Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2021

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 March 31,
(in thousands)	2021		2020
Research and development	$	1,840	$	173
General and administrative		2,046		189
	$	3,886	$	362

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, 2021		6,839,091		$	8.46		9.17
Granted		115,575		$	80.10
Exercised		(210,274	)	$	1.84
Forfeited		(11,423	)	$	7.94
Outstanding at March 31, 2021		6,732,969		$	9.90		8.96
Exercisable at March 31, 2021		1,209,260		$	1.99		8.26

Summary of Information about Stock Options Outstanding

The following table summarizes information about stock options outstanding at March 31, 2021 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 - $7.37		3,300,710		8.46	$	1.80		1,181,544	$	1.73
$7.38 - $15.93		3,118,268		9.42		12.85		26,564		12.85
$15.94 - $88.98		313,991		9.74		65.66		1,152		19.00
		6,732,969						1,209,260

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:

	Three months ended March 31,
	2021			2020
Expected volatility		117.13	%		91.60	%
Risk-free interest rate		0.76	%		1.88	%
Expected life (in years)		6.06			6.25
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, 2021		1,214,778		$	2.09
Vested		(205,316	)	$	2.31
Unvested balance at March 31, 2021		1,009,462		$	2.05