Stock-Based Compensation Expense (Tables)

6 Months Ended

Jun. 30, 2022

Share-based Payment Arrangement [Abstract]

Summary of Stock Option Activities

A summary of stock option activities for the six months ended June 30, 2022 is as follows:

	Number of Options			Weighted Average Exercise Price		Weighted Avg Remaining Contractual Life (Years)
Options outstanding as of    December 31, 2021		5,754,005		$	11.64		5.20
Issued
Granted		782,557			12.46
Exercised		(140,826	)		4.16
Forfeited		(83,717	)		14.69
Expired		(88,909	)		17.07
Options outstanding as of    June 30, 2022		6,223,110			11.80		6.84
Exercisable as of June 30, 2022		3,515,831		$	10.00		5.18

Summary of Non-Vested Restricted stock unit Activities

A summary of non-vested restricted stock unit activities for the six months ended June 30, 2022 is as follows:

				Weighted
				Average
	Number of			Grant Date
	Shares			Fair Value
Unvested at December 31, 2021		640,479		$	15.46
Granted		80,427			13.37
Vested		(104,839	)		15.64
Forfeited		(30,619	)		15.38
Unvested at June 30, 2022		585,448		$	15.14

Schedule of Stock-Based Compensation Expense

Stock-based compensation expense was classified in the accompanying condensed consolidated statements of operations and comprehensive income (loss) as follows (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Research and development	$	792	$	540	$	1,566	$	1,137
Selling, general and administrative		1,866		686		3,520		1,149
Cost of goods sold		246		180		467		359
	$	2,904	$	1,406	$	5,553	$	2,645

Schedule of Range and Weighted-average Assumptions Used in Black-Scholes Option Pricing Model to Determine the Fair Value of Stock Options

The following table presents the range and weighted-average assumptions, used in the Black-Scholes option pricing model to determine the fair value of stock options:

	Six Months Ended June 30,
	2022		2021
	Range	Weighted Average	Range	Weighted Average
Expected volatility	62.4% to 63.4%	62.7%	62.3% to 63.7%	63.6%
Risk-free interest rate	2.0% to 3.0%	2.2%	0.6% to 1.6%	1.1%
Expected life (in years)	6.0 to 10.0 years	6.1 years	5.52 to 10.00 years	6 years
Expected dividend yield	0.0%	0.0%	0.0%	0.0%
Grant date fair value	$10.74 to $12.85	$12.32	$15.60 to $19.94	$15.64

Schedule of Common stock reserved for future issuance

Each share of common stock is entitled to one vote. Common stock reserved for future issuance consisted of the following:

	June 30, 2022		December 31, 2021
Stock options issued and outstanding under the Equity Plans		6,223,110		5,754,005
Restricted stock units		585,448		640,479
Employee stock purchase plan		711,643		484,027
Total shares of common stock reserved		7,520,201		6,878,511