Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 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
	March 31,
	2019		2018
Research and development	$	760	$	907
General and administrative		1,162		1,518
Total	$	1,922	$	2,425

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

	Three Months Ended
	March 31, 2019
	Unrecognized Compensation Expense		Average Vesting Period
	($ million)		(Years)
Stock options grants	$	11.7	3.2
RSU grants		0.1	1.6
PRSU grants		—	—
ESPP		0.1	0.4