Stock-based Compensation - Stock option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022
Options
Outstanding as of December 31, 2022	3,356,937
Sesen Bio options assumed in the Merger	765,223
Granted	144,352
Forfeited	(82,427)
Expired	(38)
Outstanding as of March 31, 2023	4,184,047
Exercisable as of March 31, 2023	3,015,084
Vested and expected to vest at March 31, 2023	4,184,047
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
Granted (in USD per share)	5.64
Forfeited (in USD per share)	1.46
Expired (in USD per share)	1.46
Outstanding as of March 31, 2023 (in USD per share)	6.11
Exercisable as of March 31, 2023 (in USD per share)	5.58
Vested and expected to vest at March 31, 2023 (in USD per share)	6.11
Share based compensation arrangement by share based payment award options grants in period weighted average grant date fair value	$ 2.64	$ 0.75
Weighted average remaining contractual term (years)
Outstanding as of March 31, 2023	5 years 10 months 24 days
Exercisable as of March 31, 2023	3 years 7 months 6 days
Vested and expected to vest at March 31, 2023	5 years 10 months 24 days
Aggregate Intrinsic Value
Outstanding as of March 31, 2023	$ 6,798
Exercisable as of March 31, 2023	5,057
Vested and expected to vest at March 31, 2023	$ 6,798

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Gross number of share options (or share units) assumed in a merger during the period.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options for shares assumed in a merge during the period.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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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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Number of fully vested and expected to vest exercisable options that may be converted into shares under option plan. 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 exercise price, at which grantee can acquire shares reserved for issuance, for 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 price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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