Equity Incentive Plans (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2023

Dec. 31, 2022

Share-Based Payment Arrangement [Abstract]

Summary of Assumptions under Employee Stock Purchase Plan

Effective January 1, 2022, the number of shares of common stock available under the 2021 ESPP increased by 564,000 shares pursuant to the evergreen provision of the 2021 ESPP.

	Year Ended December 31,
	2022			2021
Expected volatility		73.00% - 75.00	%		72.00% - 74.00	%
Expected dividend yield		0	%		0	%
Expected term (in years)		0.5			0.44 - 0.5
Risk-free interest rate		0.10% - 4.65	%		0.10% - 1.00	%

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

The Company used the Black-Scholes option pricing model to estimate stock-based compensation expense for stock option awards granted during the periods presented, with the following assumptions.

	Year Ended December 31,
	2022			2021
Expected volatility		74.00% - 75.00	%		72.00% - 77.74	%
Expected dividend yield		0	%		0	%
Expected term (in years)		5.97 - 6.01			5.48 - 6.04
Risk-free interest rate		1.91% - 4.23	%		0.56% - 1.34	%

Summary of Option Activity

A summary of option activity under the 2020 Plan and the 2021 Plan during the nine months ended September 30, 2023 is as follows:

	Number of Options			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2022		7,755,303		$	8.47		8.67	$	794
Options granted—2021 Plan		3,223,400		$	2.22
Options exercised		(65,414	)	$	0.52
Options cancelled		(4,532,774	)	$	6.50
Outstanding as of September 30, 2023		6,380,515		$	6.79		5.6	$	695
Exercisable		4,231,849		$	6.86		4.4	$	472
Vested and expected to vest as of September 30, 2023		6,380,515		$	6.79		5.6	$	695

A summary of option activity under the 2020 Plan and the 2021 Plan during the year ended December 31, 2022 is as follows:

	Number of Options			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2021		5,056,743		$	8.77		9.2	$	18,503
Options granted—2021 Plan		3,292,702		$	7.91
Options exercised		(67,196	)	$	0.30
Options cancelled		(526,946	)	$	8.99
Outstanding as of December 31, 2022		7,755,303		$	8.47		8.7	$	794
Exercisable		2,330,389		$	8.74		8.3	$	388
Vested and expected to vest as of December 31, 2022		7,755,303		$	8.47		8.7	$	794

Components of Stock-based Compensation Expense

The following table presents the components of stock-based compensation expense for the Company’s stock-based awards for the periods presented (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Restricted stock awards and founders’ common stock awards	$	1	$	2	$	5	$	6
ESPP		1		58		96		316
Stock options		2,159		3,150		8,168		9,590
Total stock-based compensation expense	$	2,161	$	3,210	$	8,269	$	9,912

The following table presents the components of stock-based compensation expense for the Company’s stock-based awards for the periods presented (in thousands):

	Year Ended December 31,
	2022		2021
Restricted stock awards and founders’ common stock awards	$	11	$	9
ESPP		391		215
Stock options		13,132		7,647
Total stock-based compensation expense	$	13,534	$	7,871

Classification of Stock-based Compensation Expense

The following table presents the classification of stock-based compensation expense for the Company’s stock-based awards for the periods presented (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Research and development expenses	$	37	$	1,249	$	1,904	$	3,881
General and administrative expenses		2,124		1,961		6,365		6,031
Total stock-based compensation expense	$	2,161	$	3,210	$	8,269	$	9,912

The following table presents the classification of stock-based compensation expense for the Company’s stock-based awards for the periods presented (in thousands):

	Year Ended December 31,
	2022		2021
Research and development expenses	$	5,317	$	2,685
General and administrative expenses		8,217		5,186
Total stock-based compensation expense	$	13,534	$	7,871