Financial Instruments

12 Months Ended

Dec. 31, 2025

Financial Instruments Pledged as Collateral [Abstract]

Financial Instruments

(3)Financial Instruments

Investments

Cullinan recognized its investments by security type at December 31, 2025 as follows (in thousands):

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Short-term investments
U.S. government notes	$	159,632	$	683	$	—		$	160,315
Corporate notes		119,368		119		(7	)		119,480
Asset-backed securities		9,717		52		—			9,769
Total short-term investments		288,717		854		(7	)		289,564
Long-term investments
Corporate notes		48,134		90		(2	)		48,222
U.S. government notes		9,963		85		—			10,048
Asset-backed securities		—		—		—			—
Total long-term investments		58,097		175		(2	)		58,270
Total investments	$	346,814	$	1,029	$	(9	)	$	347,834

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

All of the Company's long-term investments as of each of December 31, 2025 and 2024 had maturities between one and two years from the respective balance sheet date. The Company did not recognize any credit loss relating to its investments during 2025 or 2024.

Fair Value of Financial Instruments

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, 2025 (in thousands):

	Level 1		Level 2		Level 3		Total
Short-term investments
U.S. government notes	$	—	$	160,315	$	—	$	160,315
Corporate notes		—		119,480		—		119,480
Asset-backed securities		—		9,769		—		9,769
Total short-term investments		—		289,564		—		289,564
Long-term investments
Corporate notes	$	—	$	48,222	$	—	$	48,222
U.S. government notes		—		10,048		—		10,048
Asset-backed securities		—		—		—		—
Total long-term investments		—		58,270		—		58,270
Total investments	$	—	$	347,834	$	—	$	347,834

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

As of December 31, 2025 and 2024, the fair values of cash and cash equivalents, prepaid expenses and other current assets, accounts payable, accrued expenses and other current liabilities approximated their carrying values due to the short-term nature of these instruments.