Share-based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Estimated Weighted Average Grant Date Fair Value per Share

The Company granted options to purchase an aggregate of 60,000 shares of common stock in the year ended December 31, 2022. The fair values of employee stock options granted in the year ended December 31, 2022 were estimated at the date of grant using the Black-Scholes model with the following assumptions and had the following estimated weighted average grant date fair value per share:

	Year Ended December 31,
	2022
Expected term	5.5 years
Expected volatility		107	%
Risk-free interest rate		3.56	%
Expected dividend yield		0	%
Weighted-average grant date fair value per share	$	1.87

Summary of Stock Option Activities

A summary of ARCA’s stock option activities for the years ended December 31, 2023 and 2022, and related information as of December 31, 2023, is as follows:

	Options Outstanding
	Number of Options			Weighted Average  Exercise Price		Weighted Average Remaining Contractual Term  (in years)		Aggregate Intrinsic Value (in thousands)
Options outstanding - December 31, 2021		904,123		$	5.59
Granted		60,000			2.31
Exercised		—			—
Forfeited and cancelled		(259,163	)		4.74
Options outstanding - December 31, 2022		704,960		$	5.62		8.29	$	18
Granted		—			—
Exercised		—			—
Forfeited and cancelled		(88,253	)		11.68
Options outstanding - December 31, 2023		616,707		$	4.76		7.35	$	—
Options exercisable - December 31, 2023		463,068		$	5.28		7.29	$	—
Options vested and expected to vest -        December 31, 2023		616,661		$	4.76		7.35	$	—

Summary of RSU Activity

A summary of RSU activity for the year ended December 31, 2023 is presented below:

	Restricted Stock Units Outstanding
	Number of Shares			Weighted Average Grant Date Fair Value
RSUs outstanding - December 31, 2021		—		$	—
Granted		91,000			2.21
Vested and released		—			—
Forfeited and cancelled		—			—
RSUs outstanding - December 31, 2022		91,000		$	2.21
Granted		—			—
Vested and released		(91,000	)		2.21
Forfeited and cancelled		—			—
RSUs outstanding - December 31, 2023		—		$	—

Summary of Non-cash, Share-based Compensation Expense

For the years ended December 31, 2023 and 2022, the Company recognized the following non-cash, share-based compensation expense (in thousands):

	Years Ended
	December 31,
	2023		2022
General and administrative	$	526	$	423
Research and development		160		133
Total	$	686	$	556