Enanta Pharmaceuticals (ENTA) 10-Q 8 Feb 24 2024 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Dec. 31, 2023	Jan. 31, 2024
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Trading Symbol	ENTA
Entity Registrant Name	ENANTA PHARMACEUTICALS, INC
Entity Central Index Key	0001177648
Current Fiscal Year End Date	--09-30
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity File Number	001-35839
Security Exchange Name	NASDAQ
Entity Tax Identification Number	04-3205099
Entity Address, Address Line One	500 Arsenal Street
Entity Address, City or Town	Watertown
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02472
City Area Code	617
Title of 12(b) Security	Common Stock, par value $0.01 per share
Local Phone Number	607-0800
Entity Incorporation, State or Country Code	DE
Document Transition Report	false
Document Quarterly Report	true
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Entity Common Stock, Shares Outstanding		21,155,983

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 39,933	$ 85,388
Short-term marketable securities	297,218	284,522
Accounts receivable	8,173	8,614
Prepaid expenses and other current assets	13,245	13,263
Income tax receivable	31,734	31,004
Total current assets	390,303	422,791
Property and equipment, net	12,119	11,919
Operating lease, right-of-use assets	21,344	22,794
Restricted cash	3,968	3,968
Other long-term assets	765	803
Total assets	428,499	462,275
Current liabilities:
Accounts payable	9,326	4,097
Accrued expenses and other current liabilities	11,603	18,339
Liability related to the sale of future royalties	36,512	35,076
Operating lease liabilities	4,966	5,275
Total current liabilities	62,407	62,787
Liability related to the sale of future royalties, net of current portion	151,612	159,429
Operating lease liabilities, net of current portion	20,524	21,238
Series 1 nonconvertible preferred stock	1,423	1,423
Other long-term liabilities	649	663
Total liabilities	236,615	245,540
Commitments and contingencies (Note 11)
Stockholders' equity:
Common stock; $0.01 par value per share, 100,000 shares authorized; 21,156 and 21,059 shares issued and outstanding at December 31, 2023 and September 30, 2023, respectively	212	211
Additional paid-in capital	432,608	424,693
Accumulated other comprehensive loss	(534)	(1,174)
Accumulated deficit	(240,402)	(206,995)
Total stockholders' equity	191,884	216,735	$ 300,837
Total liabilities and stockholders' equity	$ 428,499	$ 462,275

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares shares in Thousands	Dec. 31, 2023	Sep. 30, 2023
Statement of Financial Position [Abstract]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	100,000	100,000
Common stock, shares issued	21,156	21,059
Common stock, shares outstanding	21,156	21,059

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Total revenue	$ 18,003	$ 23,585
Operating expenses:
Research and development	36,371	40,902
General and administrative	16,518	12,696
Total operating expenses	52,889	53,598
Loss from operations	(34,886)	(30,013)
Other income (expense):
Interest expense	(3,441)	0
Interest and investment income, net	4,298	993
Total other income, net	857	993
Loss before income taxes	(34,029)	(29,020)
Income tax benefit	622	34
Net loss	$ (33,407)	$ (28,986)
Net loss per share:
Basic	$ (1.58)	$ (1.39)
Diluted	$ (1.58)	$ (1.39)
Weighted average shares outstanding:
Basic	21,088	20,816
Diluted	21,088	20,816
Royalty [Member]
Total revenue	$ 18,003	$ 22,585
License [Member]
Total revenue	$ 0	$ 1,000

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Statement of Comprehensive Income [Abstract]
Net loss	$ (33,407)	$ (28,986)
Other comprehensive income:
Net unrealized gains on marketable securities	640	1,049
Total other comprehensive income	640	1,049
Comprehensive loss	$ (32,767)	$ (27,937)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	(Accumulated Deficit) Retained Earnings [Member]
Beginning Balance at Sep. 30, 2022	$ 321,334	$ 208	$ 398,029	$ (3,724)	$ (73,179)
Beginning Balance, Shares at Sep. 30, 2022		20,791
Exercise of stock options	1,126	$ 1	1,125
Exercise of stock options, Shares		56
Vesting of restricted stock units, net of withholding	(825)		(825)
Vesting of restricted stock units, net of withholding, Shares		37
Stock-based compensation expense	7,139		7,139
Other comprehensive (loss) income	1,049			1,049
Net loss	(28,986)				(28,986)
Ending Balance at Dec. 31, 2022	300,837	$ 209	405,468	(2,675)	(102,165)
Ending Balance, Shares at Dec. 31, 2022		20,884
Beginning Balance at Sep. 30, 2022	321,334	$ 208	398,029	(3,724)	(73,179)
Beginning Balance, Shares at Sep. 30, 2022		20,791
Net loss	(133,816)
Ending Balance at Sep. 30, 2023	$ 216,735	$ 211	424,693	(1,174)	(206,995)
Ending Balance, Shares at Sep. 30, 2023		21,059
Exercise of stock options, Shares	0
Vesting of restricted stock units, net of withholding	$ (183)	$ 1	(184)
Vesting of restricted stock units, net of withholding, Shares		97
Stock-based compensation expense	8,099		8,099
Other comprehensive (loss) income	640			640
Net loss	(33,407)				(33,407)
Ending Balance at Dec. 31, 2023	$ 191,884	$ 212	$ 432,608	$ (534)	$ (240,402)
Ending Balance, Shares at Dec. 31, 2023		21,156

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities
Net loss	$ (33,407)	$ (28,986)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	8,099	7,139
Depreciation and amortization expense	642	511
Non cash interest expense associated with the sale of future royalties	299	0
Non-cash royalty revenue	487	0
Amortization (accretion) of premiums (discounts) on marketable securities	274	(339)
Change in operating assets and liabilities:
Accounts receivable	441	(2,267)
Prepaid expenses and other current assets	18	(4,501)
Income tax receivable	(730)	15
Operating lease, right-of-use assets	1,450	834
Other long-term assets	38	(5)
Accounts payable	5,174	(686)
Accrued expenses	(6,736)	(6,599)
Operating lease liabilities	(1,023)	(717)
Other long-term liabilities	(14)	(40)
Net cash used in operating activities	(24,988)	(35,641)
Cash flows from investing activities
Purchase of marketable securities	(146,845)	(67,375)
Proceeds from maturities and sale of marketable securities	134,515	104,100
Purchase of property and equipment	(787)	(3,156)
Net cash provided by (used in) investing activities	(13,117)	33,569
Cash flows from financing activities
Payments on royalty sale liability, net of imputed interest	(7,167)	0
Payments for settlement of share-based awards	(183)	(825)
Proceeds from exercise of stock options	0	1,126
Net cash provided by (used in) financing activities	(7,350)	301
Net decrease in cash, cash equivalents and restricted cash	(45,455)	(1,771)
Cash, cash equivalents and restricted cash at beginning of period	89,356	47,962
Cash, cash equivalents and restricted cash at end of period	43,901	46,191
Supplemental disclosure of noncash information:
Purchases of fixed assets included in accounts payable and accrued expenses	479	1,079
Operating lease liabilities arising from obtaining right-of-use assets	0	799
Supplemental disclosure of cash flow information
Cash paid for interest	$ 3,143	$ 0

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Sep. 30, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ (33,407)	$ (28,986)	$ (133,816)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Dec. 31, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	3 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of the Business and Basis of Presentation	1. Nature of the Business and Basis of Presentation Enanta Pharmaceuticals, Inc. (collectively with its subsidiary, the “Company”), incorporated in Delaware in 1995 , is a biotechnology company that uses its robust, chemistry-driven approach and drug discovery capabilities to discover and develop small molecule drugs with an emphasis on virology and immunology indications. The Company discovered glecaprevir, the second of two protease inhibitors discovered and developed through its collaboration with AbbVie for the treatment of chronic infection with hepatitis C virus (“HCV”). Glecaprevir is co-formulated as part of AbbVie’s leading direct-acting antiviral (“DAA”) combination treatment for HCV, which is marketed under the tradenames MAVYRET® (U.S.) and MAVIRET®(ex-U.S.) (glecaprevir/pibrentasvir). Royalties from the Company’s AbbVie collaboration and its existing financial resources provide funding to support the Company’s wholly-owned research and development programs, which are primarily focused on the following disease targets: respiratory syncytial virus (“RSV”), SARS-CoV-2, hepatitis B virus (“HBV”) and Chronic Spontaneous Urticaria (“CSU”). The Company is subject to many of the risks common to companies in the biotechnology industry, including but not limited to, the uncertainties of research and development, competition from technological innovations of others, dependence on collaborative arrangements, protection of proprietary technology, dependence on key personnel and compliance with government regulation. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approvals, prior to commercialization. These efforts require significant amounts of capital, adequate personnel and infrastructure, and extensive compliance reporting capabilities. Unaudited Interim Financial Information The condensed consolidated balance sheet as of September 30, 2023 was derived from audited financial statements but does not include all disclosures required by accounting principles generally accepted in the United States of America (“GAAP”). The accompanying unaudited condensed consolidated financial statements as of December 31, 2023 and for the three months ended December 31, 2023 and 2022 have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. These condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended September 30, 2023. In the opinion of management, all adjustments, consisting of normal recurring adjustments necessary for a fair statement of the Company’s financial position as of December 31, 2023 and results of operations for the three months ended December 31, 2023 and 2022 and cash flows for the three months ended December 31, 2023 and 2022 have been made. The results of operations for the three months ended December 31, 2023 are not necessarily indicative of the results of operations that may be expected for subsequent quarters or the year ending September 30, 2024. The accompanying condensed consolidated financial statements have been prepared in conformity with GAAP. All amounts in the condensed consolidated financial statements and in the notes to the condensed consolidated financial statements, except per share amounts, are in thousands unless otherwise indicated. The accompanying condensed consolidated financial statements have been prepared based on continuity of operations, realization of assets and the satisfaction of liabilities and commitments in the ordinary course of business. The Company began reporting a net loss in fiscal 2020 and reported a net loss of $ 33,407 for the three months ended December 31, 2023 and $ 133,816 for the year ended September 30, 2023. As of December 31, 2023, the Company had an accumulated deficit of $ 240,402 . The Company expects to continue to generate operating losses for the foreseeable future as the Company continues to advance its wholly-owned programs. As of December 31, 2023, the Company had $ 337,151 in cash, cash equivalents and short-term marketable securities. The Company expects that its cash, cash equivalents and short-term marketable securities will be sufficient to fund its operating expenses and capital expenditure requirements for at least 12 months from the issuance date of the interim condensed consolidated financial statements. The Company may seek additional funding through equity offerings, non-dilutive financings, collaborations, strategic alliances or licensing agreements. The Company may not be able to obtain sufficient financing on acceptable terms, or at all, and the Company may not be able to enter into collaborations or other arrangements. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate some or all of its research and development programs, product expansion or commercialization efforts, or the Company may be unable to continue operations.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies For the Company’s Significant Accounting Policies, please refer to its Annual Report on Form 10-K for the fiscal year ended September 30, 2023. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). Use of Estimates The preparation of condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements, and the reported amounts of revenues and expenses during the reporting period. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, management’s judgments with respect to its revenue arrangements; liability related to the sale of future royalties; valuation of stock-based awards and the accrual of research and development expenses. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Net Loss per Share Basic net loss per common share is computed by dividing the net loss by the weighted average number of shares of common stock outstanding for the period. In periods in which the Company has reported a net loss, diluted net loss per common share is the same as basic net loss per common share since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. Therefore, the Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss as its effect would have been anti-dilutive: As of December 31, 2023 2022 (in thousands) Options to purchase common stock 5,213 4,511 Unvested rTSRUs 129 151 Unvested PSUs 129 151 Unvested restricted stock units 455 439 Recently Issued Accounting Pronouncements In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures , which requires public entities to disclose information about their reportable segments’ significant expenses and other segment items on an interim and annual basis. Public entities with a single reportable segment are required to apply the disclosure requirements in ASU 2023-07, as well as all existing segment disclosures and reconciliation requirements in ASC 280 on an interim and annual basis. This amendment is effective for the Company in the fiscal year beginning October 1, 2024, with early adoption permitted. The Company is currently evaluating the potential impact that ASU 2023-07 may have on its financial statement disclosures. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures , which requires public entities, on an annual basis, to provide disclosure of specific categories in the rate reconciliation, as well as disclosure of income taxes paid disaggregated by jurisdiction. ASU 2023-09 is effective for the Company in the fiscal year beginning October 1, 2025, with early adoption permitted. The Company is currently evaluating the potential impact that ASU 2023-09 may have on its financial statement disclosures.

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities	3 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities	3. Fair Value of Financial Assets and Liabilities The following tables present information about the Company’s financial assets and liabilities that were subject to fair value measurement on a recurring basis as of December 31, 2023 and September 30, 2023, and indicate the fair value hierarchy of the valuation inputs utilized to determine such fair value: Fair Value Measurements as of December 31, 2023 Using: Level 1 Level 2 Level 3 Total (in thousands) Assets: Cash equivalents: Money market funds $ 38,905 $ — $ — $ 38,905 Marketable securities: U.S. Treasury notes 264,537 — — 264,537 Corporate bonds — 26,706 — 26,706 Commercial paper — 5,975 — 5,975 $ 303,442 $ 32,681 $ — $ 336,123 Liabilities: Series 1 nonconvertible preferred stock $ — $ — $ 1,423 $ 1,423 $ — $ — $ 1,423 $ 1,423 Fair Value Measurements as of September 30, 2023 Using: Level 1 Level 2 Level 3 Total (in thousands) Assets: Cash equivalents: Money market funds $ 55,357 $ — $ — $ 55,357 U.S. Treasury notes 29,755 — — 29,755 Marketable securities: U.S. Treasury notes 236,782 — — 236,782 Corporate bonds — 26,435 — 26,435 Commercial paper — 21,305 — 21,305 $ 321,894 $ 47,740 $ — $ 369,634 Liabilities: Series 1 nonconvertible preferred stock $ — $ — $ 1,423 $ 1,423 $ — $ — $ 1,423 $ 1,423 During the three months ended December 31, 2023 and 2022 , there were no transfers between Level 1, Level 2 and Level 3. The fair value of Level 2 instruments classified as marketable securities were determined through third-party pricing services. The pricing services use many observable market inputs to determine value, including reportable trades, benchmark yields, credit spreads, broker/dealer quotes, bids, offers, and current spot rates. The outstanding shares of Series 1 nonconvertible preferred stock as of December 31, 2023 and September 30, 2023 are measured at fair value. These outstanding shares are financial instruments that might require a transfer of assets because of the liquidation features in the contract and are therefore recorded as liabilities and measured at fair value. The fair value of the outstanding shares is based on significant inputs not observable in the market, which represent a Level 3 measurement within the fair value hierarchy. The Company utilizes a probability-weighted valuation model which takes into consideration various outcomes that may require the Company to transfer assets upon liquidation. Changes in the fair values of the Series 1 nonconvertible preferred stock are recognized in other income (expense) in the condensed consolidated statements of operations. The recurring Level 3 fair value measurements of the Company’s outstanding Series 1 nonconvertible preferred stock using probability-weighted discounted cash flow include the following significant unobservable inputs: Range December 31, September 30, Unobservable Input 2023 2023 Probabilities of payout 0 %- 65 % 0 %- 65 % Discount rate 7.25 % 7.25 % There were no changes in the fair value of nonconvertible preferred stock during the three months ended December 31, 2023 and 2022. In April 2023, the Company entered into a royalty sale agreement with an affiliate of OMERS, pursuant to which the Company was paid a $ 200,000 cash purchase price in exchange for 54.5 % of future quarterly royalty payments on net sales of MAVYRET/MAVIRET, after June 30, 2023, through June 30, 2032, subject to a cap on aggregate payments equal to 1.42 times the purchase price. The Company accounted for the upfront payment as a liability related to the sale of future royalties. The carrying value of the liability related to the sale of future royalties approximates fair value as of December 31, 2023 and is based on current estimates of future royalties expected to be paid to OMERS over the next 10 years, which are considered Level 3 inputs. See Note 7 for a rollforward of the liability.

Marketable Securities

Marketable Securities	3 Months Ended
	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	4. Marketable Securities As of December 31, 2023 and September 30, 2023, the fair value of available-for-sale marketable securities, by type of security, was as follows: December 31, 2023 Amortized Gross Gross Credit Losses Fair Value (in thousands) Corporate bonds $ 27,043 $ — $ ( 337 ) $ — $ 26,706 Commercial paper 5,975 — — — 5,975 U.S. Treasury notes 264,350 207 ( 20 ) — 264,537 $ 297,368 $ 207 $ ( 357 ) $ — $ 297,218 September 30, 2023 Amortized Gross Gross Credit Losses Fair Value (in thousands) Corporate bonds $ 27,127 $ — $ ( 692 ) $ — $ 26,435 Commercial paper 21,305 — — — 21,305 U.S. Treasury notes 236,880 12 ( 110 ) — 236,782 $ 285,312 $ 12 $ ( 802 ) $ — $ 284,522 As of December 31, 2023 and September 30, 2023 , marketable securities consisted of investments that mature within one year .

Accrued Expenses

Accrued Expenses	3 Months Ended
	Dec. 31, 2023
Payables and Accruals [Abstract]
Accrued Expenses	5. Accrued Expenses Accrued expenses and other current liabilities consisted of the following as of December 31, 2023 and September 30, 2023: December 31, September 30, 2023 2023 (in thousands) Accrued pharmaceutical drug manufacturing $ 1,099 $ 3,083 Accrued research and development expenses 3,707 6,120 Accrued payroll and related expenses 4,310 7,037 Accrued other 2,487 2,099 $ 11,603 $ 18,339

AbbVie Collaboration

AbbVie Collaboration	3 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
AbbVie Collaboration	6. AbbVie Collaboration The Company has a Collaborative Development and License Agreement (as amended, the “AbbVie Agreement”), with AbbVie to identify, develop and commercialize HCV NS3 and NS3/4A protease inhibitor compounds, including paritaprevir and glecaprevir, under which the Company has received license payments, proceeds from a sale of preferred stock, research funding payments, milestone payments and royalties totaling approximately $ 1,296,000 through December 31, 2023. Since the Company satisfied all of its performance obligations under the AbbVie Agreement by the end of fiscal 2011, all milestone payments received since then have been recognized as revenue when the milestones were achieved by AbbVie. The Company is receiving annually tiered royalties per Company protease product ranging from ten percent up to twenty percent, or on a blended basis from ten percent up to the high teens, on the portion of AbbVie’s calendar year net sales of each HCV regimen that is allocated to the protease inhibitor in the regimen. Beginning with each January 1, the cumulative net sales of a given royalty-bearing protease inhibitor product start at zero for purposes of calculating the tiered royalties on a product-by-product basis.

Liability Related to the Sale o

Liability Related to the Sale of Future Royalties	3 Months Ended
	Dec. 31, 2023
Nonmonetary Transactions [Abstract]
Liability Related to the Sale of Future Royalties	7. Liability Related to the Sale of Future Royalties In April 2023, the Company entered into a royalty sale agreement with an affiliate of OMERS, pursuant to which the Company was paid a $ 200,000 cash purchase price in exchange for 54.5 % of future quarterly royalty payments on net sales of MAVYRET/MAVIRET, after June 30, 2023, through June 30, 2032, subject to a cap on aggregate payments equal to 1.42 times the purchase price. Because the royalty sale agreement will be paid back to OMERS up to a capped amount as well as the Company’s significant continuing involvement in the generation of future cash flows under its AbbVie Agreement, the Company recorded the proceeds from the transaction as a liability on its condensed consolidated balance sheets which will be amortized as interest expense in the condensed consolidated statements of operations under the effective interest rate method over the life of the royalty sale agreement. The Company will continue to record the full amount of royalties earned on MAVYRET/MAVIRET sales as royalty revenue in the condensed consolidated statements of operations. The Company’s liability related to the sale of future royalties is estimated based on forecasted worldwide MAVYRET/MAVYRET royalties to be paid to OMERS over the course of the royalty sale agreement. This estimate requires significant judgment, including the amount and timing of royalty payments up until the end of the royalty sale agreement, which is estimated to be the stated term of June 30, 2032. As royalties are earned by OMERS, the liability is reduced on the Company’s condensed consolidated balance sheets. At December 31, 2023 , the estimated future cash flows resulted in an effective annual imputed interest rate of approximately 7.05 %. The following table summarizes the activity of the liability related to the sale of future royalties: Liability related to the sale of future royalties (in thousands) Balance - September 30, 2023 $ 194,505 Royalty payable to purchaser ( 9,822 ) Interest expense 3,441 Balance - December 31, 2023 $ 188,124

Series 1 Nonconvertible Preferr

Series 1 Nonconvertible Preferred Stock	3 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Series 1 Nonconvertible Preferred Stock	8. Series 1 Nonconvertible Preferred Stock As of December 31, 2023 , 1,930 shares of Series 1 nonconvertible preferred stock were issued and outstanding. The outstanding shares are financial instruments that might require a transfer of assets because of the liquidation features in the contract and are carried at fair value as a liability on the Company’s condensed consolidated balance sheets

Stock-Based Awards

Stock-Based Awards	3 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Stock-Based Awards	9. Stock-Based Awards The Company grants stock-based awards, including stock options, restricted stock units and other unit awards under its 2019 Equity Incentive Plan (the “2019 Plan”), which was approved by its stockholders on February 28, 2019 and amended in March 2021, March 2022 and March 2023. The Company also has outstanding stock option awards under its 2012 Equity Incentive Plan (the “2012 Plan”) but is no longer granting awards under this plan. The following table summarizes stock option activity, including performance-based options, for the year-to-date period ending December 31, 2023: Shares Weighted Weighted Aggregate (in thousands) (in years) (in thousands) Outstanding as of September 30, 2023 4,365 $ 52.68 5.9 $ — Granted 1,092 8.99 Exercised — — Forfeited ( 244 ) 38.99 Outstanding as of December 31, 2023 5,213 $ 44.17 6.7 $ 459 Options vested and expected to vest as of 5,213 $ 44.17 6.7 $ 459 Options exercisable as of December 31, 2023 3,028 $ 53.37 5.1 $ — Market and Performance-Based Stock Unit Awards The Company awards both performance share units, or PSUs, and relative total stockholder return units, or rTSRUs, to its executive officers. The number of units granted represents the target number of shares of common stock that may be earned; however, the actual number of shares that may be earned ranges from 0 % to 150 % of the target number. The number of shares cancelled represents the target number of shares, less any shares that vested. The following table summarizes PSU and rTSRU activity for the year-to-date period ending December 31, 2023: PSUs rTSRUs Shares Weighted Shares Weighted (in thousands) (in thousands) Unvested as of September 30, 2023 81 $ 58.58 81 $ 45.82 Granted 48 9.21 48 9.89 Vested — — — — Unvested as of December 31, 2023 129 $ 40.23 129 $ 32.47 Restricted Stock Units The following table summarizes the restricted stock unit activity for the year-to-date period ending December 31, 2023: Restricted Stock Weighted (in thousands) Unvested as of September 30, 2023 411 $ 51.78 Granted 162 8.99 Vested ( 116 ) 52.00 Cancelled ( 2 ) 54.27 Unvested as of December 31, 2023 455 $ 36.45 Stock-Based Compensation Expense During the three months ended December 31, 2023 and 2022 the Company recognized the following stock-based compensation expense: Three Months Ended December 31, 2023 2022 (in thousands) Research and development $ 2,055 $ 2,532 General and administrative 6,044 4,607 $ 8,099 $ 7,139 Three Months Ended December 31, 2023 2022 (in thousands) Stock options $ 4,462 $ 5,046 rTSRUs 445 461 Performance stock units 1,579 367 Restricted stock units 1,613 1,265 $ 8,099 $ 7,139 During the three months ended December 31, 2023 and 2022, the Company recognized stock-based compensation expense for performance-based stock units for which vesting became probable upon achievement of performance-based targets that occurred during the performance period. As of December 31, 2023, the Company had an aggregate of $ 60,806 of unrecognized stock-based compensation cost, which is expected to be recognized over a weighted average period of 2.2 years.

Income Taxes

Income Taxes	3 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	10. Income Taxes For the three months ended December 31, 2023 , the Company recorded an income tax benefit of $ 622 due to interest recorded on a pending federal income tax refund. For the three months ended December 31, 2022 , the Company recorded an income tax benefit of $ 34 due to the release of a state tax reserve during the period.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	11. Commitments and Contingencies Litigation and Contingencies Related to Use of Intellectual Property From time to time, the Company may become subject to legal proceedings, claims and litigation arising in the ordinary course of business. Except as described below, the Company currently is not a party to any material threatened or pending litigation. However, third parties might allege that the Company or its collaborators are infringing their patent rights or that the Company is otherwise violating their intellectual property rights. Such third parties may resort to litigation against the Company or its collaborators, which the Company has agreed to indemnify. With respect to some of these patents, the Company expects that it will be required to obtain licenses and could be required to pay license fees or royalties, or both. These licenses may not be available on acceptable terms, or at all. A costly license, or inability to obtain a necessary license, would have a material adverse effect on the Company’s financial condition, results of operations or cash flows. The Company accrues contingent liabilities when it is probable that future expenditures will be made and such expenditures can be reasonably estimated. In June 2022, the Company announced that it filed suit in the United States District Court for the District of Massachusetts on June 21, 2022, against Pfizer, Inc. seeking damages for infringement of U.S. Patent No. 11,358,953 (the ’953 Patent) in the manufacture, use and sale of Pfizer’s COVID-19 antiviral, Paxlovid ™ (nirmatrelvir tablets; ritonavir tablets). The United States Patent and Trademark Office awarded the '953 Patent to the Company in June 2022 based on the Company's July 2020 patent application describing coronavirus protease inhibitors invented by the Company. The Company is seeking fair compensation for Pfizer’s use of a coronavirus protease inhibitor claimed in the ‘953 patent. The Company records all legal expenses associated with the patent infringement suit as incurred in the condensed consolidated statements of operations. Indemnification Agreements In the ordinary course of business, the Company may provide indemnifications of varying scope and terms to customers, vendors, lessors, business partners, and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from services to be provided to the Company, or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and its executive officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. In addition, the Company maintains directors’ and officers’ insurance coverage. The Company does not believe that the outcome of any claims under indemnification arrangements will have a material effect on its financial position, results of operations or cash flows, and has not accrued any liabilities related to such obligations in its condensed consolidated financial statements as of December 31, 2023. Leases The Company leases laboratory and office space under various non-cancelable operating leases. There have been no material changes to the Company’s leases during the three months ended December 31, 2023. For additional information, please read Note 12, Leases, to the consolidated financial statements in the Company's Annual Report on Form 10-K for the fiscal year ended September 30, 2023 .

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements, and the reported amounts of revenues and expenses during the reporting period. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, management’s judgments with respect to its revenue arrangements; liability related to the sale of future royalties; valuation of stock-based awards and the accrual of research and development expenses. Estimates are periodically reviewed in light of changes in circumstances, facts and experience.
Net Loss per Share	Net Loss per Share Basic net loss per common share is computed by dividing the net loss by the weighted average number of shares of common stock outstanding for the period. In periods in which the Company has reported a net loss, diluted net loss per common share is the same as basic net loss per common share since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. Therefore, the Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss as its effect would have been anti-dilutive: As of December 31, 2023 2022 (in thousands) Options to purchase common stock 5,213 4,511 Unvested rTSRUs 129 151 Unvested PSUs 129 151 Unvested restricted stock units 455 439
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures , which requires public entities to disclose information about their reportable segments’ significant expenses and other segment items on an interim and annual basis. Public entities with a single reportable segment are required to apply the disclosure requirements in ASU 2023-07, as well as all existing segment disclosures and reconciliation requirements in ASC 280 on an interim and annual basis. This amendment is effective for the Company in the fiscal year beginning October 1, 2024, with early adoption permitted. The Company is currently evaluating the potential impact that ASU 2023-07 may have on its financial statement disclosures. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures , which requires public entities, on an annual basis, to provide disclosure of specific categories in the rate reconciliation, as well as disclosure of income taxes paid disaggregated by jurisdiction. ASU 2023-09 is effective for the Company in the fiscal year beginning October 1, 2025, with early adoption permitted. The Company is currently evaluating the potential impact that ASU 2023-09 may have on its financial statement disclosures.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Anti-dilutive Securities Excluded from the Computation of Diluted Net Loss	Therefore, the Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss as its effect would have been anti-dilutive: As of December 31, 2023 2022 (in thousands) Options to purchase common stock 5,213 4,511 Unvested rTSRUs 129 151 Unvested PSUs 129 151 Unvested restricted stock units 455 439

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	3 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Financial Assets and Liabilities that were Subject to Fair Value Measurement on Recurring Basis	The following tables present information about the Company’s financial assets and liabilities that were subject to fair value measurement on a recurring basis as of December 31, 2023 and September 30, 2023, and indicate the fair value hierarchy of the valuation inputs utilized to determine such fair value: Fair Value Measurements as of December 31, 2023 Using: Level 1 Level 2 Level 3 Total (in thousands) Assets: Cash equivalents: Money market funds $ 38,905 $ — $ — $ 38,905 Marketable securities: U.S. Treasury notes 264,537 — — 264,537 Corporate bonds — 26,706 — 26,706 Commercial paper — 5,975 — 5,975 $ 303,442 $ 32,681 $ — $ 336,123 Liabilities: Series 1 nonconvertible preferred stock $ — $ — $ 1,423 $ 1,423 $ — $ — $ 1,423 $ 1,423 Fair Value Measurements as of September 30, 2023 Using: Level 1 Level 2 Level 3 Total (in thousands) Assets: Cash equivalents: Money market funds $ 55,357 $ — $ — $ 55,357 U.S. Treasury notes 29,755 — — 29,755 Marketable securities: U.S. Treasury notes 236,782 — — 236,782 Corporate bonds — 26,435 — 26,435 Commercial paper — 21,305 — 21,305 $ 321,894 $ 47,740 $ — $ 369,634 Liabilities: Series 1 nonconvertible preferred stock $ — $ — $ 1,423 $ 1,423 $ — $ — $ 1,423 $ 1,423
Fair Value Measurements of the Company's Series 1 Nonconvertible Preferred Stock	The recurring Level 3 fair value measurements of the Company’s outstanding Series 1 nonconvertible preferred stock using probability-weighted discounted cash flow include the following significant unobservable inputs: Range December 31, September 30, Unobservable Input 2023 2023 Probabilities of payout 0 %- 65 % 0 %- 65 % Discount rate 7.25 % 7.25 %

Marketable Securities (Tables)

Marketable Securities (Tables)	3 Months Ended
	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Fair Value of Available-for-Sale Marketable Securities by Type of Security	As of December 31, 2023 and September 30, 2023, the fair value of available-for-sale marketable securities, by type of security, was as follows: December 31, 2023 Amortized Gross Gross Credit Losses Fair Value (in thousands) Corporate bonds $ 27,043 $ — $ ( 337 ) $ — $ 26,706 Commercial paper 5,975 — — — 5,975 U.S. Treasury notes 264,350 207 ( 20 ) — 264,537 $ 297,368 $ 207 $ ( 357 ) $ — $ 297,218 September 30, 2023 Amortized Gross Gross Credit Losses Fair Value (in thousands) Corporate bonds $ 27,127 $ — $ ( 692 ) $ — $ 26,435 Commercial paper 21,305 — — — 21,305 U.S. Treasury notes 236,880 12 ( 110 ) — 236,782 $ 285,312 $ 12 $ ( 802 ) $ — $ 284,522

Accrued Expenses (Tables)

Accrued Expenses (Tables)	3 Months Ended
	Dec. 31, 2023
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following as of December 31, 2023 and September 30, 2023: December 31, September 30, 2023 2023 (in thousands) Accrued pharmaceutical drug manufacturing $ 1,099 $ 3,083 Accrued research and development expenses 3,707 6,120 Accrued payroll and related expenses 4,310 7,037 Accrued other 2,487 2,099 $ 11,603 $ 18,339

Liability Related to the Sale_2

Liability Related to the Sale of Future Royalties (Tables)	3 Months Ended
	Dec. 31, 2023
Nonmonetary Transactions [Abstract]
Summary of the Liability Related to the Sale of Future Royalties	The following table summarizes the activity of the liability related to the sale of future royalties: Liability related to the sale of future royalties (in thousands) Balance - September 30, 2023 $ 194,505 Royalty payable to purchaser ( 9,822 ) Interest expense 3,441 Balance - December 31, 2023 $ 188,124

Stock-Based Awards (Tables)

Stock-Based Awards (Tables)	3 Months Ended
	Dec. 31, 2023
Summary of Stock Option Activity Including Performance Based Options	The following table summarizes stock option activity, including performance-based options, for the year-to-date period ending December 31, 2023: Shares Weighted Weighted Aggregate (in thousands) (in years) (in thousands) Outstanding as of September 30, 2023 4,365 $ 52.68 5.9 $ — Granted 1,092 8.99 Exercised — — Forfeited ( 244 ) 38.99 Outstanding as of December 31, 2023 5,213 $ 44.17 6.7 $ 459 Options vested and expected to vest as of 5,213 $ 44.17 6.7 $ 459 Options exercisable as of December 31, 2023 3,028 $ 53.37 5.1 $ —
Summary of Restricted Stock Unit Activity	The following table summarizes the restricted stock unit activity for the year-to-date period ending December 31, 2023: Restricted Stock Weighted (in thousands) Unvested as of September 30, 2023 411 $ 51.78 Granted 162 8.99 Vested ( 116 ) 52.00 Cancelled ( 2 ) 54.27 Unvested as of December 31, 2023 455 $ 36.45
Stock-Based Compensation Expense	During the three months ended December 31, 2023 and 2022 the Company recognized the following stock-based compensation expense: Three Months Ended December 31, 2023 2022 (in thousands) Research and development $ 2,055 $ 2,532 General and administrative 6,044 4,607 $ 8,099 $ 7,139 Three Months Ended December 31, 2023 2022 (in thousands) Stock options $ 4,462 $ 5,046 rTSRUs 445 461 Performance stock units 1,579 367 Restricted stock units 1,613 1,265 $ 8,099 $ 7,139
Performance Share Units and Relative Total Stockholder Return Units [Member]
Summary of PSUs and rTSRUs Activity	The following table summarizes PSU and rTSRU activity for the year-to-date period ending December 31, 2023: PSUs rTSRUs Shares Weighted Shares Weighted (in thousands) (in thousands) Unvested as of September 30, 2023 81 $ 58.58 81 $ 45.82 Granted 48 9.21 48 9.89 Vested — — — — Unvested as of December 31, 2023 129 $ 40.23 129 $ 32.47

Nature of the Business and Ba_2

Nature of the Business and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Sep. 30, 2023
Entity incorporated, in year	1995
Net loss	$ 33,407	$ 28,986	$ 133,816
Accumulated deficit	240,402		$ 206,995
Cash, cash equivalents and short-term and long-term marketable securities	$ 337,151

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Anti-dilutive Securities Excluded from the Computation of Diluted Net Loss (Detail) - shares shares in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Employee Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	5,213	4,511
Unvested rTSRUs [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	129	151
Unvested PSUs [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	129	151
Unvested Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	455	439

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities - Financial Assets and Liabilities that were Subject to Fair Value Measurement on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Assets:
Marketable securities	$ 297,218	$ 284,522
Assets, Fair Value Disclosure, Total	336,123	369,634
Liabilities:
Liabilities, Fair Value Disclosure, Total	1,423	1,423
Series 1 Nonconvertible Preferred Stock [Member]
Liabilities:
Liabilities	1,423	1,423
Level 1 [Member]
Assets:
Assets, Fair Value Disclosure, Total	303,442	321,894
Liabilities:
Liabilities, Fair Value Disclosure, Total	0	0
Level 1 [Member] | Series 1 Nonconvertible Preferred Stock [Member]
Liabilities:
Liabilities	0	0
Level 2 [Member]
Assets:
Assets, Fair Value Disclosure, Total	32,681	47,740
Liabilities:
Liabilities, Fair Value Disclosure, Total	0	0
Level 2 [Member] | Series 1 Nonconvertible Preferred Stock [Member]
Liabilities:
Liabilities	0	0
Level 3 [Member]
Assets:
Assets, Fair Value Disclosure, Total	0	0
Liabilities:
Liabilities, Fair Value Disclosure, Total	1,423	1,423
Level 3 [Member] | Series 1 Nonconvertible Preferred Stock [Member]
Liabilities:
Liabilities	1,423	1,423
Money Market Funds [Member]
Assets:
Cash equivalents	38,905	55,357
Money Market Funds [Member] | Level 1 [Member]
Assets:
Cash equivalents		55,357
Money Market Funds [Member] | Level 2 [Member]
Assets:
Cash equivalents	0	0
Money Market Funds [Member] | Level 3 [Member]
Assets:
Cash equivalents	0	0
U.S. Treasury Notes [Member]
Assets:
Cash equivalents		29,755
Marketable securities	264,537	236,782
U.S. Treasury Notes [Member] | Level 1 [Member]
Assets:
Cash equivalents		29,755
Marketable securities	264,537	236,782
U.S. Treasury Notes [Member] | Level 2 [Member]
Assets:
Cash equivalents		0
Marketable securities	0	0
U.S. Treasury Notes [Member] | Level 3 [Member]
Assets:
Cash equivalents		0
Marketable securities	0	0
Corporate Bonds [Member]
Assets:
Marketable securities	26,706	26,435
Corporate Bonds [Member] | Level 1 [Member]
Assets:
Marketable securities	0	0
Corporate Bonds [Member] | Level 2 [Member]
Assets:
Marketable securities	26,706	26,435
Corporate Bonds [Member] | Level 3 [Member]
Assets:
Marketable securities	0	0
Commercial Paper [Member]
Assets:
Marketable securities	5,975	21,305
Commercial Paper [Member] | Level 1 [Member]
Assets:
Marketable securities	0	0
Commercial Paper [Member] | Level 2 [Member]
Assets:
Marketable securities	5,975	21,305
Commercial Paper [Member] | Level 3 [Member]
Assets:
Marketable securities	$ 0	$ 0

Fair Value of Financial Asset_4

Fair Value of Financial Assets and Liabilities - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended
	Apr. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers between Level 1, Level 2 and Level 3		$ 0	$ 0
Omers Royalty Sale Agreement [Member ]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Proceeds from sale of future royalties	$ 200,000,000
Percentage of future quarterly royalty payments on net sales received in cash	54.50%
Future quarterly royalty payments, description	after June 30, 2023, through June 30, 2032, subject to a cap on aggregate payments equal to 1.42 times the purchase price.
Series 1 Nonconvertible Preferred Stock [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Change in fair value of nonconvertible preferred stock		$ 0	$ 0

Fair Value of Financial Asset_5

Fair Value of Financial Assets and Liabilities - Fair Value Measurements of the Company's Outstanding Series 1 Nonconvertible Preferred Stock (Detail) - Level 3 [Member] - Series 1 Nonconvertible Preferred Stock [Member]	Dec. 31, 2023	Sep. 30, 2023
Probabilities of Payout [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range	0	0
Probabilities of Payout [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range	65	65
Discount Rate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Range	7.25	7.25

Marketable Securities - Fair Va

Marketable Securities - Fair Value of Available-for-Sale Marketable Securities by Type of Security (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 297,368	$ 285,312
Gross Unrealized Gains	207	12
Gross Unrealized Losses	(357)	(802)
Fair Value	297,218	284,522
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	27,043	27,127
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(337)	(692)
Fair Value	26,706	26,435
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,975	21,305
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	5,975	21,305
U.S. Treasury Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	264,350	236,880
Gross Unrealized Gains	207	12
Gross Unrealized Losses	(20)	(110)
Fair Value	$ 264,537	$ 236,782

Marketable Securities - Additio

Marketable Securities - Additional Information (Detail)	3 Months Ended	12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023
Maximum [Member] | Short Term Marketable Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Maturity period of the marketable securities	1 year	1 year

Accrued Expenses - Accrued Expe

Accrued Expenses - Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Accrued expenses:
Accrued pharmaceutical drug manufacturing	$ 1,099	$ 3,083
Accrued research and development expenses	3,707	6,120
Accrued payroll and related expenses	4,310	7,037
Accrued other	2,487	2,099
Accrued expenses	$ 11,603	$ 18,339

AbbVie Collaboration - Addition

AbbVie Collaboration - Additional Information (Detail) - AbbVie [Member]	3 Months Ended
	Dec. 31, 2023 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cash consideration received under collaboration from milestone payments and royalties	$ 1,296,000
Collaboration agreement tiered royalty description	from ten percent up to twenty percent, or on a blended basis from ten percent up to the high teens, on the portion of AbbVie’s calendar year net sales

Liability Related to the Sale_3

Liability Related to the Sale of Future Royalties - Additional Information (Detail) - OMERS Royalty Purchase Agreement [Member] $ in Thousands	1 Months Ended
	Apr. 30, 2023 USD ($)	Dec. 31, 2023
Nonmonetary Transaction [Line Items]
Payment received royalty purchase agreement	$ 200,000
Percentage of future quarterly royalty payments on net sales received in cash	54.50%
Future royalty payment description	after June 30, 2023, through June 30, 2032, subject to a cap on aggregate payments equal to 1.42 times the purchase price.
Royalty purchase agreement annual imputed interest rate		7.05

Liability Related to the Sale_4

Liability Related to the Sale of Future Royalties - Summary Of The Liability Related To The Sale Of Future Royalties (Details) - Sale Of Future Royalties [Member] - OMERS Royalty Purchase Agreement [Member] $ in Thousands	3 Months Ended
	Dec. 31, 2023 USD ($)
Nonmonetary Transaction [Line Items]
Royalty liability - beginning balance	$ 194,505
Royalty payable to purchaser	(9,822)
Interest expense	3,441
Royalty liability - ending balance	$ 188,124

Series 1 Nonconvertible Prefe_2

Series 1 Nonconvertible Preferred Stock - Additional Information (Detail) - Series 1 Nonconvertible Preferred Stock [Member] shares in Thousands	Dec. 31, 2023 shares
Class Of Stock [Line Items]
Preferred stock, shares issued	1,930
Preferred stock, shares outstanding	1,930

Stock-Based Awards - Additional

Stock-Based Awards - Additional Information (Detail) - USD ($) shares in Thousands	3 Months Ended
	Dec. 31, 2023	Sep. 30, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Shares, Issued	21,156	21,059
Aggregate of unrecognized stock-based compensation cost	$ 60,806
Weighted average recognition period	2 years 2 months 12 days
Executive Officers [Member] | Relative Total Stockholder Return Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares range percentage	0%
Number of shares range percentage	150%

Stock-Based Awards - Summary of

Stock-Based Awards - Summary of Stock Option Activity Including Performance Based Options (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023
Options
Outstanding as of beginning of period	4,365
Granted	1,092
Exercised	0
Forfeited	(244)
Outstanding as of end of period	5,213	4,365
Options vested and expected to vest as of end of period	5,213
Options exercisable as of end of period	3,028
Weighted Average Exercise Price
Outstanding	$ 52.68
Granted	8.99
Exercised	0
Forfeited	38.99
Outstanding	44.17	$ 52.68
Options vested and expected to vest as of end of period	44.17
Options exercisable as of end of period	$ 53.37
Weighted Average Remaining Contractual Term
Outstanding as of end of period	6 years 8 months 12 days	5 years 10 months 24 days
Options vested and expected to vest as of end period	6 years 8 months 12 days
Options exercisable as of end of period	5 years 1 month 6 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value	$ 459	$ 0
Options vested and expected to vest as of December 31, 2021	459
Options exercisable as of end of period	$ 0

Stock-Based Awards - Summary _2

Stock-Based Awards - Summary of PSUs and rTSRUs Activity (Detail) shares in Thousands	3 Months Ended
	Dec. 31, 2023 $ / shares shares
PSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested, beginning balance | shares	81
Granted | shares	48
Vested | shares	0
Unvested, ending balance | shares	129
Weighted Average Grant Date Fair Value, Unvested beginning balance | $ / shares	$ 58.58
Weighted Average Grant Date Fair Value, Granted | $ / shares	9.21
Weighted Average Grant Date Fair Value, Vested | $ / shares	0
Weighted Average Grant Date Fair Value, Unvested ending balance | $ / shares	$ 40.23
rTSRUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested, beginning balance | shares	81
Granted | shares	48
Vested | shares	0
Unvested, ending balance | shares	129
Weighted Average Grant Date Fair Value, Unvested beginning balance | $ / shares	$ 45.82
Weighted Average Grant Date Fair Value, Granted | $ / shares	9.89
Weighted Average Grant Date Fair Value, Vested | $ / shares	0
Weighted Average Grant Date Fair Value, Unvested ending balance | $ / shares	$ 32.47

Stock-Based Awards - Summary _3

Stock-Based Awards - Summary of Restricted Stock Unit Activity (Detail) - Restricted Stock Units [Member] shares in Thousands	3 Months Ended
	Dec. 31, 2023 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested, beginning balance | shares	411
Granted | shares	162
Vested | shares	(116)
Cancelled | shares	(2)
Unvested, ending balance | shares	455
Weighted Average Grant Date Fair Value, Unvested beginning balance | $ / shares	$ 51.78
Weighted Average Grant Date Fair Value, Granted | $ / shares	8.99
Weighted Average Grant Date Fair Value, Vested | $ / shares	52
Weighted Average Grant Date Fair Value, Cancelled | $ / shares	54.27
Weighted Average Grant Date Fair Value, Unvested ending balance | $ / shares	$ 36.45

Stock-Based Awards - Stock-Base

Stock-Based Awards - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 8,099	$ 7,139
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	4,462	5,046
rTSRUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	445	461
Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	1,579	367
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	1,613	1,265
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	2,055	2,532
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 6,044	$ 4,607

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax [Line Items]
Income tax benefit	$ 622	$ 34