CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Operating expenses:
Research and development	$ 35,506	$ 33,821	$ 102,411	$ 113,308
General and administrative	13,349	10,982	39,460	31,856
Total operating expenses	48,855	44,803	141,871	145,164
Impairment of long-lived assets	0	(440)	0	(440)
Loss from operations	(48,855)	(45,243)	(141,871)	(145,604)
Other income (expense):
Interest income	8,384	5,880	22,148	15,710
Other income (expense), net	(89)	180	(205)	356
Net Loss	(40,560)	(39,183)	(119,928)	(129,538)
Net loss attributable to noncontrolling interests	0	0	(192)	(179)
Net loss attributable to common stockholders of Cullinan	(40,560)	(39,183)	(119,736)	(129,359)
Comprehensive income (loss):
Net loss	(40,560)	(39,183)	(119,928)	(129,538)
Unrealized gain on investments	1,446	574	1,099	1,550
Comprehensive loss	(39,114)	(38,609)	(118,829)	(127,988)
Comprehensive loss attributable to noncontrolling interests	0	0	(192)	(179)
Comprehensive loss attributable to Cullinan	$ (39,114)	$ (38,609)	$ (118,637)	$ (127,809)
Net loss per share attributable to common stockholders of Cullinan:
Net loss per share, basic	$ (0.69)	$ (0.91)	$ (2.3)	$ (3.15)
Net loss per share, diluted	$ (0.69)	$ (0.91)	$ (2.3)	$ (3.15)
Weighted-average shares used in computing net loss per share attributable to common stockholders of Cullinan
Weighted-average common stock outstanding - basic	58,337	42,734	52,157	41,130
Weighted-average common stock outstanding - diluted	58,337	42,734	52,157	41,130