Stockholders' Equity (Deficit) (Tables)

12 Months Ended

Dec. 31, 2020

Equity [Abstract]

Summary of Convertible Preferred Stock

As of December 31, 2019, convertible preferred stock consisted of the following (in thousands, except per share data):

Series	Shares Authorized		Shares Issued and Outstanding		Per Share Original Issue Price and Conversion Price		Liquidation Preference		Carrying Value
Series A		4,367		4,350	$	2.2615	$	9,838	$	9,773
Series B		8,108		8,108		2.8269		22,922		22,814
Series C		25,580		24,809		4.2812		106,210		102,133
Total		38,055		37,267			$	138,970	$	134,720

Summary of Stock Option Activity

Stock option activity for employee and nonemployee awards and related information is as follows (in thousands, except per share and contractual term data):

	Number of Options			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
Outstanding at December 31, 2019		1,667		$	1.08
Granted		2,291			14.24
Exercised		(119	)		0.45
Forfeited		(51	)		1.24
Outstanding at December 31, 2020		3,788		$	9.06		9.1	$	65,082
Exercisable at December 31, 2020		556		$	1.24		8.3	$	13,491

Schedule of Assumptions used in Black-Scholes Model to Determine Fair Value of Stock/Unit Option Grants and Shares Purchasable under ESPP

The assumptions used in the Black-Scholes model to determine the fair value of the stock/unit option grants and the shares purchasable under the ESPP were as follows:

	Year Ended December 31,
Stock/Unit Option Grants	2020	2019	2018
Risk-free interest rate	0.3% - 1.5%	1.4% - 2.7%	2.4% - 2.9%
Expected volatility	88% - 92%	84% - 88%	83% - 84%
Expected term (in years)	5.4 - 6.1	2.0 - 6.1	2.0 - 6.1
Expected dividend yield	—%	—%	—%

	Year Ended December 31,
ESPP	2020	2019	2018
Risk-free interest rate	0.1% - 0.2%	N/A	N/A
Expected volatility	75% - 96%	N/A	N/A
Expected term (in years)	0.5	N/A	N/A
Expected dividend yield	—%	N/A	N/A

Schedule of Allocated Stock-based Compensation Expense

The allocation of stock-based compensation expense was as follows (in thousands):

	Year Ended December 31,
	2020		2019		2018
Research and development expense	$	1,895	$	84	$	26
General and administrative expense		2,415		322		34
Total stock-based compensation expense	$	4,310	$	406	$	60

Schedule of Common Stock Reserved for Future Issuance

Common stock reserved for future issuance consisted of the following (in thousands):

	December 31,
	2020		2019
Conversion of convertible preferred stock		—		17,666
Common stock options issued and outstanding		3,788		1,667
Equity awards available for future issuance    under equity plans		2,852		1,601
Preferred and common stock warrants    outstanding		—		17
Common stock authorized under the ESPP		296		—
Total		6,936		20,951