Equity Incentive Plans and Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Restricted Stock Activity

The following table summarizes restricted stock activity during the year ended December 31, 2020:

	Number of Shares			Weighted- Average Grant Date fair value
Outstanding and unvested, as of December 31, 2019		302,211		$	1.51
Issued		—		$	—
Vested		(163,568	)	$	1.30
Repurchases		(12,121	)	$	1.22
Outstanding and unvested, as of December 31, 2020		126,522		$	1.85

Summary of Black-Scholes Option Pricing Model to Estimate Stock-based Compensation Expense for Stock Option Awards

The Company used Black-Scholes option pricing model to estimate stock-based compensation expense for stock option awards with the following assumptions:

	Year Ended December 31,
	2020		2019
Expected volatility	72.10% - 77.50%		74.80% - 82.53%
Risk-free interest rate	0.27% - 0.82%		1.43% - 2.59%
Expected dividend		—		—
Expected term (in years)	5.26 - 6.75		5.00 - 6.08
Underlying common stock fair value	6.22 - 28.79		5.15 - 7.08

Summary of Option Activity Under the 2015 Plan and 2020 Plan

A summary of option activity under the 2015 Plan and the 2020 Plan is as follows:

	Number of Options			Weighted- Average Exercise Price per Share		Weighted- Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value
Outstanding as of December 31, 2019		1,337,501		$	3.22		9.18	$	5,157
Granted		1,830,738		$	11.43
Exercised		(136,223	)	$	3.25
Forfeited		(38,161	)	$	8.13
Outstanding as of December 31, 2020		2,993,855		$	8.18		8.84	$	43,890
Exercisable as of December 31, 2020		736,601		$	4.19		8.22	$	13,664
Vested and expected to vest as of December 31, 2020		2,993,855		$	8.18		8.84	$	43,890

Summary of Black-Scholes Option Pricing Model to Estimate Stock-based Compensation Expense for 2020 Employee Stock Purchase Plan

The Company used Black-Scholes option pricing model to estimate stock-based compensation expense for the 2020 ESPP with the following assumptions:

	Year Ended December 31,
	2020			2019
Risk-free interest rate		0.11	%		—
Expected term of options (in years)		0.58			—
Expected stock price volatility		83.72	%		—
Expected dividends		—			—

Summary of Classification of Stock-based Compensation Expense

The following table presents the classification of stock-based compensation expense for the years ended December 31, 2020 and 2019 (in thousands):

	Year Ended December 31,
	2020		2019
Research and development expenses	$	1,719	$	584
General and administrative expenses		2,176		1,245
Total stock-based compensation expense	$	3,895	$	1,829