Equity Incentive Plan (Tables)

3 Months Ended

Mar. 31, 2023

Equity [Abstract]

Summary of Stock Option Activity

The following table summarizes the stock option activity for the three months ended March 31, 2023:

	Shares (in thousands)			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)
Outstanding at December 31, 2022		20,749		$	14.61		6.44
Granted		1,588		$	2.92
Exercised		—		$	—
Expired and forfeited		(961	)	$	15.52
Outstanding at March 31, 2023		21,376		$	13.70		5.61

Summary of Restricted Stock Unit Activity

The following table summarizes the restricted stock unit activity (“RSUs”) for the three months ended March 31, 2023:

	Shares (in thousands)			Weighted-Average Grant Date Fair Value
Outstanding at December 31, 2022		3,167		$	6.46
Granted		1,408		$	2.58
Released		(195	)	$	10.13
Expired and forfeited		(529	)	$	3.16
Outstanding at March 31, 2023		3,851		$	5.31

Summary of Stock-Based Compensation Expense related to Stock-Based Payment Awards Granted

The following table summarizes stock-based compensation expense related to stock-based payment awards granted pursuant to all of our equity compensation arrangements (in thousands):

	Three Months Ended March 31,
	2023		2022
Research and development	$	2,939	$	4,563
General and administrative		2,329		3,002
Sales and marketing		2,679		3,350
Total stock-based compensation expense	$	7,947	$	10,915

Summary of Fair Value of Option Grant on Grant Date Using Black-Scholes Option Pricing Model

We estimated the fair value of each option grant on the grant date using the Black-Scholes option pricing model with the following weighted-average assumptions:

	For the Three Months Ended
	March 31,
	2023			2022
Risk-free interest rate		3.7	%		2.1	%
Dividend yield		0.0	%		0.0	%
Volatility		63.9	%		59.1	%
Expected life (years)		6			6