Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2023

Share-Based Payment Arrangement [Abstract]

Summary of Stock Options Activity

A summary of stock option activity for the six months ended June 30, 2023 is as follows:

	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)
Outstanding at January 1, 2023		6,537		$	7.55		4.42	$	134
Granted		29			1.15
Exercised		(1	)		2.23
Forfeited		(301	)		6.23
Outstanding at June 30, 2023		6,264		$	7.59		3.95	$	3
Options exercisable at June 30, 2023		5,302		$	8.25		3.08	$	—
Vested or expected to vest at June 30, 2023		6,215		$	7.62		3.91	$	3

Assumptions of Estimated Fair Value of Option on the Date of Grant Using Black-Scholes Option Pricing Model

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

	Three Months Ended June 30,		Six Months Ended June 30,
	2023	2022	2023	2022
Risk-free interest rate	3.9%	3.0%–3.2%	3.5%–3.9%	1.7–3.2%
Expected term (in years)	6.1	5.6–6.3	6.1	5.6–6.3
Expected volatility	44.75%	40.5–41.5%	44.3%–44.8%	38.5–41.5%
Expected dividend yield	0.0%	0.0%	0.0%	0.0%

Summary of RSU Activity

A summary of RSU activity for the six months ended June 30, 2023 is as follows:

	Number of Shares			Weighted- Average Grant Date Fair Value		Aggregate Fair Value
Unvested balance at January 1, 2023		5,505		$	4.49
Granted		4,324			1.02
Vested		(2,531	)		4.04	$	6,132
Forfeited		(185	)		5.14
Unvested balance at June 30, 2023		7,113		$	2.46

Summary of PSU Activity

A summary of PSU activity for the six months ended June 30, 2023 is as follows:

	Number of Shares			Weighted- Average Grant Date Fair Value		Aggregate Fair Value
Unvested balance at January 1, 2023		1,262		$	4.15
Granted		—			—
Vested		(1,238	)		3.48	$	2,102
Forfeited		—			—
Unvested balance at June 30, 2023		24		$	7.89

Assumptions of Estimated Based on Monte Carlo Simulation Model

Compensation expense is based on the estimated value of the awards on the grant date, and is recognized over the period from the grant date through the expected vest dates of each vesting condition, both of which were estimated based on a Monte Carlo simulation model applying the following key assumptions:

	Three and six months ended
	June 30, 2022
Risk-free interest rate	2.8%
Volatility	79.1%
Dividend yield	0.0%
Cost of equity	13.2%

Schedule of Stock-based Compensation Expense

Stock-based compensation expense related to stock options, RSUs, SARs and PSUs for the three and six months ended June 30, 2023 and 2022 was classified in the condensed consolidated statements of operations and comprehensive loss as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
	2023		2022		2023		2022
Cost of revenue	$	11	$	26	$	37	$	61
Research and development expenses		552		694		1,252		1,289
Selling, general and administrative expenses		1,245		2,159		4,641		4,157
Total stock-based compensation	$	1,808	$	2,879	$	5,930	$	5,507

The Company recognized stock-based compensation expense for the three and six months ended June 30, 2023 and 2022 in the condensed consolidated balance sheet as follows:

	Three Months Ended June 30,					Six Months Ended June 30,
	2023		2022			2023		2022
Change in fair value of SAR Liability	$	—	$	(56	)	$	—	$	(159	)
Recognized as additional paid-in capital		1,808		2,935			5,930		5,666
Total stock-based compensation	$	1,808	$	2,879		$	5,930	$	5,507