Stock-Based Compensation (Tables)

3 Months Ended

12 Months Ended

Mar. 31, 2025

Dec. 31, 2024

Summary of Assumptions Used in Black-Scholes Option Pricing Model

	For the Three Months
	Ended March 31,
	2024
Per share fair value of common stock	$	0.62
Expected volatility		73.8	%
Expected dividends		0	%
Expected term (in years)		5.9
Risk-free rate		3.93	%

	For the Year Ended
	December 31,
	2024			2023
Per share fair value of common stock	$	0.62		$	0.52
Expected volatility		73.8	%		67.4	%
Expected dividends		0	%		0	%
Expected term (in years)		5.9			6.1
Risk-free rate		3.93	%		3.56	%

Summary of Compensation Expense Recognized

The following table illustrates the classification of stock-based compensation in the condensed statements of operations and comprehensive loss (in thousands):

	For the Three Months Ended March 31,
	2025		2024
Research and development	$	29	$	29
General and administrative		51		52
Total stock-based compensation	$	80	$	81

The following table illustrates the classification of stock-based compensation in the statements of operations (in thousands):

	For the Year Ended
	December 31,
	2024		2023
Research and development	$	169	$	111
General and administrative		150		203
Total stock-based compensation	$	319	$	314

Summary of Stock Option Activity

		Weighted-		Weighted-Average
	Number of	Average Exercise		Remaining Contractual	Intrinsic Value (In
	Options	Price		Term (In Years)	Thousands)
Outstanding as of January 1, 2025	5,435,629	$	0.43	6.06	$	2,914
Exercised	(5,416)		0.63
Forfeited/expired	(15,000)		0.09
Outstanding as of March 31, 2025	5,415,213	$	0.43	5.82	$	2,899
Options exercisable as of March 31, 2025	4,775,534	$	0.39	5.61	$	2,747
Vested and expected to vest as of March 31, 2025	5,415,213	$	0.43	5.82	$	2,899

		Weighted-		Weighted-Average
	Number of	Average		Remaining Contractual	Intrinsic Value
	Options	Exercise Price		Term (In Years)	(In Thousands)
Outstanding as of January 1, 2024	5,509,379	$	0.43	7.04	$	2,699
Granted	25,000		0.92	—		—
Exercised	(63,750)		0.08	—		—
Forfeited/expired	(35,000)		0.82	—		—
Outstanding as of December 31, 2024	5,435,629	$	0.43	6.06	$	2,914
Options exercisable as of December 31, 2024	4,582,807	$	0.38	5.78	$	2,700
Vested and expected to vest as of December 31, 2024	5,435,629	$	0.43	6.06	$	2,914

Cara Therapeutics, Inc.

Summary of Assumptions Used in Black-Scholes Option Pricing Model

	Three Months Ended
	March 31,
	2025	2024
Risk-free interest rate	—	4.12%
Expected volatility	—	89.6%
Expected dividend yield	—	0%
Expected life of employee and Board options (in years)	—	6.25

	Year Ended December 31,
	2024		2023		2022
Risk-free interest rate	4.12% - 4.34	%	3.38% - 4.65	%	1.70% - 4.21	%
Expected volatility	89.6% - 89.8	%	76.3% - 81.3	%	77.7% - 81.9	%
Expected dividend yield	0	%	0	%	0	%
Expected life of employee and Board options (in years)	6.25		6.25		6.25

Summary of Stock Option Activity

		Weighted
	Number of	Average Exercise
	Shares	Price
Outstanding, December 31, 2024	113,487	$	319.80
Granted	—		—
Exercised	—		—
Forfeited	—		—
Expired	—		—
Outstanding, March 31, 2025	113,487	$	319.80
Options exercisable, March 31, 2025	64,989

		Weighted		Aggregate
	Number of	Average Exercise		Intrinsic
	Shares	Price		Value
Outstanding, December 31, 2023	219,379	$	467.64
Granted	84,587		30.96
Exercised	—		—
Forfeited	(91,980)		182.88
Expired	(98,499)		529.29
Outstanding, December 31, 2024	113,487	$	319.86	$	—
Weighted average remaining contractual life as of December 31, 2024 (in years)	7.32
Options exercisable, December 31, 2024	61,867	$	454.26	$	—
Weighted average remaining contractual life as of December 31, 2024 (in years)	6.08
Options vested and expected to vest as of December 31, 2024	113,487	$	319.86	$	—
Weighted average remaining contractual life as of December 31, 2024 (in years)	7.32

Employees And Non-Employee Members Of Board Of Directors | Cara Therapeutics, Inc.

Summary of Restricted Stock Unit Activity

		Weighted
	Number of	Average Grant
	Units	Date Fair Value
Outstanding, December 31, 2024	26,638	$	52.53
Awarded	—		—
Vested and released	(792)		447.95
Forfeited	—		—
Outstanding, March 31, 2025	25,846	$	40.39
Restricted stock units exercisable (vested and deferred), March 31, 2025	—

		Weighted
	Number of	Average Grant
	Units	Date Fair Value
Outstanding, December 31, 2023	15,731	$	333.72
Awarded	25,108		23.76
Vested and released	(10,390)		288.72
Forfeited	(3,811)		380.52
Outstanding, December 31, 2024	26,638	$	52.53
Restricted stock units exercisable (vested and deferred), December 31, 2024	—

Stock Options | Cara Therapeutics, Inc.

Summary of Compensation Expense Recognized

	Three Months Ended
	March 31,
	2025		2024
Research and development	$	—	$	504
General and administrative		1,100		1,229
Total stock option expense	$	1,100	$	1,733

	Year Ended December 31,
	2024		2023		2022
Research and development	$	1,016	$	5,973	$	7,222
General and administrative		5,274		5,634		6,426
Total stock option expense	$	6,290	$	11,607	$	13,648

Restricted Stock Units | Cara Therapeutics, Inc.

Summary of Compensation Expense Recognized

	Three Months Ended
	March 31,
	2025			2024
Research and development	$	—	$	255
General and administrative		326		1,357
Total restricted stock unit expense	$	326	$	1,612

	Year Ended December 31,
	2024		2023		2022
Research and development	$	248	$	476	$	765
General and administrative		2,391		1,647		3,321
Total restricted stock unit expense	$	2,639	$	2,123	$	4,086