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Segment Disclosures - Schedule of Revenue and Expenses (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2026 | Mar. 31, 2026 | Jun. 30, 2025 | Mar. 31, 2025 | Jun. 30, 2026 | Jun. 30, 2025
Segment Reporting Information [Line Items] |  |  |  |  |  |
Total revenue | $ 1,418 |  | $ 18,658 |  | $ 11,677 | $ 69,575
General research and development expenses | 1,925 |  | 1,520 |  | 4,808 | 4,050
Total external costs | 9,086 |  | 5,599 |  | 20,511 | 14,394
Internal costs | 8,512 |  | 7,723 |  | 16,325 | 17,795
Research and development expenses | 17,598 |  | 13,322 |  | 36,836 | 32,189
General and administrative expenses | 7,601 |  | 6,622 |  | 18,294 | 16,050
Total operating expenses | 25,199 |  | 19,944 |  | 55,130 | 48,239
Income (loss) from operations | (23,781) |  | (1,286) |  | (43,453) | 21,336
Interest income | 3,157 |  | 1,178 |  | 4,647 | 2,133
Other income | 18 |  | 17 |  | 11 | 28
Income (loss) before income taxes | (20,606) |  | (91) |  | (38,795) | 23,497
Provision for income taxes | 60 |  | 63 |  | 119 | 126
Net income (loss) | (20,666) | $ (18,248) | (154) | $ 23,525 | (38,914) | 23,371
Varseta-M (EpCAM) |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |
Total external costs | 6,225 |  | 3,679 |  | 14,039 | 7,949
CX-801 (IFNAlpha2b) |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |
Total external costs | 437 |  | 452 |  | 781 | 940
CX-904 (EGFRxCD3) |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |
Total external costs | 227 |  | (550) |  | 468 | 561
Other Wholly Owned and Partnered Programs |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |
Total external costs | $ 272 |  | $ 498 |  | $ 415 | $ 894

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