Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2021

The following table summarizes the Company’s option activity during the three months ended March 31, 2021:

	NUMBER OF SHARES			WEIGHTED AVERAGE EXERCISE PRICE PER SHARE		WEIGHTED AVERAGE REMAINING CONTRACTUAL TERM		AGGREGATE INTRINSIC VALUE (1)
						(In years)		(In thousands)
Outstanding as of December 31, 2020		4,543,318		$	8.52		7.22	$	108,048
Granted		813,000			26.84
Exercised		(46,807	)		6.76
Forfeited/Cancelled		(161,565	)		13.76
Outstanding as of March 31, 2021		5,147,946			11.26		6.99		29,108
Exercisable as of March 31, 2021		2,707,703			6.87		5.46		22,236
Vested and expected to vest as of March 31, 2021		5,147,946			11.26		6.99		29,108

⁽¹⁾	Aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the fair value of common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock as of March 31, 2021 and December 31, 2020.

Schedule of Components and Classification of Stock-Based Compensation Expense

The following table presents the components and classification of stock-based compensation expense (in thousands):

	THREE MONTHS ENDED MARCH 31,
	2021		2020
Research and development	$	1,058	$	1,033
General and administrative		1,215		717
	$	2,273	$	1,750
Employee	$	2,239	$	1,551
Non-employee		34		199
	$	2,273	$	1,750

Service-Based Awards

Summary of Key Assumptions Used for Stock Option Valuation

The key assumptions used in the Black-Scholes option pricing model on the date of grant for options with service-based vesting conditions were as follows, presented on a weighted average basis:

	THREE MONTHS ENDED MARCH 31,
	2021			2020
Risk-free interest rate		0.65	%		1.63	%
Expected term (in years)	6.25			6.25
Expected volatility		70.25	%		66.90	%
Expected dividend yield		0.00	%		0.00	%
Fair value per share of common stock	$	16.85		$	6.33