Stock-Based Compensation and Employee Stock Purchase Program (Tables)

12 Months Ended

Dec. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Activity Under Stock Incentive Plans

The following is a summary of stock option information and weighted average exercise prices under the Company’s stock incentive plans (in thousands, except share data and price per share):

	Shares Subject to Outstanding Options			Weighted- Average Exercise Price Per Share		Aggregate Intrinsic Value
Outstanding — Balance at December 31, 2019		661,701		$	21.60	$	305
Options granted		502,494			4.28		—
Options exercised		—			—		—
Options forfeited		(174,508	)		5.91		—
Options expired		(99,928	)		25.56		—
Outstanding — Balance at December 31, 2020		889,759			14.46	$	240
Options granted		1,227,042			2.76		—
Options exercised		—			—		—
Options forfeited		(440,166	)		3.09	$	1,086
Options expired		(254,440	)		29.02		—
Outstanding — Balance at December 31, 2021		1,422,195			5.28		—
Vested and expected to vest — December 31, 2021		1,322,111			5.47		—
Exercisable —December 31, 2021		743,109		$	7.54		—

Weighted-Average Fair Value Assumption of Stock Option Awards

The fair value of stock option awards was estimated at the date of grant using a Black-Scholes option-pricing model with the following weighted-average assumption:

	Year Ended December 31,
Assumptions	2021			2020
Expected term (years)		6.31			6.48
Expected volatility		121	%		134	%
Risk-free interest rate		0.86	%		1.01	%
Expected dividend yield		—			—