Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2022

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Stock-Based Compensation Expense Recorded in Statements of Operations

The Company recorded stock-based compensation expense in the following expense categories in its accompanying statements of operations:

	Three Months Ended June 30,				Six Months Ended June 30,
(in thousands)	2022		2021		2022		2021
Research and development	$	2,472	$	2,203	$	5,672	$	4,043
General and administrative		3,556		2,034		7,185		4,080
	$	6,028	$	4,237	$	12,857	$	8,123

Summary of Stock Option Activity

The following table summarizes stock option activity for the periods indicated:

	Number of shares			Weighted average exercise price per share		Weighted average remaining contractual term (years)
Outstanding at January 1, 2022		7,179,482		$	15.36		8.66
Granted		2,705,609		$	8.32
Exercised		(124,285	)	$	1.70
Forfeited		(845,517	)	$	18.06
Outstanding at June 30, 2022		8,915,289		$	13.16		8.60
Exercisable at June 30, 2022		2,738,389		$	9.81		7.71

Summary of Information about Stock Options Outstanding

The following table summarizes information about stock options outstanding at June 30, 2022 under the Plan:

	Options Outstanding						Options Exercisable
Range of Exercise Prices	Number Outstanding		Weighted Average Remaining Contractual Life (in years)		Weighted Average Exercise Price		Number Exercisable		Weighted Average Exercise Price
$0.31 - $3.05		2,109,347		7.26	$	1.80		1,414,546	$	1.76
$3.06 - $10.34		1,068,193		9.88		4.84		4,500		10.09
$10.35 - $11.72		1,447,250		9.63		10.58		—		0.00
$11.73 - $13.04		2,253,228		8.17		12.85		1,031,129		12.85
$13.05 - $88.98		2,037,271		9.05		31.48		288,214		38.39
		8,915,289						2,738,389

Schedule of Fair Value of Each Option Estimated on Date of Grant Using Weighted Average Assumptions

The fair value of each option was estimated on the date of grant using the weighted average assumptions in the table below:

	Six months ended June 30,
	2022			2021
Expected volatility		84.82	%		115.05	%
Risk-free interest rate		2.39	%		0.93	%
Expected life (in years)		6.01			5.91
Expected dividend yield		—			—

Summary of Activity related to RSA Stock-Based Payment Awards

The following table summarizes activity related to RSA stock-based payment awards:

	Number of shares			Weighted-average grant date fair value
Unvested balance at January 1, 2022		611,608		$	2.29
Vested		(231,760	)	$	1.88
Forfeited		(23,416	)	$	1.89
Unvested balance at June 30, 2022		356,432		$	2.58

Summary of Activity related to RSU Stock-Based Payment Awards

The following table summarizes activity related to RSU stock-based payment awards:

	Number of shares		Weighted-average grant date fair value
Unvested balance at January 1, 2022		20,000	$	18.32
Granted		150,000	$	4.86
Unvested balance at June 30, 2022		170,000	$	6.44