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Equity Incentive Plan (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Summary of Stock Option Activity

The following table presents stock option activity under the Plans for the period:

		Number of Shares				Weighted- Average Exercise Price Per Share				Weighted- Average Remaining Contractual Term (in years)				Aggregate Intrinsic Value (in thousands)
Balances as of December 31, 2022			8,152,093			$	11.92				8.09			$	3,329
Stock options granted			2,602,050			$	5.17
Stock options exercised			(76,888	)		$	1.89
Stock options forfeited			(1,468,285	)		$	10.61
Balances as of December 31, 2023			9,208,970			$	10.31				7.53			$	2,930
Exercisable as of December 31, 2023			5,083,778			$	12.10				6.64			$	1,299

Summary of RSU Activity under Equity Incentive Plan

A summary of RSU activity under our equity incentive plan and related information is as follows:

		Number of Shares				Weighted-Average Grant Date Fair Value Per Share
Unvested as of December 31, 2022			550,236			$	5.58
Granted			249,615				5.95
Vested			(172,096	)			5.73
Cancelled			(132,176	)			5.67
Unvested as of December 31, 2023			495,579			$	5.69

Summary of Stock-Based Compensation Expense

The total stock-based compensation expense recognized was as follows (in thousands):

		Year Ended December 31,
		2023				2022
Research and development		$	8,878			$	8,874
General and administrative			9,305				9,642
Total stock-based compensation expense		$	18,183			$	18,516

Summary of Fair Value of Each Stock Option Issued Estimated on the Date of Grant Using the Black-Scholes Option Pricing Model

The fair value of each stock option issued was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions:

		Year Ended December 31,
		2023		2022
Expected term (in years)		5.50 - 6.08		5.50 - 6.08
Expected volatility		81.20% - 82.40%		78.80% - 85.90%
Risk-free interest rate		3.47% - 4.85%		1.49% - 4.19%
Dividend yield		—		—

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Tabular disclosure of cost recognized for award under share-based payment arrangement by plan. Includes, but is not limited to, related tax benefit.

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Tabular disclosure of the changes in outstanding nonvested restricted stock units.

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Tabular disclosure for stock option plans. Includes, but is not limited to, outstanding awards at beginning and end of year, grants, exercises, forfeitures, and weighted-average grant date fair value.

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Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions.

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