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Segment Information - Research and development costs and an allocation of indirect research and development costs to each program (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($) segment	Sep. 30, 2024 USD ($)
Segment Information
Number of operating segments | segment			1
Number of reportable segments | segment			1
Total R&D Expense	$ 62,931	$ 45,263	$ 169,741	$ 116,611
Single reportable segment
Segment Information
Total R&D Expense	62,931	45,263	169,741	116,611
Single reportable segment | Barzolvolimab/Anti-KIT Program
Segment Information
Total R&D Expense	51,619	34,393	133,967	88,643
Single reportable segment | CDX-622
Segment Information
Total R&D Expense	5,617	3,628	14,906	10,175
Single reportable segment | Other Programs
Segment Information
Total R&D Expense	$ 5,695	$ 7,242	$ 20,868	$ 17,793

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- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Amount of expense for research and development. Includes, but is not limited to, cost for computer software product to be sold, leased, or otherwise marketed and writeoff of research and development assets acquired in transaction other than business combination or joint venture formation or both. Excludes write-down of intangible asset acquired in business combination or from joint venture formation or both, used in research and development activity.

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