Stock-based Compensation -Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Options
Outstanding as of December 31, 2022 (in shares)	3,356,937
Sesen Bio options assumed in the Merger (in shares)	765,223
Exercised (in shares)	(128,716)
Granted (in shares)	2,984,152
Forfeited (in shares)	(114,454)
Expired (in shares)	(839,772)
Outstanding as of September 30, 2023 (in shares)	6,023,370	3,356,937
Exercisable as of September 30, 2023 (in shares)	2,516,594
Vested and expected to vest at September 30, 2023 (in shares)	6,023,370
Weighted average exercise price
Outstanding as of December 31, 2022 (in USD per share)	$ 1.01
Sesen Bio options assumed in the Merger (in USD per share)	27.94
Exercised (in USD per share)	1.29
Granted (in USD per share)	6.93
Forfeited (in USD per share)	5.80
Expired (in USD per share)	29.48
Outstanding as of September 30, 2023 (in USD per share)	3.94	$ 1.01
Exercisable as of September 30, 2023 (in USD per share)	1.16
Vested and expected to vest at September 30, 2023 (in USD per share)	3.94
Share based compensation arrangement by share based payment award options grants in period weighted average grant date fair value (in USD per share)	$ 4.29	$ 1.46
Weighted average remaining contractual term (years)
Outstanding as of September 30, 2023	7 years 9 months 18 days
Exercisable as of September 30, 2023	6 years
Vested and expected to vest at September 30, 2023	7 years 9 months 18 days
Aggregate Intrinsic Value
Exercised	$ 134
Outstanding as of September 30, 2023	5,929
Exercisable as of September 30, 2023	4,950
Vested and expected to vest at September 30, 2023	$ 5,929

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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