Stock-Based Compensation Expense (Tables)

9 Months Ended

Sep. 30, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock Option Activities

A summary of stock option activities for the nine months ended September 30, 2021 is as follows:

	Number of Options			Weighted Average Exercise Price		Weighted Average Grant Date Fair Value		Weighted Avg Remaining Contractual Life (Years)
Options outstanding as of    December 31, 2020		4,201,935		$	9.57				6.46
Issued
Granted		1,652,751		$	15.51	$	8.94
Exercised		(321,812	)	$	4.28	$	2.12
Forfeited		(61,053	)	$	19.47	$	10.51
Expired		(17,709	)
Options outstanding as of    September 30, 2021		5,454,112		$	11.59				6.97
Exercisable as of September 30, 2021		3,174,863		$	8.76				5.35

Summary of Non-Vested Restricted stock unit Activities

A summary of non-vested restricted stock unit activities for the nine months ended September 30, 2021 is as follows:

			Weighted
			Average
	Number of		Grant Date
	Shares		Fair Value
Unvested at December 31, 2020		—
Granted		657,729	$	15.46
Vested		—
Forfeited		—
Unvested at September 30, 2021		657,729	$	15.46

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 September 30,				Nine Months Ended September 30,
	2021		2020		2021		2020
Research and development	$	623	$	626	$	1,760	$	1,541
Selling, general and administrative		1,168		430		2,317		953
Cost of goods sold		222		185		581		454
	$	2,013	$	1,242	$	4,658	$	2,948

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:

	Nine Months Ended September 30,
	2021
	Range	Weighted Average
Expected volatility	62.3% to 63.7%	63.3%
Risk-free interest rate	0.6% to 1.6%	1.0%
Expected life (in years)	5.52 to 10.00 years	6 years
Expected dividend yield	0.0%	0.0%
Grant date fair value	$12.54 to $19.94	$15.51

On July 30, 2021, the Board of Directors approved the issuance of 640,567 equity awards to the Company's named executive officers and certain non-employee directors, consisting of 17,577 restricted stock units and 622,990 stock option awards. The awards will vest over one to four years of service.

On August 3, 2021, the Board of Directors approved the issuance of equity awards to certain non-employee directors, consisting of 40,134 restricted stock units. The awards will vest over one to three years of service.