0000950170-24-124548 | 10-Q | XBRL Viewer

Stockholders' Equity	9 Months Ended
Sep. 30, 2024
Equity [Abstract]
Stockholders' Equity	Note 7. Stockholders’ equity The Company's restated Certificate of Incorporation authorizes the Company to issue up to 160,000,000 shares, of which (i) 150,000,000 shares are designated as common stock, par value $0.001 per share, and (ii) 10,000,000 shares are designated as undesignated preferred stock, par value $0.001 per share. Each share of common stock entitles the holders to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are not entitled to receive dividends, unless declared by the board of directors. On May 10, 2024, the Company entered into a Securities Purchase Agreement ("SPA") with RA Capital Healthcare Fund, L.P. ("RA Capital"), and Boxer Capital, LLC ("Boxer Capital"), pursuant to which the Company agreed to sell to RA Capital a pre-funded warrant to purchase up to an aggregate of 5,714,285 shares of the Company's common stock and to Boxer Capital 1,142,857 shares of common stock (together, the "Securities"). The aggregate consideration for the pre-funded warrant sold to RA Capital was $100.0 million, or $17.499 per share of common stock underlying the pre-funded warrant, which, together with the exercise price per share of underlying common stock, was equal to $17.50 per share of common stock, and the aggregate consideration for the shares of common stock sold to Boxer Capital was $20.0 million, or $17.50 per share. In aggregate, the total proceeds to the Company from the sale of the Securities to RA Capital and Boxer Capital was $120.0 million, partially offset by $0.4 million of costs incurred in connection with the offering. The Securities were issued in a registered direct offering pursuant to the Company's Registration Statement on Form S-3 (File No. 333-271793) (the "RDO"). The pre-funded warrant grants to RA Capital the right to purchase shares of common stock at any time. Such right does not expire. The pre-funded warrant is subject to adjustment upon certain corporate events, including certain stock dividends and splits, combinations, reclassifications, and certain other events. The Company determined that the pre-funded warrant did not meet the classification of a liability under ASC 480, Distinguishing Liabilities from Equity. The Company concluded that the pre-funded warrant should be classified as equity based on an analysis performed under ASC 815-40, Contracts in an Entity's Own Equity. The issuance of the warrant was therefore reflected as an increase to Additional Paid-in Capital in the amount of $100.0 million. The amount of the $20.0 million in excess of the par value of the shares of common stock sold to Boxer Capital was also reflected as an increase to Additional Paid-in Capital. On May 12, 2024, the Company entered into an Exchange Agreement (the "Exchange Agreement") with RA Capital, pursuant to which RA Capital agreed to exchange 900,000 shares of the Company’s common stock for a pre-funded warrant (the “Exchange Warrant”) to purchase up to 900,000 shares of common stock. The terms of the Exchange Warrant are substantially similar to the pre-funded warrant described above. The Exchange Agreement did not have any cash impact, and therefore did not impact the statement of cash flows.

Stockholders' Equity

9 Months Ended

Sep. 30, 2024

Note 7. Stockholders’ equity

The Company's restated Certificate of Incorporation authorizes the Company to issue up to 160,000,000 shares, of which (i) 150,000,000 shares are designated as common stock, par value $0.001 per share, and (ii) 10,000,000 shares are designated as undesignated preferred stock, par value $0.001 per share. Each share of common stock entitles the holders to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are not entitled to receive dividends, unless declared by the board of directors.

On May 10, 2024, the Company entered into a Securities Purchase Agreement ("SPA") with RA Capital Healthcare Fund, L.P. ("RA Capital"), and Boxer Capital, LLC ("Boxer Capital"), pursuant to which the Company agreed to sell to RA Capital a pre-funded warrant to purchase up to an aggregate of 5,714,285 shares of the Company's common stock and to Boxer Capital 1,142,857 shares of common stock (together, the "Securities"). The aggregate consideration for the pre-funded warrant sold to RA Capital was $100.0 million, or $17.499 per share of common stock underlying the pre-funded warrant, which, together with the exercise price per share of underlying common stock, was equal to $17.50 per share of common stock, and the aggregate consideration for the shares of common stock sold to Boxer Capital was $20.0 million, or $17.50 per share. In aggregate, the total proceeds to the Company from the sale of the Securities to RA Capital and Boxer Capital was $120.0 million, partially offset by $0.4 million of costs incurred in connection with the offering. The Securities were issued in a registered direct offering pursuant to the Company's Registration Statement on Form S-3 (File No. 333-271793) (the "RDO").

The pre-funded warrant grants to RA Capital the right to purchase shares of common stock at any time. Such right does not expire. The pre-funded warrant is subject to adjustment upon certain corporate events, including certain stock dividends and splits, combinations, reclassifications, and certain other events.

The Company determined that the pre-funded warrant did not meet the classification of a liability under ASC 480, Distinguishing Liabilities from Equity. The Company concluded that the pre-funded warrant should be classified as equity based on an analysis performed under ASC 815-40, Contracts in an Entity's Own Equity. The issuance of the warrant was therefore reflected as an increase to Additional Paid-in Capital in the amount of $100.0 million. The amount of the $20.0 million in excess of the par value of the shares of common stock sold to Boxer Capital was also reflected as an increase to Additional Paid-in Capital.

On May 12, 2024, the Company entered into an Exchange Agreement (the "Exchange Agreement") with RA Capital, pursuant to which RA Capital agreed to exchange 900,000 shares of the Company’s common stock for a pre-funded warrant (the “Exchange Warrant”) to purchase up to 900,000 shares of common stock. The terms of the Exchange

Warrant are substantially similar to the pre-funded warrant described above. The Exchange Agreement did not have any cash impact, and therefore did not impact the statement of cash flows.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-14

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478448/946-505-50-6

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480237/815-40-50-6

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480008/505-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/505/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-14

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-14

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-16

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-18

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-18

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-18

+ Details

Government Grant Funding and Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs) (Tables)

9 Months Ended

Sep. 30, 2024

Research and Development Arrangement with Federal Government [Abstract]

Schedule of Activity for Grant Programs

The following table reflects activity for grant programs for the nine months ended September 30, 2024 and 2023, and end of period balances as of September 30, 2024, and December 31, 2023:


	RCA -1				RCA-2				Other Grants				Total
(In thousands)	2024		2023		2024		2023		2024		2023		2024		2023
Cash received	$	—	$	—	$	—	$	—	$	777	$	3,542	$	777	$	3,542
Grant income	$	17	$	—	$	—	$	—	$	2,086	$	2,165	$	2,103	$	2,165
Grants receivable at the end of the period	$	—	$	—	$	—	$	—	$	773	$	—	$	773	$	—
Grants repayable at the end of the period	$	5,392	$	5,496	$	1,294	$	1,317	$	—	$	—	$	6,686	$	6,813

Net loss per share attributable to common stock - Schedule of Net Loss Per Shares By Treasury Stock Method (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Numerator
Net loss attributable to common stockholders	$ (45,358)	$ (32,241)	$ (90,702)	$ (82,091)
Denominator
Weighted-average shares used in compute net loss per share, basic	43,135,464	35,783,160	39,572,673	35,756,295
Effect of dilutive securities (a)	0	0	0	0
Weighted-average shares used to compute net loss per share, diluted	43,135,464	35,783,160	39,572,673	35,756,295
Basic net loss per share	$ (1.05)	$ (0.9)	$ (2.29)	$ (2.3)
Diluted net loss per share	$ (1.05)	$ (0.9)	$ (2.29)	$ (2.3)

- 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

Amount after tax of income (loss) from continuing operations attributable to the parent.

+ References

+ Details

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Cash flows from operating activities
Net loss	$ (90,702)	$ (82,091)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	916	671
Stock-based compensation	22,868	19,828
Net accretion of available-for-sale debt securities	(8,504)	(8,042)
Change in operating lease right-of-use assets	(9)	(6)
Unrealized foreign exchange loss	1,507	0
Changes in operating assets and liabilities:
Grants receivable	(751)	1,016
Research and development tax credits receivable	(1,881)	(1,135)
Refundable income taxes	96	(4,900)
Milestone receivable	(35,000)	0
Prepaid expenses and other current assets	(1,224)	(1,653)
Accounts payable	(4,180)	(4,581)
Accrued clinical trial costs	9,870	638
Accrued personnel expenses	(318)	592
Deferred income	(621)	477
Deferred revenue	0	(12,595)
Unrecognized tax benefits	3,200	730
Net cash used in operating activities	(103,678)	(89,991)
Cash flows from investing activities
Purchases of investments	(440,596)	(193,510)
Proceeds from maturities of investments	297,309	206,265
Purchase of property and equipment	(1,481)	(1,570)
Purchase of other assets	0	(83)
Net cash used in investing activities	(144,768)	11,102
Cash flows from financing activities
Proceeds from issuance of common stock upon exercise of options and ESPP purchases	2,450	806
Proceeds from issuance of common stock and pre funded warrant	119,994
Payment of offering costs	(277)
Payment of grants repayable	(211)
Net cash provided by financing activities	121,956	806
Effects of exchange rate changes on cash, cash equivalents and restricted cash	(908)	(2,554)
Net decrease in cash, cash equivalents and restricted cash	(127,398)	(80,637)
Cash, cash equivalents and restricted cash at beginning of period	251,451	285,038
Cash, cash equivalents and restricted cash at end of period	124,053	204,401
Non-cash investing and financing activities
Capital expenditure included in accounts payable	2	320
Operating lease liabilities arising from obtaining right-of-use assets	385	1,782
Unrealized gain (loss) on available-for-sale securities	1,881	(975)
Offering costs previously included in prepaid expenses	(143)
Supplemental disclosure of cash flows
Cash paid for taxes	$ 3,576	$ 5,491

Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2024

Accounting Policies [Abstract]

Basis of presentation

The accompanying condensed consolidated financial statements and accompanying notes have been prepared in accordance with generally accepted accounting principles in the United States of America ("U.S. GAAP").

The unaudited interim condensed consolidated financial statements of the Company included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission ("SEC"). Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the consolidated financial statements as of and for the years ended December 31, 2023 and 2022, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K (File No. 001-39401). The results for any interim period are not necessarily indicative of results for any future period.

In the opinion of management, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the results for the reported interim periods. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period.

Net loss per share attributable to common stock - Schedule of Net Loss Per Shares By Treasury Stock Method (Parenthetical) (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Earnings Per Share [Abstract]
Anti-dilutive securities (in shares)	1,925,499	1,661,812	1,984,130	1,751,070

Investment Securities and Fair Value Measurements - Schedule of Investments Classified by Contractual Maturity Date (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Due in one year or less, Amortized Cost	$ 364,097	$ 281,035
Due after one year through five years, Amortized Cost	159,150	100,208
Due in one year or less, Fair value	364,966	280,739
Due after one year through five years, Fair value	160,198	100,539
Amortized Cost	523,247	381,243
Fair value	$ 525,164	$ 381,278

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 103
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-103

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481830/320-10-45-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

+ Details

Commitments and Contingencies

9 Months Ended

Sep. 30, 2024

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Note 10. Commitments and contingencies

Purchase commitments

The Company has contractual arrangements with research and development organizations and suppliers; however, these contracts are generally cancelable on 30-60 days’ notice and the obligations under these contracts are largely based on services performed. The Company may also enter into contracts in the normal course of business with clinical research organizations for clinical trials, with contract manufacturing organizations for clinical supplies and with other vendors for preclinical studies, supplies and other services and products for operating purposes. These contracts generally provide for termination on notice. As of September 30, 2024 and December 31, 2023, there were no amounts accrued related to termination charges.

The Company has entered into a Biologics Master Services Agreement (the "WuXi Agreement") with WuXi Biologics (Hong Kong) Limited ("WuXi"). The WuXi Agreement provides the terms and conditions under which WuXi will coordinate the Company’s biologics development and manufacturing services. Pursuant to the WuXi Agreement, the Company may be required to pay WuXi a royalty percentage or a one-time milestone payment on global net sales of third-party manufactured products at the Company’s election. The royalty or one-time milestone payment is only payable if the Company does not use WuXi as the manufacturer in part, or in totality. As of September 30, 2024 and December 31, 2023, there are no minimum commitments under the WuXi Agreement. Additionally, as of September 30, 2024 and December 31, 2023, there are no royalties or milestones payable.

Operating leases

The Company’s operating leases are as follows:

•

An April 2016 lease for 1,577 square meters of office and laboratory space in Gosselies, Belgium, which commenced in May 2016 and was scheduled to terminate in December 2021. In January 2021, the Company entered into an amendment to extend the lease, effective February 2021 with a termination date of January 2030, and increase the office and laboratory space by 201 square meters. There is no option within the lease agreement to extend the termination date. In October 2021, the Company entered into an amendment to increase the office and laboratory space by 453 square meters. In May 2023, the Company entered into another amendment to again increase the office and laboratory space by an additional 453 square meters for a total of 2,684 square meters. The amendment resulted in an additional $0.9 million of both right-of-use assets and liabilities.

•

A November 2021 lease for 9,068 square feet of office space in Watertown, Massachusetts, which commenced in November 2021 and terminates in February 2027. The lease is subject to fixed-rate rent escalations. There is no option within the lease agreement to extend the termination date.

•

A July 2023 lease for 859 square meters of laboratory space in Gosselies, Belgium, for which the Company took occupancy in March 2024 and will terminate in December 2028. This lease does not contain any variable lease payments. There is no option within the lease agreement to terminate nor to extend the lease prior to the termination date.

•

Various car leases that the Company enters into from time to time. The life of each car lease ranges from 48 to 60 months.

The Company identified and assessed the following estimates in recognizing the operating lease right of use assets and corresponding liabilities.

Expected lease term: The expected lease term includes non-cancelable lease periods and, when applicable, periods covered by an option to extend the lease if the Company is reasonably certain to exercise that option, as well as periods covered by an option to terminate the lease if the Company is reasonably certain not to exercise that option.

Incremental borrowing rate: As the discount rates in the Company’s lease are not implicit, management estimated the incremental borrowing rate based on the rate of interest the Company would have to pay to borrow a similar amount on a collateralized basis over a similar term.

Lease and non-lease components: The Company is required to pay fees for operating expenses in addition to monthly base rent for certain operating leases ("non-lease components"). The Company has not elected the practical expedient which allows non-lease components to be combined with lease components for all asset classes. Variable non-lease components are not included within the lease right-of-use asset and lease liability on the condensed consolidated balance sheet, and instead are reflected as expense in the period they are paid.

Rent expense was $0.4 million and $1.2 million for the three and nine months ended September 30, 2024, respectively. Rent expense was $0.3 million and $0.9 million for the three and nine months ended September 30, 2023, respectively.

The following table summarizes lease terms and discount rate:


	September 30, 2024			December 31, 2023
Weighted-average remaining lease term (years)		4.0			4.6
Weighted-average discount rate		4.74	%		4.75	%

The following table summarizes the cash flow and other information:


	Three months ended September 30,				Nine months ended September 30,
(in thousands)	2024		2023		2024		2023
Operating lease liabilities arising from obtaining right-of-use assets (non-cash)	$	150	$	723	$	385	$	1,782
Operating cash flows used in operating leases	$	380	$	316	$	1,148	$	865

As of September 30, 2024, the Company had the following future minimum lease payments under non-cancelable operating leases for the remainder of 2024 and the future years thereafter (in thousands):


Year ending December 31:
2024	$	395
2025		1,581
2026		1,543
2027		1,039
2028		852
Thereafter		628
Total lease payments		6,038
Less: interest		(510	)
Total lease liability	$	5,528
Lease liabilities, current	$	1,354
Lease liabilities, net of current portion	$	4,174

In November 2021, the Company provided a letter of credit for $142 thousand to secure its obligation under its lease in Watertown, Massachusetts. The Company maintains that amount of cash on hand (restricted) to fund any necessary draws on the letter of credit. In addition, as of September 30, 2024 and December 31, 2023, the Company had $167 thousand and $131 thousand on hand, respectively, serving as a guarantee for its lease obligation in Belgium.

These amounts have been classified as restricted cash in the condensed consolidated balance sheets as of September 30, 2024 and December 31, 2023.

Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		9 Months Ended		12 Months Ended
	May 10, 2024	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2021	May 14, 2024	May 12, 2024	Dec. 31, 2023
Class Of Stock [Line Items]
Common stock, shares authorized		150,000,000					150,000,000
Common stock, par value		$ 0.001					$ 0.001
Common stock, voting rights				Each share of common stock entitles the holders to one vote on all matters submitted to a vote of the Company’s stockholders.
Common stock, shares issued		36,527,470					35,838,080
Proceeds from Issuance or Sale of Securities	$ 120,000
Proceeds from issuance of common stock upon exercise of options and ESPP purchases		$ 2,450	$ 806
Offering Cost Incurred	400
Additional paid-in capital		$ 608,690					$ 463,799
Excess of the par value	$ 20,000
RA Capital
Class Of Stock [Line Items]
Share repurchased by prefunded warrants	5,714,285
Boxer Capital [Member]
Class Of Stock [Line Items]
Common stock, shares issued	1,142,857
Share repurchased by prefunded warrants	1,142,857
Proceeds from issuance of common stock upon exercise of options and ESPP purchases	$ 20,000
IPO
Class Of Stock [Line Items]
Capital units, authorized		160,000,000
Common stock, shares authorized		150,000,000
Common stock, par value		$ 0.001
Preferred Stock Shares Authorized		10,000,000
Preferred Stock, par value		$ 0.001
Pre-Funded Warrant
Class Of Stock [Line Items]
Share repurchased by prefunded warrants		6,614,285
Additional paid-in capital	$ 100,000
Pre-Funded Warrant \| RA Capital
Class Of Stock [Line Items]
Share repurchased by prefunded warrants	5,714,285				900,000	900,000
Amount gained from Warrant Sold	$ 100,000
Share price	$ 17.499
Pre-Funded Warrant \| RA Capital \| Maximum [Member]
Class Of Stock [Line Items]
Share repurchased by prefunded warrants						900,000
Common stock \| RA Capital
Class Of Stock [Line Items]
Share price	17.5
Common stock \| Boxer Capital [Member]
Class Of Stock [Line Items]
Share price	$ 17.5

Government Grant Funding and Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs)

9 Months Ended

Sep. 30, 2024

Research and Development Arrangement with Federal Government [Abstract]

Government Grant Funding and Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs)

Note 6. Government grant funding and potential repayment commitments under recoverable cash advance grants (RCAs)

The Company has been awarded grants from the Walloon Region, a federal region of Belgium (the "Walloon Region") and the European Union (the "Granting Agencies") to fund research and development activities. The grants reimburse a percentage (55-100%) of actual qualifying expenditures. The Company periodically submits proof of qualifying expenditures to the Granting Agencies for approval and reimbursement. To date, the Company has received funding under several grants which included no obligation to repay and two grants that include potential obligations to repay.

As the Granting Agencies do not meet the definition of a customer under Topic 606, qualifying grants receipts are recognized as grant income within other income in the condensed consolidated statement of operations and comprehensive loss.

Grants which do not include an obligation to repay

The total amount that the Granting Agencies have agreed to fund for qualifying research and development expenses is $11.9 million under these grants.

Grants which include an obligation to repay

On July 20, 2017, the Company entered into a recoverable cash advance arrangement whereby the Walloon Region will provide the Company with up to $21.1 million for a research and development program to perform clinical validation of an A2A receptor antagonist drug candidate for immune-oncology ("RCA-1").

On December 3, 2019, the Company entered into another recoverable cash advance arrangement with the Walloon Region ("RCA-2") for up to $4.8 million to be received to fund a research and development program conducted to develop a TIGIT blocking antibody with anti-tumor properties.

Under the terms of both agreements, the Company had to decide within 6 months after the end of the research period whether it would further pursue commercial development or out licensing of the drug candidate. The research period for RCA-1 ended in December 2021. The Company decided it would pursue commercialization or out licensing of RCA-1. The Company negotiated an extension on the research period for RCA-2 with the Walloon Region. The original research period for RCA-2 ended February 2021 and was extended to March 2022, after which the Company decided it would pursue commercialization or out licensing. The Company must repay 30% of the amount received under both grants by annual installments from 2023 to 2042 (the fixed annual repayments), unless the Company had decided not to pursue commercial development or out licensing of the drug candidate, applied for a waiver from the Walloon Region justifying its decision based upon the failure of the program, or returned the intellectual property to the Walloon Region. Because of the requirement to repay 30% of the amounts received under both grants, the Company records the present value of the fixed payments as grants repayable on the condensed consolidated balance sheets. The Company repaid $0.2 million of these grants in the three and nine months ended September 30, 2024.

In addition, in the event that the Company receives revenue from products or services related to the results of the research, it has to pay to the Walloon Region a 0.33% royalty on revenue resulting from RCA-1 and a 0.15% royalty on revenue resulting from RCA-2 (increased from 0.12% effective December 2021). The maximum amount payable to the Walloon Region under each grant, including the fixed annual repayments, the royalty on revenue, and the interest thereon, is twice the amount of funding received.

The Company assessed whether there is an obligation to make a royalty payment based on the probability of successful completion of the research and development and future sales and commercial success of the drug candidate. For the RCA-1, there was no grant repayable related to royalties recorded as of September 30, 2024, or December 31, 2023. For the RCA-2, the Company recorded a royalty accrual of $0.9 million as of September 30, 2024, and $0.8 million

as of December 31, 2023, due to the upfront payment from the GSK Collaboration Agreement. The royalty accrual is included in the accrued expenses and other current liabilities in the condensed consolidated balance sheets.

The Company recorded grant income in the condensed consolidated statement of operations and comprehensive loss for the three and nine months ended September 30, 2024 and 2023 for amounts of grants received from the Walloon Region in the period during which the related qualifying expenses were incurred, net of any grants repayable recorded in the condensed consolidated balance sheets.

The Company recorded receivables on the condensed consolidated balance sheets related to amounts the Walloon Region owes the Company based on qualifying expenses incurred by the Company. The Company recorded deferred income in the condensed consolidated balance sheets for amounts received from the Walloon Region in advance of incurring qualifying expenses.

The following table reflects activity for grant programs for the nine months ended September 30, 2024 and 2023, and end of period balances as of September 30, 2024, and December 31, 2023:


	RCA -1				RCA-2				Other Grants				Total
(In thousands)	2024		2023		2024		2023		2024		2023		2024		2023
Cash received	$	—	$	—	$	—	$	—	$	777	$	3,542	$	777	$	3,542
Grant income	$	17	$	—	$	—	$	—	$	2,086	$	2,165	$	2,103	$	2,165
Grants receivable at the end of the period	$	—	$	—	$	—	$	—	$	773	$	—	$	773	$	—
Grants repayable at the end of the period	$	5,392	$	5,496	$	1,294	$	1,317	$	—	$	—	$	6,686	$	6,813

$0.4 million and $0.2 million of the grants repayable was included in accrued expenses and other current liabilities as of September 30, 2024 and December 31, 2023, and the remaining balance was included in grants repayable, net of current portion in the condensed consolidated balance sheet.

Related Party Transactions - Additional Information (Details)			3 Months Ended		9 Months Ended
	May 10, 2024 USD ($) shares	Jun. 11, 2018 Investor	Sep. 30, 2024 USD ($) shares	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) shares	Sep. 30, 2023 USD ($)	May 14, 2024 shares	May 12, 2024 shares	Dec. 31, 2023 shares
Related Party Transaction [Line Items]
Net product sales \| $			$ 0	$ 0	$ 35,000,000	$ 12,595,000
Pre-funded warrant			36,527,470		36,527,470				35,838,080
Proceeds from Issuance of Common Stock \| $					$ 2,450,000	$ 806,000
Pre-Funded Warrant
Related Party Transaction [Line Items]
Share repurchased by prefunded warrants			6,614,285		6,614,285
Boxer Capital
Related Party Transaction [Line Items]
Pre-funded warrant	1,142,857
Proceeds from Issuance of Common Stock \| $	$ 20,000,000
Share repurchased by prefunded warrants	1,142,857
RA Capital
Related Party Transaction [Line Items]
Share repurchased by prefunded warrants	5,714,285
RA Capital \| Pre-Funded Warrant
Related Party Transaction [Line Items]
Share repurchased by prefunded warrants	5,714,285						900,000	900,000
Amount gained from Warrant Sold \| $	$ 100,000,000
RA Capital \| Maximum \| Pre-Funded Warrant
Related Party Transaction [Line Items]
Share repurchased by prefunded warrants								900,000
RA Capital Healthcare Fund, L.P \| Minimum
Related Party Transaction [Line Items]
Ownership percentage	10.00%
RA Capital Healthcare Fund, L.P \| Maximum
Related Party Transaction [Line Items]
Ownership percentage							10.00%
Royalty Transfer Agreement
Related Party Transaction [Line Items]
Royalty owed to charitable foundation \| $			$ 0		$ 0
Royalty Transfer Agreement \| MPM Oncology Charitable Foundation, Inc. and UBS Optimus Foundation
Related Party Transaction [Line Items]
Number of investors \| Investor		2
Obligation to pay royalties					royalty equal to a total of 1% of its net product sales each year within 120 days following each year end.
Percentage of royalty required to pay		1.00%
Royalty Transfer Agreement \| Product
Related Party Transaction [Line Items]
Net product sales \| $					$ 0

Summary of significant accounting policies - Additional Information (Details) - shares	Sep. 30, 2024	Dec. 31, 2023
Pre-funded warrant	36,527,470	35,838,080
Pre-Funded Warrant
Share repurchased by prefunded warrants	6,614,285

Commitments and Contingencies (Tables)

9 Months Ended

Sep. 30, 2024

Commitments and Contingencies Disclosure [Abstract]

Schedule of Lease Terms and Discount Rate

The following table summarizes lease terms and discount rate:


	September 30, 2024			December 31, 2023
Weighted-average remaining lease term (years)		4.0			4.6
Weighted-average discount rate		4.74	%		4.75	%

Schedule of Cash Flow and Other Information

The following table summarizes the cash flow and other information:


	Three months ended September 30,				Nine months ended September 30,
(in thousands)	2024		2023		2024		2023
Operating lease liabilities arising from obtaining right-of-use assets (non-cash)	$	150	$	723	$	385	$	1,782
Operating cash flows used in operating leases	$	380	$	316	$	1,148	$	865

Schedule of Future Minimum Lease Payments Under Non-cancelable Operating Leases

As of September 30, 2024, the Company had the following future minimum lease payments under non-cancelable operating leases for the remainder of 2024 and the future years thereafter (in thousands):


Year ending December 31:
2024	$	395
2025		1,581
2026		1,543
2027		1,039
2028		852
Thereafter		628
Total lease payments		6,038
Less: interest		(510	)
Total lease liability	$	5,528
Lease liabilities, current	$	1,354
Lease liabilities, net of current portion	$	4,174

Nature of Business and Basis of Presentation

9 Months Ended

Sep. 30, 2024

Disclosure Text Block [Abstract]

Nature of Business and Basis of Presentation

Note 1. Nature of Business and Basis of Presentation

Description of business

iTeos Therapeutics, Inc. ("iTeos Inc." or the "Company"), a Delaware corporation headquartered in Watertown, Massachusetts (incorporated on October 4, 2019), is the successor to iTeos Belgium SA (iTeos Belgium) a company organized under the laws of Belgium in 2011 and headquartered in Charleroi, Belgium. The Company is a clinical stage biopharmaceutical company pioneering the discovery and development of a new generation of immuno-oncology therapeutics for people living with cancer. By leveraging its deep understanding of the tumor immunology and immunosuppressive pathways we design novel product candidates with optimized pharmacologic properties to improve clinical outcomes by restoring the immune response against cancer. The Company is focused on advancing its innovative pipeline of monoclonal antibodies (mAbs) and small molecules for the treatment of cancer, especially solid tumors. Our three clinical-stage programs target novel, validated immuno-oncology pathways, including the TIGIT/CD226 pathway with TIGIT (T cell immunoreceptor with lg and ITIM domains) and the adenosine pathway with A2AR (adenosine 2A receptor) and ENT1 (equilibrative nucleoside transporter 1).

The Company’s lead antibody product candidate, belrestotug, also known as EOS-448/GSK4428859A, is an antagonist of TIGIT, an immune checkpoint with multiple mechanisms of action. Belrestotug was selected for its target affinity with TIGIT, potency and potential to engage the Fc gamma receptor (FcγR), a key regulator of immune response which triggers a multi-faceted mechanism of action that improves antitumor efficacy. This multi-faceted mechanism includes the activation of dendritic cells, natural killer cells, and macrophages, and the promotion of cytokine release and antibody-dependent cellular cytotoxicity (ADCC) activity. In 2020, the Company initiated an open-label Phase 1/2a clinical trial of belrestotug in adult cancer patients with advanced solid tumors. In April 2021, the Company reported preliminary safety, pharmacokinetic, engagement and pharmacodynamic data, indicating target engagement and early evidence of clinical activity as a single agent.

On June 11, 2021, the Company's wholly owned subsidiary, iTeos Belgium S.A., and GlaxoSmithKline Intellectual Property (No. 4) Limited, or GSK, executed a Collaboration and License Agreement, or the GSK Collaboration Agreement, which became effective on July 26, 2021. Pursuant to the GSK Collaboration Agreement, the Company granted GSK a license under certain of its intellectual property rights to develop, manufacture, and commercialize products comprised of or containing belrestotug, which license is exclusive in all countries outside of the United States and co-exclusive, with iTeos, in the United States. GSK and iTeos intend to develop belrestotug in combination, including with other oncology assets of GSK, and iTeos and GSK will jointly own the intellectual property created under the GSK Collaboration Agreement that covers such combinations. In partnership with GSK, the Company is enrolling patients in a randomized, double-blind Phase 3 registrational trial, GALAXIES Lung-301, assessing the doublet of GSK's anti-PD-1 (Jemperli (dostarlimab-gxly)) with belrestotug versus placebo and pembrolizumab in patients with first-line PD-L1 high non-small cell lung cancer (NSCLC). The Company is also enrolling patients with first line PD-L1 high NSCLC in a randomized Phase 2 platform study, GALAXIES Lung-201, assessing dostarlimab with belrestotug and in combination with GSK'608, GSK's investigational anti-CD96 antibody, nelistotug. In September 2024, the Company announced that it had observed a clinically meaningful objective response rate across each dostarlimab with belrestotug dosing cohort in the GALAXIES Lung-201 study and a safety profile that was broadly consistent with the known safety profile of combination therapies with checkpoint inhibitors. In addition, the Company is enrolling patients in a Phase 2 platform study, GALAXIES H&N-202, assessing the belrestotug and dostarlimab doublet and a triplet with GSK’s anti-CD96 antibody, nelistotug (GSK’608) with first-line, PD-L1 positive advanced or metastatic head and neck squamous cell carcinoma (HNSCC) and a Phase 2 expansion trial assessing belrestotug and dostarlimab with first-line, PD-L1 positive advanced or metastatic HNSCC. In the TIG-006 trial assessing the doublet of dostarlimab with belrestotug in patients with first-line HNSCC (Cohorts 2C and 2D), we completed enrollment in the first portion of the Phase 2 expansion part of the trial. We and GSK agreed to not continue beyond stage 1 recruitment in these open-label cohorts in order to focus on the randomized, controlled GALAXIES H&N-202 platform study. The Company and GSK continue to explore two novel triplets in selected advanced solid tumors both in Phase 1b trials: belrestotug with dostarlimab and nelistotug, GSK’s investigational anti-CD96 antibody, and belrestotug with dostarlimab and GSK’s anti-PVRIG antibody (GSK’562).

The Company's next most advanced program is inupadenant, also known as EOS-850, a next-generation A2AR antagonist tailored to overcome the specific adenosine-mediated immunosuppression found in tumor microenvironment. The Company investigated inupadenant in an open-label multi-arm Phase 1/2a clinical trial in adult cancer patients with advanced solid tumors. In April 2020, the Company reported preliminary safety data and early evidence of clinical activity as a single agent. The single-agent dose-escalation and expansion portions of the Company's Phase 1/2a clinical trial of inupadenant have demonstrated durable monotherapy antitumor activity in some patients with advanced solid tumors and

safety consistent with previously reported results. The Company also completed enrollment of patients in the escalation portion (Part 1) of an ongoing two-part Phase 2 trial in post-IO metastatic NSCLC to evaluate the combination of inupadenant with platinum-doublet chemotherapy compared to standard platinum-doublet chemotherapy.

The Company continues to progress research programs focused on additional targets that complement its TIGIT and adenosine pathway programs or address additional immunosuppressive pathways. The most recent program to enter the clinic is EOS-984, a potentially first-in-class small molecule focused on a new mechanism in the adenosine pathway by targeting ENT1, a dominant transporter of adenosine on lymphocytes involved in T cell metabolism, expansion, effector function, and survival. The Company's expertise also allows it to integrate a biomarker-rich strategy into its clinical programs to measure the activity of a product candidate in patients, seek to optimize combination agents and identify patients it deems most likely to benefit from treatment.

The Company began its research and development activities as a spin-off of Ludwig Cancer Research and has built significant expertise in designing novel cancer immunotherapies. The Company's internal research and development team has extensive expertise in tumor immunology, characterization of immunosuppressive mechanisms in the tumor microenvironment, pharmacology and translational medicine. The Company has also built discovery capabilities to develop both small molecules and antibodies with differentiated and optimized product profiles for targets validated by a strong scientific rationale.

On December 2, 2020, iTeos Securities Corporation (iTeos SC) was incorporated as a Massachusetts Security Corporation. It is a wholly-owned subsidiary of iTeos Inc. On July 27, 2021, iTeos BE, LLC (iTeos LLC) was incorporated as a Delaware Limited Liability Company. It is a wholly-owned subsidiary of iTeos Belgium.

Liquidity and capital resources

Since inception, the Company’s activities have consisted primarily of performing research and development to advance its product candidates. The Company had a net loss of $45.4 million and $90.7 million for the three and nine months ended September 30, 2024, respectively. As of September 30, 2024, the Company had retained earnings of $33.9 million. As of November 12, 2024, the issuance date of the condensed consolidated financial statements for the period ended September 30, 2024, the Company expects that its cash and cash equivalents would be sufficient to fund its operating expenses, capital expenditure requirements and debt service payments for at least 12 months.

The Company may seek additional funding in order to reach its development and commercialization objectives. The Company may not be able to obtain funding on acceptable terms, or at all, and the Company may not be able to enter into collaborations or other arrangements. The terms of any funding 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 portfolio expansion or commercialization efforts, which could adversely affect its business prospects.

The Company’s future results of operations involve a number of risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, uncertainty regarding results of clinical trials and reaching milestones, uncertainty of regulatory approval of the Company’s current or future product candidates, uncertainty of market acceptance of the Company’s product candidates, if approved, competition from substitute products and larger companies, securing and protecting proprietary technology, strategic relationships and dependence on key individuals and sole source suppliers. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities and may not ultimately lead to a marketing approval and commercialization of a product.

The Company’s product candidates require approvals from the U.S. Food and Drug Administration ("FDA") and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. The Company's product candidates may fail to receive the necessary approvals. If the Company was denied approval, approval was delayed or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. The Company will need to generate significant revenue to achieve sustained profitability, and it may never do so.

Basis of presentation

Stock-based Compensation - Summary of Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Shares
Outstanding as of December 31, 2023	8,270,220
Granted	2,582,470
Forfeited	(482,899)
Exercised	(412,459)
Outstanding as of September 30, 2024	9,957,332	8,270,220
Exercisable at September 30, 2024	5,645,152
Weighted-Average Exercise Price Per Share
Outstanding as of December 31, 2023	$ 17.73
Granted	12.93
Forfeited	29.32
Exercised	5.33
Outstanding as of September 30, 2024	16.43	$ 17.73
Exercisable at September 30, 2024	$ 16.79
Weighted-Average Remaining Contractual Term
Options outstanding	7 years 2 months 12 days	6 years 6 months
Exercisable at September 30, 2024	5 years 10 months 24 days
Aggregate Intrinsic Value
Outstanding as of September 30, 2024	$ 11,979
Exercisable at September 30, 2024	$ 11,902

Supplemental Balance Sheet Information - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Property Plant And Equipment [Line Items]
Total property and equipment	$ 10,326	$ 9,078
Accumulated depreciation and amortization	(4,954)	(4,382)
Property & equipment, net	5,372	4,696
Scientific Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	4,719	3,434
Furniture & office equipment
Property Plant And Equipment [Line Items]
Total property and equipment	1,259	1,467
Leasehold Improvements & Assets under Construction
Property Plant And Equipment [Line Items]
Total property and equipment	$ 4,348	$ 4,177

Stock-based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
	Jul. 15, 2020	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Jan. 01, 2024	Dec. 31, 2023
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage upon sale				25.00%
Stock options vesting period				36 months
Weighted-average estimated fair value of options awarded (in dollars per share)				$ 9.26	$ 12.35
Stock-based compensation expense		$ 7,543	$ 7,057	$ 22,868	$ 19,828
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation, stock options expiry period				10 years
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation, stock options expiry period				7 years
2020 ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance		580,443		580,443
Percentage of outstanding shares increase in shares reserved for issuance	1.00%
Percentage of purchase price to fair market value				85.00%
Estimated weighted-average fair value of issued shares		$ 6.45		$ 6.45
Maximum increase in common stock shares reserved for issuance	634,969
Stock Issued under Employee Stock Purchase Plans		32,199		32,199
Non Vested Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation costs for non-vested stock awards		$ 45,800		$ 45,800
Recognition period for compensation cost not yet recognized (in years, months, and days)				2 years 6 months
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense		6,500	6,800	$ 20,100	19,100
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation costs for non-vested stock awards		5,800		$ 5,800
Recognition period for compensation cost not yet recognized (in years, months, and days)				2 years 3 months 18 days
Stock-based compensation expense		900	200	$ 2,500	600
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense		$ 100	$ 100	$ 200	$ 100
2019 Stock Option And Grant Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options authorized		3,464,316		3,464,316
Stock options issued during period				0
Amendment to 2019 Stock Option and Grant Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage upon sale	100.00%
2020 Stock Option and Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Cumulative increase in common stock reserve for issuance, percentage	5.00%
Common stock reserved for future issuance							9,115,915
Cumulative increase in common stock reserve for issuance		11,624,288		11,624,288		1,791,904

Net loss per share attributable to common stock (Tables)

9 Months Ended

Sep. 30, 2024

Earnings Per Share [Abstract]

Schedule of Net Loss Per Shares By Treasury Stock Method

The following table summarizes the impact of the treasury stock method:


Net loss per share	Three Months Ended September 30,						Nine Months Ended September 30,
(in thousands, except per share amounts)	2024			2023			2024			2023
Numerator
Net loss attributable to common stockholders	$	(45,358	)	$	(32,241	)	$	(90,702	)	$	(82,091	)
Denominator
Weighted-average shares used in compute net loss per share, basic		43,135,464			35,783,160			39,572,673			35,756,295
Effect of dilutive securities (a)		—			—			—			—
Weighted-average shares used to compute net loss per share, diluted		43,135,464			35,783,160			39,572,673			35,756,295
Net loss per share:
Basic	$	(1.05	)	$	(0.90	)	$	(2.29	)	$	(2.30	)
Diluted	$	(1.05	)	$	(0.90	)	$	(2.29	)	$	(2.30	)

(a) The common stock equivalents, which equaled 1,925,499 and 1,984,130 stock awards outstanding for the three and nine months ended September 30, 2024, respectively, and 1,661,812 and 1,751,070 for the three and nine months ended September 30, 2023, were excluded for the period then ended, respectively, due to their anti-dilutive effect.

Supplemental Balance Sheet Information

9 Months Ended

Sep. 30, 2024

Supplemental Balance Sheet Information [Abstract]

Supplemental Balance Sheet Information

Note 4. Supplemental balance sheet information

Property and equipment

Property and equipment, net consisted of the following:


(in thousands)	September 30, 2024			December 31, 2023
Scientific equipment	$	4,719		$	3,434
Furniture & office equipment		1,259			1,467
Leasehold improvements & assets under construction		4,348			4,177
Total		10,326			9,078
Accumulated depreciation and amortization		(4,954	)		(4,382	)
Property & equipment, net	$	5,372		$	4,696

Depreciation and amortization expense was $0.3 million and $0.9 million for the three and nine months ended September 30, 2024, respectively, and $0.2 million and $0.7 million for the three and nine months ended September 30, 2023, respectively.

Other accrued expenses

Other accrued expenses consisted of the following:


(in thousands)	September 30, 2024		December 31, 2023
Accrued professional and other fees		943		102
Total other accrued expenses	$	943	$	102

The accrued expenses and other current liabilities presentation on the balance sheet has been further disaggregated compared to the presentation reflected in the 10-K for the year ended December 31, 2023. The prior period balance sheet has been amended to reflect the updated presentation.

Investment securities and fair value measurements - Summary of Financial Instruments Measured at Fair Value on a Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 633,902	$ 609,684
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	108,739	228,406
U.S. government agency bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	81,714	193,076
U.S. treasury bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	343,054	103,597
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	100,395	84,605
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	451,793	332,003
Level 1 \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	108,739	228,406
Level 1 \| U.S. treasury bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	343,054	103,597
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	182,109	277,681
Level 2 \| U.S. government agency bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	81,714	193,076
Level 2 \| Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 100,395	$ 84,605

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Income Tax Contingency [Line Items]
Effective income tax rate reconciliation, at Federal statutory income tax rate, Percent	21.00%	21.00%
Effective income tax rate reconciliation tax credits foreign			25.00%	25.00%
Liability for accrual of additional interest expense	$ 1,100		$ 3,200
Effective tax rate	(5.20%)	3.50%	(8.00%)	(1.50%)
Unrecognized tax benefits			$ 3,200	$ 730
Unrecognized tax benefits income tax interest accrued	$ 7,100		$ 7,100

Investment Securities and Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2024

Fair Value Disclosures [Abstract]

Summary of Financial Instruments Measured at Fair Value on a Recurring Basis

The following tables set forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy as of September 30, 2024 and December 31, 2023:


	September 30, 2024
(in thousands)	Level 1		Level 2		Level 3		Total
Money market funds	$	108,739	$	—	$	—	$	108,739
U.S. government agency bonds		—		81,714		—		81,714
U.S. treasury bonds		343,054		—		—		343,054
Corporate debt securities		—		100,395		—		100,395
Totals	$	451,793	$	182,109	$	—	$	633,902


	December 31, 2023
(in thousands)	Level 1		Level 2		Level 3		Total
Money market funds	$	228,406	$	—	$	—	$	228,406
U.S. government agency bonds		—		193,076		—		193,076
U.S. treasury bonds		103,597		—		—		103,597
Corporate debt securities		—		84,605		—		84,605
Totals	$	332,003	$	277,681	$	—	$	609,684

Summary of Amortized Cost, Fair Value, and Unrealized Losses by Type of Security

The following table presents the amortized cost, fair value, and unrealized gains and losses by major security type, for the fixed income securities held by the Company:


	September 30, 2024
(in thousands)	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
U.S. government agency bonds	$	81,478	$	251	$	(15	)	$	81,714
U.S. treasury bonds		341,655		1,446		(46	)		343,055
Corporate debt securities		100,114		281		—			100,395
Totals	$	523,247	$	1,978	$	(61	)	$	525,164


	December 31, 2023
(in thousands)	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
U.S. government agency bonds	$	193,231	$	90	$	(245	)	$	193,076
U.S. treasury bonds		103,476		156		(35	)		103,597
Corporate debt securities		84,536		114		(45	)		84,605
Totals	$	381,243	$	360	$	(325	)	$	381,278

Schedule of Investments Classified by Contractual Maturity Date

The following table presents the amortized cost and fair value of the Company's fixed income securities by maturity grouping as of September 30, 2024.


	September 30, 2024
(in thousands)	Amortized cost		Fair value
Due in one year or less	$	364,097	$	364,966
Due after one year through five years		159,150		160,198
Due after five years through ten years		—		—
Due after ten years		—		—
Total	$	523,247	$	525,164


	December 31, 2023
(in thousands)	Amortized cost		Fair value
Due in one year or less	$	281,035	$	280,739
Due after one year through five years		100,208		100,539
Due after five years through ten years		—		—
Due after ten years		—		—
Total	$	381,243	$	381,278

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-9

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

+ Details

Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Amortized cost of short-term investments	$ 364,097	$ 364,097
Amortized cost of long-term investments	$ 159,150	$ 159,150
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	36,527,470	35,838,080
Common stock, shares outstanding	36,527,470	35,838,080

Commitments and Contingencies -Schedule Of Cash Flow And Other Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Operating lease liabilities arising from obtaining right-of-use assets (non-cash)	$ 150	$ 723	$ 385	$ 1,782
Operating cash flows used in operating leases	$ 380	$ 316	$ 1,148	$ 865

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Revenue:
License and collaboration revenue	$ 0	$ 0	$ 35,000	$ 12,595
Total revenue	0	0	35,000	12,595
Operating expenses:
Research and development expenses	36,686	30,638	107,924	85,523
General and administrative expenses	12,112	12,642	37,272	38,027
Total operating expenses	48,798	43,280	145,196	123,550
Loss from operations	(48,798)	(43,280)	(110,196)	(110,955)
Other income and expenses:
Grant income	631	631	2,103	2,165
Research and development tax credits	172	417	1,867	1,146
Interest income	8,010	8,039	23,213	23,932
Other (expense) income, net	(3,130)	771	(972)	2,870
Loss before income tax expense	(43,115)	(33,422)	(83,985)	(80,842)
Income tax expense	(2,243)	1,181	(6,717)	(1,249)
Net loss	$ (45,358)	$ (32,241)	$ (90,702)	$ (82,091)
Basic net loss per share	$ (1.05)	$ (0.9)	$ (2.29)	$ (2.3)
Diluted net loss per share	$ (1.05)	$ (0.9)	$ (2.29)	$ (2.3)
Weighted-average common shares outstanding - basic	43,135,464	35,783,160	39,572,673	35,756,295
Weighted-average common shares outstanding - diluted	43,135,464	35,783,160	39,572,673	35,756,295
Net Income (Loss)	$ (45,358)	$ (32,241)	$ (90,702)	$ (82,091)
Foreign currency translation adjustments	2,808	(736)	392	(2,638)
Unrealized gain (loss) on available-for-sale securities	2,785	646	1,881	(975)
Comprehensive loss	$ (39,765)	$ (32,331)	$ (88,429)	$ (85,704)

Income Taxes - Schedule of Income (Loss) Before Income Taxes, Income Tax Benefit (Expense) and Effective Income Tax Rates (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Income Tax Disclosure [Abstract]
Domestic	$ (16,882)	$ (20,393)	$ (59,690)	$ (56,577)
Foreign	(26,233)	(13,029)	(24,295)	(24,265)
Loss before income tax expense	(43,115)	(33,422)	(83,985)	(80,842)
Income tax expense	$ (2,243)	$ 1,181	$ (6,717)	$ (1,249)
Effective tax rate	(5.20%)	3.50%	(8.00%)	(1.50%)

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 48
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-48

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-30

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 270
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (ee)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 7: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(11))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-31

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 235
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477314/942-235-S99-1

Reference 11: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(10))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(15))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

+ Details

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (ee)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 231
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482663/740-10-55-231

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-9

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.7)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-8

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-10

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(9))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Subparagraph (a)
-SubTopic 20
-Topic 740
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482659/740-20-45-2

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h))
-SubTopic 10
-Topic 235
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

+ Details

Investment Securities and Fair Value Measurements - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers within hierarchy	$ 0	$ 0	$ 0	$ 0
Accretion on its available-for-sale debt securities	3,000,000	2,700,000	8,600,000	8,100,000
Interest Income [Member] \| Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available-for-sale securities, Estimated Fair Value	$ 5,000,000	$ 5,400,000	$ 14,600,000	$ 15,900,000

Supplemental Balance Sheet Information - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Payables and Accruals [Abstract]
Accrued professional and other fees	$ 943	$ 102
Total accrued expenses and other current liabilities	$ 943	$ 102

Commitments and Contingencies - Schedule Of Lease Terms And Discount Rate (Details)	Sep. 30, 2024	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Weighted-average remaining lease term (years)	4 years	4 years 7 months 6 days
Weighted-average discount rate	4.74%	4.75%

Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2024	Nov. 30, 2024
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Document Quarterly Report	true
Document Transition Report	false
Trading Symbol	ITOS
Entity Registrant Name	iTeos Therapeutics, Inc.
Entity Central Index Key	0001808865
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Incorporation, State or Country Code	DE
Entity Shell Company	false
Entity File Number	001-39401
Entity Tax Identification Number	84-3365066
Entity Address Address Line1	321 Arsenal St
Entity Address City Or Town	Watertown
Entity Address State Or Province	MA
Entity Address Postal Zip Code	02472
City Area Code	339
Local Phone Number	217 0162
Entity Common Stock Shares Outstanding		36,533,918
Security12b Title	Common stock, $0.001 par value per share
Security Exchange Name	NASDAQ

Net loss per share attributable to common stock

9 Months Ended

Sep. 30, 2024

Earnings Per Share [Abstract]

Net loss per share attributable to common stock

Note 12. Net loss per share attributable to common stock

The Company granted certain stock options under the 2019 Plan, and currently grants certain stock options under the 2020 Plan, which are considered common stock equivalents. Unvested restricted stock units granted under the 2020 Plan are also considered common stock equivalents. The Company uses the treasury stock method to calculate weighted-average diluted shares outstanding. For the periods ending September 30, 2024 and September 30, 2023, the common stock equivalents were excluded from the calculation of net loss per share due to their anti-dilutive effect.

The following table summarizes the impact of the treasury stock method:


Net loss per share	Three Months Ended September 30,						Nine Months Ended September 30,
(in thousands, except per share amounts)	2024			2023			2024			2023
Numerator
Net loss attributable to common stockholders	$	(45,358	)	$	(32,241	)	$	(90,702	)	$	(82,091	)
Denominator
Weighted-average shares used in compute net loss per share, basic		43,135,464			35,783,160			39,572,673			35,756,295
Effect of dilutive securities (a)		—			—			—			—
Weighted-average shares used to compute net loss per share, diluted		43,135,464			35,783,160			39,572,673			35,756,295
Net loss per share:
Basic	$	(1.05	)	$	(0.90	)	$	(2.29	)	$	(2.30	)
Diluted	$	(1.05	)	$	(0.90	)	$	(2.29	)	$	(2.30	)

In accordance with ASC 260, Earnings Per Share, the shares of common stock underlying the pre-funded warrants are considered shares issuable for little or no cash consideration, and are therefore included in the calculation of basic net loss per share in the above table.

Stock-based Compensation

9 Months Ended

Sep. 30, 2024

Share-Based Payment Arrangement [Abstract]

Stock-based compensation

Note 8. Stock-based compensation

General

Stock options expire seven to 10 years from the date of grant. Generally, the exercise price of all stock options will be equal to the closing market price on The Nasdaq Global Market of one share of the Company’s common stock on the date of grant, or if no closing price is reported for such date, the closing price on the next immediately preceding date for which a closing price is reported. The stock options generally vest 25% upon the one-year anniversary of the service inception date and then ratably each month over the remaining 36 months. Upon termination of service, any unvested stock options are automatically returned to Company. Vested stock options that are not exercised within the specified period, according to the terms and conditions of the option plan, following the termination as an employee, consultant, or service provider to the Company are surrendered back to the Company. Those stock options are added back to the pool and made available for future grants.

2019 Stock Option and Grant Plan

The Company’s 2019 Stock Option and Grant Plan (the "2019 Plan") provided for the Company to grant stock options and other stock-based awards to employees and non-employees to purchase the Company’s common stock. Total authorized options under the 2019 Stock Option and Grant Plan is 3,464,316. The 2020 Plan (as defined below) replaced the 2019 Plan and no further issuances will be made under the 2019 Plan. However, the 2019 Plan continues to govern outstanding equity awards granted thereunder.

On July 15, 2020, the Company’s board of directors approved an amendment to stock options outstanding under the 2019 Stock Option and Grant Plan to provide for immediate 100% vesting for all outstanding options under the plan upon the consummation of a Sale Event, as defined by the amendment.

2020 Stock Option and Incentive Plan

The 2020 Stock Option and Incentive Plan (the "2020 Plan") was approved by the Company's board of directors on July 15, 2020, and the Company’s stockholders on July 20, 2020 and became effective on July 22, 2020. On April 21, 2022, our board of directors adopted an amendment to the 2020 Plan, the amended and restated 2020 Stock Option and Incentive Plan (the "Amended 2020 Plan") to increase the limit on total annual compensation (equity and cash) to non-employee directors. The Amended 2020 Plan was approved by the Company's stockholders and became effective on June 9, 2022. The Amended 2020 Plan provides for the grant of incentive stock options, non-qualified stock options, stock appreciation rights, restricted stock units, restricted stock awards, unrestricted stock awards, cash-based awards and dividend equivalent rights to the Company’s officers, employees, directors and consultants. The number of shares of common stock reserved for issuance as of December 31, 2023 under the Amended 2020 Plan was 9,115,915 and will be increased each January 1 by 5% of the number of shares of the Company’s common stock outstanding on the immediately preceding December 31 or such lesser number of shares as determined by the compensation committee of the Company's board of directors. Accordingly, on January 1, 2024, the number of shares of common stock reserved and available for issuance under the Amended 2020 Plan increased by 1,791,904. The number of shares of common stock reserved for issuance as of September 30, 2024 under the Amended 2020 Plan was 11,624,288, which includes the impact of exercises of stock options to purchase shares of common stock out of and cancellations of stock options to purchase shares of common stock added back into this reserve to date.

Employee Stock Purchase Plan

The 2020 Employee Stock Purchase Plan (the "2020 ESPP") was approved by the Company's board of directors on July 15, 2020, and the Company’s stockholders on July 20, 2020, and became effective on July 22, 2020. The number of shares of common stock reserved for issuance as of September 30, 2024 under the 2020 ESPP was 580,443. The ESPP provides that the number of shares reserved and available for issuance will automatically increase each January 1 thereafter by the lesser of 634,969 shares of common stock, 1% of the outstanding number of shares of common stock on the immediately preceding December 31, or such lesser number of shares as determined by the Company’s compensation committee. There was no increase to the number of shares of common stock reserved and available for issuance under the 2020 ESPP on January 1, 2024. There were 32,199 shares issued under the 2020 ESPP during the three and nine months ended September 30, 2024. The purchase price of the stock is equal to 85% of the lesser of the market value of such shares at either first date of the offering period or the last date of the offering period. The estimated fair value of the purchase options for the offering period that was open as of the end of the three and nine months ended

September 30, 2024 was $6.45 per share. The assumptions utilized to estimate the fair value are included in the assumption table below.

Stock-Based Compensation Expense

Stock-based compensation expense is classified in the condensed consolidated statements of operations and comprehensive loss as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2024		2023		2024		2023
Research and development	$	2,622	$	1,809	$	6,902	$	4,694
General and administrative		4,921		5,248		15,966		15,134
Total stock-based compensation expense	$	7,543	$	7,057	$	22,868	$	19,828

Of the $7.5 million and $22.9 million of stock-based compensation expense recognized during the three and nine months ended September 30, 2024, $6.5 million and $20.1 million related to stock options, respectively, $0.9 million and $2.5 million related to restricted stock units, respectively, and $0.1 million and $0.2 million related to ESPP awards, respectively. Of the $7.1 million and $19.8 million of stock-based compensation expense recognized during the three and nine months ended September 30, 2023, $6.8 million and $19.1 million related to stock options, respectively, $0.2 million and $0.6 million related to restricted stock units, respectively, and $0.1 million related to ESPP awards in both periods.

Stock Options

The following table summarizes stock option activity for the nine months ended September 30, 2024:


	Stock Options
	Shares			Weighted average exercise price		Weighted average remaining contractual life (in years)		Aggregate intrinsic value (in thousands)
Outstanding as of December 31, 2023		8,270,220		$	17.73	6.5
Granted		2,582,470			12.93
Forfeited		(482,899	)		29.32
Exercised		(412,459	)		5.33
Outstanding as of September 30, 2024		9,957,332		$	16.43		7.2	$	11,979
Exercisable at September 30, 2024		5,645,152		$	16.79		5.9	$	11,902

The weighted-average grant-date fair value of options awarded during the nine months ended September 30, 2024 and 2023 was $9.26 per share and $12.35 per share, respectively. As of September 30, 2024, there was a total of $45.8 million of unrecognized employee compensation costs related to non-vested stock option awards expected to be recognized over a weighted average period of 2.5 years.

The Company estimates the fair value of stock-based compensation utilizing the Black-Scholes option pricing model, which is dependent upon several variables, such as expected term, volatility, risk-free interest rate, and expected dividends. Each of these inputs is subjective and generally requires significant judgment to determine.

The following table summarizes the range of key assumptions used to determine the fair value of stock options granted during:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2024			2023			2024			2023
Stock Options:
Risk-free interest rate	3.69% - 4.45%			4.11% - 4.20%			3.69% - 4.64%			3.46% - 4.22%
Expected term (in years)		6			6		5.5 - 6			5.5 - 6
Expected volatility	76% - 82%				82	%	76% - 84%			82% - 96%
Expected dividend yield		0	%	0%				0	%	0%
Estimated fair value of common stock	$15.01 - $17.46			$13.36 - $13.81			$10.21 - $17.46			$13.36 - $21.15
ESPP Awards:
Risk-free interest rate	-				5.44	%		5.39	%		5.44	%
Expected term (in years)	-				0.5			0.5			0.5
Expected volatility	-				95	%		80	%		95	%
Expected dividend yield	-				0	%		0	%		0	%
Estimated fair value of common stock	-			$15.85			$16.98			$15.85

Restricted Stock Units

The Company issued restricted stock units during the nine months ended September 30, 2024, which vest over a four-year period. The following table summarizes the Company’s restricted stock unit activity:


	Shares			Weighted average grant date fair value
Unvested as of December 31, 2023		517,625		$	11.81
Issued		289,965			11.58
Vested		(1,875	)		35.86
Cancelled		(15,000	)		19.44
Unvested as of September 30, 2024		790,715		$	11.53

As of September 30, 2024, there was $5.8 million of unrecognized stock-based compensation expense related to restricted stock units that are expected to vest. These costs are expected to be recognized over a weighted-average period of 2.3 years.

Supplemental Balance Sheet Information (Tables)

9 Months Ended

Sep. 30, 2024

Supplemental Balance Sheet Information [Abstract]

Schedule of Property and Equipment, Net

Property and equipment, net consisted of the following:


(in thousands)	September 30, 2024			December 31, 2023
Scientific equipment	$	4,719		$	3,434
Furniture & office equipment		1,259			1,467
Leasehold improvements & assets under construction		4,348			4,177
Total		10,326			9,078
Accumulated depreciation and amortization		(4,954	)		(4,382	)
Property & equipment, net	$	5,372		$	4,696

Schedule of Accrued Expenses and Other Current Liabilities

consisted of the following:


(in thousands)	September 30, 2024		December 31, 2023
Accrued professional and other fees		943		102
Total other accrued expenses	$	943	$	102

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ (45,358)	$ (7,128)	$ (38,216)	$ (32,241)	$ (34,300)	$ (15,551)	$ (90,702)	$ (82,091)

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-6

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-9

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 60
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476176/805-60-65-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 323
-Name Accounting Standards Codification
-Section 65
-Paragraph 2
-Subparagraph (g)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478666/740-323-65-2

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-28

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482765/220-10-50-6

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-3

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480175/815-40-65-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-8

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-4

Reference 17: http://www.xbrl.org/2003/role/exampleRef
-Topic 946
-SubTopic 830
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479168/946-830-55-10

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479105/946-220-45-7

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(18))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(9))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-09(1)(d))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-3

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 23: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 32: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-60B

Reference 33: http://www.xbrl.org/2003/role/disclosureRef
-Topic 205
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483499/205-20-50-7

Reference 34: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 35: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482790/220-10-45-1A

Reference 36: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482790/220-10-45-1B

Reference 37: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

+ Details

Commitments and Contingencies - Additional Information (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024 USD ($) m² ft²	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) m² ft²	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)	May 31, 2023 USD ($) m²	Nov. 30, 2021 USD ($)
Other Commitments [Line Items]
Land subject to leases \| m²	1,577		1,577
Right of use assets	$ 5,514,000		$ 5,514,000		$ 6,036,000
Liability	5,528,000		5,528,000
Operating leases, rent expense	400,000	$ 300,000	$ 1,200,000	$ 900,000
Extension of office lease			In January 2021, the Company entered into an amendment to extend the lease, effective February 2021 with a termination date of January 2030, and increase the office and laboratory space
Wu Xi Agreement
Other Commitments [Line Items]
Minimum commitments	0		$ 0		0
Payments for Royalties			0		0
Gosselies, Belgium
Other Commitments [Line Items]
Operating lease, Hand serving to secure lease obligation	$ 167,000		$ 167,000		131,000
Watertown Massachusetts [Member]
Other Commitments [Line Items]
Land subject to leases \| ft²	9,068		9,068
Operating lease, Letter of credit to secure lease obligation							$ 142,000
Office and Laboratory Space \| Gosselies, Belgium
Other Commitments [Line Items]
Lease commencement date			May 31, 2016
Lease expiration date			Dec. 31, 2021
Lessee, operating lease, existence of option to extend [true false]			false
Lessee, operating lease, existence of option to terminate [true false]			false
Office and Laboratory Space \| Gosselies, Belgium \| AmendmentToExtendLeaseMember
Other Commitments [Line Items]
Increase land subject to leases \| m²	201		201			453
Area of lease land \| m²						2,684
Right of use assets						$ 900,000
Liability						$ 900,000
Office and Laboratory Space \| Gosselies, Belgium \| Agreement To Extend Lease Member
Other Commitments [Line Items]
Lease commencement date			Feb. 28, 2021
Lease expiration date			Jan. 31, 2030
Increase land subject to leases \| ft²	453		453
Office \| Cambridge, Massachusetts
Other Commitments [Line Items]
Lease expiration date			Feb. 28, 2027
Office \| Watertown Massachusetts [Member]
Other Commitments [Line Items]
Lease commencement date			Nov. 30, 2021
Laboratory space \| Gosselies, Belgium
Other Commitments [Line Items]
Land subject to leases \| m²	859		859
Contract Termination
Other Commitments [Line Items]
Restructuring charges			$ 0		$ 0
Minimum
Other Commitments [Line Items]
Contractual Agreement Cancelation Notice period			30 days
Average car lease duration	48 months		48 months
Maximum
Other Commitments [Line Items]
Contractual Agreement Cancelation Notice period			60 days
Average car lease duration	60 months		60 months

Stock-based Compensation - Schedule of Fair Value Assumptions for Stock Options Granted (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate, Minimum	3.69%	4.11%	3.69%	3.46%
Risk-free interest rate, maximum	4.45%	4.20%	4.64%	4.22%
Expected term (in years)	6 years	6 years
Expected Volatility, minimum	76.00%		76.00%	82.00%
Expected Volatility, maximum	82.00%	82.00%	84.00%	96.00%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	0 years	6 months	6 months	6 months
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Estimated fair value of common stock	$ 0	$ 15.85	$ 16.98	$ 15.85
Risk-free interest rate	0.00%	5.44%	5.39%	5.44%
Expected volatility	0.00%	95.00%	80.00%	95.00%
Minimum \| Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)			5 years 6 months	5 years 6 months
Estimated fair value of common stock	$ 15.01	$ 13.36	$ 10.21	$ 13.36
Maximum \| Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)			6 years	6 years
Estimated fair value of common stock	$ 17.46	$ 13.81	$ 17.46	$ 21.15

Supplemental Balance Sheet Information - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Supplemental Balance Sheet Information [Abstract]
Depreciation and amortization	$ 300	$ 200	$ 916	$ 671

Investment Securities and Fair Value Measurements - Summary of Amortized Cost, Fair Value, and Unrealized Losses by Type of Security (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	$ 523,247	$ 381,243
Gross unrealized gains	1,978	360
Gross unrealized losses	(61)	(325)
Fair value	525,164	381,278
U.S. government agency bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	81,478	193,231
Gross unrealized gains	251	90
Gross unrealized losses	(15)	(245)
Fair value	81,714	193,076
U.S. treasury bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	341,655	103,476
Gross unrealized gains	1,446	156
Gross unrealized losses	(46)	(35)
Fair value	343,055	103,597
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	100,114	84,536
Gross unrealized gains	281	114
Gross unrealized losses	0	(45)
Fair value	$ 100,395	$ 84,605

- Definition

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

+ References

+ Details

Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 123,744	$ 251,177
Short-term investments (amortized cost of $364,097)	364,966	280,739
Grants receivable	773	0
Research and development tax credits receivable	759	135
Refundable income taxes	6,271	6,365
Milestone receivable	35,000	0
Prepaid expenses and other current assets	13,362	12,236
Total current assets	544,875	550,652
Property and equipment, net	5,372	4,696
Long-term investments (amortized cost of $159,150)	160,198	100,539
Research and development tax credits receivable, net of current portion	5,880	4,508
Restricted cash	310	274
Right of use assets	5,514	6,036
Other assets	928	883
Total assets	723,077	667,588
Current liabilities:
Accounts payable	7,154	11,293
Other accrued expenses	943	102
Accrued clinical trial costs	17,608	6,956
Accrued personnel expenses	8,306	8,562
Payable for investments	0	9,787
Deferred income	1,449	2,063
Lease liabilities	1,354	1,251
Total current liabilities	36,814	40,014
Grants repayable, net of current portion	6,267	6,609
Lease liabilities, net of current portion	4,174	4,807
Unrecognized tax benefits	44,130	40,930
Total liabilities	91,385	92,360
Commitments and contingencies (Note 10)
Stockholders’ equity:
Common stock, $0.001 par value: 150,000,000 shares authorized at September 30, 2024 and December 31, 2023; 36,527,470 and 35,838,080 shares issued and outstanding, respectively	37	36
Additional paid-in capital	608,690	463,799
Accumulated other comprehensive loss	(10,966)	(13,240)
Retained earnings	33,931	124,633
Total stockholders’ equity	631,692	575,228
Total liabilities and stockholders’ equity	$ 723,077	$ 667,588

Stock-based Compensation - Summary of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 7,543	$ 7,057	$ 22,868	$ 19,828
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	2,622	1,809	6,902	4,694
General and Administrative Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 4,921	$ 5,248	$ 15,966	$ 15,134

- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 1D
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480483/718-10-35-1D

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480483/718-10-35-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(01)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(02)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(03)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(04)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(01)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(02)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(03)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iv)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(v)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

License and Collaboration Agreements - Additional Information (Details) - USD ($)		3 Months Ended			9 Months Ended
	Jun. 11, 2021	Sep. 30, 2024	Jun. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Research And Development Arrangement Contract To Perform For Others [Line Items]
Upfront payment received					$ 625,000,000
License and collaboration revenue		$ 0		$ 0	35,000,000	$ 12,595,000
Accounts payable		7,154,000			7,154,000		$ 11,293,000
Accrued clinical trial costs		17,608,000			17,608,000		6,956,000
Increase (Decrease) in Commodity Contract Assets and Liabilities					0
Adimab L L C
Research And Development Arrangement Contract To Perform For Others [Line Items]
Maximum additional receivable based on achievement of research milestones					14,500,000
Adimab L L C \| License revenue
Research And Development Arrangement Contract To Perform For Others [Line Items]
Additional Milestone Payment Accrued 1			$ 1,000,000		4,000,000
Amount of development milestone		3,000,000			3,000,000
License agreement milestone payments paid					9,400,000
Adimab L L C \| Development Regulatory and Sales Milestone
Research And Development Arrangement Contract To Perform For Others [Line Items]
Maximum option fees receivable based on achievement of research milestones		45,800,000			45,800,000
GSK
Research And Development Arrangement Contract To Perform For Others [Line Items]
Upfront payment received	$ 625,000,000
Milestone payments	$ 1,450,000,000
Eligible royalty payments percentage	20.00%
Accrued expenses and other current liabilities		9,500,000			9,500,000
Accounts payable		3,000,000			3,000,000
Accrued clinical trial costs		6,500,000			6,500,000
Deferred Revenue		0			0		$ 0
Costs related to the cost-sharing provisions		$ 11,400,000			$ 34,200,000
Costs related to global development plan					60.00%
GSK \| License revenue
Research And Development Arrangement Contract To Perform For Others [Line Items]
License and collaboration revenue			$ 35,000,000		$ 35,000,000	$ 12,600,000
Related Party \| GSK
Research And Development Arrangement Contract To Perform For Others [Line Items]
Operating Costs And Expenses					$ 900,000,000

Stock-based Compensation - Schedule of Restricted Stock Unit Activity (Details) - Restricted Stock Units	9 Months Ended
	Sep. 30, 2024 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested as of December 31, 2023, Shares \| shares	517,625
Issued, Shares \| shares	289,965
Vested, Shares \| shares	(1,875)
Cancelled, Shares \| shares	(15,000)
Unvested as of September 30, 2024 \| shares	790,715
Unvested as of December 31, 2023, Weighted average grant date fair value \| $ / shares	$ 11.81
Issued, Weighted average grant date fair value \| $ / shares	11.58
Vested, Weighted average grant date fair value \| $ / shares	35.86
Cancelled, Weighted average grant date fair value \| $ / shares	19.44
Unvested as of September 30, 2024, Weighted average grant date fair value \| $ / shares	$ 11.53

License and Collaboration Agreements

9 Months Ended

Sep. 30, 2024

License Agreements [Abstract]

License and collaboration agreements

Note 5. License and collaboration agreements

Adimab

In January 2017, the Company entered into a collaboration agreement (as amended, the "Adimab Agreement") with Adimab, LLC ("Adimab"). Adimab has developed an antibody discovery and optimization technology platform. This collaboration enables the Company’s research and development efforts on discovery and optimization of new antibodies against immuno-oncology targets the Company may identify.

Under the terms of the Adimab Agreement, Adimab has granted the Company a worldwide, non-exclusive research license for a one-year research term period and evaluation period for up to 18 months per research program. The Company is required to use commercially reasonable efforts to perform its research activities under the Adimab Agreement and, if the Company exercises its right to obtain a development and commercialization license, the Company is required to use commercially reasonable efforts to pursue development and commercialization of a product directed to the applicable target. Under the terms of the Adimab Agreement, the Company granted Adimab a worldwide, non-exclusive license under all of its patents and know-how that are reasonably necessary or useful for Adimab to perform its research activities under the Adimab Agreement.

In February 2021, the Company entered into an amendment to the Adimab Agreement (the "Amended Adimab Agreement"). The Amended Adimab Agreement specifies different milestone payments for new products that are derived from research programs beginning after February 22, 2021 (the "New Products"). For New Products, on a per target basis, the Company may be required to pay development, regulatory and commercial milestone payments totaling up to an aggregate of $45.8 million for the first three products and additional milestone payments up to $14.5 million for each additional product.

The Company will pay Adimab low to mid single-digit percentage royalties on a country-by-country and product-by-product basis, on worldwide net product sales of licensed products. Royalties are payable on a licensed product-by-licensed product and country-by-country basis until the later of (i) expiration of the last valid claim of a licensed patent

right that covers such licensed product in such country, and (ii) ten years following the first commercial sale of such licensed product in such country.

Through September 30, 2024, the Company has paid a total of $9.4 million to Adimab relating to milestones under the Adimab Agreement. The Company made a $1.0 million payment to Adimab in the first quarter of 2024 relating to a milestone that occurred during the fourth quarter of 2023. The Company also made a $3.0 million payment in the three months ended September 30, 2024 in connection with a development milestone that occurred early in the third quarter of 2024. The Company paid a total of $4.0 million in the nine months ended September 30, 2024 relating to milestones that occurred under the Adimab Agreement. As of the date of these condensed consolidated financial statements, the Company has not pursued any additional targets under the Adimab agreement that could potentially result in such milestone payments.

Adimab controls the filing, prosecution, maintenance and enforcement of the intellectual property that it licenses to the Company under the Adimab Agreement. The Company has the right to enforce such licensed intellectual property against infringement if the infringement is competitive with the Company’s licensed products and Adimab does not pursue enforcement. The Company controls the filing, prosecution, maintenance and enforcement of the intellectual property the Company licenses to Adimab under the Adimab Agreement and all program antibody patents.

The term of the Adimab Agreement will continue until the last to expire royalty term on a product-by-product and country-by-country basis if the Company exercises its option, or in the event no option is exercised, the conclusion of the last-to-expire evaluation term, unless terminated earlier by either party. Each party has the right to terminate the Adimab Agreement due to the other party’s uncured material breach or the Company’s abandonment of the product.

GlaxoSmithKline ("GSK")

Summary of Agreement

On June 11, 2021, the Company’s wholly owned subsidiary, iTeos Belgium S.A., and GSK executed a Collaboration and License Agreement (the "GSK Collaboration Agreement"), pursuant to which the Company agreed to grant GSK a license under certain of the Company’s intellectual property rights to develop, manufacture, and commercialize products comprised of or containing the Company’s antibody product, belrestotug. Under the GSK Collaboration Agreement, GSK agreed to make an upfront nonrefundable payment of $625.0 million to the Company within 10 business days of the date on which the GSK Collaboration Agreement became effective, which occurred on July 26, 2021. Additionally, the Company is eligible to receive up to $1.45 billion in milestone payments, contingent upon the belrestotug program achieving certain development and commercial milestones. Within the collaboration, GSK and the Company agree to share responsibility and costs for the global development of belrestotug beyond the Phase 1 study (the "Global Development Plan") and will jointly commercialize and equally split profits in the United States. Outside of the United States, GSK will receive an exclusive license for commercialization, and the Company is eligible to receive tiered double digit royalty payments up to 20% during a customary royalty term.

Collaboration

The Company concluded that the GSK Collaboration Agreement is under the scope of ASC 808 as both parties will actively participate in a joint operating activity and are exposed to significant risks and rewards that depend on the activity’s commercial success. ASC 808 provides that certain transactions between collaborative arrangement participants should be accounted for as revenue under ASC 606 when the collaborative arrangement participant is a customer in the context of a unit of account. In those situations, all of the guidance in ASC 606 should be applied, including recognition, measurement, presentation, and disclosure requirements related to such unit of account. The unit-of-account guidance in ASC 808, which aligns with the guidance in ASC 606 (that is, a distinct good or service) is used when an entity is assessing whether the collaborative arrangement or a part of the arrangement is within the scope of ASC 606.

The Company determined that the co-development in Phases 2 and 3 and the co-commercialization efforts of the GSK Collaboration Agreement represent joint operating activities in which both parties are active participants and of which both parties are exposed to significant risks and rewards that are dependent on the success of the activities. Accordingly, the Company is accounting for these activities in accordance with ASC No. 808, Collaborative Arrangements (ASC 808). Additionally, the Company has determined that in the context of these activities, GSK does not represent a customer as contemplated by ASC 606-10-15, Revenue from Contracts with Customers – Scope and Scope Exceptions. As a result, these activities are accounted for as a component of the related expense in the period incurred in accordance with ASC 730, Research and Development. Additionally, reimbursements received from GSK in connection with the joint operating activities are recognized as a reduction to research and development expense.

GSK is responsible for 60% of the costs related to the Global Development Plan. During the three and nine months ended September 30, 2024, the Company recorded to research and development expense $11.4 million and $34.2 million related to the cost-sharing provisions of the GSK Collaboration Agreement. $9.5 million of these costs are payable to

GSK; $3.0 million of which is recorded in accounts payable and $6.5 million of which is recorded in accrued clinical trial costs in the condensed consolidated balance sheet as of September 30, 2024. The Company and GSK have collectively agreed to spend an aggregate of $900.0 million on the Global Development Plan.

Revenue Recognition

The Company also evaluated the elements of the GSK Collaboration Agreement in accordance with the provisions of ASC 606 and concluded that the contract counterparty, GSK, is a customer. The Company’s arrangement with GSK contains the following material promises under the contract at inception: (i) transfer of the license under certain of the Company’s intellectual property related to belrestotug, (ii) completion of the Phase 1 clinical study related to belrestotug, (iii) transfer of “Know How” under the belrestotug intellectual property, and (iv) manufacturing until the “Know How” transfer is complete. The Company evaluated the above material promises under ASC 606 and determined that it has one combined performance obligation. These promises are considered to be outputs of the Company's ordinary activities and ongoing major operations. As GSK provided the Company consideration in exchange for these promises, GSK meets the definition of a customer under ASC 606-10-20 in the context of the combined performance obligation. These promises are distinct from the co-development and co-commercialization activities in which the Company and GSK jointly participate. Accordingly, the context in which GSK is a customer is limited to the material promises described above.

The transaction price totaling $625.0 million was comprised of the upfront license payment. As of September 30, 2024, no development or regulatory milestones have been assessed as probable of being reached and thus have been fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of the milestones is outside the control of the Company and contingent upon success in future clinical trials and the licensee’s efforts. Any consideration related to sales-based milestones will be recognized when the related sales occur as they were determined to relate predominantly to the license granted to GSK and therefore have also been excluded from the transaction price. The Company is applying the royalty exception for sales-based royalties and will not recognize revenue until the subsequent sale of product occurs.

The transaction price is being recognized as revenue over time as the costs to complete the Phase 1 study, perform interim clinical supply manufacturing, and perform the know-how transfer are incurred. The performance obligation was fully completed in the three months ended March 31, 2023. Revenue was recognized using a percent complete method based on costs incurred compared with the total expected costs to be incurred (cost to cost measure of progress). There were no outputs from the performance obligation. As a result, an input method was appropriate. A cost-to-cost measure of progress provides a faithful depiction of the transfer of services to the customer since the predominant inputs to the performance obligation were labor costs, research and development supplies and manufacturing supplies related to the Phase 1 Study, clinical manufacturing and know-how transfer.

The Company recognized $35.0 million of revenue during the nine months ended September 30, 2024, relating to the dosing of the first patient in the Phase 3 study for GALAXIES-301 in collaboration with GSK. The Company determined as of the quarter ended June 30, 2024 that the milestone that triggered a $35.0 million payment from GSK was probable to occur, and the Company therefore deemed it probable that there would not be a significant reversal of the related revenue recorded in the quarter ended June 30, 2024. The dosing occurred in early July 2024. The entirety of the milestone payment was recognized as revenue at once because the one combined performance obligation identified within the GSK contract had been fully satisfied in the first quarter of 2023. During the nine months ended September 30, 2023, the Company recognized the remaining revenue relating to the upfront payment totaling $12.6 million with respect to the GSK Collaboration Agreement. The revenue was classified as license and collaboration revenue in the accompanying condensed consolidated statements of operations. There was no deferred revenue remaining as of September 30, 2024 or December 31, 2023.

Contract Assets and Liabilities

There were no remaining contract assets or liabilities as of the period ended September 30, 2024.

MSD International GmbH

On December 10, 2019, the Company entered into a Clinical Trial Collaboration and Supply Agreement (the "MSD Agreement") with MSD International GmbH ("MSD"), a subsidiary of Merck & Co., Inc. Under the MSD Agreement, the Company sponsors a clinical trial in which both the Company’s compound and MSD’s compound are dosed in combination. The Company conducts the research at its own cost and MSD contributes its compound towards the study at no cost to the Company. The parties equally own the clinical data and inventions from the study, with the exception of inventions relating solely to each party’s compound class. The MSD Agreement will expire upon the delivery of a written report on the results of the study, unless earlier terminated or agreed by the parties.

The Company began receiving compounds from MSD on April 1, 2020 and the Company began the research study in the third quarter of 2020. The terms of the MSD Agreement meet the criteria under ASC 808, as both parties are active participants in the activity and are exposed to the risks and rewards dependent on the commercial success of the activity. ASC 808 does not provide guidance on how to account for the activities under the collaboration, and the Company determined that neither party met the definition of a customer under ASC 606, Revenue from Contracts with Customers. Accordingly, the Company considered other guidance to determine the accounting for the respective elements of the arrangement. The Company accounted for the collaboration activities by analogy to ASC Topic 845, Nonmonetary Transactions, and recognized nonmonetary income with an offsetting entry to expense for amounts received from MSD within research and development expense in the condensed consolidated statement of operations and comprehensive loss.

Commitments and Contingencies - Schedule of Future Minimum Lease Payments Under Non-cancelable Operating Leases (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Leases [Abstract]
2024	$ 395
2025	1,581
2026	1,543
2027	1,039
2028	852
Thereafter	628
Total lease payments	6,038
Less: interest	(510)
Total lease liability	5,528
Lease liabilities, current	1,354	$ 1,251
Lease liabilities, net of current portion	$ 4,174	$ 4,807

Income Taxes (Tables)

9 Months Ended

Sep. 30, 2024

Income Tax Disclosure [Abstract]

Schedule of Income (Loss) Before Income Taxes, Income Tax Benefit (Expense) and Effective Income Tax Rates

The following table presents the loss before income taxes, income tax expense and effective income tax rates for all periods presented:


(Loss) income before income tax expense	Three Months Ended September 30,						Nine Months Ended September 30,
(in thousands)	2024			2023			2024			2023
Domestic		(16,882	)		(20,393	)		(59,690	)		(56,577	)
Foreign		(26,233	)		(13,029	)		(24,295	)		(24,265	)
Loss before income tax expense		(43,115	)		(33,422	)		(83,985	)		(80,842	)
Income tax expense		(2,243	)		1,181			(6,717	)		(1,249	)
Effective tax rate	(5.2)%			3.5%			(8.0)%			(1.5)%

Government Grant Funding and Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs) - Additional Information (Details) - USD ($) $ in Thousands			3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 03, 2019	Jul. 20, 2017	Sep. 30, 2024	Sep. 30, 2024	Dec. 31, 2023	Dec. 31, 2021	Sep. 30, 2023
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research and development expenses				$ 11,900
Percentage of royalty on revenue				30.00%		0.12%
Repayment of grants			$ 200	$ 200
Grant repayable			6,686	6,686			$ 6,813
Accrued Expenses and Other Current Liabilities
Research And Development Arrangement Contract To Perform For Others [Line Items]
Grant repayable			400	$ 400	$ 200
RCA-1
Research And Development Arrangement Contract To Perform For Others [Line Items]
Recoverable cash advance		$ 21,100
Percentage of royalty on revenue				0.33%
Grant repayable			5,392	$ 5,392			5,496
RCA-2
Research And Development Arrangement Contract To Perform For Others [Line Items]
Recoverable cash advance	$ 4,800
Percentage of royalty on revenue				0.15%
Grant repayable			1,294	$ 1,294			$ 1,317
Royalty accruals				$ 900	800
RCA-1 and RCA-2
Research And Development Arrangement Contract To Perform For Others [Line Items]
Percentage of repayment amount received under grant				30.00%
Research And Development And Future Sales
Research And Development Arrangement Contract To Perform For Others [Line Items]
Grant repayable			$ 0	$ 0	$ 0
Minimum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Percentage of grant reimburse of actual qualifying expenditures				55.00%
Minimum \| RCA-1 and RCA-2
Research And Development Arrangement Contract To Perform For Others [Line Items]
Term of repayment amount received under grant				2023
Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Percentage of grant reimburse of actual qualifying expenditures				100.00%
Maximum \| RCA-1 and RCA-2
Research And Development Arrangement Contract To Perform For Others [Line Items]
Term of repayment amount received under grant				2042

Government Grant Funding and Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs) - Schedule of Activity for Grant Programs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cash received			$ 777	$ 3,542
Grant income	$ 631	$ 631	2,103	2,165
Grants receivable	773	0	773	0	$ 0
Grant repayable	6,686	6,813	6,686	6,813
RCA-1
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cash received				0
Grant income			17	0
Grants receivable		0		0
Grant repayable	5,392	5,496	5,392	5,496
RCA-2
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cash received				0
Grant income				0
Grant repayable	1,294	1,317	1,294	1,317
Other Grants
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cash received			777	3,542
Grant income			2,086	2,165
Grants receivable	$ 773	$ 0	$ 773	$ 0

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Sep. 30, 2024 shares
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	During the three months ended September 30, 2024, one of our officers and directors terminated a “Rule 10b5-1 trading arrangement”, as defined in Item 408(a) of Regulation S-K, and subsequently adopted a Rule 10b5-1 trading arrangement. We describe the material terms of these trading arrangements below. On July 16, 2024, Michel Detheux, our President and Chief Executive Officer and a member of our board of directors, terminated a Rule 10b5-1 trading plan that he had originally adopted on March 11, 2024. The plan was for the sale of up to an aggregate of 294,464 shares of our common stock. Sales of shares under the plan were scheduled to occur from June 10, 2024 through the termination of plan on June 7, 2025. On July 16, 2024, Dr. Detheux and MG3A, a Belgian partnership of which Dr. Detheux is the manager, entered into a Rule 10b5-1 trading plan that provides that Dr. Detheux and MG3A, each acting through a broker, may sell up to an aggregate of 294,464 shares of our common stock and 313,442 shares of our common stock, respectively, in each case subject to adjustments for any stock split, reverse stock split, stock dividend or change in our capitalization. Sales of shares under the plan may only occur from November 15, 2024 through the termination of the plan on October 15, 2025, subject to earlier termination upon the sale of all shares subject to the plan, upon termination by Dr. Detheux and MG3A or the broker, or as otherwise provided in the plan.
Michel Detheux
Trading Arrangements, by Individual
Name	Michel Detheux
Title	President and Chief Executive Officer
Rule 10b5-1 Arrangement Terminated	true
Termination Date	July 16, 2024
Aggregate Available	294,464
Dr. Detheux and MG3A
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	July 16, 2024
Rule 10b5-1 Arrangement Terminated	true
Termination Date	October 15, 2025
Arrangement Duration	334 days
MG3A
Trading Arrangements, by Individual
Aggregate Available	313,442

Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2024

Share-Based Payment Arrangement [Abstract]

Summary of Stock-Based Compensation Expense

Stock-based compensation expense is classified in the condensed consolidated statements of operations and comprehensive loss as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2024		2023		2024		2023
Research and development	$	2,622	$	1,809	$	6,902	$	4,694
General and administrative		4,921		5,248		15,966		15,134
Total stock-based compensation expense	$	7,543	$	7,057	$	22,868	$	19,828

Summary of Stock Options Activity

The following table summarizes stock option activity for the nine months ended September 30, 2024:


	Stock Options
	Shares			Weighted average exercise price		Weighted average remaining contractual life (in years)		Aggregate intrinsic value (in thousands)
Outstanding as of December 31, 2023		8,270,220		$	17.73	6.5
Granted		2,582,470			12.93
Forfeited		(482,899	)		29.32
Exercised		(412,459	)		5.33
Outstanding as of September 30, 2024		9,957,332		$	16.43		7.2	$	11,979
Exercisable at September 30, 2024		5,645,152		$	16.79		5.9	$	11,902

Schedule of Fair Value Assumptions for Stock Options Granted

The following table summarizes the range of key assumptions used to determine the fair value of stock options granted during:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2024			2023			2024			2023
Stock Options:
Risk-free interest rate	3.69% - 4.45%			4.11% - 4.20%			3.69% - 4.64%			3.46% - 4.22%
Expected term (in years)		6			6		5.5 - 6			5.5 - 6
Expected volatility	76% - 82%				82	%	76% - 84%			82% - 96%
Expected dividend yield		0	%	0%				0	%	0%
Estimated fair value of common stock	$15.01 - $17.46			$13.36 - $13.81			$10.21 - $17.46			$13.36 - $21.15
ESPP Awards:
Risk-free interest rate	-				5.44	%		5.39	%		5.44	%
Expected term (in years)	-				0.5			0.5			0.5
Expected volatility	-				95	%		80	%		95	%
Expected dividend yield	-				0	%		0	%		0	%
Estimated fair value of common stock	-			$15.85			$16.98			$15.85

Schedule of Restricted Stock Unit Activity

The following table summarizes the Company’s restricted stock unit activity:


	Shares			Weighted average grant date fair value
Unvested as of December 31, 2023		517,625		$	11.81
Issued		289,965			11.58
Vested		(1,875	)		35.86
Cancelled		(15,000	)		19.44
Unvested as of September 30, 2024		790,715		$	11.53

Related Party Transactions

9 Months Ended

Sep. 30, 2024

Related Party Transactions

Note 11. Related party transactions

On June 11, 2018, the Company entered into a Royalty Transfer Agreement with the charitable foundations of two of its investors (MPM Oncology Charitable Foundation, Inc. and UBS Optimus Foundation), which requires it to pay a royalty equal to a total of 1% of its net product sales each year within 120 days following each year end. Such agreement was entered into as a result of the capital contributions received from the investors. As the Company has no product sales to date, no royalties were owed to these charitable foundations as of September 30, 2024.

Boxer Capital is considered a related party to the Company due to its Chief Executive Officer serving as a member of the Company's Board of Directors. The Company issued 1,142,857 shares of its common stock to Boxer Capital for total proceeds of $20.0 million pursuant to the SPA dated May 10, 2024.

RA Capital has historically been a related party to the Company due to its partner serving on the Company's Board of Directors and its beneficial ownership of the Company which exceeded 10%. RA Capital's partner resigned from the Company's Board of Directors effective December 5, 2023. The Company issued to RA Capital a pre-funded warrant to purchase 5,714,285 shares of its common stock for total proceeds of $100.0 million pursuant to the SPA dated May 10, 2024. On May 14, 2024, RA Capital exchanged 900,000 shares of the Company's common stock for a pre-funded warrant to purchase up to 900,000 shares of the Company's common stock. Upon the execution of the Exchange Agreement, RA Capital's beneficial ownership fell below the 10% principal owner threshold per ASC 850, Related Party Transactions.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-5

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-6

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(g)(3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(e))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/850/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-6

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

+ Details

Nature of Business and Basis of Presentation - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Net Income (Loss)	$ (45,358)	$ (7,128)	$ (38,216)	$ (32,241)	$ (34,300)	$ (15,551)	$ (90,702)	$ (82,091)
Retained earnings	$ 33,931						$ 33,931		$ 124,633

- Definition

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

+ References

+ Details

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Retained Earnings
Beginning balance at Dec. 31, 2022	$ 663,332	$ 36	$ 435,665	$ (9,644)	$ 237,275
Beginning balance (in shares) at Dec. 31, 2022		35,611,219
Stock-based compensation	5,807		5,807
Common stock issued upon exercises of options	578		578
Common stock issued upon exercises of options (in shares)		149,408
Currency translation adjustment	(2,006)			(2,006)
Unrealized gain (loss) on available-for-sale securities	102			102
Net loss	(15,551)				(15,551)
Ending balance at Mar. 31, 2023	652,262	$ 36	442,050	(11,548)	221,724
Ending balance (in shares) at Mar. 31, 2023		35,760,627
Beginning balance at Dec. 31, 2022	663,332	$ 36	435,665	(9,644)	237,275
Beginning balance (in shares) at Dec. 31, 2022		35,611,219
Net loss	(82,091)
Ending balance at Sep. 30, 2023	598,262	$ 36	456,299	(13,256)	155,183
Ending balance (in shares) at Sep. 30, 2023		35,784,958
Beginning balance at Mar. 31, 2023	652,262	$ 36	442,050	(11,548)	221,724
Beginning balance (in shares) at Mar. 31, 2023		35,760,627
Stock-based compensation	6,964		6,964
Common stock issued upon exercises of options	218		218
Common stock issued upon exercises of options (in shares)		21,292
Currency translation adjustment	104			104
Unrealized gain (loss) on available-for-sale securities	(1,722)			(1,722)
Net loss	(34,300)				(34,300)
Ending balance at Jun. 30, 2023	623,526	$ 36	449,232	(13,166)	187,424
Ending balance (in shares) at Jun. 30, 2023		35,781,919
Stock-based compensation	7,057		7,057
Common stock issued upon exercises of options, ESPP purchases, and release of restricted stock units	10		10
Common stock issued upon exercises of options, ESPP purchases, and release of restricted stock units (in shares)		3,039
Currency translation adjustment	(736)			(736)
Unrealized gain (loss) on available-for-sale securities	646			646
Net loss	(32,241)				(32,241)
Ending balance at Sep. 30, 2023	598,262	$ 36	456,299	(13,256)	155,183
Ending balance (in shares) at Sep. 30, 2023		35,784,958
Beginning balance at Dec. 31, 2023	575,228	$ 36	463,799	(13,240)	124,633
Beginning balance (in shares) at Dec. 31, 2023		35,838,080
Stock-based compensation	7,263		7,263
Common stock issued upon exercises of options	22		22
Common stock issued upon exercises of options (in shares)		5,676
Currency translation adjustment	(2,265)			(2,265)
Unrealized gain (loss) on available-for-sale securities	(832)			(832)
Net loss	(38,216)				(38,216)
Ending balance at Mar. 31, 2024	541,200	$ 36	471,084	(16,337)	86,417
Ending balance (in shares) at Mar. 31, 2024		35,843,756
Beginning balance at Dec. 31, 2023	$ 575,228	$ 36	463,799	(13,240)	124,633
Beginning balance (in shares) at Dec. 31, 2023		35,838,080
Common stock issued upon exercises of options (in shares)	412,459
Net loss	$ (90,702)
Ending balance at Sep. 30, 2024	631,692	$ 37	608,691	(10,967)	33,931
Ending balance (in shares) at Sep. 30, 2024		36,527,470
Beginning balance at Mar. 31, 2024	541,200	$ 36	471,084	(16,337)	86,417
Beginning balance (in shares) at Mar. 31, 2024		35,843,756
Stock-based compensation	8,062		8,062
Common stock issued upon exercises of options, ESPP purchases, and release of restricted stock units	2,383		2,383
Common stock issued upon exercises of options, ESPP purchases, and release of restricted stock units (in shares)		433,332
Issuance of common stock and pre-funded warrants, net of offering costs	119,574	$ 1	119,573
Issuance of common stock and pre-funded warrants, net of offering costs (in shares)		1,142,857
Exchange of common stock for pre-funded warrants (in shares)		(900,000)
Currency translation adjustment	(151)			(151)
Unrealized gain (loss) on available-for-sale securities	(72)			(72)
Net loss	(7,128)				(7,128)
Ending balance at Jun. 30, 2024	663,868	$ 37	601,102	(16,560)	79,289
Ending balance (in shares) at Jun. 30, 2024		36,519,945
Stock-based compensation	7,543		7,543
Common stock issued upon exercises of options, ESPP purchases, and release of restricted stock units	46		46
Common stock issued upon exercises of options, ESPP purchases, and release of restricted stock units (in shares)		7,525
Currency translation adjustment	2,808			2,808
Unrealized gain (loss) on available-for-sale securities	2,785			2,785
Net loss	(45,358)				(45,358)
Ending balance at Sep. 30, 2024	$ 631,692	$ 37	$ 608,691	$ (10,967)	$ 33,931
Ending balance (in shares) at Sep. 30, 2024		36,527,470

Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2024

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Note 2. Summary of significant accounting policies

The Company’s significant accounting policies are disclosed in the audited consolidated financial statements for the year ended December 31, 2023, and notes thereto, which are included in the Company’s Annual Report on Form 10-K that was filed with the SEC on March 6, 2024. Since the date of those financial statements, the Company issued pre-funded warrants to purchase up to a total of 6,614,285 shares of its common stock. The Company evaluated the pre-funded warrants under ASC 480, Distinguishing Liabilities from Equity, and determined that the pre-funded warrants did not meet the criteria for liability classification. As such, the pre-funded warrants are recorded as equity in the statement of stockholders' equity. The shares underlying the pre-funded warrants are included in the calculation of basic net loss per share because they are considered shares issuable for little or no consideration under ASC 260, Earnings Per Share. There have been no other material changes to significant accounting policies.

From time to time, new accounting pronouncements are issued that the Company adopts as of the specified effective date. The Company does not believe that the adoption of any recently issued standards have or may have a material impact on its condensed consolidated financial statements and disclosures.

Income Taxes

9 Months Ended

Sep. 30, 2024

Income Tax Disclosure [Abstract]

Income Taxes

Note 9. Income taxes

The following table presents the loss before income taxes, income tax expense and effective income tax rates for all periods presented:


(Loss) income before income tax expense	Three Months Ended September 30,						Nine Months Ended September 30,
(in thousands)	2024			2023			2024			2023
Domestic		(16,882	)		(20,393	)		(59,690	)		(56,577	)
Foreign		(26,233	)		(13,029	)		(24,295	)		(24,265	)
Loss before income tax expense		(43,115	)		(33,422	)		(83,985	)		(80,842	)
Income tax expense		(2,243	)		1,181			(6,717	)		(1,249	)
Effective tax rate	(5.2)%			3.5%			(8.0)%			(1.5)%

The Company's effective tax rates were (5.2)% and (8.0)% for the three and nine months ended September 30, 2024, respectively. They differed from the federal and foreign statutory rates of 21% and 25%, respectively, primarily due to income tax expense resulting from investment income generated by marketable investments held by iTeos LLC, which is not consolidated for U.S. income tax purposes. The Company incurred income tax expense, despite a loss before income taxes, due to taxable interest income generated by a subsidiary of iTeos Belgium which cannot be offset by the net operating losses of iTeos or iTeos Belgium. In addition, the Company recorded an additional liability of $1.1 million

and $3.2 million during the three and nine months ended September 30, 2024, respectively, related to the accrual of additional interest expense on the unrecognized tax benefits liability, all of which was included in the unrecognized tax benefits liability in the condensed consolidated balance sheet as of September 30, 2024. The Company's uncertain tax position relates to the Company’s allocation of revenue between the U.S. and Belgium under the GSK Agreement. As the uncertain tax position relates to the Company’s allocation of that revenue between the U.S. and Belgium under the GSK Agreement, the additional recognition of revenue under that agreement may increase the liability for the uncertain tax position. As of September 30, 2024, the Company had accrued interest and penalties relating to uncertain tax positions of $7.1 million, all of which was included in unrecognized tax benefits liability in the condensed consolidated balance sheet as of September 30, 2024.

The Company's effective tax rate was 3.5% for the three months ended September 30, 2023, and (1.5)% for the nine months ended September 30, 2023. The rates differed from the federal and foreign statutory rates of 21% and 25%, respectively, in the three and nine months ended September 30, 2023 primarily due to no additional revenue recognized for tax purposes in 2023 under the GSK Collaboration Agreement, which resulted in a loss before income taxes. Income tax expense resulted from the investment income generated by marketable investments held by iTeos LLC, which is not consolidated for U.S. income tax purposes.

- Definition

The entire disclosure for income tax.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 231
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482663/740-10-55-231

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12C

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12B

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477891/740-270-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-13

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/740/tableOfContent

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-14

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-21

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-17

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482603/740-30-50-2

+ Details

Investment Securities and Fair Value Measurements

9 Months Ended

Sep. 30, 2024

Fair Value Disclosures [Abstract]

Investment Securities and Fair Value Measurements

Note 3. Investment securities and fair value measurements


	September 30, 2024
(in thousands)	Level 1		Level 2		Level 3		Total
Money market funds	$	108,739	$	—	$	—	$	108,739
U.S. government agency bonds		—		81,714		—		81,714
U.S. treasury bonds		343,054		—		—		343,054
Corporate debt securities		—		100,395		—		100,395
Totals	$	451,793	$	182,109	$	—	$	633,902


	December 31, 2023
(in thousands)	Level 1		Level 2		Level 3		Total
Money market funds	$	228,406	$	—	$	—	$	228,406
U.S. government agency bonds		—		193,076		—		193,076
U.S. treasury bonds		103,597		—		—		103,597
Corporate debt securities		—		84,605		—		84,605
Totals	$	332,003	$	277,681	$	—	$	609,684

Money market funds are classified within Level 1 of the fair value hierarchy because they are valued using quoted market prices in an active market. U.S. treasury securities are also classified as Level 1 because they are valued using quoted prices. U.S. government agency and corporate securities are classified within Level 2 of the fair value hierarchy because they are valued using market-based models that consider inputs such as yield, prices of comparable securities, coupon rate, maturity, and credit quality.

During the periods presented, the Company has not changed the manner in which it values assets and liabilities that are measured at fair value. The Company recognizes transfers between levels of the fair value hierarchy as of the end of the reporting period. There were no transfers within the hierarchy during the three and nine months ended September 30, 2024 and 2023.

The Company's fixed income securities held as of September 30, 2024 and December 31, 2023 with original maturity dates beyond three months are classified as available-for-sale. The following table presents the amortized cost, fair value, and unrealized gains and losses by major security type, for the fixed income securities held by the Company:


	September 30, 2024
(in thousands)	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
U.S. government agency bonds	$	81,478	$	251	$	(15	)	$	81,714
U.S. treasury bonds		341,655		1,446		(46	)		343,055
Corporate debt securities		100,114		281		—			100,395
Totals	$	523,247	$	1,978	$	(61	)	$	525,164


	December 31, 2023
(in thousands)	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
U.S. government agency bonds	$	193,231	$	90	$	(245	)	$	193,076
U.S. treasury bonds		103,476		156		(35	)		103,597
Corporate debt securities		84,536		114		(45	)		84,605
Totals	$	381,243	$	360	$	(325	)	$	381,278

The following table presents the amortized cost and fair value of the Company's fixed income securities by maturity grouping as of September 30, 2024.


	September 30, 2024
(in thousands)	Amortized cost		Fair value
Due in one year or less	$	364,097	$	364,966
Due after one year through five years		159,150		160,198
Due after five years through ten years		—		—
Due after ten years		—		—
Total	$	523,247	$	525,164


	December 31, 2023
(in thousands)	Amortized cost		Fair value
Due in one year or less	$	281,035	$	280,739
Due after one year through five years		100,208		100,539
Due after five years through ten years		—		—
Due after ten years		—		—
Total	$	381,243	$	381,278

There were no securities with expected credit losses or non-credit related impairment as of September 30, 2024 or December 31, 2023. There were no sales of securities which resulted in a realized loss during the three and nine months ended September 30, 2024. The Company recognized $5.0 million and $14.6 million of interest income earned from its available-for-sale debt securities and cash and cash equivalents during the three and nine months ended September 30, 2024, respectively. The Company recognized $3.0 million and $8.6 million of accretion on its available-for-sale debt securities during the three and nine months ended September 30, 2024. The accretion recognized was recorded to interest income during these periods. The Company recognized $5.4 million and $15.9 million of interest income earned from its available-for-sale debt securities and money market funds during the three and nine months ended September 30, 2023, respectively. The Company also recognized $2.7 million and $8.1 million of accretion on its available-for-sale debt securities, which was recorded to interest income, during the three and nine months ended September 30, 2023.

- 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
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 107
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-107

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2E

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 940
-SubTopic 820
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478119/940-820-50-1

+ Details