412	$ 224,638	$ 211,656
Operating expenses:
Research and development	94,757	72,180	253,333	213,930
General and administrative	23,771	33,141	67,977	92,403
Total operating expenses	118,528	105,321	321,310	306,333
Operating loss	(102,703)	(72,909)	(96,672)	(94,677)
Other income (expense):
Interest income	4,172	1,240	11,414	3,450
Interest expense	(5,158)	0	(13,064)	0
Other, net	306	(377)	821	675
Total other (loss) income	(680)	863	(829)	4,125
Loss before income tax expense and noncontrolling interest	(103,383)	(72,046)	(97,501)	(90,552)
Income tax expense	742	0	759	0
Net loss including noncontrolling interest	(104,125)	(72,046)	(98,260)	(90,552)
Net loss attributable to noncontrolling interest, net of tax	(1,179)	0	(2,664)	0
Net loss attributable to Arrowhead Pharmaceuticals, Inc.	$ (102,946)	$ (72,046)	$ (95,596)	$ (90,552)
Net loss per share attributable to Arrowhead Pharmaceuticals, Inc.:
Basic (in dollars per share)	$ (0.96)	$ (0.68)	$ (0.90)	$ (0.86)
Diluted (in dollars per share)	$ (0.96)	$ (0.68)	$ (0.90)	$ (0.86)
Weighted-average shares used in calculating
Basic (in shares)	107,004	105,753	106,597	105,273
Diluted (in shares)	107,004	105,753	106,597	105,273
Other comprehensive loss, net of tax:
Foreign currency translation adjustments	$ (79)	$ (33)	$ (275)	$ (71)
Comprehensive loss	$ (104,204)	$ (72,079)	$ (98,535)	$ (90,623)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Non- controlling Interest
Beginning balance at Sep. 30, 2021	$ 408,822	$ 197	$ 1,053,386	$ (69)	$ (644,692)	$ 0
Beginning balance (in shares) at Sep. 30, 2021		104,327,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	24,504		24,504
Exercise of stock options	2,145		2,145
Exercise of stock options (in shares)		208,000
Common stock - restricted stock units vesting (in shares)		263,000
Foreign currency translation adjustments	(39)			(39)
Net loss	(62,872)				(62,872)
Ending balance at Dec. 31, 2021	372,560	$ 197	1,080,035	(108)	(707,564)	0
Ending balance (in shares) at Dec. 31, 2021		104,798,000
Beginning balance at Sep. 30, 2021	408,822	$ 197	1,053,386	(69)	(644,692)	0
Beginning balance (in shares) at Sep. 30, 2021		104,327,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Foreign currency translation adjustments	(71)
Net loss	(90,552)
Ending balance at Jun. 30, 2022	474,177	$ 198	1,189,113	(140)	(735,244)	20,250
Ending balance (in shares) at Jun. 30, 2022		105,795,000
Beginning balance at Dec. 31, 2021	372,560	$ 197	1,080,035	(108)	(707,564)	0
Beginning balance (in shares) at Dec. 31, 2021		104,798,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	33,802		33,802
Exercise of stock options	1,537		1,537
Exercise of stock options (in shares)		237,000
Common stock - restricted stock units vesting	0	$ 1	(1)
Common stock - restricted stock units vesting (in shares)		667,000
Foreign currency translation adjustments	1			1
Net loss	44,366				44,366
Ending balance at Mar. 31, 2022	452,266	$ 198	1,115,373	(107)	(663,198)	0
Ending balance (in shares) at Mar. 31, 2022		105,702,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	33,391		33,391
Exercise of stock options	599		599
Exercise of stock options (in shares)		53,000
Common stock - restricted stock units vesting (in shares)		40,000
Foreign currency translation adjustments	(33)			(33)
Net loss	(72,046)				(72,046)
Ending balance at Jun. 30, 2022	474,177	$ 198	1,189,113	(140)	(735,244)	20,250
Ending balance (in shares) at Jun. 30, 2022		105,795,000
Beginning balance at Sep. 30, 2022	418,339	$ 198	1,219,213	(136)	(820,755)	19,819
Beginning balance (in shares) at Sep. 30, 2022		105,960,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	19,390		19,390
Exercise of stock options	576		576
Exercise of stock options (in shares)		82,000
Common stock - restricted stock units vesting	0	$ 1	(1)
Common stock - restricted stock units vesting (in shares)		98,000
Foreign currency translation adjustments	(122)			(122)
Interest in joint venture	(486)					(486)
Net loss	(41,325)				(41,325)
Ending balance at Dec. 31, 2022	396,372	$ 199	1,239,178	(258)	(862,080)	19,333
Ending balance (in shares) at Dec. 31, 2022		106,140,000
Beginning balance at Sep. 30, 2022	$ 418,339	$ 198	1,219,213	(136)	(820,755)	19,819
Beginning balance (in shares) at Sep. 30, 2022		105,960,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	343,801
Foreign currency translation adjustments	$ (275)
Net loss	(95,596)
Ending balance at Jun. 30, 2023	381,985	$ 199	1,281,393	(411)	(916,351)	17,155
Ending balance (in shares) at Jun. 30, 2023		107,102,000
Beginning balance at Dec. 31, 2022	396,372	$ 199	1,239,178	(258)	(862,080)	19,333
Beginning balance (in shares) at Dec. 31, 2022		106,140,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	20,612		20,612
Exercise of stock options	520		520
Exercise of stock options (in shares)		64,000
Common stock - restricted stock units vesting (in shares)		665,000
Foreign currency translation adjustments	(74)			(74)
Interest in joint venture	(999)					(999)
Net loss	48,675				48,675
Ending balance at Mar. 31, 2023	465,106	$ 199	1,260,310	(332)	(813,405)	18,334
Ending balance (in shares) at Mar. 31, 2023		106,869,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	19,947		19,947
Exercise of stock options	1,136		1,136
Exercise of stock options (in shares)		198,000
Common stock - restricted stock units vesting (in shares)		35,000
Foreign currency translation adjustments	(79)			(79)
Interest in joint venture	(1,179)					(1,179)
Interest in joint venture	60,000		39,750			20,250
Net loss	(102,946)				(102,946)
Ending balance at Jun. 30, 2023	$ 381,985	$ 199	$ 1,281,393	$ (411)	$ (916,351)	$ 17,155
Ending balance (in shares) at Jun. 30, 2023		107,102,000

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (98,260)	$ (90,552)
Adjustments to reconcile net loss to net cash flow from operating activities
Stock-based compensation	59,949	91,697
Depreciation and amortization	8,634	7,761
(Accretion) amortization of note premiums/discounts	(1,030)	2,013
Non-cash interest expense on liability related to the sale of future royalties	13,064	0
Unrealized losses on marketable securities	0	5,755
Changes in operating assets and liabilities:
Accounts receivable	164	10,016
Prepaid expenses and other current assets	27,913	(8,867)
Accounts payable	5,001	(3,563)
Accrued expenses	(32,082)	1,713
Deferred revenue	(113,144)	(87,100)
Operating lease liabilities	1,158	3,733
Net cash used in operating activities	(128,633)	(67,394)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(112,830)	(20,066)
Purchases of investments	(233,984)	(223,391)
Proceeds from maturities of investments	220,150	201,595
Net cash used in investing activities	(126,664)	(41,862)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from the exercises of stock options	2,232	4,331
Proceeds from the sale of future royalties	250,000	0
Proceeds from investment in joint venture	0	60,000
Proceeds from additional tenant improvement allowance	669	0
Net cash provided by financing activities	252,901	64,331
Net decrease in cash, cash equivalents and restricted cash	(2,396)	(44,925)
Effect of exchange rate on cash, cash equivalents and restricted cash	(275)	(70)
CASH, CASH EQUIVALENTS AND RESTRICTED CASH:
BEGINNING OF PERIOD	108,005	184,434
END OF PERIOD	105,334	139,439
Supplementary disclosures:
Interest paid	0	0
Income taxes (paid) refunded	$ 0	$ 0

Organization and Significant Ac

Organization and Significant Accounting Policies	9 Months Ended
	Jun. 30, 2023
Accounting Policies [Abstract]
Organization and Significant Accounting Policies	ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES General and Recent Developments Arrowhead Pharmaceuticals, Inc. and its subsidiaries (referred to herein collectively as the “Company”) are primarily engaged in developing medicines that treat intractable diseases by silencing the genes that cause them. Using a broad portfolio of RNA chemistries and efficient modes of delivery, the Company’s 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. The Company’s RNAi-based therapeutics may leverage this natural pathway of gene silencing to target and shut down specific disease-causing genes. The following table presents the Company’s current pipeline: Therapeutic Area Name Stage Product Rights Cardiometabolic ARO-APOC3 Phase 2b and Phase 3 Arrowhead ARO-ANG3 Phase 2b Arrowhead Olpasiran Phase 3 Amgen Pulmonary ARO-ENAC2 Pre-Clinical Arrowhead ARO-RAGE Phase 1/2 Arrowhead ARO-MUC5AC Phase 1/2a Arrowhead ARO-MMP7 Phase 1/2a Arrowhead Liver GSK-4532990 (formerly ARO-HSD) Phase 2 GSK Fazirsiran Phase 3 Takeda and Arrowhead JNJ-3989 Phase 2 Janssen HZN-457 (formerly ARO-XDH) Phase 1 Horizon ARO-C3 Phase 1/2 Arrowhead ARO-PNPLA3 (formerly JNJ-75220795) Phase 1 Arrowhead Muscle ARO-DUX4 Pre-Clinical Arrowhead Central Nervous System (CNS) ARO-SOD1 Pre-Clinical Arrowhead The Company operates lab facilities in San Diego, California and Madison, Wisconsin, where its 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 three quarters of fiscal 2023, the Company continued to develop and advance its pipeline and partnered candidates. Several key recent developments include: • hosted a Research & Development (R&D) Day on June 1, 2023 to discuss progress of the Company's pipeline of RNAi Therapeutics, at which the following updates were discussed: ◦ ARO-RAGE showed continued dose response with single inhaled dose of 184 mg achieving mean knockdown of 90% and max of 95%; ◦ adipose delivery platform achieved single dose target gene silencing of greater than 90% with six months of duration in non-human primates; ◦ improved hepatic dimer platform achieved equivalent or better knockdown of two target genes with longer duration than monomer mixture in non-human primates; ◦ TRiM™ platform now has potential to address multiple cell types including liver, solid tumors, lung, central nervous system, skeletal muscle, and adipose; ◦ announced progress towards the Company's "20 in 25" goal to grow its pipeline of RNAi therapeutics that leverage the proprietary Targeted RNAi Molecule (TRiM™) platform to a total of 20 clinical stage or marketed products in the year 2025; • presented updated data from the Phase 2 SEQUOIA study of investigational RNAi therapy Fazirsiran in patients with alpha-1 antitrypsin deficiency liver disease which included: ◦ Fazirsiran reduced serum Z-AAT concentration in a dose-dependent manner; ◦ Fazirsiran significantly reduced liver Z-AAT; ◦ Fazirsiran consistently reduced hepatic globule burden; ◦ Fazirsiran treatment reduced histological signs of hepatic inflammation; ◦ 50% of the pooled Fazirsiran treated patients showed at least a one-point improvement in METAVIR liver fibrosis versus 38% in the placebo group; ◦ Fazirsiran has been well tolerated to date; ◦ pulmonary function test results (FEV1 and DLCO) for both Fazirsiran and placebo were stable over time with no apparent dose-dependent effects; ◦ updated Phase 2 clinical data were presented at the European Association for the Study of the Liver (EASL) Congress 2023 in an oral presentation titled, “Fazirsiran reduces liver Z-alpha-1 antitrypsin synthesis, decreases globule burden and improves histological measures of liver disease in adults with alpha-1 antitrypsin deficiency: a randomized placebo-controlled phase 2 study”; • presented interim data from the ongoing Phase 2 GATEWAY clinical study of ARO-ANG3 which included: ◦ mean reduction in LDL-C of 48.1% (200mg) and 44.0% (300mg); ◦ ANPTL3 inhibition with ARO-ANG3 also reduced HDL-C, non-HDL-C, and triglycerides, consistent with published human genetic data; ◦ safety and tolerability; • completed enrollment of the Phase 3 PALISADE clinical trial evaluating ARO-APOC3 for treatment of familial chylomicronemia syndrome; • announced interim results from ARO-RAGE administration in Part 1 of the ongoing Phase 1/2 study in normal healthy volunteers which included: ◦ reductions in soluble RAGE (sRAGE) as measured in serum after two doses on Day 1 and Day 29; ◦ duration of pharmacologic effect persisted for at least 6 weeks after the second administration of the 92 mg does with further follow up ongoing; ◦ reduction in sRAGE as measured in bronchoalveolar lavage fluid (BALF) at Day 31 after a single dose; ◦ reduction in in serum sRAGE was observed after a single dose; ◦ the pooled placebo groups experienced a mean sRAGE increase of 8% in BALF and a mean decrease of 1% serum; ◦ safety and tolerability; • expanded TRiM TM platform to include an optimized intrathecal administration for CNS delivery with distribution throughout the brain and in all relevant brain cell types. The first development candidate to utilize this new delivery platform is ARO-SOD1. In June 2023, the Company filed a clinical trial application (CTA) for approval to initiate a Phase 1 clinical study. In preclinical studies, ARO-SOD1 achieved 95% spinal cord tissue mRNA knockdown after a single intrathecal dose in human SOD1 transgenic rats and maintained greater than 80% spinal cord tissue mRNA knockdown three months after a single intrathecal dose in non-human primates; • dosed the first patient in Takeda’s Phase 3 REDWOOD clinical study of Fazirsiran for the treatment of alpha-1 antitrypsin deficiency associated liver diseases, triggering a $40.0 million milestone payment to the Company which was paid in the third quarter of fiscal 2023; • dosed the first patient in GSK’s Phase 2b trial of GSK4532990, formerly called ARO-HSD, an investigational RNAi therapeutic for the treatment of patients with non-alcoholic steatohepatitis (NASH), triggering a $30.0 million milestone payment to the Company which was paid in the third quarter of fiscal 2023; • announced that the U.S. Food and Drug Administration (FDA) has granted Fast Track designation to ARO-APOC3 for reducing triglycerides in adult patients with familial chylomicronemia syndrome (FCS). ARO-APOC3 was previously granted Orphan Drug designation by the FDA and the European Union; • announced interim results from Part 1 of AROC3-1001, an ongoing Phase 1/2 clinical study of ARO-C3, which included: ◦ a dose-dependent reduction in serum C3, with 88% mean reduction at highest dose tested; ◦ a dose-dependent reduction in AH50, a marker of alternative complement pathway hemolytic activity, with 91% mean reduction at highest dose tested; ◦ duration of pharmacologic effect supportive of quarterly or less frequent subcutaneous dose administration; ◦ safety and tolerability; • received notice from Janssen of its decision to voluntarily terminate the Research Collaboration and Option Agreement (the “Janssen Collaboration Agreement”) between the Company and Janssen. The Company regained full rights to ARO-PNPLA3, formerly called JNJ-75220795, upon termination of the Janssen Collaboration Agreement, which took effect on April 7, 2023. ARO-PNPLA3 is in Phase 1 clinical trials that are now being developed by the Company; • initiated dosing in ARO-MMP7-1001 (NCT05537025), a Phase 1/2a single ascending dose and multiple ascending dose clinical study to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of ARO-MMP7, an investigational RNAi therapeutic designed to reduce expression of matrix metalloproteinase 7 (MMP7) as a potential treatment for idiopathic pulmonary fibrosis (IPF), in up to 56 healthy volunteers and in up to 21 patients with IPF; • enrolled the first subject in a Phase 1 randomized, placebo-controlled trial to assess the safety tolerability, pharmacokinetics and pharmacodynamics of a development-stage medicine, HZN-457 (previously known as ARO-XDH), which is out-licensed to Horizon, triggering a $15.0 million milestone payment to the Company which was paid in the second quarter of fiscal 2023; • enrolled the first subject in Amgen’s Phase 3 trial of Olpasiran, triggering a $25.0 million milestone payment to the Company which was paid in the second quarter of fiscal 2023; • entered into a Royalty Purchase Agreement (the “Royalty Pharma Agreement”) with Royalty Pharma Investments 2019 ICAV (“Royalty Pharma”) on November 9, 2022, pursuant to which Royalty Pharma paid $250.0 million upfront (See Note 11 — Liability Related to the Sale of Future Royalties of Notes to Consolidated Financial Statements of Part I, “Item 1. Financial Statements.”); • announced top line results from the SEQUOIA Phase 2 Study of Fazirsiran in patients with Alpha-1 Antitrypsin Deficiency-Associated Liver Disease in which: ◦ fibrosis regression was observed in 50% of patients receiving Fazirsiran; ◦ median reductions of 94% of Z-AAT accumulation in the liver and mean reductions of 68% in histologic globule burden were observed; ◦ treatment emergent adverse events were generally well balanced between Fazirsiran and placebo groups; ◦ results were consistent with AROAAT-2002 open-label study previously published in The New England Journal of Medicine. Consolidation and Basis of Presentation The interim Consolidated Financial Statements include the accounts of Arrowhead Pharmaceuticals, Inc. and its subsidiaries (wholly-owned subsidiaries and a variable interest entity for which the Company is the primary beneficiary). Subsidiaries refer to Arrowhead Madison, Inc., Visirna Therapeutics, Inc. (“Visirna”), and Arrowhead Australia Pty Ltd. For subsidiaries in which the Company owns or is exposed to less than 100% of the economics, the Company records net loss attributable to noncontrolling interests in its consolidated statements of operations equal to the percentage of the economic or ownership interests retained in such entity by the respective noncontrolling party. The interim Consolidated Financial Statements have been prepared in conformity with U.S. generally accepted accounting principles (“GAAP”). The financial data of the Company included herein are unaudited. In the opinion of management, all material adjustments of a normal recurring nature have been made to present fairly the Company’s financial position at June 30, 2023 and the results of operations and cash flows for the periods presented. All intercompany transactions and balances have been eliminated. Certain prior period amounts have been reclassified to conform with the current period presentation. Certain financial information that is normally included in annual financial statements prepared in accordance with GAAP, but that is not required for interim reporting purposes, has been omitted from the accompanying interim consolidated financial statements and related notes. Readers are urged to review the Company’s Annual Report on Form 10-K for the year ended September 30, 2022 for more complete descriptions and discussions. Operating results and cash flows for the nine months ended June 30, 2023 are not necessarily indicative of the results that may be expected for the fiscal year ending September 30, 2023. Liquidity The Company’s primary sources of financing have been through the sale of its securities, revenue from its licensing and collaboration agreements and the sale of certain future royalties. 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 and as the Company plans to increase its internal manufacturing capabilities. At June 30, 2023, the Company had $105.3 million in cash and cash equivalents (including $7.3 million in restricted cash), $346.4 million in short-term investments and $42.8 million in long-term investments to fund operations. During the nine months ended June 30, 2023, the Company’s cash and cash equivalents and investments balance increased by $12.2 million which was primarily due to the $250.0 million upfront payment received from Royalty Pharma (Note 11) and $110.0 million in milestone payments from the Company’s collaboration and license agreements, partially offset by cash used to fund its operations. In total, the Company is eligible to receive up to $3.4 billion in developmental, regulatory and sales milestones, and may receive various royalties on net sales from its licensing and collaboration agreements, subject to the terms and conditions of those agreements. The revenue recognition for these collaboration agreements is discussed further in Note 2. 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 for the fiscal year ended September 30, 2022. 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 for the fiscal year ended September 30, 2022.

Collaboration and License Agree

Collaboration and License Agreements	9 Months Ended
	Jun. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaboration and License Agreements	COLLABORATION AND LICENSE AGREEMENTS The following table provides a summary of revenue recognized: Three Months Ended June 30, Nine Months Ended June 30, 2023 2022 2023 2022 (in thousands) GSK $ 277 $ — $ 29,600 $ 120,000 Horizon 1,539 6,666 23,206 21,251 Takeda 14,009 25,507 146,477 67,100 Janssen — 239 355 3,305 Amgen — — 25,000 — Total $ 15,825 $ 32,412 $ 224,638 $ 211,656 The following table summarizes the balance of receivables and contract liabilities related to the Company’s collaboration and license agreements: June 30, 2023 September 30, 2022 (in thousands) Receivables included in accounts receivable $ 1,539 $ 6,174 Contract liabilities included in deferred revenue $ 16,905 $ 130,049 Glaxosmithkline Intellectual Property (No. 3) Limited (“GSK”) On November 22, 2021, GSK and the Company entered into an Exclusive License Agreement (the “GSK License Agreement”). Under the GSK License Agreement, GSK has received an exclusive license for GSK-4532990 (formerly ARO-HSD). The exclusive license is worldwide with the exception of greater China. The Company completed its Phase 1/2 study of GSK-4532990, and GSK is wholly responsible for all clinical development and commercialization of GSK-4532990 in its territory. Under the terms of the agreement, the Company has received an upfront payment of $120.0 million and recognized an additional $30.0 million at the start of a Phase 2 trial. The Company is also eligible for an additional payment of $100.0 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 $190.0 million at first commercial sale, and up to $590.0 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. 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 the 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, which 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 GSK-4532990 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 was fully recognized during the six months ended March 31, 2022. Further, GSK dosed the first patient in a Phase 2 trial in March 2023, triggering a $30.0 million milestone payment to the Company which was paid in the third quarter of fiscal 2023. There were no contract assets and liabilities recorded as of June 30, 2023. Horizon Therapeutics Ireland DAC (“Horizon”) On June 18, 2021, Horizon and the Company entered into a collaboration and license agreement (the “Horizon License Agreement”). Under the terms of the Horizon License Agreement, Horizon received a worldwide exclusive license for HZN-457, a clinical-stage medicine being developed by Horizon as a potential treatment for people with uncontrolled gout. The Company conducted all activities through the preclinical stages of development of, and Horizon is now wholly responsible for clinical development and commercialization of, HZN-457. The Company received $40.0 million as an upfront payment in July 2021 and an additional $15.0 million upon Horizon’s initiation of a Phase 1 clinical trial in January 2023, and is eligible to receive up to $645.0 million in additional 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. 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 HZN-457 (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 is responsible for managing future clinical development and commercialization of HZN-457. 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 allocated the total $40.0 million initial transaction price to its one distinct performance obligation for the HZN-457 license and the associated Horizon R&D Services. Revenue was recognized on a straight-line basis over the timeframe for completing the Horizon R&D Services. The Company determined that the straight-line basis was appropriate as its efforts were expended evenly over the course of completing its performance obligation. Further, Horizon enrolled the first subject in December 2022 in a Phase 1 randomized, placebo-controlled trial to assess the safety, tolerability, pharmacokinetics and pharmacodynamics of HZN-457, triggering a $15.0 million milestone payment to the Company which was paid in the second quarter of fiscal 2023. There was $1.5 million in contract assets recorded as accounts receivable and $0 contract liabilities as of June 30, 2023. Takeda Pharmaceutical Company Limited (“Takeda”) On October 7, 2020, Takeda and the Company entered into an Exclusive License and Co-Funding Agreement (the “Takeda License Agreement”). Under the Takeda License Agreement, Takeda and the Company will co-develop its Fazirsiran 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, Fazirsiran, 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 received an exclusive license to commercialize Fazirsiran, while the Company will be eligible to receive tiered royalties of 20% to 25% on net sales. The Company received $300.0 million as an upfront payment in January 2021, recognized an additional $40.0 million upon Takeda’s initiation of a Phase 3 clinical study in March 2023, and is eligible to receive potential development, regulatory and commercial milestones of up to $527.5 million. 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 Fazirsiran 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 are recorded as research and development expenses or general and administrative expenses, as appropriate. The Company has allocated the total $300.0 million initial transaction price to its one distinct performance obligation for the Fazirsiran license and the associated Takeda R&D Services. Revenue is 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). The Company previously expected these clinical trials to extend to September 2025 in order to demonstrate long term safety and efficacy in the open label extension (OLE) part of the studies; however, Takeda now intends to initiate a new OLE study available to patients participating in these Phase 2 studies that will initiate as early as the fourth quarter of fiscal 2023. Based on this new information, patients enrolled in the SEQUOIA and AROAAT2002 studies are expected to complete their Phase 2 study visits between June 2023 and June 2024, shortening the Company’s performance obligation. As a result, effective the second quarter of fiscal 2023, the Company changed its estimates of the revenue recognition to better reflect this newly estimated performance period. The effect of these changes in estimates resulted in accelerated revenue by $61.4 million, or $0.58 per share (diluted) for each of the three and nine months ended June 30, 2023. There were $16.9 million of contract liabilities recorded as deferred revenue, of which $16.9 million was classified as current as of June 30, 2023. In March 2023, Takeda dosed the first patient in the Phase 3 REDWOOD clinical study of Fazirsiran, triggering a $40.0 million milestone payment to the Company which was paid in the third quarter of fiscal 2023. The Company also recorded $1.4 million as accrued expenses as of June 30, 2023 that was primarily driven by co-development and co-commercialization activities. Janssen Pharmaceuticals, Inc. (“Janssen”) On October 3, 2018, Janssen, part of the Janssen Pharmaceutical Companies of Johnson & Johnson, and the Company entered into a License Agreement (the “Janssen License Agreement”) and the Janssen Collaboration Agreement. The Company also entered into a stock purchase agreement with JJDC, Inc. (“JJDC”), Johnson & Johnson’s venture capital arm (the “JJDC Stock Purchase Agreement”). Under the Janssen License Agreement, Janssen 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 (ARO-HBV). Under the terms of the Janssen License Agreement, the Company has received $175.0 million as an upfront payment, $75.0 million in the form of an equity investment by JJDC in the Company’s common stock under the JJDC Stock Purchase Agreement, and milestone and option payments totaling $73.0 million, and the Company may receive up to $0.8 billion in development and sales milestone payments for the Janssen License Agreement. The Company is further eligible to receive tiered royalties on product sales up to mid-teens under the Janssen License Agreement. In May 2021, Janssen exercised its option right for JNJ-75220795 (ARO-JNJ1) which resulted in a $10.0 million milestone payment to the Company. This $10.0 million milestone payment was recognized entirely as of September 30, 2021. The Company 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. On April 7, 2023, Janssen voluntarily terminated the Janssen Collaboration Agreement. Upon termination, the Company regained full rights to ARO-PNPLA3, formerly called JNJ-75220795, the only candidate for which Janssen had exercised its option. At the inception of 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 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 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. There were no contract assets and liabilities recorded as of June 30, 2023. Amgen Inc. (“Amgen”) On September 28, 2016, Amgen and the Company entered into two collaboration and license agreements and a common stock purchase agreement. Under the Second Collaboration and License Agreement (the “Olpasiran Agreement”), Amgen received a worldwide, exclusive license to the Company’s novel RNAi Olpasiran 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 first collaboration and license agreement (the “First Collaboration and License Agreement” or the “ARO-AMG1 Agreement”), Amgen received an option to a worldwide, exclusive license to 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 Olpasiran Agreement and the ARO-AMG1 Agreement, the Company has received $35.0 million in upfront payments and $21.5 million in the form of an equity investment by Amgen in the Company’s common stock. Further, the Company received additional an $55.0 million in milestone payments; $10.0 million upon Amgen’s initiation of Phase 1 study in September 2018, $20.0 million upon its initiation of a Phase 2 clinical study in July 2020, and $25.0 million upon its first subject enrollment in a Phase 3 trial in December 2022. The Company has substantially completed its performance obligations under the Olpasiran Agreement and the ARO-AMG1 Agreement. There were no contract assets and liabilities recorded as of June 30, 2023. In November 2022, Royalty Pharma and the Company entered into the Royalty Pharma Agreement. In consideration for the payments under the Royalty Pharma Agreement, Royalty Pharma is entitled to receive all royalties otherwise payable by Amgen to the Company under the Olpasiran Agreement. The Company remains eligible to receive up to an additional $535.0 million in remaining development, regulatory and sales milestone payments payable from Amgen and Royalty Pharma. See Note 11. Joint Venture and License Agreement with Visirna Therapeutics, Inc. (“Visirna”) On April 25, 2022, Visirna and the Company entered into a License Agreement (the “Visirna License Agreement”), pursuant to which Visirna received an exclusive license to develop, manufacture and commercialize four of the Company’s

Property and Equipment

Property and Equipment	9 Months Ended
	Jun. 30, 2023
Property, Plant and Equipment [Abstract]
Property and Equipment	PROPERTY AND EQUIPMENT The following table summarizes the Company’s major classes of property and equipment: June 30, 2023 September 30, 2022 (in thousands) Computers, software, office equipment and furniture $ 2,198 $ 2,182 Land 2,996 2,996 Research equipment 50,472 38,283 Leasehold improvements 96,344 42,017 Construction in progress 118,279 56,373 270,289 141,851 Less: Accumulated depreciation and amortization (38,920) (31,554) Property and equipment, net $ 231,369 $ 110,297 Depreciation and amortization expense for property and equipment for the three months ended June 30, 2023 and 2022 was $2.9 million and $2.2 million, respectively. Depreciation and amortization expense for property and equipment for the nine months ended June 30, 2023 and 2022 was $7.4 million and $6.5 million, respectively. The increase in the construction in progress during the nine months ended June 30, 2023 was mainly due to the continuing developments of manufacturing, laboratory and office facilities in Verona, Wisconsin as well as a new laboratory and office facility in San Diego, California. In May 2023, the Company completed the development of the San Diego facility, which resulted in the reclassification of construction in progress as leasehold improvements as of June 30, 2023. See Note 7.

Investments

Investments	9 Months Ended
	Jun. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Investments	INVESTMENTS The Company’s investments consisted of the following: As of June 30, 2023 (in thousands) Adjusted Basis Gross Gross Fair Value Short-term investments (due within one year) Held to maturity debt securities $ 346,369 $ — $ (4,204) $ 342,165 Held to maturity certificate of deposit — — — — Total short-term investments $ 346,369 $ — $ (4,204) $ 342,165 Long-term investments (due within one through three years) Held to maturity debt securities $ 42,758 $ — $ (294) $ 42,464 Total long-term investments $ 42,758 $ — $ (294) $ 42,464 As of September 30, 2022 (in thousands) Adjusted Basis Gross Gross Fair Value Short-term investments (due within one year) Held to maturity debt securities $ 218,391 $ — $ (3,661) $ 214,730 Held to maturity certificate of deposit 50,000 — — 50,000 Total short-term investments $ 268,391 $ — $ (3,661) $ 264,730 Long-term investments (due within one through three years) Held to maturity debt securities $ 105,872 $ — $ (5,569) $ 100,303 Total long-term investments $ 105,872 $ — $ (5,569) $ 100,303

Intangible Assets

Intangible Assets	9 Months Ended
	Jun. 30, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	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 following table presents the components of intangible assets: Gross Carrying Amount Accumulated Amortization Impairment Net Carrying Amount Useful Lives (in thousands) (in years) As of June 30, 2023 Patents $ 21,728 $ 12,933 $ — $ 8,795 14 License 3,129 1,237 — 1,892 21 Total intangible assets, net $ 24,857 $ 14,170 $ — $ 10,687 As of September 30, 2022 Patents $ 21,728 $ 11,770 $ — $ 9,958 14 License 3,129 1,125 — 2,004 21 Total intangible assets, net $ 24,857 $ 12,895 $ — $ 11,962 Intangible assets are reviewed annually for impairment and more frequently if potential impairment indicators exist. No impairment indicators were identified during the nine months ended June 30, 2023 and 2022. Intangible assets with definite useful lives are amortized on a straight-line basis over their useful lives. Intangible assets amortization expense was $0.4 million for each of the three months ended June 30, 2023 and 2022, and $1.3 million and for each of the nine months ended June 30, 2023 and 2022. None of the intangible assets with definite useful lives are anticipated to have a residual value. The following table presents the estimated future amortization expense related to intangible assets as of June 30, 2023: Amortization Expense Year Ending September 30, (in thousands) 2023 (remainder) $ 425 2024 1,700 2025 1,700 2026 1,700 2027 1,700 Thereafter 3,462 Total $ 10,687

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Jun. 30, 2023
Equity [Abstract]
Stockholders' Equity	STOCKHOLDERS’ EQUITY The following table summarizes the Company’s shares of common stock and preferred stock: Shares Par Value Authorized Issued Outstanding (in thousands) As of June 30, 2023 Common stock $ 0.001 290,000 107,102 107,102 Preferred stock $ 0.001 5,000 — — As of September 30, 2022 Common stock $ 0.001 145,000 105,960 105,960 Preferred stock $ 0.001 5,000 — — On March 16, 2023, the Company’s stockholders approved an increase in authorized common shares, par value 0.001 per share, from 145,000,000 to 290,000,000. The amendment to the Amended and Restated Certificate of Incorporation was filed on April 27, 2023. As of June 30, 2023 and September 30, 2022, respectively, 12,914,571 and 14,000,392 shares of common stock were reserved for issuance upon exercise of options and vesting of restricted stock units granted or available for grant under the Company’s 2004 Equity Incentive Plan, 2013 Incentive Plan, and 2021 Incentive Plan, as well as for inducement grants made to new employees under Rule 5635(c)(4) of the Nasdaq Listing Rules. On December 2, 2022, the Company entered into an open market sale agreement (the “Open Market Sale 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 (“ATM Offering”). The Company is not required to sell shares under the Open Market Sale 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 Open Market Sale Agreement. Unless otherwise terminated, the ATM Offering shall terminate upon the earlier of (i) the sale of all shares of common stock subject to the Sales Agreement and (ii) the termination of the Sales Agreement as permitted therein. The Company and Jefferies may each terminate the Open Market Sale Agreement at any time upon prior notice. As of June 30, 2023, no shares have been issued under the Open Market Sale Agreement.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Jun. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	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 June 30, 2023. Commitments On December 20, 2021, the Company completed a purchase of 13 acres of land in the Verona Technology Park in Verona, Wisconsin, which is being developed into an approximately 160,000 square foot drug manufacturing facility and an approximately 140,000 square foot laboratory and office facility which will support the Company’s process development and analytical activities. As of June 30, 2023, the Company has incurred $102.7 million and intends to spend an additional $160.0 million to $180.0 million to complete the build out of the facilities. As part of this acquisition, the Company entered into a development agreement with the City of Verona to construct certain infrastructure improvements within the tax incremental district and will be reimbursed up to $16.0 million by the City of Verona by future tax increment revenue generated from the developed property. The total amount of funding that the City of Verona will pay under the Tax Incremental Financing program is not guaranteed and will depend on future tax revenues generated from the developed property. The Company will also receive up to $2.5 million of refundable Wisconsin state income tax credits from the Wisconsin Economic Development Corporation (WEDC) as incentives to invest in the local community and create new jobs. 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 it may develop using these licensed technologies. These agreements and other similar

Leases

Leases	9 Months Ended
	Jun. 30, 2023
Leases [Abstract]
Leases	LEASES On November 19, 2021, the Company entered into a 15-year lease for approximately 144,000 square feet of office and research and development laboratory space in San Diego, California. This new facility accommodates increased personnel for its expanding pipeline of current and future drug candidates. The lease payments, which began on April 19, 2023, the rent commencement date, will be approximately $119.0 million over the initial 15-year term. The Company also estimates annual operating expenses to be approximately $3.0 million for the first year of the lease, and these payments will continue throughout the initial 15-year term. The Company expects to pay approximately $32.0 million for leasehold improvements, net of tenant improvement allowances. Pursuant to the lease, within twelve months of the expiration of the initial 15-year term, the Company has the option to extend the lease for up to one additional ten-year term, with certain annual increases in base rent. Further, the lease agreement grants the Company the right to receive an Additional Tenant Improvement Allowance (“ATIA”) funded by the lessor. The maximum amount of ATIA is $7.2 million, and as of June 30, 2023, the Company has received approximately $0.7 million, which has been recorded as other liabilities on its consolidated balance sheets. The Company will repay the ATIA through equal monthly payments, including 7% interest per annum over the base term, starting from the rent commencement date. Interest begins accruing on the date the lessor first disburses the ATIA. Other Significant Leases Pasadena, California : The Company leases 49,000 square feet of office space located at 177 Colorado Blvd. for its corporate headquarters from 177 Colorado Owner, LLC, which lease expires on April 30, 2027. The lease contains an option to renew for one term of five years. San Diego, California : The Company subleased space from Halozyme, Inc. for additional research and development space in San Diego, California. The term of this sublease commenced on April 1, 2020 and ended on January 14, 2023. On December 23, 2022, the Company entered into a new six-month lease agreement with 11404 & 11408 Sorrento Valley Owner (DE) LLC, effective January 15, 2023. The lease ended on July 15, 2023. Madison, Wisconsin : The Company leases space for office and laboratory facilities, which expires on September 30, 2031. The lease contains options to renew for two terms of five years. After accounting for additional rental square feet added pursuant to amendments to the lease agreement in 2019 and 2020, the Company currently leases a total of 111,000 square feet. The components of lease assets and liabilities along with their classification on the Company’s consolidated balance sheets were as follows: Lease Assets and Liabilities Classification June 30, 2023 September 30, 2022 (in thousands) Operating lease assets Right-of-use assets $ 40,667 $ 58,291 Current operating lease liabilities Lease liabilities 2,823 2,776 Non-current operating lease liabilities Lease liabilities, net of current portion 79,911 78,800 Three Months Ended June 30, Nine Months Ended June 30, Lease Cost Classification 2023 2022 2023 2022 (in thousands) Operating lease cost Research and development $ 3,323 $ 2,974 $ 7,735 $ 4,757 General and administrative expense 509 448 1,542 1,288 Variable lease cost (1) Research and development 257 179 627 519 General and administrative expense — — — — Total $ 4,089 $ 3,601 $ 9,904 $ 6,564 (1) Variable lease cost is primarily related to operating expenses associated with the Company’s operating leases. There was $0.6 million and $0.2 million short-term lease cost during the three months ended June 30, 2023, and 2022, respectively. There was $1.2 million and $0.7 million short-term lease cost during the nine months ended June 30, 2023, and 2022, respectively. The following table presents payments of operating lease liabilities on an undiscounted basis as of June 30, 2023: Year Amounts (in thousands) 2023 (remainder of fiscal year) $ 1,143 2024 8,094 2025 11,800 2026 12,148 2027 11,320 2028 and thereafter 102,812 Total $ 147,317 Less imputed interest $ (64,583) Total operating lease liabilities (includes current portion) $ 82,734 Supplemental cash flow and other information related to leases was as follows: Nine Months Ended June 30, 2023 2022 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases (in thousands) 4,430 3,398 June 30, 2023 2022 Weighted-average remaining lease term (in years) 13.4 7.3 Weighted-average discount rate 8.0 % 8.5 %

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Jun. 30, 2023
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	STOCK-BASED COMPENSATION The Company has three plans that provide for equity-based compensation. Under the 2004 Equity Incentive Plan (the “2004 Plan”) and 2013 Incentive Plan (the “2013 Plan”), 68,555 and 3,440,076 shares, respectively, of the Company’s common stock are reserved for grants of stock options and restricted stock awards to employees and directors as of June 30, 2023. On March 18, 2021, the Company’s Board of Directors approved the Arrowhead Pharmaceuticals, Inc. 2021 Incentive Plan (the “2021 Plan”), which authorized 8,000,000 shares (subject to certain adjustments) available for grants of stock options, stock appreciation rights, restricted and unrestricted stock, performance awards, cash awards and other awards convertible into or otherwise based on shares of the Company’s common stock. The maximum number of shares authorized under the 2021 Plan will be (i) reduced by any shares subject to awards made under the 2013 Plan after January 1, 2021, and (ii) increased by any shares subject to outstanding awards under the 2013 Plan as of January 1, 2021 that, after January 1, 2021, are canceled, expired, forfeited or otherwise not issued under such awards (other than as a result of being tendered or withheld to pay the exercise price or withholding taxes in connection with any such awards) or settled in cash. As of June 30, 2023, the total number of shares reserved for issuance was 6,186,644 shares, which included 197,596 shares that were forfeited under the 2013 Plan, and 1,977,114 shares have been granted under the 2021 Plan. In addition, there were 712,454 shares reserved for options and 746,175 shares reserved for restricted stock units issued as inducement grants to new employees granted outside of the Company’s equity-based compensation plans under Rule 5635(c)(4) of the Nasdaq Listing Rules. The following table presents a summary of awards outstanding: As of June 30, 2023 2004 Plan 2013 Plan 2021 Plan Inducement Awards Total Granted and outstanding awards: Options 68,555 1,550,951 33,838 712,454 2,365,798 Restricted stock units — 1,889,125 1,686,766 746,175 4,322,066 Total 68,555 3,440,076 1,720,604 1,458,629 6,687,864 The following table summarizes stock-based compensation expenses included in operating expenses: Three Months Ended June 30, Nine Months Ended June 30, 2023 2022 2023 2022 (in thousands) Research and development 8,982 8,098 26,129 23,958 General and administrative 10,965 25,292 33,820 67,739 Total $ 19,947 $ 33,390 $ 59,949 $ 91,697 Stock Option Awards The following table presents a summary of the stock option activity for the nine months ended June 30, 2023: Shares Weighted- Weighted- Aggregate Outstanding at September 30, 2022 2,721,384 $ 20.73 Granted 32,151 33.03 Cancelled or expired (43,936) 62.31 Exercised (343,801) 6.48 Outstanding at June 30, 2023 2,365,798 $ 22.20 4.4 years $ 43,813,599 Exercisable at June 30, 2023 2,188,690 $ 20.28 4.2 years $ 43,480,339 The aggregate intrinsic values represents the amount by which the market price of the underlying stock exceeds the exercise price of the option. The total intrinsic value of the options exercised during the three months ended June 30, 2023 and 2022 was $6.5 million and $1.6 million, respectively. The total intrinsic value of the options exercised during the nine months ended June 30, 2023 and 2022 was $10.1 million and $24.9 million, respectively. Stock-based compensation expense related to stock options outstanding for the three months ended June 30, 2023 and 2022, was $2.1 million and $2.6 million, respectively. Stock-based compensation expense related to stock options for the nine months ended June 30, 2023 and 2022 was $6.7 million and $8.3 million, respectively. As of June 30, 2023, the pre-tax compensation expense for all outstanding unvested stock options in the amount of $5.3 million will be recognized in the Company’s results of operations over a weighted average period of 12 months. 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, the existing models do not necessarily provide a reliable single measure of the fair value of its employee stock options. The following table provides the assumptions used in the calculation of grant-date fair values of these stock options based on the Back-Scholes option pricing model: Nine Months Ended June 30, 2023 2022 (5) Expected dividend yield (1) — N/A Risk-free interest rate (2) 3.69 % N/A Expected volatility (3) 86.4 % N/A Expected term (in years) (4) 6.25 N/A Weighted average grant date fair value per share of options granted $ 24.80 N/A (1) The dividend yield is zero as the Company currently does not pay a dividend. (2) The risk-free interest rate is based on that of the U.S. Treasury yields with equivalent terms in effect at the time of the grant. (3) Volatility is estimated based on volatility average of the Company’s common stock price. (4) The expected term represents the period of time that stock options granted are expected to be outstanding, by using historical exercise patterns and post-vesting termination behavior. (5) No options were granted during the nine months ended June 30, 2022. Restricted Stock Units Restricted stock units (“RSUs”), including market-based, time-based and performance-based awards, have been granted under the Company’s 2013 and 2021 Plans and as inducements grants granted outside of the Company’s equity-based compensation plans. 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 Weighted- Outstanding at September 30, 2022 4,069,431 $ 62.96 Granted 1,144,594 34.27 Vested (798,271) 53.72 Forfeited (93,688) 54.58 Outstanding at June 30, 2023 4,322,066 $ 57.45 The fair value of RSUs was determined based on the closing price of the Company’s common stock on the grant date, with consideration given to the probability of achieving service and/or performance conditions for awards. For the three months ended June 30, 2023 and 2022, the Company recorded $17.8 million and $33.7 million of expense

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Jun. 30, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS The Company employs a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The fair value of a financial instrument is the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date using the exit price. Accordingly, when market observable data are not readily available, the Company’s own assumptions are used to reflect those that market participants would be presumed to use in pricing the asset or liability at the measurement date. Assets and liabilities recorded at fair value on the consolidated balance sheets are categorized based on the level of judgment associated with inputs used to measure their fair values and the level of market price observability, as follows: Level 1 Unadjusted quoted prices are available in active markets for identical assets or liabilities as of the reporting date. Level 2 Pricing inputs are other than quoted prices in active markets, which are based on the following: • Quoted prices for similar assets or liabilities in active markets; • Quoted prices for identical or similar assets or liabilities in non-active markets; or • Either directly or indirectly observable inputs as of the reporting date. Level 3 Pricing inputs are unobservable and significant to the overall fair value measurement, and the determination of fair value requires significant management judgment or estimation. In certain cases, inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, the level in the fair value hierarchy within which the fair value measurement in its entirety falls has been determined based on the lowest level input that is significant to the fair value measurement in its entirety. Thus, a Level 3 fair value measurement may include inputs that are observable (Level 1 or Level 2) and unobservable (Level 3). The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and consideration of factors specific to the asset or liability. The Company uses prices and inputs that are current as of the measurement date, including during periods of market disruption. In periods of market disruption, the ability to observe prices and inputs may be reduced for many instruments. This condition could cause an instrument to be reclassified from Level 1 to Level 2, or from Level 2 to Level 3. The Company recognizes transfers between levels at either the actual date of the event or a change in circumstances that caused the transfer. At June 30, 2023 and September 30, 2022, the Company did not have any financial assets or financial liabilities based on Level 3 measurements. The following table presents information about the Company’s assets and liabilities measured at fair value on a recurring basis, and indicates the fair value hierarchy of the valuation techniques utilized by the Company: June 30, 2023 Level 1 Level 2 Level 3 Total (in thousands) Financial assets: U.S. government bonds $ 27,092 $ — $ — $ 27,092 Municipal securities — 7,033 — 7,033 Commercial notes — 62,755 — 62,755 Corporate debt securities — 287,749 — 287,749 Certificate of deposits — — — — Money market instruments 49,199 — — 49,199 September 30, 2022 Level 1 Level 2 Level 3 Total (in thousands) U.S. government bonds $ 1,973 $ — $ — $ 1,973 Commercial notes — 41,727 — 41,727 Corporate debt securities — 271,333 — 271,333 Certificate of deposits 50,000 — — 50,000 Money market instruments 39,262 — — 39,262

Liability Related to the Sale o

Liability Related to the Sale of Future Royalties	9 Months Ended
	Jun. 30, 2023
Liability Related To The Sale Of Future Royalties [Abstract]
Liability Related to the Sale of Future Royalties	LIABILITY RELATED TO THE SALE OF FUTURE ROYALTIES On November 9, 2022, the Company and Royalty Pharma entered into the Royalty Pharma Agreement, pursuant to which Royalty Pharma agreed to pay up to $410.0 million in cash to the Company in consideration for the Company’s future royalty interest in Olpasiran, a small interfering RNA (siRNA) originally developed by the Company and licensed to Amgen in 2016 under the Olpasiran Agreement. Pursuant to the Royalty Pharma Agreement, Royalty Pharma paid $250.0 million upfront and agreed to pay up to an additional $160.0 million in aggregate one-time milestone payments due if and when the following milestone events occur: (i) $50.0 million on completion of enrollment in the OCEAN Phase 3 clinical trial for Olpasiran, (ii) $50.0 million upon receipt of FDA approval of Olpasiran for an approved indication (reduction in the risk of myocardial infarction, urgent coronary revascularization, or coronary heart disease death in adults with established cardiovascular disease and elevated Lp(a)), and (iii) $60.0 million upon Royalty Pharma’s receipt of at least $70.0 million of royalty payments under the Royalty Pharma Agreement in any single calendar year. In consideration for the payment of the foregoing amounts under the Royalty Pharma Agreement, Royalty Pharma is entitled to receive all royalties otherwise payable by Amgen to the Company under the Olpasiran Agreement. The Company remains eligible to receive any milestone payments potentially payable by Amgen under the Olpasiran Agreement. The Company has evaluated the terms of the Royalty Pharma Agreement and concluded in accordance with the relevant accounting guidance that the Company accounted for the transaction as debt and the funding of $250.0 million from Royalty Pharma was recorded as a liability related to the sale of future royalties on its consolidated balance sheets. The Company is not obligated to repay this upfront funding received under the Royalty Pharma Agreement. This liability is amortized over the expected repayment term using an effective interest rate method. The effective interest rate is calculated based on the rate that would enable the debt to be repaid in full over the anticipated life of the arrangement. The interest rate may vary during the term of the agreement depending on a number of factors, including the amount and timing of forecasted net revenues which affects the repayment timing and ultimate amount of repayment. The Company will evaluate the effective interest rate periodically based on its current revenue forecasts utilizing the prospective method. For the three and nine months ended June 30, 2023, the Company recognized non-cash interest expense of $5.2 million and $13.1 million, respectively, on the consolidated statements of operations and comprehensive loss.

Earnings Per Share

Earnings Per Share	9 Months Ended
	Jun. 30, 2023
Earnings Per Share [Abstract]
Earnings Per Share	EARNINGS PER SHAREThe following table presents the computation of basic and diluted earnings per share for the nine months ended June 30, 2023 and 2022. Three Months Ended June 30, Nine Months Ended June 30, 2023 2022 2023 2022 (in thousands, except per share amounts) Numerator: Net loss $ (102,946) $ (72,046) $ (95,596) $ (90,552) Denominator: Weighted-average basic shares outstanding 107,004 105,753 106,597 105,273 Effect of dilutive securities — — — — Weighted-average diluted shares outstanding 107,004 105,753 106,597 105,273 Basic earnings per share $ (0.96) $ (0.68) $ (0.90) $ (0.86) Diluted earnings per share $ (0.96) $ (0.68) $ (0.90) $ (0.86)

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Jun. 30, 2023	Jun. 30, 2022
Pay vs Performance Disclosure
Net loss	$ (102,946)	$ 48,675	$ (41,325)	$ (72,046)	$ 44,366	$ (62,872)	$ (95,596)	$ (90,552)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Jun. 30, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Organization and Significant _2

Organization and Significant Accounting Policies (Policies)	9 Months Ended
	Jun. 30, 2023
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 for the fiscal year ended September 30, 2022.

Organization and Significant _3

Organization and Significant Accounting Policies (Tables)	9 Months Ended
	Jun. 30, 2023
Accounting Policies [Abstract]
Schedule of Company's Current Pipeline	The following table presents the Company’s current pipeline: Therapeutic Area Name Stage Product Rights Cardiometabolic ARO-APOC3 Phase 2b and Phase 3 Arrowhead ARO-ANG3 Phase 2b Arrowhead Olpasiran Phase 3 Amgen Pulmonary ARO-ENAC2 Pre-Clinical Arrowhead ARO-RAGE Phase 1/2 Arrowhead ARO-MUC5AC Phase 1/2a Arrowhead ARO-MMP7 Phase 1/2a Arrowhead Liver GSK-4532990 (formerly ARO-HSD) Phase 2 GSK Fazirsiran Phase 3 Takeda and Arrowhead JNJ-3989 Phase 2 Janssen HZN-457 (formerly ARO-XDH) Phase 1 Horizon ARO-C3 Phase 1/2 Arrowhead ARO-PNPLA3 (formerly JNJ-75220795) Phase 1 Arrowhead Muscle ARO-DUX4 Pre-Clinical Arrowhead Central Nervous System (CNS) ARO-SOD1 Pre-Clinical Arrowhead

Collaboration and License Agr_2

Collaboration and License Agreements (Tables)	9 Months Ended
	Jun. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Revenue	The following table provides a summary of revenue recognized: Three Months Ended June 30, Nine Months Ended June 30, 2023 2022 2023 2022 (in thousands) GSK $ 277 $ — $ 29,600 $ 120,000 Horizon 1,539 6,666 23,206 21,251 Takeda 14,009 25,507 146,477 67,100 Janssen — 239 355 3,305 Amgen — — 25,000 — Total $ 15,825 $ 32,412 $ 224,638 $ 211,656
Schedule of Receivables and Contract Liabilities	The following table summarizes the balance of receivables and contract liabilities related to the Company’s collaboration and license agreements: June 30, 2023 September 30, 2022 (in thousands) Receivables included in accounts receivable $ 1,539 $ 6,174 Contract liabilities included in deferred revenue $ 16,905 $ 130,049

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Jun. 30, 2023
Property, Plant and Equipment [Abstract]
Summary of Property and Equipment	The following table summarizes the Company’s major classes of property and equipment: June 30, 2023 September 30, 2022 (in thousands) Computers, software, office equipment and furniture $ 2,198 $ 2,182 Land 2,996 2,996 Research equipment 50,472 38,283 Leasehold improvements 96,344 42,017 Construction in progress 118,279 56,373 270,289 141,851 Less: Accumulated depreciation and amortization (38,920) (31,554) Property and equipment, net $ 231,369 $ 110,297

Investments (Tables)

Investments (Tables)	9 Months Ended
	Jun. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Summary of Short-term and Long-term Investments and Marketable Securities	The Company’s investments consisted of the following: As of June 30, 2023 (in thousands) Adjusted Basis Gross Gross Fair Value Short-term investments (due within one year) Held to maturity debt securities $ 346,369 $ — $ (4,204) $ 342,165 Held to maturity certificate of deposit — — — — Total short-term investments $ 346,369 $ — $ (4,204) $ 342,165 Long-term investments (due within one through three years) Held to maturity debt securities $ 42,758 $ — $ (294) $ 42,464 Total long-term investments $ 42,758 $ — $ (294) $ 42,464 As of September 30, 2022 (in thousands) Adjusted Basis Gross Gross Fair Value Short-term investments (due within one year) Held to maturity debt securities $ 218,391 $ — $ (3,661) $ 214,730 Held to maturity certificate of deposit 50,000 — — 50,000 Total short-term investments $ 268,391 $ — $ (3,661) $ 264,730 Long-term investments (due within one through three years) Held to maturity debt securities $ 105,872 $ — $ (5,569) $ 100,303 Total long-term investments $ 105,872 $ — $ (5,569) $ 100,303

Intangible Assets (Tables)

Intangible Assets (Tables)	9 Months Ended
	Jun. 30, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Finite-Lived Intangible Assets	The following table presents the components of intangible assets: Gross Carrying Amount Accumulated Amortization Impairment Net Carrying Amount Useful Lives (in thousands) (in years) As of June 30, 2023 Patents $ 21,728 $ 12,933 $ — $ 8,795 14 License 3,129 1,237 — 1,892 21 Total intangible assets, net $ 24,857 $ 14,170 $ — $ 10,687 As of September 30, 2022 Patents $ 21,728 $ 11,770 $ — $ 9,958 14 License 3,129 1,125 — 2,004 21 Total intangible assets, net $ 24,857 $ 12,895 $ — $ 11,962
Schedule of Intangible Assets Future Amortization Expense	The following table presents the estimated future amortization expense related to intangible assets as of June 30, 2023: Amortization Expense Year Ending September 30, (in thousands) 2023 (remainder) $ 425 2024 1,700 2025 1,700 2026 1,700 2027 1,700 Thereafter 3,462 Total $ 10,687

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Jun. 30, 2023
Equity [Abstract]
Schedule of Shares of Common Stock and Preferred Stock	The following table summarizes the Company’s shares of common stock and preferred stock: Shares Par Value Authorized Issued Outstanding (in thousands) As of June 30, 2023 Common stock $ 0.001 290,000 107,102 107,102 Preferred stock $ 0.001 5,000 — — As of September 30, 2022 Common stock $ 0.001 145,000 105,960 105,960 Preferred stock $ 0.001 5,000 — —

Leases (Tables)

Leases (Tables)	9 Months Ended
	Jun. 30, 2023
Leases [Abstract]
Schedule of Lease Assets and Liabilities and Lease Cost	The components of lease assets and liabilities along with their classification on the Company’s consolidated balance sheets were as follows: Lease Assets and Liabilities Classification June 30, 2023 September 30, 2022 (in thousands) Operating lease assets Right-of-use assets $ 40,667 $ 58,291 Current operating lease liabilities Lease liabilities 2,823 2,776 Non-current operating lease liabilities Lease liabilities, net of current portion 79,911 78,800 Three Months Ended June 30, Nine Months Ended June 30, Lease Cost Classification 2023 2022 2023 2022 (in thousands) Operating lease cost Research and development $ 3,323 $ 2,974 $ 7,735 $ 4,757 General and administrative expense 509 448 1,542 1,288 Variable lease cost (1) Research and development 257 179 627 519 General and administrative expense — — — — Total $ 4,089 $ 3,601 $ 9,904 $ 6,564
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 June 30, 2023: Year Amounts (in thousands) 2023 (remainder of fiscal year) $ 1,143 2024 8,094 2025 11,800 2026 12,148 2027 11,320 2028 and thereafter 102,812 Total $ 147,317 Less imputed interest $ (64,583) Total operating lease liabilities (includes current portion) $ 82,734 Supplemental cash flow and other information related to leases was as follows: Nine Months Ended June 30, 2023 2022 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases (in thousands) 4,430 3,398 June 30, 2023 2022 Weighted-average remaining lease term (in years) 13.4 7.3 Weighted-average discount rate 8.0 % 8.5 %

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Jun. 30, 2023
Share-Based Payment Arrangement [Abstract]
Summary of Awards Outstanding	The following table presents a summary of awards outstanding: As of June 30, 2023 2004 Plan 2013 Plan 2021 Plan Inducement Awards Total Granted and outstanding awards: Options 68,555 1,550,951 33,838 712,454 2,365,798 Restricted stock units — 1,889,125 1,686,766 746,175 4,322,066 Total 68,555 3,440,076 1,720,604 1,458,629 6,687,864
Share-Based Payment Arrangement, Expensed	The following table summarizes stock-based compensation expenses included in operating expenses: Three Months Ended June 30, Nine Months Ended June 30, 2023 2022 2023 2022 (in thousands) Research and development 8,982 8,098 26,129 23,958 General and administrative 10,965 25,292 33,820 67,739 Total $ 19,947 $ 33,390 $ 59,949 $ 91,697
Summarized Information about Stock Options	The following table presents a summary of the stock option activity for the nine months ended June 30, 2023: Shares Weighted- Weighted- Aggregate Outstanding at September 30, 2022 2,721,384 $ 20.73 Granted 32,151 33.03 Cancelled or expired (43,936) 62.31 Exercised (343,801) 6.48 Outstanding at June 30, 2023 2,365,798 $ 22.20 4.4 years $ 43,813,599 Exercisable at June 30, 2023 2,188,690 $ 20.28 4.2 years $ 43,480,339
Assumptions Used to Value Stock Options	The following table provides the assumptions used in the calculation of grant-date fair values of these stock options based on the Back-Scholes option pricing model: Nine Months Ended June 30, 2023 2022 (5) Expected dividend yield (1) — N/A Risk-free interest rate (2) 3.69 % N/A Expected volatility (3) 86.4 % N/A Expected term (in years) (4) 6.25 N/A Weighted average grant date fair value per share of options granted $ 24.80 N/A (1) The dividend yield is zero as the Company currently does not pay a dividend. (2) The risk-free interest rate is based on that of the U.S. Treasury yields with equivalent terms in effect at the time of the grant. (3) Volatility is estimated based on volatility average of the Company’s common stock price. (4) The expected term represents the period of time that stock options granted are expected to be outstanding, by using historical exercise patterns and post-vesting termination behavior. (5) No options were granted during the nine months ended June 30, 2022.
Summary of Share Activity Related to RSUs	The following table summarizes the activity of the Company’s RSUs: Number of Weighted- Outstanding at September 30, 2022 4,069,431 $ 62.96 Granted 1,144,594 34.27 Vested (798,271) 53.72 Forfeited (93,688) 54.58 Outstanding at June 30, 2023 4,322,066 $ 57.45

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Jun. 30, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements for Assets and Liabilities Measured at Fair Value on Recurring Basis	The following table presents information about the Company’s assets and liabilities measured at fair value on a recurring basis, and indicates the fair value hierarchy of the valuation techniques utilized by the Company: June 30, 2023 Level 1 Level 2 Level 3 Total (in thousands) Financial assets: U.S. government bonds $ 27,092 $ — $ — $ 27,092 Municipal securities — 7,033 — 7,033 Commercial notes — 62,755 — 62,755 Corporate debt securities — 287,749 — 287,749 Certificate of deposits — — — — Money market instruments 49,199 — — 49,199 September 30, 2022 Level 1 Level 2 Level 3 Total (in thousands) U.S. government bonds $ 1,973 $ — $ — $ 1,973 Commercial notes — 41,727 — 41,727 Corporate debt securities — 271,333 — 271,333 Certificate of deposits 50,000 — — 50,000 Money market instruments 39,262 — — 39,262

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Jun. 30, 2023
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table presents the computation of basic and diluted earnings per share for the nine months ended June 30, 2023 and 2022. Three Months Ended June 30, Nine Months Ended June 30, 2023 2022 2023 2022 (in thousands, except per share amounts) Numerator: Net loss $ (102,946) $ (72,046) $ (95,596) $ (90,552) Denominator: Weighted-average basic shares outstanding 107,004 105,753 106,597 105,273 Effect of dilutive securities — — — — Weighted-average diluted shares outstanding 107,004 105,753 106,597 105,273 Basic earnings per share $ (0.96) $ (0.68) $ (0.90) $ (0.86) Diluted earnings per share $ (0.96) $ (0.68) $ (0.90) $ (0.86)

Organization and Significant _4

Organization and Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Nov. 09, 2022	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2023	Sep. 30, 2022
Organization And Significant Accounting Policies [Line Items]
Cash, cash equivalents and restricted cash		$ 105,300		$ 105,300
Restricted cash		7,300		7,300
Short term investments		346,369		346,369	$ 268,391
Long-term investments		42,758		42,758	$ 105,872
Increase in cash and investments				12,200
Development regulatory and sales milestones payments		3,400,000		3,400,000
Horizon and Amgen
Organization And Significant Accounting Policies [Line Items]
Upfront milestone payment received				110,000
Takeda | License and Co-Funding Agreement
Organization And Significant Accounting Policies [Line Items]
Milestone payment receivable		40,000		40,000
GSK | Collaboration and License agreements
Organization And Significant Accounting Policies [Line Items]
Milestone payment receivable		30,000		30,000
Horizon
Organization And Significant Accounting Policies [Line Items]
Upfront milestone payment received		$ 15,000	$ 15,000
Amgen
Organization And Significant Accounting Policies [Line Items]
Upfront milestone payment received			$ 25,000
Royalty Pharma
Organization And Significant Accounting Policies [Line Items]
Upfront milestone payment received	$ 250,000			$ 250,000

Collaboration and License Agr_3

Collaboration and License Agreements - Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Revenue	$ 15,825	$ 32,412	$ 224,638	$ 211,656
GSK
Disaggregation of Revenue [Line Items]
Revenue	277	0	29,600	120,000
Horizon
Disaggregation of Revenue [Line Items]
Revenue	1,539	6,666	23,206	21,251
Takeda
Disaggregation of Revenue [Line Items]
Revenue	14,009	25,507	146,477	67,100
Janssen
Disaggregation of Revenue [Line Items]
Revenue	0	239	355	3,305
Amgen
Disaggregation of Revenue [Line Items]
Revenue	$ 0	$ 0	$ 25,000	$ 0

Collaboration and License Agr_4

Collaboration and License Agreements - Receivables and Contract Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Receivables included in accounts receivable	$ 1,539	$ 6,174
Contract liabilities included in deferred revenue	$ 16,905	$ 130,049

Collaboration and License Agr_5

Collaboration and License Agreements - Glaxosmithkline Intellectual Property (No. 3) Limited (Details) - USD ($)	Nov. 22, 2021	Oct. 03, 2018	Jun. 30, 2023	Sep. 30, 2022
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liabilities			$ 16,905,000	$ 74,099,000
Collaboration and License agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Initial transaction price		$ 252,700,000
GSK | Collaboration and License agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment	$ 120,000,000
Milestone payment receivable at start of phase two	30,000,000
Milestone payment receivable upon achievement of phase two and first patient dosed in phase three	100,000,000
Initial transaction price	120,000,000
Milestone payment receivable			30,000,000
Contract assets			0
Contract liabilities			$ 0
GSK | Collaboration and License agreements | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Commercial milestone payments at first commercial sale	190,000,000
Sales-related milestone payments	$ 590,000,000

Collaboration and License Agr_6

Collaboration and License Agreements - Horizon Therapeutics Ireland DAC (Details)		3 Months Ended
	Jun. 18, 2021 USD ($) obligation bundle	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Jan. 31, 2023 USD ($)	Sep. 30, 2022 USD ($)	Jul. 31, 2021 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development regulatory and sales milestones payments		$ 3,400,000,000
Contract liabilities		16,905,000			$ 74,099,000
Horizon
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront milestone payment received		15,000,000	$ 15,000,000
Horizon | ARO-XDH
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Cash received as due under collaboration agreement						$ 40,000,000
Milestone payment				$ 15,000,000
Number of distinct performance obligations | obligation	1
Initial transaction price	$ 40,000,000
Contract assets		1,500,000
Contract liabilities		$ 0
Horizon | License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of distinct bundle | bundle	1
Number of distinct performance obligations | obligation	1
Horizon | Maximum | ARO-XDH
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development regulatory and sales milestones payments	$ 645,000,000

Collaboration and License Agr_7

Collaboration and License Agreements - Takeda Pharmaceutical Company Limited (Details) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
	Oct. 07, 2020 USD ($) bundle obligation	Jun. 30, 2023 USD ($) $ / shares	Jun. 30, 2022 USD ($) $ / shares	Jun. 30, 2023 USD ($) $ / shares	Jun. 30, 2022 USD ($) $ / shares	Mar. 31, 2023 USD ($)	Sep. 30, 2022 USD ($)	Jan. 31, 2021 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development regulatory and sales milestones payments		$ 3,400,000		$ 3,400,000
Revenues		$ 15,825	$ 32,412	$ 224,638	$ 211,656
Diluted (in dollars per share) | $ / shares		$ (0.96)	$ (0.68)	$ (0.90)	$ (0.86)
Deferred revenue, net of current portion		$ 0		$ 0			$ 55,950
Deferred revenue		16,905		16,905			$ 74,099
Takeda | License and Co-Funding Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Cash received as due under collaboration agreement								$ 300,000
Milestone payment						$ 40,000
Number of distinct performance obligations | obligation	1
Number of distinct bundle | bundle	1
Initial transaction price	$ 300,000
Revenues		$ 61,400		$ 61,400
Diluted (in dollars per share) | $ / shares		$ 0.58		$ 0.58
Milestone payment receivable		$ 40,000		$ 40,000
Takeda | License and Co-Funding Agreement | Deferred Revenue
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue, net of current portion		16,900		16,900
Deferred revenue		16,900		16,900
Takeda | License and Co-Funding Agreement | Accrued Expenses
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue		1,400		1,400
Takeda | License and Co-Funding Agreement | Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of eligible to receive tiered royalties on net sales	20%
Takeda | License and Co-Funding Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of eligible to receive tiered royalties on net sales	25%
Development regulatory and sales milestones payments		$ 527,500		$ 527,500

Collaboration and License Agr_8

Collaboration and License Agreements - Janssen Pharmaceuticals, Inc. (Details) - USD ($)	Oct. 03, 2018	Jun. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	May 31, 2021
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development, regulatory and sales milestones payments		$ 3,400,000,000
Deferred revenue		16,905,000	$ 74,099,000
Collaboration and License agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Initial transaction price	$ 252,700,000
JJDC | Collaboration and License agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment	175,000,000
JJDC | Common Stock Purchase Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Proceeds from the issuance of common stock	75,000,000
Janssen
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment	73,000,000
Janssen | License Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development, regulatory and sales milestones payments	800,000,000
Janssen | JNJ-75220795 (ARO-JNJ1)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment				$ 10,000,000	$ 10,000,000
Janssen | JNJ-3989 (ARO-HBV) Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment	$ 25,000,000
Contract assets		0
Deferred revenue		$ 0

Collaboration and License Agr_9

Collaboration and License Agreements - Amgen, Inc (Details)	Sep. 28, 2016 USD ($) agreement	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)	Sep. 30, 2022 USD ($)	Jul. 31, 2020 USD ($)	Sep. 30, 2018 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liabilities		$ 16,905,000		$ 74,099,000
Amgen | Collaboration and License agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of agreements | agreement	2
Amgen | Olpasiran and ARO-AMG1 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment	$ 35,000,000
Proceeds from the issuance of common stock	$ 21,500,000
Milestone payments		55,000,000	$ 25,000,000		$ 20,000,000	$ 10,000,000
Contract assets		0
Contract liabilities		0
Amgen | Olpasiran Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional remaining development regulatory and sales milestones payments		$ 535,000,000

Collaboration and License Ag_10

Collaboration and License Agreements - Joint Venture and License Agreement with Visirna Therapeutics, Inc. (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Apr. 25, 2022	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Sep. 30, 2022
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Proceeds from investment in joint venture				$ 0	$ 60,000
Revenue		$ 15,825	$ 32,412	224,638	$ 211,656
Deferred revenue		16,905		16,905		$ 74,099
Visirna Therapeutics, Inc. | Visirna License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue				900
Contract assets		0		0
Deferred revenue		$ 0		$ 0
Visirna Therapeutics, Inc. | Visirna License Agreement | Variable Interest Entity, Primary Beneficiary
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Proceeds from investment in joint venture	$ 60,000

Property and Equipment - Summar

Property and Equipment - Summary of Property and Equipment (Detail) - USD ($) $ in Thousands	Jun. 30, 2023	Sep. 30, 2022
Property, Plant and Equipment [Abstract]
Computers, software, office equipment and furniture	$ 2,198	$ 2,182
Land	2,996	2,996
Research equipment	50,472	38,283
Leasehold improvements	96,344	42,017
Construction in progress	118,279	56,373
Property and equipment, gross	270,289	141,851
Less: Accumulated depreciation and amortization	(38,920)	(31,554)
Property and equipment, net	$ 231,369	$ 110,297

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense for property and equipment	$ 2.9	$ 2.2	$ 7.4	$ 6.5

Investments - Summary of Short-

Investments - Summary of Short-term, Long-term Investments and Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Sep. 30, 2022
Schedule Of Held To Maturity Securities And Marketable Securities [Line Items]
Short-term investments, Held to maturity, Adjusted Bases	$ 346,369	$ 268,391
Short-term investments, Held to maturity, Gross Unrealized Gains	0	0
Short-term investments, Held to maturity, Gross Unrealized Losses	(4,204)	(3,661)
Short-term investments, Held to maturity, Fair Value	342,165	264,730
Long-term investments, Held to maturity, Adjusted Basis	42,758	105,872
Long-term investments, Held to maturity, Gross Unrealized Gains	0	0
Long-term investments, Held to maturity, Gross Unrealized Losses	(294)	(5,569)
Long-term investments, Held to maturity, Fair Value	42,464	100,303
Debt securities
Schedule Of Held To Maturity Securities And Marketable Securities [Line Items]
Short-term investments, Held to maturity, Adjusted Bases	346,369	218,391
Short-term investments, Held to maturity, Gross Unrealized Gains	0	0
Short-term investments, Held to maturity, Gross Unrealized Losses	(4,204)	(3,661)
Short-term investments, Held to maturity, Fair Value	342,165	214,730
Long-term investments, Held to maturity, Adjusted Basis	42,758	105,872
Long-term investments, Held to maturity, Gross Unrealized Gains	0	0
Long-term investments, Held to maturity, Gross Unrealized Losses	(294)	(5,569)
Long-term investments, Held to maturity, Fair Value	42,464	100,303
Certificate of deposits
Schedule Of Held To Maturity Securities And Marketable Securities [Line Items]
Short-term investments, Held to maturity, Adjusted Bases	0	50,000
Short-term investments, Held to maturity, Gross Unrealized Gains	0	0
Short-term investments, Held to maturity, Gross Unrealized Losses	0	0
Short-term investments, Held to maturity, Fair Value	$ 0	$ 50,000

Intangible Assets - Schedule of

Intangible Assets - Schedule of Intangible Assets (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Sep. 30, 2022
Finite Lived Intangible Assets [Line Items]
Net Carrying Amount	$ 10,687,000		$ 10,687,000		$ 11,962,000
Amortization expense	400,000	$ 400,000	1,300,000	$ 1,300,000
Novartis
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	24,857,000		24,857,000		24,857,000
Accumulated Amortization	14,170,000		14,170,000		12,895,000
Impairment	0		0		0
Net Carrying Amount	10,687,000		10,687,000		11,962,000
Novartis | Patents
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	21,728,000		21,728,000		21,728,000
Accumulated Amortization	12,933,000		12,933,000		11,770,000
Impairment	0		0		0
Net Carrying Amount	$ 8,795,000		$ 8,795,000		$ 9,958,000
Useful Lives	14 years		14 years		14 years
Novartis | License
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 3,129,000		$ 3,129,000		$ 3,129,000
Accumulated Amortization	1,237,000		1,237,000		1,125,000
Impairment	0		0		0
Net Carrying Amount	$ 1,892,000		$ 1,892,000		$ 2,004,000
Useful Lives	21 years		21 years		21 years

Intangible Assets - Expected Fu

Intangible Assets - Expected Future Amortization (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Sep. 30, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
2023 (remainder)	$ 425
2024	1,700
2025	1,700
2026	1,700
2027	1,700
Thereafter	3,462
Net Carrying Amount	$ 10,687	$ 11,962

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($)	Dec. 02, 2022	Jun. 30, 2023	Apr. 27, 2023	Apr. 26, 2023	Mar. 16, 2023	Sep. 30, 2022
Class Of Stock [Line Items]
Common stock, par value (in dollars per share)		$ 0.001			$ 0.001	$ 0.001
Common stock, shares authorized (in shares)		290,000,000	290,000,000	145,000,000		145,000,000
Common stock, shares issued (in shares)		107,102,000				105,960,000
Common stock, shares outstanding (in shares)		107,102,000				105,960,000
Preferred stock, par value (in dollars per share)		$ 0.001				$ 0.001
Preferred stock, shares authorized (in shares)		5,000,000				5,000,000
Preferred stock, shares issued (in shares)		0				0
Preferred stock, shares outstanding (in shares)		0				0
At The Market Agreement
Class Of Stock [Line Items]
Shares issued		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%
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 (in shares)		12,914,571				14,000,392

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) ft² in Thousands		3 Months Ended		9 Months Ended
	Dec. 20, 2021 USD ($) ft² a	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)
Other Commitments [Line Items]
Contingent liabilities		$ 0		$ 0
Tax increment financing award	$ 16,000,000
State income tax credits	$ 2,500,000
Technology License Commitments
Other Commitments [Line Items]
Milestone payments		0	$ 0	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 (in sq ft) | ft²	160
Laboratory and Office Facility | Wisconsin
Other Commitments [Line Items]
Planned area of the site (in sq ft) | ft²	140
Facilities
Other Commitments [Line Items]
Capital expenditures incurred		102,700,000		102,700,000
Facilities | Minimum
Other Commitments [Line Items]
Amount intends to invest for buildout of the facilities		160,000,000		160,000,000
Facilities | Maximum
Other Commitments [Line Items]
Amount intends to invest for buildout of the facilities		$ 180,000,000		$ 180,000,000

Leases - Narrative (Details)

Leases - Narrative (Details) $ in Thousands		3 Months Ended		9 Months Ended
	Nov. 19, 2021 USD ($) ft² option	Jun. 30, 2023 USD ($) ft² option	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) ft² option	Jun. 30, 2022 USD ($)	Dec. 23, 2022
Lessee Lease Description [Line Items]
Estimated lease payments		$ 147,317		$ 147,317
Short-term lease cost		600	$ 200	1,200	$ 700
Research Facility in San Diego | California
Lessee Lease Description [Line Items]
Lease term	15 years
Office space leases (in sq ft) | ft²	144,000
Estimated lease payments	$ 119,000
Estimated payments for operating expenses	3,000
Payments for leasehold improvements, net of tenant improvement allowances	$ 32,000
Operating lease renewal term	10 years
Maximum additional tenant improvement allowance		7,200		7,200
Additional tenant improvement allowance liability		$ 700		$ 700
Additional tenant improvement allowance interest per annum		7%		7%
Research Facility in San Diego | California | Sorrento Valley Owner (DE) LLC
Lessee Lease Description [Line Items]
Lease term						6 months
Research Facility in San Diego | California | Maximum
Lessee Lease Description [Line Items]
Number of options to renew | option	1
Corporate Headquarters In Pasadena | California
Lessee Lease Description [Line Items]
Office space leases (in sq ft) | ft²	49,000
Corporate Headquarters In Pasadena | California | Colorado Owner, LLC
Lessee Lease Description [Line Items]
Number of options to renew | option		1		1
Operating lease renewal term		5 years		5 years
Research Facility in Madison | Wisconsin
Lessee Lease Description [Line Items]
Office space leases (in sq ft) | ft²		111,000		111,000
Number of options to renew | option		2		2
Operating lease renewal term		5 years		5 years

Leases - Components of Lease As

Leases - Components of Lease Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Sep. 30, 2022
Lease Assets and Liabilities
Right-of-use assets	$ 40,667		$ 40,667		$ 58,291
Lease liabilities	2,823		2,823		2,776
Lease liabilities, net of current portion	79,911		79,911		$ 78,800
Lease Cost
Total	4,089	$ 3,601	9,904	$ 6,564
Research and development
Lease Cost
Operating lease cost	3,323	2,974	7,735	4,757
Variable lease cost (1)	257	179	627	519
General and administrative expense
Lease Cost
Operating lease cost	509	448	1,542	1,288
Variable lease cost (1)	$ 0	$ 0	$ 0	$ 0

Leases - Summary of Maturities

Leases - Summary of Maturities of Operating Lease Liabilities on an Undiscounted Basis (Details) $ in Thousands	Jun. 30, 2023 USD ($)
Leases [Abstract]
2023 (remainder of fiscal year)	$ 1,143
2024	8,094
2025	11,800
2026	12,148
2027	11,320
2028 and thereafter	102,812
Total	147,317
Less imputed interest	(64,583)
Total operating lease liabilities (includes current portion)	$ 82,734

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow and Other Information Related to Leases (Details) - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Leases [Abstract]
Operating cash flows from operating leases	$ 4,430	$ 3,398
Weighted-average remaining lease term (in years)	13 years 4 months 24 days	7 years 3 months 18 days
Weighted-average discount rate	8%	8.50%

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Mar. 18, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized (in shares)	6,186,644		6,186,644
Granted (in shares)			32,151
Stock-based compensation expense	$ 19,947	$ 33,390	$ 59,949	$ 91,697
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Intrinsic value of options exercised	6,500	1,600	10,100	24,900
Stock-based compensation expense	2,100	2,600	6,700	8,300
Unrecognized pre-tax compensation expense	5,300		$ 5,300
Weighted average period to recognize pre-tax compensation expense			12 months
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	17,800	$ 33,700	$ 53,200	$ 83,400
Weighted average period to recognize pre-tax compensation expense			2 years 3 months 18 days
Unrecognized pre-tax compensation expense	$ 131,600		$ 131,600
2004 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance (in shares)	68,555		68,555
2013 Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance (in shares)	3,440,076		3,440,076
Number of shares forfeited (in shares)			197,596
2021 Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized (in shares)					8,000,000
Granted (in shares)			1,977,114
Inducement Awards | Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance (in shares)	712,454		712,454
Inducement Awards | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance (in shares)	746,175		746,175

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Granted and Outstanding Shares (Details) - shares	Jun. 30, 2023	Sep. 30, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options outstanding (in shares)	2,365,798	2,721,384
Total (in shares)	6,687,864
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)	4,322,066	4,069,431
2004 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options outstanding (in shares)	68,555
Total (in shares)	68,555
2004 Equity Incentive Plan | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)	0
2013 Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options outstanding (in shares)	1,550,951
Total (in shares)	3,440,076
2013 Incentive Plan | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)	1,889,125
2021 Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options outstanding (in shares)	33,838
Total (in shares)	1,720,604
2021 Incentive Plan | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)	1,686,766
Inducement Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options outstanding (in shares)	712,454
Total (in shares)	1,458,629
Inducement Awards | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)	746,175

Stock-Based Compensation - Expe

Stock-Based Compensation - Expenses Included in Operating Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 19,947	$ 33,390	$ 59,949	$ 91,697
Research and development
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	8,982	8,098	26,129	23,958
General and administrative expense
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 10,965	$ 25,292	$ 33,820	$ 67,739

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summarize Information about Stock Options (Details) - USD ($)	9 Months Ended
	Jun. 30, 2023
Shares
Beginning balance (in shares)	2,721,384
Granted (in shares)	32,151
Cancelled (in shares)	(43,936)
Exercised (in shares)	(343,801)
Ending balance (in shares)	2,365,798
Number of Options Outstanding, Exercisable (in shares)	2,188,690
Weighted- Average Exercise Price Per Share
Beginning balance (in dollars per share)	$ 20.73
Granted (in dollars per share)	33.03
Cancelled (in dollars per share)	62.31
Exercised (in dollars per share)	6.48
Ending balance (in dollars per share)	22.20
Weighted-Average Exercise Price Per Share, Exercisable (in dollars per share)	$ 20.28
Weighted- Average Remaining Contractual Term (Years)	4 years 4 months 24 days
Weighted-Average Remaining Contractual Term, Exercisable	4 years 2 months 12 days
Aggregate Intrinsic Value	$ 43,813,599
Aggregate Intrinsic Value, Exercisable	$ 43,480,339

Stock-Based Compensation - Assu

Stock-Based Compensation - Assumptions Used to Value Stock Options (Details)	9 Months Ended
	Jun. 30, 2023 $ / shares
Share-Based Payment Arrangement [Abstract]
Dividend yield	0%
Risk-free interest rate	3.69%
Expected volatility	86.40%
Expected life (in years)	6 years 3 months
Weighted average grant date fair value per share of options granted	$ 24.80

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of RSUs Activity (Details) - Restricted Stock Units (RSUs)	9 Months Ended
	Jun. 30, 2023 $ / shares shares
Number of RSUs
Beginning of period (in shares) | shares	4,069,431
Granted (in shares) | shares	1,144,594
Vested (in shares) | shares	(798,271)
Forfeited (in shares) | shares	(93,688)
End of period (in shares) | shares	4,322,066
Weighted- Average Grant Date Fair Value Per Share
Beginning balance (in dollars per share) | $ / shares	$ 62.96
Granted (in dollars per share) | $ / shares	34.27
Vested (in dollars per share) | $ / shares	53.72
Forfeited (in dollars per share) | $ / shares	54.58
Ending balance (in dollars per share) | $ / shares	$ 57.45

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value Measurements for Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Jun. 30, 2023	Sep. 30, 2022
Money market instruments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market instruments	$ 49,199	$ 39,262
U.S. government bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	27,092	1,973
Municipal securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	7,033
Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	62,755	41,727
Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	287,749	271,333
Certificate of deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Certificate of deposits	0	50,000
Level 1 | Money market instruments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market instruments	49,199	39,262
Level 1 | U.S. government bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	27,092	1,973
Level 1 | Municipal securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	0
Level 1 | Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	0	0
Level 1 | Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	0	0
Level 1 | Certificate of deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Certificate of deposits	0	50,000
Level 2 | Money market instruments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market instruments	0	0
Level 2 | U.S. government bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	0	0
Level 2 | Municipal securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	7,033
Level 2 | Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	62,755	41,727
Level 2 | Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	287,749	271,333
Level 2 | Certificate of deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Certificate of deposits	0	0
Level 3 | Money market instruments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market instruments	0	0
Level 3 | U.S. government bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	0	0
Level 3 | Municipal securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	0
Level 3 | Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	0	0
Level 3 | Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	0	0
Level 3 | Certificate of deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Certificate of deposits	$ 0	$ 0

Liability Related to the Sale_2

Liability Related to the Sale of Future Royalties (Details) - USD ($) $ in Thousands		3 Months Ended	9 Months Ended
	Nov. 09, 2022	Jun. 30, 2023	Jun. 30, 2023	Jun. 30, 2022
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Non-cash interest expense on liability related to the sale of future royalties			$ 13,064	$ 0
Royalty Pharma Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment	$ 250,000
Milestone payment receivable	160,000
Milestone payment receivable upon achievement of enrollment in phase 3 clinical trial	50,000
Milestone payment receivable upon FDA approval	50,000
Milestone payment receivable upon receipt of royalty payments	60,000
Royalty payment threshold	70,000
Liability related to the sale of future royalties		$ 250,000	250,000
Non-cash interest expense on liability related to the sale of future royalties		$ 5,200	$ 13,100
Royalty Pharma Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Initial transaction price	$ 410,000

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Jun. 30, 2023	Jun. 30, 2022
Numerator:
Net loss	$ (102,946)	$ 48,675	$ (41,325)	$ (72,046)	$ 44,366	$ (62,872)	$ (95,596)	$ (90,552)
Denominator:
Weighted-average basic shares outstanding (in shares)	107,004			105,753			106,597	105,273
Effect of dilutive securities (in shares)	0			0			0	0
Weighted-average diluted shares outstanding (in shares)	107,004			105,753			106,597	105,273
Basic (in dollars per share)	$ (0.96)			$ (0.68)			$ (0.90)	$ (0.86)
Diluted (in dollars per share)	$ (0.96)			$ (0.68)			$ (0.90)	$ (0.86)
Potentially dilutive securities excluded from computation of diluted earnings per share (in shares)	3,467						4,024