0001628280-25-024666 | 10-Q | XBRL Viewer | Arrowhead Pharmaceuticals INC

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Collaboration and License Agreements - Amgen, Inc (Details)	Mar. 31, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2016 agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 43,268,000	$ 0
Amgen Incorporated \| Olpasiran Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of agreements \| agreement			2
Contract assets	0
Deferred revenue	0
Amgen Incorporated \| Olpasiran Agreement \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional remaining development regulatory and sales milestones payments	$ 485,000,000

Net Income (Loss) Per Share

6 Months Ended

Mar. 31, 2025

Earnings Per Share [Abstract]

Net Income (Loss) Per Share

NET INCOME (LOSS) PER SHARE

The following table presents the computation of basic and diluted net income (loss) per share for the three and six months ended March 31, 2025 and 2024.


	Three Months Ended March 31,				Six Months Ended March 31,
	2025		2024		2025		2024
	(in thousands, except per share amounts)
Numerator:
Net income (loss) attributable to Arrowhead Pharmaceuticals, Inc.	$	370,445	$	(125,300)	$	197,360	$	(258,164)

Denominator:
Weighted-average basic shares outstanding (1)	133,363		123,285		129,059		115,307
Effect of dilutive securities	1,121		—		1,206		—
Weighted-average diluted shares outstanding (1)	134,484		123,285		130,265		115,307

Basic net income (loss) per share	$	2.78	$	(1.02)	$	1.53	$	(2.24)
Diluted net income (loss) per share	$	2.75	$	(1.02)	$	1.52	$	(2.24)

(1) Includes shares of common stock into which the Avoro Pre-Funded Warrants may be exercised. See Note 6.

The following table sets forth the potentially dilutive securities that have been excluded from the calculation of diluted net income (loss) per share because to include them would be anti-dilutive.


	Three Months Ended March 31,		Six Months Ended March 31,
	2025	2024	2025	2024
	(in thousands)
Options	760	595	750	657
Restricted stock units	5,289	3,411	4,567	3,931
Total	6,049	4,006	5,317	4,588

Financing Agreement - Principal Repayment Related to Credit Facility (Details) - Financing Agreement - Secured Debt - Line of Credit $ in Thousands	Mar. 31, 2025 USD ($)
Line of Credit Facility [Line Items]
2025 (remainder)	$ 50,000
2026	40,000
2027	40,000
2028	15,000
2029	15,000
Thereafter	203,063
Total	$ 363,063

Stock-Based Compensation

6 Months Ended

Mar. 31, 2025

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

STOCK-BASED COMPENSATION

The Company has three plans that provide for equity-based compensation.

Under the 2013 Incentive Plan (the “2013 Plan”), 2,391,211 shares of the Company’s common stock are reserved for grants of stock options and restricted stock awards to employees and directors as of March 31, 2025.

Under the 2021 Incentive Plan (the “2021 Plan”), 8,000,000 shares (subject to certain adjustments) of the

Company’s common stock are reserved 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 March 31, 2025, the total number of shares available for issuance was 2,282,102 shares, which includes 166,023 and 331,638 shares that were forfeited under the 2013 and 2021 Plans, respectively, and 6,215,559 shares have been granted under the 2021 Plan.

Under the Company’s Inducement Plan (the “Inducement Plan”), 832,950 shares of the Company’s common stock are authorized for issuance pursuant to grants of stock options, stock appreciation rights, restricted and unrestricted stock, stock units (including restricted stock units), performance awards, cash awards, and other awards convertible into or otherwise based on shares of the Company’s common stock. Awards under the Inducement Plan may only be granted to new employees of the Company in accordance with the provisions of Rule 5635(c)(4) of the Nasdaq Listing Rules. As of March 31, 2025, the total number of shares remaining available for issuance was 392,611 shares, and 507,340 shares have been granted under the Inducement Plan.

In addition, prior to adoption of the Inducement Plan, the Company previously granted stand-alone inducement awards in the form of stock options and restricted stock units outside of the Company’s equity plans to new employees under Rule 5635(c)(4) of the Nasdaq Listing Rules. As of March 31, 2025, there were 602,355 and 151,500 shares underlying outstanding stand-alone inducement options and restricted stock units, respectively.

The following table presents a summary of awards outstanding attributable to Arrowhead Pharmaceuticals, Inc.:


	March 31, 2025
	2013 Plan	2021 Plan	Inducement Awards	Total
Granted and outstanding awards:
Options	891,211	32,151	602,355	1,525,717
Restricted stock units	1,500,000	3,939,734	494,009	5,933,743
Total	2,391,211	3,971,885	1,096,364	7,459,460

The following table summarizes stock-based compensation expenses included in operating expenses:


	Three Months Ended March 31,				Six Months Ended March 31,
	2025		2024		2025		2024
	(in thousands)
Research and development	$	7,264	$	7,097	$	14,110	$	15,413
General and administrative	7,817		9,491		15,147		18,860
Total	$	15,081	$	16,588	$	29,257	$	34,273

Stock Option Awards

The following table presents a summary of the stock option activity for the six months ended March 31, 2025:


	Shares	Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
Outstanding at September 30, 2024	1,978,516	$	23.39
Granted	—	—
Cancelled or expired	(30,466)	43.12
Exercised	(422,333)	7.67
Outstanding at March 31, 2025	1,525,717	$	27.35	3.7	$	3,831,887
Exercisable at March 31, 2025	1,525,717	$	27.35	3.7	$	3,831,887

The aggregate intrinsic values represent 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 March 31, 2025 and 2024 was $3.7 million and $2.5 million, respectively. The total intrinsic value of the options exercised during the six months ended March 31, 2025 and 2024 was $4.6 million and $3.1 million, respectively.

Stock-based compensation expense related to stock options outstanding for the three months ended March 31, 2025 and 2024, was $3.0 thousand and $0.6 million, respectively. Stock-based compensation expense related to stock options outstanding for the six months ended March 31, 2025 and 2024, was $0.1 million and $2.1 million, respectively.

As of March 31, 2025, the pre-tax compensation expense for all outstanding unvested stock options is considered nominal.

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 pricing 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. No options were granted during the six months ended March 31, 2025 and 2024.

Visirna ESOP: On October 1, 2023, Visirna, a subsidiary of the Company, granted 7,500,000 stock options to its employees from the Employee Stock Option Plan (the “Visirna ESOP”), which authorizes 20,000,000 shares for issuance. The Visirna ESOP is independently managed by Visirna, including the valuation process. For the three months ended March 31, 2025 and 2024, stock-based compensation expense related to the Visirna ESOP was $0.9 million and $1.2 million, respectively. For the six months ended March 31, 2025 and 2024, stock-based compensation expense related to the Visirna ESOP was $1.9 million and $3.2 million, respectively.

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, the Inducement Plan, and as inducements awards 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 RSUs	Weighted- Average Grant Date Fair Value Per Share
Outstanding at September 30, 2024	4,913,312	$	49.61
Granted	2,576,819	19.88
Vested	(1,337,263)	44.15
Forfeited	(219,125)	33.97
Outstanding at March 31, 2025	5,933,743	$	38.49

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 March 31, 2025 and 2024, the Company recorded $15.1 million and $16.0 million of expense related to RSUs, respectively. For the six months ended March 31, 2025 and 2024, the Company recorded $29.2 million and $32.2 million of expense related to RSUs, respectively. As of March 31, 2025, there was $97.9 million of total unrecognized compensation cost related to RSUs that is expected to be recognized over a weighted-average period of 1.8 years.

Income Taxes	6 Months Ended
Income Taxes	Mar. 31, 2025
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES The Company's estimated annual effective tax rate significantly fluctuates for fiscal year 2025 with small changes to the Company’s estimated income. For the three months ended March 31, 2025, the Company has recorded a discrete income tax expense of $1.8 million. The income tax provision for the three months ended March 31, 2024, resulted in no tax expense. For the six months ended March 31, 2025, the Company has recorded a discrete income tax expense of $1.9 million and for the six months ended March 31, 2024, the Company has recorded a discrete income tax benefit of $3.3 million. Income tax expense for the three and six months ended March 31, 2025 was based on actual year to date income recorded and statutory tax rates. The Company does not anticipate any changes in its unrecognized tax benefits over the next 12 months. Due to the presence of net operating loss carryforwards, all of the income tax years remain open for examination domestically. The Company has not been notified that it is under audit by the Internal Revenue Service or foreign taxing authorities; however, the Company has been notified of an income tax examination by the state of California. There are no other audits in any other jurisdictions.

- Definition

The entire disclosure for income tax.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482603/740-30-50-2

+ Details

Stockholders' Equity - Narrative (Details) - USD ($)			6 Months Ended
Stockholders' Equity - Narrative (Details) - USD ($)	Nov. 25, 2024	Dec. 02, 2022	Mar. 31, 2025	Mar. 31, 2024	Sep. 30, 2024
Class Of Stock [Line Items]
Common stock, share reserve for issuance (in shares)			2,282,102
Warrant exercise price (in dollars per share)	$ 0.001
Number of securities called by warrants (in shares)	917,441
Warrants purchase price (in dollars per share)	$ 27.25
Proceeds from the issuance of warrants	$ 25,000,000.0		$ 25,000,000	$ 0
Number of warrants exercised (in shares)			0
Private Placement
Class Of Stock [Line Items]
Shares of common stock issued (in shares)	11,926,301
Common stock sold price (in dollars per share)	$ 27.25
Proceeds from sale of stock	$ 325,000,000.0
At The Market Agreement
Class Of Stock [Line Items]
Shares issued to institutional investors (in shares)			0
Maximum \| At The Market Agreement
Class Of Stock [Line Items]
Common stock shares value reserved for future issuance		$ 250,000,000
Percentage of commission to sales agent		3.00%
2013 and 2021 Incentive Plans and other inducement grants
Class Of Stock [Line Items]
Common stock, share reserve for issuance (in shares)			10,134,173		11,492,293

Financing Agreement - Schedule of Outstanding Balance of Credit Facility (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended		12 Months Ended
	Mar. 31, 2025	Mar. 31, 2025	Mar. 31, 2024	Sep. 30, 2024
Line of Credit Facility [Line Items]
Less: Current portion of credit facility	$ (65,000)	$ (65,000)		$ 0
Less: Payments		(151,625)	$ 0
Secured Debt \| Financing Agreement \| Line of Credit
Line of Credit Facility [Line Items]
Initial Term Loan	363,063	363,063
Less: Unamortized debt discount and issuance costs	(14,135)	(14,135)		(15,817)
Less: Current portion of credit facility	(65,000)	(65,000)		0
Less: Payments	(151,625)			0
Credit facility, net of current portion	208,927	208,927		393,183
Secured Debt \| Financing Agreement, Initial Term Loan \| Line of Credit
Line of Credit Facility [Line Items]
Initial Term Loan	400,000	400,000		400,000
Secured Debt \| Financing Agreement, Initial Term Loan Interest \| Line of Credit
Line of Credit Facility [Line Items]
Initial Term Loan	$ 39,687	$ 39,687		$ 9,000

Liability Related to the Sale of Future Royalties (Tables)

6 Months Ended

Mar. 31, 2025

Schedule of Liability Related to the Sale of Future Royalties

The following table presents the activity with respect to the liability related to the sale of future royalties.


	March 31, 2025		September 30, 2024
	(in thousands)
Beginning carrying value	$	341,361	$	268,326
Milestone payment received	—		50,000
Non-cash interest expense recognized	10,915		23,035
Ending carrying value	$	352,276	$	341,361

Fair Value Measurements - Schedule of Fair Value Measurements for Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Sep. 30, 2024
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 911,700	$ 578,276
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	911,700	578,276
Cash equivalents	166,443	66,966
Total financial assets	1,078,143	645,242
Fair Value, Measurements, Recurring \| Money market instruments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	137,535	66,966
Fair Value, Measurements, Recurring \| Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	28,908
Fair Value, Measurements, Recurring \| U.S. government and agency securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	277,170	160,723
Fair Value, Measurements, Recurring \| Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	113,387	179,714
Fair Value, Measurements, Recurring \| Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	521,143	237,839
Fair Value, Measurements, Recurring \| Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Cash equivalents	137,535	66,966
Total financial assets	137,535	66,966
Fair Value, Measurements, Recurring \| Level 1 \| Money market instruments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	137,535	66,966
Fair Value, Measurements, Recurring \| Level 1 \| Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0
Fair Value, Measurements, Recurring \| Level 1 \| U.S. government and agency securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	911,700	578,276
Cash equivalents	28,908	0
Total financial assets	940,608	578,276
Fair Value, Measurements, Recurring \| Level 2 \| Money market instruments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Fair Value, Measurements, Recurring \| Level 2 \| Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	28,908
Fair Value, Measurements, Recurring \| Level 2 \| U.S. government and agency securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	277,170	160,723
Fair Value, Measurements, Recurring \| Level 2 \| Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	113,387	179,714
Fair Value, Measurements, Recurring \| Level 2 \| Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	521,143	237,839
Fair Value, Measurements, Recurring \| Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Cash equivalents	0	0
Total financial assets	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Money market instruments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0
Fair Value, Measurements, Recurring \| Level 3 \| U.S. government and agency securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 0	$ 0

Collaboration and License Agreements - Sarepta Therapeutics, Inc. (Details) $ in Thousands				3 Months Ended		6 Months Ended
	Feb. 14, 2025 USD ($)	Feb. 07, 2025 USD ($)	Nov. 25, 2024 USD ($) program obligation	Mar. 31, 2025 USD ($)	Mar. 31, 2024 USD ($)	Mar. 31, 2025 USD ($)	Mar. 31, 2024 USD ($)	Sep. 30, 2024 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue				$ 542,709	$ 0	$ 545,209	$ 3,551
Accounts receivable				2,365		2,365		$ 0
Contract liabilities included in deferred revenue				43,268		43,268		$ 0
Sarepta
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue						542,700
Accounts receivable				2,400		2,400
Contract liabilities included in deferred revenue				$ 43,300		43,300
Sarepta \| Sarepta Collaboration Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of performance obligations \| obligation			17
Upfront payment	$ 500,000					500,000
Proceeds from sale of stock		$ 325,000
Equity premium		$ 83,600				83,612
Annual fees			$ 250,000			250,000
Annual installment			$ 50,000
Annual installments period			5 years
Fixed consideration						833,612
Total transaction price						$ 904,855
Enrollment related milestone payments			$ 300,000
Number of collaboration programs \| program			13
Collaboration agreement termination notice period prior to any regulatory approval of a licensed product			30 days
Sarepta \| Sarepta Collaboration Agreement \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of new target programs \| program			6
Regulatory milestone payments			$ 180,000
Sales-related milestone payments			700,000
Sarepta \| Sarepta Collaboration Agreement \| Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory milestone payments			110,000
Sales-related milestone payments			$ 500,000

Balance Sheet Accounts (Tables)

6 Months Ended

Mar. 31, 2025

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Property and Equipment

The following table summarizes the Company’s major classes of property, plant and equipment:


	March 31, 2025		September 30, 2024
	(in thousands)
Land	$	2,996	$	2,996
Buildings	248,893		75,988
Research equipment	60,259		65,353
Manufacturing equipment	13,812		—
Furniture	5,594		5,594
Computers and software	1,033		981
Leasehold improvements	104,401		104,410
Construction in progress	16,245		188,731
	453,233		444,053
Less: Accumulated depreciation and amortization	(68,430)		(58,021)
Property, plant and equipment, net	$	384,803	$	386,032

Schedule of Accrued Expenses

Accrued expenses consisted of the following as of:


	March 31, 2025		September 30, 2024
	(in thousands)
Accrued R&D expenses	$	42,963	$	28,069
Accrued R&D expenses; co-development	28,755		23,351
Accrued capital expenditures	358		4,206
Other	6,374		7,391
Total accrued expenses	$	78,450	$	63,017

Intangible Assets

6 Months Ended

Mar. 31, 2025

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 March 31, 2025
Patents	$	21,728	$	15,649	$	—	$	6,079	14
License	3,129		1,497		—		1,632		21
Total intangible assets, net	$	24,857	$	17,146	$	—	$	7,711

As of September 30, 2024
Patents	$	21,728	$	14,873	$	—	$	6,855	14
License	3,129		1,422		—		1,707		21
Total intangible assets, net	$	24,857	$	16,295	$	—	$	8,562

Intangible assets are reviewed annually for impairment and more frequently if potential impairment indicators exist. No impairment indicators were identified during the six months ended March 31, 2025 and 2024.

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 the three months ended March 31, 2025 and 2024, and $0.9 million for each of six months ended March 31, 2025 and 2024. 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 March 31, 2025:


	Amortization Expense
Year Ending September 30,	(in thousands)
2025 (remainder)	$	849
2026	1,700
2027	1,700
2028	1,700
2029	795
2030 and thereafter	967
Total	$	7,711

Stock-Based Compensation - Schedule of RSUs Activity (Details) - Restricted stock units	6 Months Ended
	Mar. 31, 2025 $ / shares shares
Number of RSUs
Beginning of period (in shares) \| shares	4,913,312
Granted (in shares) \| shares	2,576,819
Vested (in shares) \| shares	(1,337,263)
Forfeited (in shares) \| shares	(219,125)
End of period (in shares) \| shares	5,933,743
Weighted- Average Grant Date Fair Value Per Share
Beginning balance (in dollars per share) \| $ / shares	$ 49.61
Granted (in dollars per share) \| $ / shares	19.88
Vested (in dollars per share) \| $ / shares	44.15
Forfeited (in dollars per share) \| $ / shares	33.97
Ending balance (in dollars per share) \| $ / shares	$ 38.49

Collaboration and License Agreements - Sarepta Therapeutics, Inc. Consideration Components (Details) - Sarepta - Sarepta Collaboration Agreement - USD ($) $ in Thousands				6 Months Ended
	Feb. 14, 2025	Feb. 07, 2025	Nov. 25, 2024	Mar. 31, 2025
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment	$ 500,000			$ 500,000
Annual fees			$ 250,000	250,000
Equity premium		$ 83,600		83,612
Fixed consideration				833,612
Estimated variable consideration				71,243
Total transaction price				$ 904,855

Financing Agreement (Tables)

6 Months Ended

Mar. 31, 2025

Debt Disclosure [Abstract]

Schedule of Line of Credit Facilities

The outstanding balance of the Credit Facility consisted of the following:


	March 31, 2025		September 30, 2024
	(in thousands)
Initial Term Loan	$	400,000	$	400,000
Accumulated interest on the Initial Term Loan	39,687		9,000
Less: Unamortized debt discount and issuance costs	(14,135)		(15,817)
Less: Current portion of credit facility	(65,000)		—
Less: Payments	(151,625)		—
Credit facility, net of current portion	$	208,927	$	393,183

Schedule of Interest Expense Recognized Related To Credit Facility

The following table sets forth total interest expense recognized related to the Credit Facility:


	Three Months Ended March 31,				Six Months Ended March 31,
	2025		2024		2025		2024
	(in thousands)
Amortization of debt discount and issuance costs	$	1,129	$	—	$	1,682	$	—
Contractual interest expense	15,009		—		30,687		—
Total interest expense	$	16,138	$	—	$	32,369	$	—

Schedule of Maturities of Long-Term Debt

The amounts shown in the table below, related to the Credit Facility, represent the maximum payments the Company is obligated to make to the Lenders during the indicated periods. Principal repayment of up to $160.0 million is scheduled through the fifth year, in line with the contractual terms of the Credit Facility. Actual payments may vary and could be lower than the amounts presented in the table.


Year	Amounts
	(in thousands)
2025 (remainder)	$	50,000
2026	40,000
2027	40,000
2028	15,000
2029	15,000
Thereafter	203,063
Total	$	363,063

Stock-Based Compensation - Schedule of Information about Stock Options (Details)	6 Months Ended
	Mar. 31, 2025 USD ($) $ / shares shares	Mar. 31, 2024 shares
Shares
Beginning balance (in shares) \| shares	1,978,516
Granted (in shares) \| shares	0	0
Cancelled or expired (in shares) \| shares	(30,466)
Exercised (in shares) \| shares	(422,333)
Ending balance (in shares) \| shares	1,525,717
Number of Options Outstanding, Exercisable (in shares) \| shares	1,525,717
Weighted- Average Exercise Price Per Share
Beginning balance (in dollars per share) \| $ / shares	$ 23.39
Granted (in dollars per share) \| $ / shares	0
Cancelled or expired (in dollars per share) \| $ / shares	43.12
Exercised (in dollars per share) \| $ / shares	7.67
Ending balance (in dollars per share) \| $ / shares	27.35
Weighted-Average Exercise Price Per Share, Exercisable (in dollars per share) \| $ / shares	$ 27.35
Weighted- Average Remaining Contractual Term (Years)	3 years 8 months 12 days
Weighted-Average Remaining Contractual Term, Exercisable	3 years 8 months 12 days
Aggregate Intrinsic Value \| $	$ 3,831,887
Aggregate Intrinsic Value, Exercisable \| $	$ 3,831,887

Stock-Based Compensation (Tables)

6 Months Ended

Mar. 31, 2025

Share-Based Payment Arrangement [Abstract]

Schedule of Awards Outstanding

The following table presents a summary of awards outstanding attributable to Arrowhead Pharmaceuticals, Inc.:


	March 31, 2025
	2013 Plan	2021 Plan	Inducement Awards	Total
Granted and outstanding awards:
Options	891,211	32,151	602,355	1,525,717
Restricted stock units	1,500,000	3,939,734	494,009	5,933,743
Total	2,391,211	3,971,885	1,096,364	7,459,460

Schedule of Share-Based Payment Arrangement, Expensed

The following table summarizes stock-based compensation expenses included in operating expenses:


	Three Months Ended March 31,				Six Months Ended March 31,
	2025		2024		2025		2024
	(in thousands)
Research and development	$	7,264	$	7,097	$	14,110	$	15,413
General and administrative	7,817		9,491		15,147		18,860
Total	$	15,081	$	16,588	$	29,257	$	34,273

Schedule of Summarized Information about Stock Options

The following table presents a summary of the stock option activity for the six months ended March 31, 2025:


	Shares	Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
Outstanding at September 30, 2024	1,978,516	$	23.39
Granted	—	—
Cancelled or expired	(30,466)	43.12
Exercised	(422,333)	7.67
Outstanding at March 31, 2025	1,525,717	$	27.35	3.7	$	3,831,887
Exercisable at March 31, 2025	1,525,717	$	27.35	3.7	$	3,831,887

Schedule of Share Activity Related to RSUs

The following table summarizes the activity of the Company’s RSUs:


	Number of RSUs	Weighted- Average Grant Date Fair Value Per Share
Outstanding at September 30, 2024	4,913,312	$	49.61
Granted	2,576,819	19.88
Vested	(1,337,263)	44.15
Forfeited	(219,125)	33.97
Outstanding at March 31, 2025	5,933,743	$	38.49

Cover - shares	6 Months Ended
Cover - shares	Mar. 31, 2025	May 01, 2025
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2025
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		138,100,435
Entity Central Index Key	0000879407
Current Fiscal Year End Date	--09-30
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	Q2
Amendment Flag	false

Organization and Significant Accounting Policies - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended	6 Months Ended
	Feb. 24, 2025	Feb. 07, 2025	Mar. 31, 2025	Mar. 31, 2025	Sep. 30, 2024	Mar. 31, 2024	Sep. 30, 2023
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Cash, cash equivalents and restricted cash			$ 185,709	$ 185,709	$ 102,685	$ 127,704	$ 110,891
Restricted cash			2,100	2,100
Available-for-sale securities			911,700	911,700	$ 578,276
Increase (decrease) in cash and investments				416,400
Development regulatory and sales milestones payments			13,300,000	$ 13,300,000
Sarepta \| Sarepta Collaboration Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Proceeds from sale of stock		$ 325,000
Shares of common stock issued (in shares)		11,926,301
Common stock sold price (in dollars per share)		$ 27.25
Upfront payment	$ 500,000
Annual fees		$ 250,000
Annual installments period		5 years
Enrollment related milestone payments		$ 300,000
Future potential milestone payments		$ 10,000,000
GSK \| GSK-HBV Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development milestone payments			$ 2,500

Balance Sheet Accounts

6 Months Ended

Mar. 31, 2025

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Balance Sheet Accounts

BALANCE SHEET ACCOUNTS

Property, Plant and Equipment

The following table summarizes the Company’s major classes of property, plant and equipment:


	March 31, 2025		September 30, 2024
	(in thousands)
Land	$	2,996	$	2,996
Buildings	248,893		75,988
Research equipment	60,259		65,353
Manufacturing equipment	13,812		—
Furniture	5,594		5,594
Computers and software	1,033		981
Leasehold improvements	104,401		104,410
Construction in progress	16,245		188,731
	453,233		444,053
Less: Accumulated depreciation and amortization	(68,430)		(58,021)
Property, plant and equipment, net	$	384,803	$	386,032

Depreciation and amortization expense for property, plant and equipment for the three months ended March 31, 2025 and 2024 was $5.6 million and $4.1 million, respectively. Depreciation and amortization expense for property, plant and equipment for the six months ended March 31, 2025 and 2024 was $10.4 million and $7.9 million, respectively.

During the first quarter of fiscal 2025, the Company completed the build out of its manufacturing facility in Verona, Wisconsin. This resulted in the reclassification of $172.9 million from construction in progress to buildings and $13.8 million to manufacturing equipment as of March 31, 2025. Additionally, the Company began depreciating the newly completed manufacturing facility over a 39-year period and the manufacturing equipment over 7- or 10-year periods.

During the first quarter of fiscal 2024, the Company completed the build out of its laboratory and office facilities in Verona, Wisconsin, which resulted in the reclassification of $76.0 million from construction in progress to buildings as of March 31, 2025.

Accrued Expenses

Accrued expenses consisted of the following as of:


	March 31, 2025		September 30, 2024
	(in thousands)
Accrued R&D expenses	$	42,963	$	28,069
Accrued R&D expenses; co-development	28,755		23,351
Accrued capital expenditures	358		4,206
Other	6,374		7,391
Total accrued expenses	$	78,450	$	63,017

Balance Sheet Accounts - Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Sep. 30, 2024
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 453,233	$ 444,053
Less: Accumulated depreciation and amortization	(68,430)	(58,021)
Property, plant and equipment, net	384,803	386,032
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,996	2,996
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	248,893	75,988
Research equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	60,259	65,353
Manufacturing equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	13,812	0
Furniture
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	5,594	5,594
Computers and software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,033	981
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	104,401	104,410
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 16,245	$ 188,731

Leases - Schedule of Cash Flow and Other Information Related to Leases (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Cash received for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 0	$ 0	$ 0	$ 3,099
Right-of-use assets obtained in exchange for amended operating lease liabilities	0	0	0	64
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 3,840	$ 2,046	$ 7,680	$ 4,016
Weighted-average remaining lease term (in years)	12 years 1 month 6 days	13 years	12 years 1 month 6 days	13 years
Weighted-average discount rate	8.00%	8.00%	8.00%	8.00%

Stock-Based Compensation - Schedule of Expenses Included in Operating Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 15,081	$ 16,588	$ 29,257	$ 34,273
Research and development
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	7,264	7,097	14,110	15,413
General and administrative expense
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 7,817	$ 9,491	$ 15,147	$ 18,860

Stockholders' Equity (Tables)

6 Months Ended

Mar. 31, 2025

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 March 31, 2025
Common stock	$	0.001	290,000	138,062	138,062
Preferred stock	$	0.001	5,000	—	—

As of September 30, 2024
Common stock	$	0.001	290,000	124,376	124,376
Preferred stock	$	0.001	5,000	—	—

- Definition

Tabular disclosure of an entity's stock, including par or stated value per share, number and dollar amount of share subscriptions, shares authorized, shares issued, shares outstanding, number and dollar amount of shares held in an employee trust, dividend per share, total dividends, share conversion features, par value plus additional paid in capital, the value of treasury stock and other information necessary to a fair presentation, and EPS information. Stock by class includes common, convertible, and preferred stocks which are not redeemable or redeemable solely at the option of the issuer. Includes preferred stock with redemption features that are solely within the control of the issuer and mandatorily redeemable stock if redemption is required to occur only upon liquidation or termination of the reporting entity. If more than one issue is outstanding, state the title of each issue and the corresponding dollar amount; dollar amount of any shares subscribed but unissued and the deduction of subscriptions receivable there from; number of shares authorized, issued, and outstanding.

+ References

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+ Details

Net Income (Loss) Per Share (Tables)

6 Months Ended

Mar. 31, 2025

Earnings Per Share [Abstract]

Schedule of Earnings Per Share, Basic and Diluted

The following table presents the computation of basic and diluted net income (loss) per share for the three and six months ended March 31, 2025 and 2024.


	Three Months Ended March 31,				Six Months Ended March 31,
	2025		2024		2025		2024
	(in thousands, except per share amounts)
Numerator:
Net income (loss) attributable to Arrowhead Pharmaceuticals, Inc.	$	370,445	$	(125,300)	$	197,360	$	(258,164)

Denominator:
Weighted-average basic shares outstanding (1)	133,363		123,285		129,059		115,307
Effect of dilutive securities	1,121		—		1,206		—
Weighted-average diluted shares outstanding (1)	134,484		123,285		130,265		115,307

Basic net income (loss) per share	$	2.78	$	(1.02)	$	1.53	$	(2.24)
Diluted net income (loss) per share	$	2.75	$	(1.02)	$	1.52	$	(2.24)

(1) Includes shares of common stock into which the Avoro Pre-Funded Warrants may be exercised. See Note 6.

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

The following table sets forth the potentially dilutive securities that have been excluded from the calculation of diluted net income (loss) per share because to include them would be anti-dilutive.


	Three Months Ended March 31,		Six Months Ended March 31,
	2025	2024	2025	2024
	(in thousands)
Options	760	595	750	657
Restricted stock units	5,289	3,411	4,567	3,931
Total	6,049	4,006	5,317	4,588

Collaboration and License Agreements - Receivables and Contract Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Sep. 30, 2024
Collaboration And License Agreements [Abstract]
Receivables included in accounts receivable	$ 2,365	$ 0
Contract liabilities included in deferred revenue	$ 43,268	$ 0

Leases (Tables)

6 Months Ended

Mar. 31, 2025

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	March 31, 2025		September 30, 2024
		(in thousands)

Operating lease assets	Right-of-use assets	$	44,452	$	45,255
Current operating lease liabilities	Lease liabilities	6,782		6,342
Non-current operating lease liabilities	Lease liabilities, net of current portion	107,529		111,027


			Three Months Ended March 31,				Six Months Ended March 31,
Lease Cost	Classification		2025		2024		2025		2024
		(in thousands)

Operating lease cost	Research and development		$	2,709	$	2,572	$	5,520	$	5,566
	General and administrative expense		500		491		993		967

Variable lease cost (1)	Research and development		951		836		1,937		1,615
	General and administrative expense		—		—		—		—

Total			$	4,160	$	3,899	$	8,450	$	8,148

(1) Variable lease cost is primarily related to operating expenses associated with the Company’s operating leases.

Schedule of Maturities of Operating Lease Liabilities on an Undiscounted Basis

The following table presents maturities of operating lease liabilities on an undiscounted basis as of March 31, 2025:


Year	Amounts
	(in thousands)
2025 (remainder)	$	7,776
2026	15,799
2027	14,974
2028	13,619
2029	13,905
2030 and thereafter	114,790
Total	$	180,863
Less imputed interest	$	(66,552)
Total operating lease liabilities (includes current portion)	$	114,311

Supplemental cash flow and other information related to leases was as follows:


	Three Months Ended March 31,				Six Months Ended March 31,
	2025		2024		2025			2024
	(in thousands)
Cash received for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	—	$	—	$	—		$	3,099
Right-of-use assets obtained in exchange for amended operating lease liabilities	$	—	$	—	$	—		$	64
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	3,840	$	2,046	$	7,680		$	4,016

					March 31,
					2025			2024
Weighted-average remaining lease term (in years)					12.1			13.0
Weighted-average discount rate					8.0		%	8.0		%

Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2025	Sep. 30, 2024
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	290,000,000	290,000,000
Common stock, shares issued (in shares)	138,062,000	124,376,000
Common stock, shares outstanding (in shares)	138,062,000	124,376,000

Commitments and Contingencies (Details) ft² in Thousands	Mar. 31, 2025 USD ($) ft²
Other Commitments [Line Items]
Contingent liabilities	$ 0
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	$ 292,600,000
Amount intends to invest for buildout of the facilities	$ 3,700,000

Stockholders' Equity

6 Months Ended

Mar. 31, 2025

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 March 31, 2025
Common stock	$	0.001	290,000	138,062	138,062
Preferred stock	$	0.001	5,000	—	—

As of September 30, 2024
Common stock	$	0.001	290,000	124,376	124,376
Preferred stock	$	0.001	5,000	—	—

As of March 31, 2025 and September 30, 2024, respectively, 10,134,173 and 11,492,293 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 2013 and 2021 Incentive Plans, as well as for other inducement grants made to new employees under Rule 5635(c)(4) of the Nasdaq Listing Rules.

On November 25, 2024, the Company entered into a Securities Purchase Agreement (the “Securities Purchase Agreement”) with an institutional and accredited investor for a private placement of pre-funded warrants to purchase shares of common stock with an exercise price of $0.001 per share (“Avoro Pre-Funded Warrants”). Pursuant to the Securities Purchase Agreement, the Company sold pre-funded warrants to purchase up to 917,441 shares of common stock at a purchase price of $27.25 per pre-funded warrant, for an aggregate value of approximately $25.0 million. The outstanding Avoro Pre-Funded Warrants are exercisable at any time and do not have an expiration date.

The Company determined that the Avoro Pre-Funded Warrants are freestanding financial instruments because they (i) are immediately exercisable, (ii) do not embody an obligation for the Company to repurchase its shares, (iii) permit the holders to receive a fixed number of shares of common stock upon exercise, and (iv) are indexed to the Company’s common stock. As such, the Company evaluated the Avoro Pre-Funded Warrants to determine whether they represent instruments that require liability classification pursuant to the guidance in ASC 480. However, the Company concluded that the Avoro Pre-Funded Warrants are not a liability within the scope of ASC 480 due to their characteristics. Further, the Company determined that the Avoro Pre-Funded Warrants do not meet the definition of a derivative under ASC 815 because they do not meet the criteria regarding no or little initial net investment. Accordingly, the Company assessed the Avoro Pre-Funded Warrants relative to the guidance in ASC 815-40, Contracts in Entity's Own Equity, to determine the appropriate treatment. The Company concluded that the Avoro Pre-funded Warrants are both indexed to its own stock and meet all other conditions for equity classification. Accordingly, the Company has classified the Avoro Pre-funded Warrants as permanent equity. As of March 31, 2025, no shares underlying the Avoro Pre-Funded Warrants had been exercised.

In connection with the Sarepta Collaboration Agreement, on November 25, 2024, the Company entered into the Stock Purchase Agreement with an affiliate of Sarepta for a private placement of shares of common stock of the Company (the “Private Placement”). Pursuant to the Stock Purchase Agreement, the Company sold 11,926,301 shares of common stock, at a price per share of $27.25, for an aggregate value of approximately $325.0 million. The Private Placement closed on February 7, 2025.

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 Open Market Sale Agreement and (ii) the termination of the Open Market Sale Agreement as permitted therein. The Company and Jefferies may each terminate the Open Market Sale Agreement at any time upon prior notice. As of March 31, 2025, no shares have been issued under the Open Market Sale Agreement.

- Definition

The entire disclosure for equity.

+ References

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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-18

+ Details

Balance Sheet Accounts - Narrative (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2025	Mar. 31, 2024
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense for property and equipment	$ 5.6	$ 4.1		$ 10.4	$ 7.9
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, reclassification			$ 76.0	172.9
Construction In Progress Reclassified To Building
Property, Plant and Equipment [Line Items]
Property, plant and equipment, reclassification				(172.9)
Manufacturing equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, reclassification				$ 13.8
Manufacturing equipment \| Minimum
Property, Plant and Equipment [Line Items]
Useful life	7 years			7 years
Manufacturing equipment \| Maximum
Property, Plant and Equipment [Line Items]
Useful life	10 years			10 years
Construction In Progress Reclassified To Manufacturing Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, reclassification				$ (13.8)
Manufacturing Facility
Property, Plant and Equipment [Line Items]
Useful life	39 years			39 years
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, reclassification			$ (76.0)

Stockholders' Equity - Schedule of Shares of Common Stock and Preferred Stock (Details) - $ / shares	Mar. 31, 2025	Sep. 30, 2024
Equity [Abstract]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	290,000,000	290,000,000
Common stock, shares issued (in shares)	138,062,000	124,376,000
Common stock, shares outstanding (in shares)	138,062,000	124,376,000
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

Insider Trading Arrangements

3 Months Ended

Mar. 31, 2025

Trading Arrangements, by Individual

Material Terms of Trading Arrangement

During the quarter ended March 31, 2025, no director or officer (as defined in Exchange Act Rule 16a-1(f)) adopted or terminated trading plans intended to satisfy Rule 10b5-1(c), except as set forth in the following table:

Name

Title

Adoption or Termination Date

Plan Start Date

Plan End Date

Vesting and

Subject to

Sell-To-

Cover (1)

Other
Shares
Being Sold
(Subject to
Certain
Conditions)

Ken Myszkowski

Chief Financial Officer

Terminated on 1/6/2025

6/11/2024

2/28/2025

n/a

115,000

Ken Myszkowski

Chief Financial Officer

1/7/2025

4/10/2025

12/31/2025

n/a

170,599

James Hamilton

Chief Medical Officer, Head of R&D

2/24/2025

5/28/2025

11/30/2026

n/a

60,000

Christopher Anzalone

Chief Executive Officer

Terminated on 3/12/2025

12/4/2024

12/31/2026

2,082,892

n/a

(1) This column indicates the total number of shares vesting in connection with equity awards, not the number of shares to be sold. The actual number of shares to be sold will be a smaller number based on whatever is required to satisfy payment of applicable withholding taxes under sell-to-cover arrangements.

Non-Rule 10b5-1 Arrangement Adopted

false

Non-Rule 10b5-1 Arrangement Terminated

false

James Hamilton [Member]

Trading Arrangements, by Individual

Name

James Hamilton

Title

Chief Medical Officer, Head of R&D

Rule 10b5-1 Arrangement Adopted

true

2/24/2025

11/30/2026

551 days

60,000

Christopher Anzalone [Member]

Trading Arrangements, by Individual

Name

Christopher Anzalone

Title

Chief Executive Officer

Rule 10b5-1 Arrangement Terminated

true

Termination Date

3/12/2025

Aggregate Available

2,082,892

Ken Myszkowski 2024 Plan [Member] | Ken Myszkowski [Member]

Trading Arrangements, by Individual

Name

Ken Myszkowski

Title

Chief Financial Officer

Rule 10b5-1 Arrangement Terminated

true

Termination Date

1/6/2025

Aggregate Available

115,000

Ken Myszkowski 2025 Plan [Member] | Ken Myszkowski [Member]

Trading Arrangements, by Individual

Name

Ken Myszkowski

Title

Chief Financial Officer

Rule 10b5-1 Arrangement Adopted

true

1/7/2025

12/31/2025

265 days

170,599

Liability Related to the Sale of Future Royalties - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended
	Nov. 30, 2022	Jun. 30, 2024	Mar. 31, 2025	Sep. 30, 2024
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment received			$ 0	$ 50,000
Royalty Pharma Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received	$ 250,000
Milestone payment receivable	160,000
Milestone payment receivable upon FDA approval	50,000
Milestone payment receivable upon receipt of royalty payments	60,000
Royalty payment threshold	70,000
Milestone payment received		$ 50,000
Liability related to the sale of future royalties, interest rate			6.30%
Royalty Pharma Agreement \| Amgen Incorporated
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment receivable upon achievement of enrollment in phase 3 clinical trial			$ 50,000
Maximum \| Royalty Pharma Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Initial transaction price	$ 410,000

Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Non- controlling Interest
Beginning balance (in shares) at Sep. 30, 2023		107,312,000
Beginning balance at Sep. 30, 2023	$ 287,162	$ 200	$ 1,300,395	$ (3,222)	$ (1,026,030)	$ 15,819
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	19,694		19,694
Exercise of stock options (in shares)		34,000
Exercise of stock options	267		267
Common stock - restricted stock units vesting (in shares)		154,000
Foreign currency translation adjustments	58			58
Unrealized gains (losses) on available-for-sale securities	1,909			1,909
Net income (loss)	(135,376)				(132,864)	(2,512)
Ending balance (in shares) at Dec. 31, 2023		107,500,000
Ending balance at Dec. 31, 2023	173,714	$ 200	1,320,356	(1,255)	(1,158,894)	13,307
Beginning balance (in shares) at Sep. 30, 2023		107,312,000
Beginning balance at Sep. 30, 2023	287,162	$ 200	1,300,395	(3,222)	(1,026,030)	15,819
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Foreign currency translation adjustments	2
Unrealized gains (losses) on available-for-sale securities	2,125
Net income (loss)	(262,372)
Ending balance (in shares) at Mar. 31, 2024		124,133,000
Ending balance at Mar. 31, 2024	495,405	$ 217	1,768,866	(1,095)	(1,284,194)	11,611
Beginning balance (in shares) at Dec. 31, 2023		107,500,000
Beginning balance at Dec. 31, 2023	173,714	$ 200	1,320,356	(1,255)	(1,158,894)	13,307
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	17,750		17,750
Exercise of stock options (in shares)		120,000
Exercise of stock options	1,512		1,512
Common stock - restricted stock units vesting (in shares)		723,000
Common stock - restricted stock units vesting	0	$ 1	(1)
Common stock issued, net of offering costs (in shares)		15,790,000
Common stock issued, net of offering costs	429,265	$ 16	429,249
Foreign currency translation adjustments	(56)			(56)
Unrealized gains (losses) on available-for-sale securities	216			216
Net income (loss)	(126,996)				(125,300)	(1,696)
Ending balance (in shares) at Mar. 31, 2024		124,133,000
Ending balance at Mar. 31, 2024	495,405	$ 217	1,768,866	(1,095)	(1,284,194)	11,611
Beginning balance (in shares) at Sep. 30, 2024		124,376,000
Beginning balance at Sep. 30, 2024	191,063	$ 217	1,806,000	4,750	(1,625,523)	5,619
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	15,209		15,209
Exercise of stock options (in shares)		70,000
Exercise of stock options	634		634
Common stock - restricted stock units vesting (in shares)		209,000
Issuance of pre-funded warrants	25,000		25,000
Foreign currency translation adjustments	(106)			(106)
Unrealized gains (losses) on available-for-sale securities	(507)			(507)
Net income (loss)	(175,218)				(173,085)	(2,133)
Ending balance (in shares) at Dec. 31, 2024		124,655,000
Ending balance at Dec. 31, 2024	56,075	$ 217	1,846,843	4,137	(1,798,608)	3,486
Beginning balance (in shares) at Sep. 30, 2024		124,376,000
Beginning balance at Sep. 30, 2024	$ 191,063	$ 217	1,806,000	4,750	(1,625,523)	5,619
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	422,333
Foreign currency translation adjustments	$ (506)
Unrealized gains (losses) on available-for-sale securities	146
Net income (loss)	192,645
Ending balance (in shares) at Mar. 31, 2025		138,062,000
Ending balance at Mar. 31, 2025	684,225	$ 230	2,106,864	4,390	(1,428,163)	904
Beginning balance (in shares) at Dec. 31, 2024		124,655,000
Beginning balance at Dec. 31, 2024	56,075	$ 217	1,846,843	4,137	(1,798,608)	3,486
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	16,027		16,027
Exercise of stock options (in shares)		353,000
Exercise of stock options	2,619		2,619
Common stock - restricted stock units vesting (in shares)		1,128,000
Common stock - restricted stock units vesting	1	$ 1
Common stock issued, net of offering costs (in shares)		11,926,000
Common stock issued, net of offering costs	241,387	$ 12	241,375
Foreign currency translation adjustments	(400)			(400)
Unrealized gains (losses) on available-for-sale securities	653			653
Net income (loss)	367,863				370,445	(2,582)
Ending balance (in shares) at Mar. 31, 2025		138,062,000
Ending balance at Mar. 31, 2025	$ 684,225	$ 230	$ 2,106,864	$ 4,390	$ (1,428,163)	$ 904

Collaboration and License Agreements - Takeda Pharmaceutical Company Limited (Details)	1 Months Ended
	Jan. 31, 2021 USD ($)	Oct. 31, 2020 bundle	Mar. 31, 2025 USD ($)	Sep. 30, 2024 USD ($)	Mar. 31, 2023 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development regulatory and sales milestones payments			$ 13,300,000,000
Deferred revenue			43,268,000	$ 0
Accrued expenses			78,450,000	$ 63,017,000
Takeda \| License and Co-Funding Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of distinct bundle \| bundle		1
Initial transaction price	$ 300,000,000
Milestone payment					$ 40,000,000
Deferred revenue			0
Accrued expenses			28,800,000
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		20.00%
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		25.00%
Development regulatory and sales milestones payments			$ 527,500,000

Organization and Significant Accounting Policies (Tables)

6 Months Ended

Mar. 31, 2025

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	plozasiran	Phase 3	Arrowhead
	zodasiran	Phase 2b	Arrowhead
	olpasiran	Phase 3	Amgen
	ARO-PNPLA3	Phase 1	Arrowhead
	GSK-4532990	Phase 2b	GSK
	ARO-INHBE	Phase 1/2a	Arrowhead
	ARO-ALK7	Phase 1	Arrowhead
Pulmonary	ARO-RAGE	Phase 1/2a	Arrowhead
	SRP-1002 (ARO-MMP7)	Phase 1/2a	Sarepta
Liver	fazirsiran	Phase 3	Takeda and Arrowhead
	GSK5637608	Phase 2	GSK
Neuromuscular	SRP-1001 (ARO-DUX4)	Phase 1/2a	Sarepta
	SRP-1003 (ARO-DM1)	Phase 1/2a	Sarepta
Central Nervous System (CNS)	SRP-1004 (ARO-ATXN2)	Phase 1/2a	Sarepta
Other	ARO-C3	Phase 1/2a	Arrowhead
	ARO-CFB	Phase 1/2a	Arrowhead

Stock-Based Compensation - Narrative (Details) - USD ($)		3 Months Ended		6 Months Ended
	Oct. 01, 2023	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024	Sep. 30, 2024	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, share reserve for issuance (in shares)		2,282,102		2,282,102
Granted (in shares)				0	0
Number of options outstanding (in shares)		1,525,717		1,525,717		1,978,516
Stock-based compensation expense		$ 15,081,000	$ 16,588,000	$ 29,257,000	$ 34,273,000
Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)		5,933,743		5,933,743		4,913,312
Stock-based compensation expense		$ 15,100,000	16,000,000.0	$ 29,200,000	32,200,000
Unrecognized pre-tax compensation expense		97,900,000		$ 97,900,000
Weighted average period to recognize pre-tax compensation expense				1 year 9 months 18 days
Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Intrinsic value of options exercised		3,700,000	2,500,000	$ 4,600,000	3,100,000
Stock-based compensation expense		$ 3,000.0	600,000	$ 100,000	2,100,000
2013 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserve for issuance (in shares)		2,391,211		2,391,211
Number of shares forfeited (in shares)				166,023
Number of options outstanding (in shares)		891,211		891,211
2013 Plan \| Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)		1,500,000		1,500,000
2021 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized (in shares)							8,000,000
Number of shares forfeited (in shares)				331,638
Granted (in shares)				6,215,559
Number of options outstanding (in shares)		32,151		32,151
2021 Plan \| Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)		3,939,734		3,939,734
Inducement Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized (in shares)		832,950		832,950
Common stock, share reserve for issuance (in shares)		392,611		392,611
Granted (in shares)				507,340
Number of options outstanding (in shares)		602,355		602,355
Inducement Awards \| Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)		151,500		151,500
Visirna ESOP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized (in shares)	20,000,000
Granted (in shares)	7,500,000
Stock-based compensation expense		$ 900,000	$ 1,200,000	$ 1,900,000	$ 3,200,000

Leases - Narrative (Details) ft² in Thousands, $ in Millions	3 Months Ended			6 Months Ended		15 Months Ended
	Mar. 31, 2025 USD ($) ft² option	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Mar. 31, 2025 USD ($) ft² option	Mar. 31, 2024 USD ($)	Dec. 31, 2024 USD ($)
Lessee Lease Description [Line Items]
Short-term lease cost \| $	$ 0.0	$ 0.0		$ 0.0	$ 0.0
Corporate Headquarters In Pasadena \| California
Lessee Lease Description [Line Items]
Office space leases (in sq ft) \| ft²	49			49
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 San Diego \| California
Lessee Lease Description [Line Items]
Office space leases (in sq ft) \| ft²	144			144
Operating lease renewal term	10 years			10 years
Lease term	15 years			15 years
Proceeds from additional tenant improvement allowance \| $			$ 3.1			$ 30.8
Research Facility in San Diego \| California \| Maximum
Lessee Lease Description [Line Items]
Number of options to renew \| option	1			1
Research Facility in Madison \| Wisconsin
Lessee Lease Description [Line Items]
Office space leases (in sq ft) \| ft²	107			107
Number of options to renew \| option	2			2
Operating lease renewal term	5 years			5 years

Investments

6 Months Ended

Mar. 31, 2025

Investments, Debt and Equity Securities [Abstract]

Investments

INVESTMENTS

The Company’s investments consisted of the following:


	As of March 31, 2025
	(in thousands)
	Adjusted Basis		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value


Available-for-sale securities	$	910,744	$	1,063	$	(107)	$	911,700

Total current investments	$	910,744	$	1,063	$	(107)	$	911,700


	As of September 30, 2024
	(in thousands)
	Adjusted Basis		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value


Available-for-sale securities	$	577,465	$	837	$	(26)	$	578,276

Total current investments	$	577,465	$	837	$	(26)	$	578,276

The following table summarizes the contract maturity of the available-for-sale securities as of:


	March 31, 2025		September 30, 2024
	(in thousands)


Within one year	$	422,082	$	578,276
After one to two years	301,085		—
After two to three years	188,533		—
Total	$	911,700	$	578,276

As of March 31, 2025 and September 30, 2024, the gross unrealized losses were immaterial. The Company has determined that the available-for-sale securities that were in an unrealized loss position did not have any credit loss impairment as of March 31, 2025 and 2024.

Financing Agreement - Narrative (Details) - USD ($) $ in Thousands			3 Months Ended	6 Months Ended		12 Months Ended
	Feb. 24, 2025	Aug. 07, 2024	Mar. 31, 2025	Mar. 31, 2025	Mar. 31, 2024	Sep. 30, 2024
Line of Credit Facility [Line Items]
Repayments of credit facility				$ 151,625	$ 0
Sarepta \| Sarepta Collaboration Agreement
Line of Credit Facility [Line Items]
Upfront payment	$ 500,000
Financing Agreement \| Line of Credit
Line of Credit Facility [Line Items]
Debt instrument term		7 years
Interest rate		15.00%
Secured Debt \| Financing Agreement \| Line of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 500,000
Long-term line of credit		400,000
Line of credit facility, remaining borrowing capacity		$ 100,000
Repayments of credit facility			$ 151,625			$ 0
Debt instrument, covenant, minimum liquidity cash, cash equivalents and investments			100,000	100,000
Market capitalization threshold			1,500,000	1,500,000
Principal repayment schedule through fifth year			160,000	$ 160,000
Secured Debt \| Financing Agreement \| Line of Credit \| GSK-HBV Agreement
Line of Credit Facility [Line Items]
Repayments of credit facility			$ 1,600
Repayments of debt, percentage of milestone payment			65.00%
Secured Debt \| Financing Agreement, Amendment \| Line of Credit
Line of Credit Facility [Line Items]
Repayments of credit facility			$ 150,000

Investments (Tables)

6 Months Ended

Mar. 31, 2025

Investments, Debt and Equity Securities [Abstract]

Schedule of Short-term and Long-term Investments and Marketable Securities

The Company’s investments consisted of the following:


	As of March 31, 2025
	(in thousands)
	Adjusted Basis		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value


Available-for-sale securities	$	910,744	$	1,063	$	(107)	$	911,700

Total current investments	$	910,744	$	1,063	$	(107)	$	911,700


	As of September 30, 2024
	(in thousands)
	Adjusted Basis		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value


Available-for-sale securities	$	577,465	$	837	$	(26)	$	578,276

Total current investments	$	577,465	$	837	$	(26)	$	578,276

Schedule of Contract Maturity of Available for Sale Securities

The following table summarizes the contract maturity of the available-for-sale securities as of:


	March 31, 2025		September 30, 2024
	(in thousands)


Within one year	$	422,082	$	578,276
After one to two years	301,085		—
After two to three years	188,533		—
Total	$	911,700	$	578,276

Collaboration and License Agreements (Tables)

6 Months Ended

Mar. 31, 2025

Collaboration And License Agreements [Abstract]

Schedule of Revenue

The following table provides a summary of revenue recognized:


	Three Months Ended March 31,				Six Months Ended March 31,
	2025		2024		2025		2024
	(in thousands)
GSK	$	3	$	—	$	2,503	$	2,685
Takeda	—		—		—		866
Sarepta	542,706		—		542,706		—
Total	$	542,709	$	—	$	545,209	$	3,551

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:


	March 31, 2025		September 30, 2024
	(in thousands)
Receivables included in accounts receivable	$	2,365	$	—
Contract liabilities included in deferred revenue	$	43,268	$	—

Collaborative Arrangement and Arrangement Other than Collaborative

The fixed and estimated variable consideration of $904.9 million was allocated in accordance to the following table:


	March 31, 2025
	(in thousands)
Upfront payment	$	500,000
Annual fees	250,000
Equity premium	83,612
Fixed consideration	$	833,612
Estimated variable consideration	71,243
Total transaction price	$	904,855

Financing Agreement - Schedule of Interest Expense Recognized Related to Credit Facility (Details) - Secured Debt - Financing Agreement - Line of Credit - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Line of Credit Facility [Line Items]
Amortization of debt discount and issuance costs	$ 1,129	$ 0	$ 1,682	$ 0
Contractual interest expense	15,009	0	30,687	0
Total interest expense	$ 16,138	$ 0	$ 32,369	$ 0

Commitments and Contingencies	6 Months Ended
Commitments and Contingencies	Mar. 31, 2025
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 March 31, 2025. Commitments The Company owns land in the Verona Technology Park in Verona, Wisconsin, where it has constructed an approximately 160,000 square foot drug manufacturing facility and an approximately 140,000 square foot laboratory and office facility to support manufacturing process development and analytical activities. As of March 31, 2025, the build-out of these facilities was completed, with total costs incurred of $292.6 million. The Company has an expected outstanding balance of approximately $3.7 million remaining to be settled.

Collaboration and License Agreements - GlaxoSmithKline Intellectual Property (No. 3) Limited (“GSK”) (Details) - USD ($)		1 Months Ended	3 Months Ended
	Nov. 22, 2021	Dec. 31, 2023	Mar. 31, 2025	Sep. 30, 2024	Dec. 11, 2023	Jun. 30, 2023
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue			$ 43,268,000	$ 0
GSK \| GSK-HSD License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Initial transaction price	$ 120,000,000
Milestone payment receivable						$ 30,000,000
Milestone payment receivable upon achievement of phase two and first patient dosed in phase three	100,000,000
GSK \| GSK-HSD License Agreement \| 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
GSK \| GSK-HBV Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Initial transaction price		$ 2,700,000
Development milestone payments			2,500,000
Deferred revenue			$ 0
GSK \| GSK-HBV Agreement \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development and sales milestone payments					$ 830,000,000

Intangible Assets - Schedule of Expected Future Amortization (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Sep. 30, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
2025 (remainder)	$ 849
2026	1,700
2027	1,700
2028	1,700
2029	795
2030 and thereafter	967
Net Carrying Amount	$ 7,711	$ 8,562

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 192,645	$ (262,372)
Adjustments to reconcile net income (loss) to net cash flow from operating activities
Stock-based compensation	31,236	37,444
Depreciation and amortization	11,319	8,788
(Accretion) amortization of note premiums/discounts	(2,788)	896
Realized loss on investments	0	(80)
Non-cash interest expense on liability related to the sale of future royalties	10,915	12,612
Non-cash interest expense on credit facility	32,369	0
Changes in operating assets and liabilities:
Accounts receivable	(2,365)	0
Prepaid expenses and other assets	(20,936)	(2,643)
Accounts payable	(1,717)	(8,402)
Accrued expenses	18,921	(11)
Deferred revenue	43,268	(866)
Operating lease, net	(2,255)	4,417
Other	3,169	0
Net cash provided by (used in) operating activities	313,781	(210,217)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(12,813)	(102,731)
Purchases of investments	(677,892)	(309,982)
Proceeds from sales and maturities of investments	347,402	208,615
Net cash used in investing activities	(343,303)	(204,098)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from the exercises of stock options	3,253	1,779
Proceeds from the issuance of common stock, net of offering costs	241,388	429,265
Proceeds from the issuance of warrants	25,000	0
Payments of debt issuance costs	(5,000)	0
Repayments of credit facility	(151,625)	0
Net cash provided by financing activities	113,016	431,044
Net increase in cash, cash equivalents and restricted cash	83,494	16,729
Effect of exchange rate on cash, cash equivalents and restricted cash	(470)	84
CASH, CASH EQUIVALENTS AND RESTRICTED CASH:
BEGINNING OF PERIOD	102,685	110,891
END OF PERIOD	185,709	127,704
Supplementary disclosure of cash flows:
Interest paid	(19)	0
Income taxes paid	(81)	(3,014)
Supplemental disclosure of non-cash investing activities:
Capital expenditures included in accrued expenses	$ 358	$ 7,265

Financing Agreement

6 Months Ended

Mar. 31, 2025

Debt Disclosure [Abstract]

Financing Agreement

FINANCING AGREEMENT

On August 7, 2024 (the “Closing Date”), the Company entered into the Financing Agreement with the guarantors party thereto, the lenders party thereto (the “Lenders”), and Sixth Street Lending Partners (“Sixth Street”), as the administrative agent and collateral agent for the Lenders. The Financing Agreement establishes a senior secured term loan facility of $500.0 million (the “Credit Facility”), consisting of $400.0 million funded on the Closing Date and an additional $100.0 million available at the Company’s option, subject to mutual agreement with Sixth Street, over the seven-year term. The loans under the Credit Facility bear interest at an annual rate 15.0%, and the interest is paid in kind and added to the outstanding principal balance of the Credit Facility each period. The outstanding principal balance of this Credit Facility, including amounts representing accrued but unpaid interest previously paid in kind, is due and payable on August 7, 2031.

The Company is permitted to use the net proceeds for working capital, capital expenditures and general corporate purposes of the Company and its subsidiaries.

The Company will have the right to prepay loans under the Credit Facility at any time. The Company is required to partially repay loans under the Credit Facility with proceeds from certain asset sales, condemnation events and extraordinary receipts, subject, in some cases, to reinvestment rights. If the Company repays in full the aggregate principal outstanding under the Credit Facility and such payment in full occurs on or prior to August 7, 2028, the Company will be required to make an additional payment to the lenders under the Credit Facility on such date in an amount necessary for the lenders to achieve a multiple of two times on invested capital of the aggregate principal amount funded on the Closing Date. If such payment in full occurs after August 7, 2028, the Company will be required to make an additional payment to the lenders under the Credit Facility on such date in an amount necessary for the lenders to achieve the greater of the

multiple of two times on invested capital of the aggregate principal amount funded on the Closing Date and the present value of all interest payments that would have been payable from such date through the maturity date of the Credit Facility.

On November 26, 2024, the Company entered into an amendment to the Financing Agreement (the "Amendment") to modify, amongst other things, some of the prepayment terms of the loans under the Credit Facility, including, the prepayment terms related to the Sarepta Collaboration Agreement. The Amendment was effective on February 14, 2025, following the closing of the Sarepta Collaboration Agreement and receipt of the $500.0 million upfront payment from Sarepta. As a result, the Company paid $150.0 million of the loans under the Credit Facility during the second quarter of fiscal 2025.

The Amendment was accounted for as a debt modification under ASC 470-50, “Debt—Modification and extinguishments” since the amendment did not result in substantially different terms. In connection with the Amendment, the Company did not incur significant third-party fees.

The Company also paid $1.6 million during the second quarter of fiscal 2025, representing 65% of the milestone payments from GSK under the Credit Facility term. See Note 2.

All obligations under the Financing Agreement will be secured on a first-priority basis, subject to certain exceptions, by security interests in substantially all assets of the Company and material subsidiaries of the Company, including its intellectual property, and will be guaranteed by material subsidiaries of the Company, including foreign subsidiaries, subject to certain exceptions.

The Financing Agreement contains customary covenants, including, without limitation, a financial covenant to maintain liquidity (cash, cash equivalents and investments) of at least $100.0 million if the Company’s market capitalization is above $1.5 billion, and negative covenants that, subject to certain exceptions, restrict indebtedness, liens, investments (including acquisitions), fundamental changes, asset sales and licensing transactions, dividends, modifications to material agreements, payment of subordinated indebtedness, and other matters customarily restricted in such agreements. The Company is subject to restrictions on sales and licensing transactions with respect to certain core intellectual property, subject to certain exceptions, including certain transactions related to areas outside the United States, United Kingdom, European Union, Japan and China.

The Financing Agreement contains certain embedded features that were identified and evaluated as not material to the consolidated financial statements.

The outstanding balance of the Credit Facility consisted of the following:


	March 31, 2025		September 30, 2024
	(in thousands)
Initial Term Loan	$	400,000	$	400,000
Accumulated interest on the Initial Term Loan	39,687		9,000
Less: Unamortized debt discount and issuance costs	(14,135)		(15,817)
Less: Current portion of credit facility	(65,000)		—
Less: Payments	(151,625)		—
Credit facility, net of current portion	$	208,927	$	393,183

The following table sets forth total interest expense recognized related to the Credit Facility:


	Three Months Ended March 31,				Six Months Ended March 31,
	2025		2024		2025		2024
	(in thousands)
Amortization of debt discount and issuance costs	$	1,129	$	—	$	1,682	$	—
Contractual interest expense	15,009		—		30,687		—
Total interest expense	$	16,138	$	—	$	32,369	$	—


Year	Amounts
	(in thousands)
2025 (remainder)	$	50,000
2026	40,000
2027	40,000
2028	15,000
2029	15,000
Thereafter	203,063
Total	$	363,063

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2025	Sep. 30, 2024
Current assets:
Cash, cash equivalents and restricted cash	$ 185,709	$ 102,685
Accounts receivable	2,365	0
Available-for-sale securities, at fair value	911,700	578,276
Prepaid expenses	23,769	9,537
Other current assets	11,677	4,973
Total current assets	1,135,220	695,471
Property, plant and equipment, net	384,803	386,032
Intangible assets, net	7,711	8,562
Right-of-use assets	44,452	45,255
Other assets	1,312	4,482
Total Assets	1,573,498	1,139,802
Current liabilities:
Accounts payable	9,980	11,388
Accrued expenses	78,450	63,017
Accrued payroll and benefits	16,613	21,989
Lease liabilities	6,782	6,342
Deferred revenue	43,268	0
Credit facility	65,000	0
Other liabilities	448	432
Total current liabilities	220,541	103,168
Long-term liabilities:
Lease liabilities, net of current portion	107,529	111,027
Liability related to the sale of future royalties	352,276	341,361
Credit facility, net of current portion	208,927	393,183
Total long-term liabilities	668,732	845,571
Commitments and contingencies (Note 7)
Noncontrolling interest and stockholders’ equity:
Common stock, $0.001 par value: Authorized 290,000 shares; issued and outstanding 138,062 and 124,376 shares	230	217
Additional paid-in capital	2,106,864	1,806,000
Accumulated other comprehensive income	4,390	4,750
Accumulated deficit	(1,428,163)	(1,625,523)
Total Arrowhead Pharmaceuticals, Inc. stockholders’ equity	683,321	185,444
Noncontrolling interest	904	5,619
Total noncontrolling interest and stockholders’ equity	684,225	191,063
Total Liabilities, Noncontrolling Interest and Stockholders’ Equity	$ 1,573,498	$ 1,139,802

Fair Value Measurements (Tables)

6 Months Ended

Mar. 31, 2025

Fair Value Disclosures [Abstract]

Schedule of 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:


	March 31, 2025
	Level 1		Level 2		Level 3		Total
	(in thousands)

Available-for-sale securities
U.S. government and agency securities	$	—	$	277,170	$	—	$	277,170
Commercial notes	—		113,387		—		113,387
Corporate debt securities	—		521,143		—		521,143
Total available-for-sale securities	—		911,700		—		911,700
Cash equivalents
Money market instruments	137,535		—		—		137,535
Commercial notes	—		28,908		—		28,908
Total cash equivalents	137,535		28,908		—		166,443
Total financial assets	$	137,535	$	940,608	$	—	$	1,078,143


	September 30, 2024
	Level 1		Level 2		Level 3		Total
	(in thousands)

Available-for-sale securities
U.S. government and agency securities	$	—	$	160,723	$	—	$	160,723
Commercial notes	—		179,714		—		179,714
Corporate debt securities	—		237,839		—		237,839
Total available-for-sale securities	—		578,276		—		578,276
Cash equivalents
Money market instruments	66,966		—		—		66,966
Total cash equivalents	66,966		—		—		66,966
Total financial assets	$	66,966	$	578,276	$	—	$	645,242

Net Income (Loss) Per Share - Schedule of Antidilutive Securities (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted earnings per share (in shares)	6,049	4,006	5,317	4,588
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted earnings per share (in shares)	760	595	750	657
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted earnings per share (in shares)	5,289	3,411	4,567	3,931

Investments - Schedule of Short-term, Long-term Investments and Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Sep. 30, 2024
Schedule Of Held To Maturity Securities And Marketable Securities [Line Items]
Current investments, Adjusted Basis	$ 910,744	$ 577,465
Current investments, Gross Unrealized Gains	1,063	837
Current investments, Gross Unrealized Losses	(107)	(26)
Current investments, Fair Value	911,700	578,276
Available-for-sale securities
Schedule Of Held To Maturity Securities And Marketable Securities [Line Items]
Current investments, Adjusted Basis	910,744	577,465
Current investments, Gross Unrealized Gains	1,063	837
Current investments, Gross Unrealized Losses	(107)	(26)
Current investments, Fair Value	$ 911,700	$ 578,276

Organization and Significant Accounting Policies

6 Months Ended

Mar. 31, 2025

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	plozasiran	Phase 3	Arrowhead
	zodasiran	Phase 2b	Arrowhead
	olpasiran	Phase 3	Amgen
	ARO-PNPLA3	Phase 1	Arrowhead
	GSK-4532990	Phase 2b	GSK
	ARO-INHBE	Phase 1/2a	Arrowhead
	ARO-ALK7	Phase 1	Arrowhead
Pulmonary	ARO-RAGE	Phase 1/2a	Arrowhead
	SRP-1002 (ARO-MMP7)	Phase 1/2a	Sarepta
Liver	fazirsiran	Phase 3	Takeda and Arrowhead
	GSK5637608	Phase 2	GSK
Neuromuscular	SRP-1001 (ARO-DUX4)	Phase 1/2a	Sarepta
	SRP-1003 (ARO-DM1)	Phase 1/2a	Sarepta
Central Nervous System (CNS)	SRP-1004 (ARO-ATXN2)	Phase 1/2a	Sarepta
Other	ARO-C3	Phase 1/2a	Arrowhead
	ARO-CFB	Phase 1/2a	Arrowhead

The Company operates lab facilities in California and Wisconsin, where its research and development activities, including the development of RNAi therapeutics, take place. The Company also operates an active pharmaceutical ingredient manufacturing and supporting laboratory facility in Verona, Wisconsin. The Company’s principal executive offices are located in Pasadena, California.

Thus far in fiscal 2025, the Company has continued to develop and advance its pipeline and partnered candidates. Several key recent developments include:

•Announced Topline results from Part 2 of a Phase 1/2 clinical study of ARO-C3, the Company’s investigational RNAi therapeutic designed to reduce liver production of complement component 3 (C3) as a potential therapy for various complement mediated diseases. ARO-C3 achieved reductions in alternative pathway complement activity and proteinuria;

•Showcased preclinical data supporting the advancement of two first-in-class clinical stage, RNAi-based investigational therapeutics being developed by the Company for the treatment of obesity and metabolic diseases;

•Announced preclinical results on ARO-ALK7, which is the first RNAi-based therapy designed to silence adipocyte expression of the ACVR1 to reduce the production of Activin receptor-like kinase 7 (ALK7), which acts as a receptor in a pathway that regulates energy homeostasis in adipose tissue. Arrowhead received regulatory clearance to initiate a Phase 1/2a clinical trial of ARO-ALK7 in New Zealand, which the company anticipates will begin dosing in the second quarter of 2025;

•Entered into a global licensing and collaboration agreement with Sarepta Therapeutics, Inc (“Sarepta”) on November 25, 2024, which closed on February 7, 2025. Closing of the transaction was subject to the expiration or termination of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 and other customary conditions. Upon closing, the Company received $325.0 million through the purchase of 11,926,301 shares of Company common stock by Sarepta, at a price per share of $27.25, and received $500.0 million as an upfront payment on February 24, 2025. The Company will also receive $250.0 million to be paid in equal installments over five years and is eligible to receive an additional $300.0 million in near-term payments. Additionally, the Company is eligible to receive royalties on commercial sales and up to approximately $10.0 billion in future potential milestone payments;

•Submitted a New Drug Application (NDA) to the U.S. Food and Drug Administration (FDA) on November 16, 2024, which was accepted for filing on January 17, 2025. The FDA provided a Prescription Drug User Fee Act (PDUFA) action date of November 18, 2025, and indicated it is not currently planning to hold an advisory committee meeting;

•GSK dosed its fifth patient in a Phase 2 trial in December 2024, triggering a $2.5 million milestone payment to the Company which was paid in the second quarter of fiscal 2025;

•Announced that the Company has dosed the first subjects in a Phase 1/2a clinical trial of ARO-INHBE; and

•Presented interim results from a Phase 1/2a clinical study of ARO-CFB at the 8th Complement-Based Drug Development Summit. The study resulted in multiple promising findings including: (1) ARO-CFB led to dose dependent reductions in circulating CFB protein by up to 90% with greater than 3 months duration, (2) single and multiple doses of ARO-CFB led to near complete inhibition of alternative pathway activity based on Wieslab AP, and (3) single and multiple doses of ARO-CFB led to near complete inhibition of alternative pathway hemolytic activity, measured by AH50.

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., Arrowhead Australia Pty Ltd., Arrowhead Pharmaceuticals Ireland Limited, Arrowhead Pharmaceuticals NZ Limited and Visirna Therapeutics, Inc. (“Visirna”). 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 as of March 31, 2025 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, 2024 for more complete descriptions and discussions. Operating results and cash flows for the six months ended March 31, 2025 are not necessarily indicative of the results that may be expected for the fiscal year ending September 30, 2025.

Liquidity

The Company’s primary sources of financing have been through the sale of its equity securities, credit facility, revenue from its licensing and collaboration agreements and the sale of certain future royalties. Research and development activities have required significant 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. Additionally, significant investment will be required as the Company’s pipeline matures into later stage clinical trials and commercialization efforts.

As of March 31, 2025, the Company had $185.7 million in cash, cash equivalents and restricted cash ($2.1 million in restricted cash) and $911.7 million in available-for-sale securities to fund operations. During the six months ended March 31, 2025, the Company’s cash, cash equivalents and restricted cash and investments balance increased by $416.4

million, which was primarily due to the $500.0 million as an upfront payment and $325.0 million in the form of an equity investment under the Sarepta agreement, partially offset by ongoing expenses related to the Company’s research and development programs and repayments on the credit facility.

In total, the Company is eligible to receive up to $13.3 billion in additional 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.

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, 2024.

Recent Accounting Pronouncements

In January 2025, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, in November 2024, and ASU 2025-01, Clarifying the Effective Date. These updates require entities to provide disaggregated disclosures of income statement expenses. The ASUs do not affect the expense captions presented on the face of the income statement but instead require the disaggregation of certain expense captions into specified categories within the footnotes to the financial statements. The ASUs will become effective for the Company beginning October 1, 2027, and are not expected to have a material impact on its consolidated financial statements and related disclosures.

In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, to improve its income tax disclosure requirements. Under the guidance, entities must annually (1) disclose specific categories in the rate reconciliation and (2) provide additional information for reconciling items that meet a quantitative threshold. This ASU will become effective for the Company beginning October 1, 2025, and is not expected to have a material impact on its consolidated financial statements and related disclosures.

In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which is intended to improve reportable segment disclosure requirements, primarily through additional disclosures about significant segment expenses. This ASU requires public companies with a single reportable segment to provide all disclosures required under ASC 280. In addition, this ASU requires public companies to include in interim reports all disclosures related to a reportable segment’s profit or loss and assets that are currently required in annual reports. While the ASU implements further segment disclosure requirements, it does not change how an entity identifies its operating or reportable segments and it will have no impact on the Company’s consolidated financial condition, results of operations or cash flows. This ASU is applicable to the Company’s Annual Report on Form 10-K for the fiscal year ending September 30, 2025, and subsequent interim periods. Early adoption is permitted and the amendments must be applied retrospectively to all prior periods presented.

Intangible Assets - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024	Sep. 30, 2024
Finite Lived Intangible Assets [Line Items]
Net Carrying Amount	$ 7,711		$ 7,711		$ 8,562
Amortization expense	400	$ 400	900	$ 900
Novartis
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	24,857		24,857		24,857
Accumulated Amortization	17,146		17,146		16,295
Impairment	0		0		0
Net Carrying Amount	7,711		7,711		8,562
Novartis \| Patents
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	21,728		21,728		21,728
Accumulated Amortization	15,649		15,649		14,873
Impairment	0		0		0
Net Carrying Amount	$ 6,079		$ 6,079		$ 6,855
Useful Lives (in years)	14 years		14 years		14 years
Novartis \| License
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 3,129		$ 3,129		$ 3,129
Accumulated Amortization	1,497		1,497		1,422
Impairment	0		0		0
Net Carrying Amount	$ 1,632		$ 1,632		$ 1,707
Useful Lives (in years)	21 years		21 years		21 years

Collaboration and License Agreements - Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Disaggregation of Revenue [Line Items]
Revenue	$ 542,709	$ 0	$ 545,209	$ 3,551
GSK
Disaggregation of Revenue [Line Items]
Revenue	3	0	2,503	2,685
Takeda
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	866
Sarepta
Disaggregation of Revenue [Line Items]
Revenue	$ 542,706	$ 0	$ 542,706	$ 0

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Intangible Assets (Tables)

6 Months Ended

Mar. 31, 2025

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 March 31, 2025
Patents	$	21,728	$	15,649	$	—	$	6,079	14
License	3,129		1,497		—		1,632		21
Total intangible assets, net	$	24,857	$	17,146	$	—	$	7,711

As of September 30, 2024
Patents	$	21,728	$	14,873	$	—	$	6,855	14
License	3,129		1,422		—		1,707		21
Total intangible assets, net	$	24,857	$	16,295	$	—	$	8,562

Schedule of Intangible Assets Future Amortization Expense

The following table presents the estimated future amortization expense related to intangible assets as of March 31, 2025:


	Amortization Expense
Year Ending September 30,	(in thousands)
2025 (remainder)	$	849
2026	1,700
2027	1,700
2028	1,700
2029	795
2030 and thereafter	967
Total	$	7,711

Liability Related to the Sale of Future Royalties

6 Months Ended

Mar. 31, 2025

LIABILITY RELATED TO THE SALE OF FUTURE ROYALTIES

In November 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, originally developed by the Company and licensed to Amgen in September 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. During the third quarter of fiscal 2024, Amgen completed enrollment of the Phase 3 OCEAN(a) outcomes trial of olpasiran, which triggered a $50.0 million milestone payment that the Company received in the same quarter.

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 and $50.0 million from Royalty Pharma were recorded as liabilities related to the sale of future royalties on its consolidated balance sheets. The Company is not obligated to repay these funds received under the Royalty Pharma Agreement.

The Company records the obligations at their carrying value using the effective interest method. In order to amortize the sale of future royalties, the Company utilizes the prospective method to estimate the future royalties to be paid by the Company to the counterparty over the life of the arrangement. Under the prospective method, a new effective interest rate is determined based on the revised estimate of remaining cash flows. The new rate is the discount rate that equates the present value of the revised estimate of remaining cash flows with the carrying amount of the debt, and it will be used to recognize non-cash interest expense for the remaining periods. The Company periodically assesses the amount and the timing of expected royalty payments using a combination of internal projections and forecasts from external sources. The estimates of future net product sales (and resulting royalty payments) are based on key assumptions including population, penetration, probability of success and sales price, among others. To the extent such payments are greater or less than the Company’s initial estimates or the timing of such payments is different than its original estimates, the Company will prospectively adjust the amortization of the royalty financing obligations and the effective interest rate. As of March 31, 2025, the estimated effective interest rate was 6.3%.

The following table presents the activity with respect to the liability related to the sale of future royalties.


	March 31, 2025		September 30, 2024
	(in thousands)
Beginning carrying value	$	341,361	$	268,326
Milestone payment received	—		50,000
Non-cash interest expense recognized	10,915		23,035
Ending carrying value	$	352,276	$	341,361

Fair Value Measurements

6 Months Ended

Mar. 31, 2025

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 Company’s valuation techniques and inputs used to measure fair value and the definition of the three levels (Level 1, Level 2, and Level 3) of the fair value hierarchy are disclosed in Note 10 - Fair Value Measurements of Notes to Consolidated Financial Statements of Part IV, “Item 15. Exhibits and Financial Statement Schedules” of its Annual Report on Form 10-K for the year ended September 30, 2024.

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. As of March 31, 2025 and September 30, 2024, the Company did not have any financial assets or financial liabilities based on Level 3 measurements.


	March 31, 2025
	Level 1		Level 2		Level 3		Total
	(in thousands)

Available-for-sale securities
U.S. government and agency securities	$	—	$	277,170	$	—	$	277,170
Commercial notes	—		113,387		—		113,387
Corporate debt securities	—		521,143		—		521,143
Total available-for-sale securities	—		911,700		—		911,700
Cash equivalents
Money market instruments	137,535		—		—		137,535
Commercial notes	—		28,908		—		28,908
Total cash equivalents	137,535		28,908		—		166,443
Total financial assets	$	137,535	$	940,608	$	—	$	1,078,143


	September 30, 2024
	Level 1		Level 2		Level 3		Total
	(in thousands)

Available-for-sale securities
U.S. government and agency securities	$	—	$	160,723	$	—	$	160,723
Commercial notes	—		179,714		—		179,714
Corporate debt securities	—		237,839		—		237,839
Total available-for-sale securities	—		578,276		—		578,276
Cash equivalents
Money market instruments	66,966		—		—		66,966
Total cash equivalents	66,966		—		—		66,966
Total financial assets	$	66,966	$	578,276	$	—	$	645,242

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
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-Section 55
-Paragraph 107
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+ Details

Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Income Statement [Abstract]
Revenue	$ 542,709	$ 0	$ 545,209	$ 3,551
Operating expenses:
Research and development	133,102	101,122	270,104	217,613
General and administrative	28,405	25,069	55,315	48,674
Total operating expenses	161,507	126,191	325,419	266,287
Operating income (loss)	381,202	(126,191)	219,790	(262,736)
Other income (expense):
Interest income	9,615	6,250	17,217	9,052
Interest expense	(21,639)	(7,244)	(43,285)	(12,611)
Other, net	438	189	779	610
Total other expense	(11,586)	(805)	(25,289)	(2,949)
Income (loss) before income tax expense and noncontrolling interest	369,616	(126,996)	194,501	(265,685)
Income tax expense (benefit)	1,753	0	1,856	(3,313)
Net income (loss) including noncontrolling interest	367,863	(126,996)	192,645	(262,372)
Net loss attributable to noncontrolling interest, net of tax	(2,582)	(1,696)	(4,715)	(4,208)
Net income (loss) attributable to Arrowhead Pharmaceuticals, Inc.	$ 370,445	$ (125,300)	$ 197,360	$ (258,164)
Net income (loss) per share attributable to Arrowhead Pharmaceuticals, Inc.:
Basic (in dollars per share)	$ 2.78	$ (1.02)	$ 1.53	$ (2.24)
Diluted (in dollars per share)	$ 2.75	$ (1.02)	$ 1.52	$ (2.24)
Weighted-average shares used in calculating
Basic (in shares)	133,363	123,285	129,059	115,307
Diluted (in shares)	134,484	123,285	130,265	115,307
Other comprehensive income (loss), net of tax:
Unrealized gains on available-for-sale securities	$ 653	$ 216	$ 146	$ 2,125
Foreign currency translation adjustments	(400)	(56)	(506)	2
Comprehensive income (loss)	$ 368,116	$ (126,836)	$ 192,285	$ (260,245)

Balance Sheet Accounts - Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued R&D expenses	$ 42,963	$ 28,069
Accrued R&D expenses; co-development	28,755	23,351
Accrued capital expenditures	358	4,206
Other	6,374	7,391
Total accrued expenses	$ 78,450	$ 63,017

Net Income (Loss) Per Share - Schedule of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Numerator:
Net income (loss) attributable to Arrowhead Pharmaceuticals, Inc.	$ 370,445	$ (125,300)	$ 197,360	$ (258,164)
Denominator:
Weighted-average basic shares outstanding (in shares)	133,363	123,285	129,059	115,307
Effect of dilutive securities (in shares)	1,121	0	1,206	0
Weighted-average diluted shares outstanding (in shares)	134,484	123,285	130,265	115,307
Basic net income (loss) per share (in dollars per share)	$ 2.78	$ (1.02)	$ 1.53	$ (2.24)
Diluted net income (loss) per share (in dollars per share)	$ 2.75	$ (1.02)	$ 1.52	$ (2.24)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

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+ Details

Leases - Schedule of Components of Lease Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024	Sep. 30, 2024
Lease Assets and Liabilities
Right-of-use assets	$ 44,452		$ 44,452		$ 45,255
Lease liabilities	6,782		6,782		6,342
Lease liabilities, net of current portion	107,529		107,529		$ 111,027
Lease Cost
Total	4,160	$ 3,899	8,450	$ 8,148
Research and development
Lease Cost
Operating lease cost	2,709	2,572	5,520	5,566
Variable lease cost	951	836	1,937	1,615
General and administrative expense
Lease Cost
Operating lease cost	500	491	993	967
Variable lease cost	$ 0	$ 0	$ 0	$ 0

Stock-Based Compensation - Schedule of Granted and Outstanding Shares (Details) - shares	Mar. 31, 2025	Sep. 30, 2024
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options outstanding (in shares)	1,525,717	1,978,516
Total (in shares)	7,459,460
Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)	5,933,743	4,913,312
2013 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options outstanding (in shares)	891,211
Total (in shares)	2,391,211
2013 Plan \| Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)	1,500,000
2021 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options outstanding (in shares)	32,151
Total (in shares)	3,971,885
2021 Plan \| Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)	3,939,734
Inducement Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options outstanding (in shares)	602,355
Total (in shares)	1,096,364
Inducement Awards \| Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based payment award (in shares)	494,009

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details

Leases - Schedule of Maturities of Operating Lease Liabilities on an Undiscounted Basis (Details) $ in Thousands	Mar. 31, 2025 USD ($)
Leases [Abstract]
2025 (remainder)	$ 7,776
2026	15,799
2027	14,974
2028	13,619
2029	13,905
2030 and thereafter	114,790
Total	180,863
Less imputed interest	(66,552)
Total operating lease liabilities (includes current portion)	$ 114,311

Liability Related to the Sale of Future Royalties - Activity (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Sep. 30, 2024
Liability, Sale Of Future Royalties [Roll Forward]
Beginning carrying value	$ 341,361	$ 268,326	$ 268,326
Milestone payment received	0		50,000
Non-cash interest expense recognized	10,915	$ 12,612	23,035
Ending carrying value	$ 352,276		$ 341,361

Collaboration and License Agreements

6 Months Ended

Mar. 31, 2025

Collaboration And License Agreements [Abstract]

Collaboration and License Agreements

COLLABORATION AND LICENSE AGREEMENTS

The following table provides a summary of revenue recognized:


	Three Months Ended March 31,				Six Months Ended March 31,
	2025		2024		2025		2024
	(in thousands)
GSK	$	3	$	—	$	2,503	$	2,685
Takeda	—		—		—		866
Sarepta	542,706		—		542,706		—
Total	$	542,709	$	—	$	545,209	$	3,551

The following table summarizes the balance of receivables and contract liabilities related to the Company’s

collaboration and license agreements:


	March 31, 2025		September 30, 2024
	(in thousands)
Receivables included in accounts receivable	$	2,365	$	—
Contract liabilities included in deferred revenue	$	43,268	$	—

GlaxoSmithKline Intellectual Property (No. 3) Limited (“GSK”)

GSK-HSD License Agreement

On November 22, 2021, GSK and the Company entered into an Exclusive License Agreement (the “GSK-HSD License Agreement”). Under the GSK-HSD 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. GSK is wholly responsible for all clinical development and commercialization of GSK-4532990 in its territory.

The Company has completed its performance obligation related to this agreement, and the upfront payment of $120.0 million was fully recognized in the year ended September 30, 2022. Further, GSK dosed the first patient in a Phase 2b trial in March 2023 and paid a $30.0 million milestone payment to the Company in the third quarter of fiscal 2023.

The Company is eligible for an additional payment of $100.0 million upon achieving 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.

GSK-HBV Agreement

On December 11, 2023, the Company entered into an Amended and Restated License Agreement with GSK (the “GSK-HBV Agreement”) pursuant to which GSK received a worldwide, exclusive license to develop and commercialize daplusiran/tomligisiran (GSK5637608, formerly JNJ-3989), the Company’s third-generation subcutaneously administered RNAi therapeutic candidate being developed as a potential therapy for patients with chronic hepatitis B virus infection.

Under the terms of the GSK-HBV Agreement, the Company received $2.7 million in December 2023, upon signing the amended GSK-HBV Agreement. Further, GSK dosed the fifth patient in a Phase 2 trial in December 2024, triggering a $2.5 million milestone payment to the Company which was paid in the second quarter of fiscal 2025. The Company is eligible to receive up to $830.0 million in development and sales milestone payments under the GSK-HBV Agreement.

As of March 31, 2025, the Company recorded an insignificant amount in accounts receivable and no liabilities.

Horizon Therapeutics Ireland DAC (“Horizon”)

In June 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.

On October 6, 2023, Amgen completed its acquisition of Horizon and subsequently notified the Company of Amgen’s intent to terminate the HZN-457 license. Horizon exercised its right to terminate the Horizon License Agreement for convenience, which took effect on December 21, 2023.

Takeda Pharmaceutical Company Limited (“Takeda”)

In October 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 the Company’s fazirsiran program (formerly TAK-999 and ARO-AAT), 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 received an exclusive license to commercialize fazirsiran and will lead the global commercialization strategy, while the Company will be eligible to receive tiered royalties of 20% to 25% on net sales.

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.

Under the terms of the Takeda License Agreement, the Company received $300.0 million as an upfront payment in January 2021 and an additional $40.0 million upon Takeda’s initiation of a Phase 3 REDWOOD clinical study of fazirsiran in March 2023, and is eligible to receive up to $527.5 million in additional potential development, regulatory and commercial milestones.

The Company 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. The Company has substantially completed its performance obligation under the Takeda License Agreement by December 31, 2023. As such, all revenue has been fully recognized as of December 31, 2023. There were no further deferred revenue and contract liabilities as of March 31, 2025.

The Company recorded $28.8 million as accrued expenses as of March 31, 2025 that was primarily driven by co-development and co-commercialization activities.

Janssen Pharmaceuticals, Inc. (“Janssen”)

On April 7, 2023, Janssen voluntarily terminated its collaboration agreement with the Company and the Company regained full rights to ARO-PNPLA3, formerly called JNJ-75220795. ARO-PNPLA3 is in Phase 1 clinical trials, which are now being developed by the Company.

Further, on December 11, 2023, the Company entered into the GSK-HBV Agreement, as discussed above, pursuant to which GSK received an exclusive license for JNJ-3989 (formerly ARO-HBV). JNJ-3989 had previously been licensed to Janssen in October 2018.

Amgen Inc. (“Amgen”)

In September 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 (previously referred to as AMG- 890 or ARO-LPA) program. These RNAi molecules are designed to reduce elevated lipoprotein(a), which is a genetically validated, independent risk factor for atherosclerotic cardiovascular disease. Under the Olpasiran Agreement, Amgen is wholly responsible for clinical development and commercialization.

The Company has substantially completed its performance obligations under the Olpasiran Agreement. There were no contract assets and liabilities recorded as of March 31, 2025.

In November 2022, Royalty Pharma Investments 2019 ICAV (“Royalty Pharma”) and the Company entered into a Royalty Purchase Agreement with Royalty Pharma (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 $485.0 million in remaining development, regulatory and sales milestone payments payable from Amgen and Royalty Pharma. See Note 11.

Sarepta Therapeutics, Inc.

On November 25, 2024, the Company entered into an Exclusive License and Collaboration Agreement (the “Sarepta Collaboration Agreement”) with Sarepta for the development and commercialization of multiple clinical and preclinical programs in rare, genetic diseases of the muscle, central nervous system, and lungs. The Company concurrently entered into a Stock Purchase Agreement (the “Stock Purchase Agreement”) with Sarepta (see Note 6).

Under the Sarepta Collaboration Agreement, Sarepta received an exclusive worldwide license to SRP-1001 (formerly ARO-DUX4), SRP-1003 (formerly ARO-DM1), SRP-1002 (formerly ARO-MMP7), and SRP-1004 (formerly ARO-ATXN2) clinical stage programs (the “C1” programs). Sarepta also received an exclusive sublicensable worldwide license to the Company’s ARO-HTT, ARO-ATXN1, and ARO-ATXN3 preclinical stage programs (the “C2” programs). The Company will perform certain research and development activities for the C1 and C2 programs.

Further, Sarepta may select up to six gene targets for which the Company will perform discovery, optimization and

preclinical development activities to identify RNAi compounds against each selected target (the “C3” programs). Upon target acceptance, Sarepta will receive an exclusive license to the Company’s intellectual property rights to exploit compounds directed to those targets and is wholly responsible for clinical development and commercialization of each compound after the Company delivers a CTA ready data package (the "CTA package").

The Company identified 17 performance obligations under the Sarepta Collaboration Agreement. The four C1 licenses are distinct performance obligations from the four C1 research and development performance obligations since the customer can use and benefit from the licenses separately. The performance obligations for the licenses were satisfied during the quarter upon delivery and the research and development performance obligations will be satisfied as the work is performed. The remaining nine performance obligations include three C2 preclinical stage program licenses and research and development activities, and six C3 unidentified discovery target licenses and research and development activity. Each of the three C2 programs and the six C3 programs were determined to represent one performance obligation, as the customer cannot benefit from the use of the product license at the point of transfer until the specified research and development activities are performed. As such, each of the C2 and C3 product licenses and respective research and development work will be combined to form one performance obligation. For these nine performance obligations, revenue will be recognized over time as the work is performed.

For performance obligations recognized over time, the estimated performance period over which revenue will be recognized is determined to be the period over which the Company estimates it will perform the research and development activities. The Company determined that the most appropriate method of measuring progress for these performance obligations is an input method based on research and development costs in the program budget. Accordingly, the Company has estimated the total cost required to complete its obligation and recognized an amount of revenue equal to the proportion of services performed, which is reassessed on an ongoing basis as the program progresses. In the period an agreement expires or is terminated, remaining deferred revenue, if any, is recognized as revenue.

Under the terms of the Sarepta Collaboration Agreement, the Company received an upfront payment of $500.0 million on February 14, 2025. In addition, on February 7, 2025, the Company received $325.0 million in the form of an equity investment under the Stock Purchase Agreement. Based upon the Company's share price on February 7, 2025, (the “Closing Date”), the difference between the $325.0 million and the fair value of the shares on the Closing date resulted in a premium of $83.6 million. The premium is included as part of the total consideration of the Sarepta Collaboration Agreement for revenue recognition purposes. The Company expects to receive $250.0 million to be paid in annual installments of $50.0 million over the first five years of the agreement. The Company is also eligible receive reimbursement of certain costs related to carrying out the research and development activities for the C1 programs. The fixed consideration of $833.6 million and an estimated variable consideration of $71.2 million were allocated to all performance obligations based on their relative standalone selling price. Standalone selling prices for the product licenses were determined using an adjusted market-based approach through the net present value of the expected future cash flows for each program. The standalone selling prices for the research and development work were determined based on an expected cost plus margin approach. The fixed and estimated variable consideration of $904.9 million was allocated in accordance to the following table:


	March 31, 2025
	(in thousands)
Upfront payment	$	500,000
Annual fees	250,000
Equity premium	83,612
Fixed consideration	$	833,612
Estimated variable consideration	71,243
Total transaction price	$	904,855

The Company estimates the stand-alone selling price for each distinct performance obligation, which involves assumptions that may require significant judgment. The Company’s estimates of the stand-alone selling price for license-related performance obligations includes forecasted revenues and expenses, phase dates, probability of success, development timelines, and the discount rate. The estimates of the stand-alone selling price for research and development or other service-related performance obligations generally include forecasting the expected costs of satisfying a performance obligation at market rates. The Company identified a discount for accounting revenue recognition purposes which was allocated proportionally to each of the performance obligations based upon their standalone selling price.

The Company will receive reimbursement of certain costs related to carrying out the research and development activities for the C1 programs as well as development milestone payments of up to $300.0 million. Further, for each of the

13 programs, the Company is eligible to receive regulatory milestone payments between $110.0 million and $180.0 million per program. Variable consideration associated with the milestones that may be achieved will be allocated to the performance obligation to which it is determined to be related, which will be the respective development work that is being reimbursed and the respective programs to which the milestones relate. ARO-DM1 Development Milestones will be allocated between the license and development work based on the allocation of the standalone selling price. The Company constrained all of the ARO-DM1 Development Milestones and other development milestones as there is a high degree of uncertainty around the occurrence of those events.

The Company is also eligible to receive sales milestone payments between $500.0 million and $700.0 million per program as well as tiered royalties on net sales of licensed products of up to the low double digits, subject to the terms and conditions of the Sarepta Collaboration Agreement. The Company has applied the sales-based scope exception to the sales milestones and the royalty-based payments.

The Sarepta Collaboration Agreement commenced in February 2025 and may be terminated by either party in the event of a material breach as defined therein. In addition, Sarepta may voluntarily terminate the Sarepta Collaboration Agreement with 30 days' written notice to the Company if terminated prior to any regulatory approval of a licensed product. Unless earlier terminated, the Sarepta Collaboration Agreement expires on a product-by-product and country-by-country basis, upon the date of expiration of the relevant royalty term for such product in such country.

As of March 31, 2025, the Company recorded $542.7 million in revenue from Sarepta, $2.4 million in accounts receivable and $43.3 million in deferred revenue. The recognition of the remaining revenue for the performance obligations is dependent upon the time it takes to complete the respective research and development activities and in consideration of the timing of the selection of the C3 programs. Accordingly, the end dates are subject to change. The Company expects to recognize the unsatisfied performance obligations in accordance with the various agreements, and all performance obligations are currently estimated to be fully satisfied by March 31, 2031.

Organization and Significant Accounting Policies (Policies)	6 Months Ended
	Mar. 31, 2025
Accounting Policies [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements In January 2025, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, in November 2024, and ASU 2025-01, Clarifying the Effective Date. These updates require entities to provide disaggregated disclosures of income statement expenses. The ASUs do not affect the expense captions presented on the face of the income statement but instead require the disaggregation of certain expense captions into specified categories within the footnotes to the financial statements. The ASUs will become effective for the Company beginning October 1, 2027, and are not expected to have a material impact on its consolidated financial statements and related disclosures. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, to improve its income tax disclosure requirements. Under the guidance, entities must annually (1) disclose specific categories in the rate reconciliation and (2) provide additional information for reconciling items that meet a quantitative threshold. This ASU will become effective for the Company beginning October 1, 2025, and is not expected to have a material impact on its consolidated financial statements and related disclosures. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which is intended to improve reportable segment disclosure requirements, primarily through additional disclosures about significant segment expenses. This ASU requires public companies with a single reportable segment to provide all disclosures required under ASC 280. In addition, this ASU requires public companies to include in interim reports all disclosures related to a reportable segment’s profit or loss and assets that are currently required in annual reports. While the ASU implements further segment disclosure requirements, it does not change how an entity identifies its operating or reportable segments and it will have no impact on the Company’s consolidated financial condition, results of operations or cash flows. This ASU is applicable to the Company’s Annual Report on Form 10-K for the fiscal year ending September 30, 2025, and subsequent interim periods. Early adoption is permitted and the amendments must be applied retrospectively to all prior periods presented.

Leases

6 Months Ended

Mar. 31, 2025

Leases [Abstract]

Leases

LEASES

Pasadena, California: The Company leases 49,000 square feet of office space located at 177 East 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 additional five-year term. The Company is not reasonably certain that it will exercise this option to renew and therefore it is not included in right-of-use assets and liabilities as of March 31, 2025.

San Diego, California: The Company leases 144,000 square feet of office and research and development laboratory space located at 10102 Hoyt Park from 11404 & 11408 Sorrento Valley Owner, LLC, which lease expires on April 30, 2038. 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. The Company is not reasonably certain that it will exercise this option to renew and therefore it is not included in right-of-use assets and liabilities as of March 31, 2025.

The lease agreement, as amended, granted the Company the right to receive an Additional Tenant Improvement Allowance (“ATIA”) funded by the lessor. The Company received $30.8 million in ATIA, including a final payment of $3.1 million during the first quarter of fiscal 2024. As a result, the Company remeasured its lease liability and right-of-use assets to reflect these additional allowances and the related increased lease payments. The Company has further concluded that these ATIAs have no effects on the classification of the lease.

Madison, Wisconsin: The Company leases 107,000 square feet space located at 502 South Rosa Road for its office and laboratory facilities, which lease expires on September 30, 2031. The lease contains options to renew for two terms of five years. The Company is not reasonably certain that it will exercise this option and therefore it is not included in right-of-use assets and liabilities as of March 31, 2025.

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	March 31, 2025		September 30, 2024
		(in thousands)

Operating lease assets	Right-of-use assets	$	44,452	$	45,255
Current operating lease liabilities	Lease liabilities	6,782		6,342
Non-current operating lease liabilities	Lease liabilities, net of current portion	107,529		111,027


			Three Months Ended March 31,				Six Months Ended March 31,
Lease Cost	Classification		2025		2024		2025		2024
		(in thousands)

Operating lease cost	Research and development		$	2,709	$	2,572	$	5,520	$	5,566
	General and administrative expense		500		491		993		967

Variable lease cost (1)	Research and development		951		836		1,937		1,615
	General and administrative expense		—		—		—		—

Total			$	4,160	$	3,899	$	8,450	$	8,148

(1) Variable lease cost is primarily related to operating expenses associated with the Company’s operating leases.

There was no short-term lease cost during the three and six months ended March 31, 2025 and 2024, respectively.

The following table presents maturities of operating lease liabilities on an undiscounted basis as of March 31, 2025:


Year	Amounts
	(in thousands)
2025 (remainder)	$	7,776
2026	15,799
2027	14,974
2028	13,619
2029	13,905
2030 and thereafter	114,790
Total	$	180,863
Less imputed interest	$	(66,552)
Total operating lease liabilities (includes current portion)	$	114,311

Supplemental cash flow and other information related to leases was as follows:


	Three Months Ended March 31,				Six Months Ended March 31,
	2025		2024		2025			2024
	(in thousands)
Cash received for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	—	$	—	$	—		$	3,099
Right-of-use assets obtained in exchange for amended operating lease liabilities	$	—	$	—	$	—		$	64
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	3,840	$	2,046	$	7,680		$	4,016

					March 31,
					2025			2024
Weighted-average remaining lease term (in years)					12.1			13.0
Weighted-average discount rate					8.0		%	8.0		%

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Pay vs Performance Disclosure
Net income (loss) attributable to Arrowhead Pharmaceuticals, Inc.	$ 370,445	$ (125,300)	$ 197,360	$ (258,164)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ 1,753	$ 0	$ 1,856	$ (3,313)

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

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+ Details

Investments - Schedule of Contract Maturity of Available for Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Sep. 30, 2024
Investments, Debt and Equity Securities [Abstract]
Within one year	$ 422,082	$ 578,276
After one to two years	301,085	0
After two to three years	188,533	0
Available-for-sale securities	$ 911,700	$ 578,276

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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+ Details