Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2020

Stock-Based Compensation

Summary of stock option activity

		Weighted		Weighted
		Average		Average
		Exercise		Remaining
		Price		Contractual
	Shares	Per Share		Term (In Years)
Options Outstanding at December 31, 2019	1,699,202	$	44.87	8.0
Granted	1,490,925	$	10.42
Exercised	(36,960)	$	3.85
Canceled	(78,335)	$	35.80
Options Outstanding at September 30, 2020	3,074,832	$	28.89	8.4
Options Vested and Expected to Vest at September 30, 2020	2,888,532	$	30.19	8.4
Options Exercisable at September 30, 2020	871,007	$	80.35	6.2
Shares Available for Grant Under the 2008 Plan	907,673

Schedule of stock-based compensation expense

	Three months ended September 30,				Nine months ended September 30,
	2020		2019		2020		2019
	(In thousands)				(In thousands)
Research and development	$	642	$	330	$	1,294	$	1,740
General and administrative		608		377		1,364		2,124
Total stock-based compensation expense	$	1,250	$	707	$	2,658	$	3,864

Schedule of assumptions used for the fair value of employee stock options granted

	Three months ended September 30,				Nine months ended September 30,
	2020		2019		2020		2019
Expected stock price volatility	98	%	91	%	91 - 98	%	91	%
Expected option term	6.0	Years	6.0	Years	6.0	Years	6.0	Years
Risk-free interest rate	0.5	%	1.6 - 1.9	%	0.5 - 0.6	%	1.6 - 2.5	%
Expected dividend yield	None		None		None		None