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Segment Reporting - Summary of Financial Information of Reportable Segment (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 R&D program expense |  | $ 44,437 |  | $ 61,030 |  | $ 86,560 | $ 102,489
Equity-based compensation |  |  |  |  |  | 16,063 | 19,261
Loss from operations |  | (57,254) |  | (75,798) |  | (110,951) | (130,794)
Interest income |  | 3,648 |  | 5,924 |  | 7,746 | 12,504
Other expense, net |  | (98) |  | (181) |  | (160) | (266)
Net loss |  | (53,704) | $ (49,661) | (70,055) | $ (48,501) | (103,365) | (118,556)
Operating Segments [Member] |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |
Total R&D program expense |  | 31,062 |  | 27,008 |  | 59,387 | 54,669
Equity-based compensation |  | 8,447 |  | 9,887 |  | 16,063 | 19,261
R&D personnel and operations |  | 9,070 |  | 9,741 |  | 18,909 | 19,572
General and administrative personnel |  | 3,589 |  | 3,335 |  | 7,384 | 6,824
License agreement obligations |  | 0 |  | 20,115 |  | 0 | 20,153
Other segment expenses | [1] | 5,086 |  | 5,712 |  | 9,208 | 10,315
Loss from operations |  | (57,254) |  | (75,798) |  | (110,951) | (130,794)
Interest income |  | 3,648 |  | 5,924 |  | 7,746 | 12,504
Other expense, net |  | (98) |  | (181) |  | (160) | (266)
Net loss |  | (53,704) |  | (70,055) |  | (103,365) | (118,556)
Operating Segments [Member] | CLN-049 [Member] |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |
Total R&D program expense |  | 6,009 |  | 4,898 |  | 11,068 | 8,793
Operating Segments [Member] | CLN-617 [Member] |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |
Total R&D program expense |  | 79 |  | 1,403 |  | 764 | 3,196
Operating Segments [Member] | CLN-619 [Member] |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |
Total R&D program expense |  | 1,102 |  | 7,317 |  | 3,573 | 13,435
Operating Segments [Member] | CLN-978 [Member] |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |
Total R&D program expense |  | 10,532 |  | 5,393 |  | 20,197 | 10,066
Operating Segments [Member] | Early-stage programs [Member |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |
Total R&D program expense |  | 1,116 |  | 1,986 |  | 1,825 | 3,008
Operating Segments [Member] | Velinotamig [Member] |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |
Total R&D program expense |  | 3,951 |  | 10 |  | 6,754 | 10
Operating Segments [Member] | Zipalertinib [Member] |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |
Total R&D program expense |  | $ 8,273 |  | $ 6,001 |  | $ 15,206 | $ 16,161
[1] | Other segment expenses for the three and six months ended June 30, 2026 and 2025 include legal fees relating to patent and corporate matters; professional fees for accounting, auditing, tax, and administrative consulting services; insurance costs; marketing expenses; depreciation; and other operating costs.

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