Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2019

Stock-Based Compensation

Summary of Stock-Based Compensation Expense Recognized

The following table presents stock-based compensation expense recognized for stock options, restricted stock units, or RSUs, performance-based restricted stock units, or PRSUs, and the Company’s employee stock purchase program, or ESPP, in the Company’s statements of operations (in thousands):

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2019		2018		2019		2018
Research and development	$	767	$	983	$	1,527	$	1,890
General and administrative		1,156		1,620		2,318		3,138
Total	$	1,923	$	2,603	$	3,845	$	5,028

Summary of Total Unrecognized Stock-Based Compensation Expense, Net of Estimated Forfeitures

	At June 30, 2019
	Unrecognized Compensation Expense		Average Vesting Period
	($ thousands)		(Years)
Stock options grants	$	11,208	3.0
RSU grants		—	—
PRSU grants		—	—
ESPP		29	0.2