Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Assumptions Used to Determine Grant Date Fair Value of Stock Options Granted

The following table presents, on a weighted average basis, the assumptions used in the Black-Scholes option-pricing model to determine the grant-date fair value of stock options granted to employees and directors:

	Year Ended December 31,
	2021			2020
Risk-free interest rate		0.90	%		0.91	%
Expected term (in years)		6.03			5.97
Expected volatility		58	%		54	%
Expected dividend yield		0	%		0	%

Summary of Stock Option Activity

The following table summarizes the Company’s option activity since December 31, 2020:

	Number of Shares			Weighted Average Exercise Price		Weighted Average Contractual Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Outstanding as of December 31, 2020		2,261,234		$	8.17		6.22	$	26,671
Granted		1,326,675			34.60
Exercised		(588,461	)		1.65
Forfeited		(200,060	)		28.10
Expired		(1,838	)		31.76
Outstanding as of December 31, 2021		2,797,550		$	20.64		7.54	$	14,625
Vested and expected to vest as of December 31, 2021		2,797,550		$	20.64		7.54	$	14,625
Options exercisable as of December 31, 2021		1,371,048		$	11.80		6.11	$	13,143

Schedule of Stock-Based Compensation Expense

The Company recorded stock-based compensation expense in the following expense categories of its consolidated statements of operations (in thousands):

	Year Ended December 31,
	2021		2020
Cost of revenue	$	72	$	27
Research, development and clinical trials expenses		1,114		396
Selling, general and administrative expenses		5,692		1,991
	$	6,878	$	2,414