Stock-Based Compensation (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2024

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Schedule of Stock-based Compensation Expense

Stock-based compensation expense was as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2024		2023		2024		2023
Research and development	$	312	$	3,254	$	232	$	10,191
General and administrative		4,635		7,214		15,657		20,594
Total stock-based compensation expense	$	4,947	$	10,468	$	15,889	$	30,785

Stock-based compensation expense was as follows:

	Years Ended December 31,
(in thousands)	2023		2022
Research and development	$	13,167	$	14,014
General and administrative		27,612		27,301
Total stock-based compensation expense	$	40,779	$	41,315

Summary of Restricted Common Stock Activity

The following table summarizes restricted common stock activity for the nine months ended September 30, 2024:

	Shares			Weighted Average Grant Date Fair Value
Unvested at January 1, 2024		141,516		$	200.79
Granted		10,652			17.71
Forfeited		(48,999	)		191.82
Vested		(54,469	)		198.95
Unvested at September 30, 2024		48,700		$	171.35

The following table summarizes restricted common stock activity for the year ended December 31, 2023:

	Shares			Weighted Average Grant Date Fair Value
Unvested at January 1, 2023		97,352		$	316.25
Granted		99,130			138.46
Forfeited		(14,901	)		263.58
Vested		(40,065	)		304.52
Unvested at December 31, 2023		141,516		$	200.79

Summary of Stock Option Activity

The following table summarizes stock option activity (in thousands, except share and per share data):

	Shares			Weighted Average Exercise Price		Weighted Average Contractual Life (in years)		Aggregate Intrinsic Value
Options outstanding at January 1, 2024		453,902		$	317.63		7.95	$	—
Granted		—			—		—		—
Exercised		—			—		—		—
Forfeited		(189,901	)		260.36		—		—
Options outstanding at September 30, 2024		264,001		$	358.80		6.88	$	—
Options vested and exercisable at September 30, 2024		199,117		$	402.73		6.56	$	—

The following table summarizes stock option activity (in thousands, except share and per share data):

	Shares			Weighted Average Exercise Price		Weighted Average Contractual Life		Aggregate Intrinsic Value
Options outstanding at January 1, 2023		344,469		$	409.63		8.3	$	786
Granted		164,319			143.52		—		57
Exercised		—			—		—		—
Forfeited		(54,886	)		373.75		—		82
Options outstanding at December 31, 2023		453,902		$	317.63		7.9	$	—
Options vested and exercisable at December 31, 2023		197,136		$	433.78		7.2	$	—

Schedule of Estimated Fair Value Weighted-Average Assumptions Using Black-Scholes Option-Pricing Model

The fair value was estimated on the date of grant using the Black-Scholes option-pricing model, with the following weighted-average assumptions:

	Years Ended December 31,
	2023			2022
Expected term (in years)		6.11			6.07
Expected volatility		94	%		90	%
Risk-free interest rate		3.52	%		2.00	%
Expected dividend yield		—			—
Fair value of common stock	$	143.52		$	172.04