Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2024

Financial Instruments Pledged as Collateral [Abstract]

Schedule of Short-term and Long-term Investment Marketable Securities by Security Type

Cullinan recognized its investments by security type at December 31, 2024 as follows (in thousands):

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Short-term investments
Corporate notes	$	211,584	$	343	$	(6	)	$	211,921
U.S. government notes		78,874		81		—			78,955
Asset-backed securities		25,084		12		—			25,096
Total short-term investments		315,542		436		(6	)		315,972
Long-term investments
U.S. government notes		118,423		88		(188	)		118,323
Corporate notes		77,196		9		(472	)		76,733
Asset-backed securities		9,384		—		—			9,384
Total long-term investments		205,003		97		(660	)		204,440
Total investments	$	520,545	$	533	$	(666	)	$	520,412

Cullinan recognized its investments by security type at December 31, 2023 as follows (in thousands):

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Short-term investments
U.S. government notes	$	208,289	$	221	$	(16	)	$	208,494
Corporate notes		99,359		27		(275	)		99,111
Asset-backed securities		61,114		3		(89	)		61,028
Total short-term investments		368,762		251		(380	)		368,633
Total investments	$	368,762	$	251	$	(380	)	$	368,633

Summary of Fair Value of Financial Assets Measured on Recurring Basis

The following table sets forth the fair value of Cullinan’s financial assets that were measured at fair value on a recurring basis as of December 31, 2024 (in thousands):

	Level 1		Level 2		Level 3		Total
Short-term investments
Corporate notes	$	—	$	211,921	$	—	$	211,921
U.S. government notes		—		78,955		—		78,955
Asset-backed securities		—		25,096		—		25,096
Total short-term investments		—		315,972		—		315,972
Long-term investments
U.S. government notes	$	—	$	118,323	$	—	$	118,323
Corporate notes		—		76,733		—		76,733
Asset-backed securities		—		9,384		—		9,384
Total long-term investments		—		204,440		—		204,440
Total investments	$	—	$	520,412	$	—	$	520,412

The following table sets forth the fair value of Cullinan’s financial assets that were measured at fair value on a recurring basis as of December 31, 2023 (in thousands):

	Level 1		Level 2		Level 3		Total
Short-term investments
U.S. government notes	$	—	$	208,494	$	—	$	208,494
Corporate notes		—		99,111		—		99,111
Asset-backed securities		—		61,028		—		61,028
Total short-term investments		—		368,633		—		368,633
Total investments	$	—	$	368,633	$	—	$	368,633