Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

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:

	Fiscal Year Ended
	December 31, 2020			December 28, 2019
Risk-free interest rate		0.91	%		2.29	%
Expected term (in years)		5.97			6.02
Expected volatility		54	%		52	%
Expected dividend yield		0	%		0	%

Summary of Stock Option Activity

The following table summarizes the Company’s option activity since December 28, 2019:

	Number of Shares			Weighted Average Exercise Price		Weighted Average Contractual Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Outstanding as of December 28, 2019		1,952,300		$	5.31		5.87	$	26,415
Granted		603,336			15.69
Exercised		(217,965	)		1.04
Forfeited		(65,566	)		10.01
Expired		(10,871	)		43.96
Outstanding as of December 31, 2020		2,261,234		$	8.17		6.22	$	26,671
Vested and expected to vest as of December 31, 2020		2,261,234		$	8.17		6.22	$	26,671
Options exercisable as of December 31, 2020		1,425,910		$	4.26		4.73	$	22,363

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):

	Fiscal Year Ended
	December 31, 2020		December 28, 2019
Cost of revenue	$	27	$	17
Research, development and clinical trials expenses		396		104
Selling, general and administrative expenses		1,991		733
	$	2,414	$	854