Stock-Based Compensation Expense

3 Months Ended

Mar. 31, 2022

Share-based Payment Arrangement [Abstract]

Stock Based Compensation Expense

6. Stock-based Compensation Expense

Stock-based Compensation Expenses

The following tables present the Company's stock-based compensation for equity-settled awards by type and financial statement lines included in the accompanying unaudited condensed consolidated statement of operations and comprehensive loss for the three months ended March 31:

	Three Months Ended March 31,
	2022		2021
	(in thousands)
Options	$	883	$	494
RSUs	511			-
Total stock-based compensation expense	$	1,394	$	494
	Three Months Ended March 31,
	2022		2021
	(in thousands)
Cost of sales	$	101	$	61
Selling, general and administrative		978		292
Research and development		315		141
Total stock-based compensation expense	$	1,394	$	494

Compensation cost related to unvested stock options and RSUs will generally be amortized on a straight-line basis over the remaining average service period. The following table presents the unamortized compensation cost and weighted average service period of all unvested outstanding awards as of March 31, 2022.

	Unamortized Compensation Costs		Weighted Average Service Period
	(in thousands)		(years)
Options	$	8,674	2.3
RSUs		13,394	1.2
Total unamortized compensation cost	$	22,068

Plan Activities

The following table summarizes stock option activity under the Company's incentive plans:

	Number of Shares			Weighted Average Exercise Price Per Share		Weighted- Average Remaining Contractual Life	Aggregate Intrinsic Value
						(in years)	(in thousands)
Options outstanding, December 31, 2021		3,119,993		$	7.59
Granted		—
Forfeited		(33,599	)	$	7.92
Exercised		(61,438	)	$	3.94		$	123
Options outstanding, March 31, 2022		3,024,956		$	7.66	7.4	$	427
Options vested and exercisable, March 31, 2022		1,527,230		$	4.96	5.8	$	427
Vested and expected to vest after March 31, 2022		2,840,872		$	7.48	7.3	$	427

The weighted-average grant-date fair value of options granted during the three months ended March 31, 2022 and 2021 was $5.72 per share and $11.26 per share, respectively.

The following table summarizes the non-vested stock options as of March 31, 2022 and December 31, 2021:

	Number of Shares		Weighted Average Grant Date Fair Value
Non-vested Options, December 31, 2021		1,632,852	$	7.09
Non-vested Options, March 31, 2022		1,497,827	$	7.19

The total fair value of shares vested during the three months ended March 31, 2022 and 2021 was $0.7 million and $0.7 million, respectively.

Certain stock option grants under the 2017 Plan allow the recipient to exercise the options prior to the options becoming fully vested. Under the 2017 Plan, the Company retains the right to repurchase common shares that have been issued upon early exercise of options at the original issue price. During the three months ended March 31, 2022, the Company did not repurchase shares. There was no material amount of shares of common stock subject to repurchase as of March 31, 2022. Cash received for the early exercise of unvested stock options is initially recorded as a liability and are released to equity over the vesting period. During three months ended March 31, 2022 and 2021, early exercised stock options vested were immaterial.

The following table summarizes RSU activity under the Company's incentive plans:

	Number of Shares			Weighted Average Grant Date Fair Value
RSUs outstanding, December 31, 2021		338,149		$	9.37
Granted		2,370,259		$	5.37
Forfeited		(5,646	)	$	7.78
RSUs outstanding, March 31, 2022		2,702,762		$	5.86