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

3 Months Ended

Mar. 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, 2020		889,759		$	14.46	$	240
Options granted		566,853			3.03
Options exercised		—			—
Options forfeited		(105,342	)		3.66
Options expired		(11,120	)		226.32
Outstanding — Balance at March 31, 2021		1,340,150		$	8.72	$	7,035
Vested and expected to vest — March 31, 2021		1,304,842		$	8.83	$	7,010
Exercisable — March 31, 2021		527,259		$	16.68	$	346

Weighted-Average Fair Value Assumption of Stock Option Awards

Thefairvalueofstockoption awardswasestimatedatthedate ofgrant usinga Black-Scholes option-pricingmodel withthefollowingweighted-averageassumption:

	Three Months Ended March 31,
Assumptions	2021		2020
Expected term (years)		6.03		6.03
Expected volatility	121.2%		122.5%
Risk-free interest rate	0.62%		1.40%
Expected dividend yield		—		—