Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-based Compensation Expense Recognized

Stock‑based compensation expense recognized was as follows (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Research and development	$	285	$	9	$	545	$	20
General and administrative		824		40		1,538		87
Total stock-based compensation expense	$	1,109	$	49	$	2,083	$	107

Weighted-Average Assumptions used in Estimating Fair Value of each Stock Options using Black-Scholes Option-Pricing Model

The fair value of each stock option was estimated using the Black‑Scholes option‑pricing model with the following weighted-average assumptions:

	Six Months Ended June 30,
	2021			2020
Risk-free interest rate		0.80	%		1.43	%
Expected volatility		89.34	%		78.15	%
Expected term (in years)		6.10			6.61
Expected dividend yield		—			—

Summary of Option Activity Changes in Shares Available for Grant under the 2020 Plan

Changes in shares available for grant under the 2020 Plan during the six months ended June 30, 2021 were as follows:

	Shares Available for Grant
Shares available for grant at December 31, 2020		3,742,235
2020 Plan reserve increase on January 1, 2021		1,624,259
Options and restricted stock units granted		(661,928	)
Options forfeited, cancelled, or expired		2,400
Shares available for grant at June 30, 2021		4,706,966

Summary of Option Activity under the 2020 Plan

A summary of stock option activity under the 2020 Plan for the six months ended June 30, 2021 was as follows:

	Shares			Weighted- Average Exercise price per Share		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Balance at December 31, 2020		1,974,870		$	9.31	7.98		$	49,275
Granted		658,776			20.96
Exercised		(148,544	)		1.27
Forfeited/expired		(2,400	)		21.40
Balance at June 30, 2021		2,482,702		$	12.87		8.17	$	7,700
Expected to vest		1,855,435		$	16.54		9.19	$	2,210
Options exercisable		627,267		$	2.01		5.18	$	5,491

Summary of Stock Options Outstanding and Exercisable under the 2020 Plan

Stock options outstanding and exercisable under the 2020 Plan consisted of the following at June 30, 2021:

	Employees and Directors				Non-employees
Exercise Price ($)	Shares Outstanding		Shares Exercisable		Shares Outstanding		Shares Exercisable
0.16 to 1.00		226,980		226,980		—		—
1.04 to 1.49		468,273		240,028		142,014		121,522
17.00 to 19.94		819,872		33,028		195,453		—
20.55 to 29.41		630,110		5,709		—		—
Total		2,145,235		505,745		337,467		121,522

Summary of Restricted Stock Activity

A summary of RSU activity for the six months ended June 30, 2021 is as follows:

	Share Equivalent			Weighted- Average Grant Date Fair Value
Non-vested at December 31, 2020		—		$	—
Granted		3,152			21.15
Vested		(1,576	)		21.15
Non-vested at June 30, 2021		1,576		$	21.15