Stock Based Compensation (Tables)

9 Months Ended

Sep. 30, 2021

Stock Based Compensation

Schedule of Stock-based compensation expense

Stock-based compensation expense recorded in the statements of operations is as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2021		2020		2021		2020
Research and development expenses	$	182	$	24	$	344	$	78
General and administrative expenses		396		51		724		149
Total	$	578	$	75	$	1,068	$	227

Schedule of assumptions used in the Black-Scholes option-pricing model to determine the fair value of stock options granted

	September 30,		December 31,
	2021		2020
Risk‑free interest rate	0.99	%	0.53	%
Expected volatility	74	%	75	%
Expected dividend yield	—		—
Expected term (in years)	6.02		5.99

Summary of the stock option activity

		Weighted‑		Weighted‑
		Average		Average	Aggregate
	Number of	Exercise		Contractual	Intrinsic
	Shares	Price		Term	Value (2)
				(in years)	(in thousands)
Outstanding as of December 31, 2020	1,625,256	$	1.88
Granted	1,166,904		9.36
Exercised	(401,322)		2.18
Forfeited	(21,275)		3.07
Outstanding as of September 30, 2021	2,369,563	$	5.51	8.99	$	20,029
Vested and exercisable as of September 30, 2021	391,322	$	1.84	7.68	$	4,746
Unvested and exercisable as of September 30, 2021 (1)	1,978,241	$	6.24	9.25	$	15,283
(1) This represents the number of unvested options outstanding as of September 30, 2021 that are expected to vest in the future.
(2) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the estimated fair value of the common stock for the options that were in the money as of September 30, 2021.

Summary of unvested restricted stock

		Weighted‑
		Average
		Grant‑Date
	Shares	Fair Value
Unvested as of December 31, 2020	11,537	$	0.007
Vested	(11,537)		0.007
Unvested as of September 30, 2021	—	$	—