Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock-based Awards for 2008 Plan and 2015 Plan

The following table provides a summary of stock-based awards for the 2008 Plan and 2015 Plan for the six months ended June 30, 2019 and 2018:

	Six months ended June 30, 2019									Six months ended June 30, 2018
	Stock Options			RSUs			Total			Stock Options			RSUs			Total
Outstanding as of December 31		3,077,264			156,250			3,233,514			1,916,832			86,875			2,003,707
Granted		339,125			—			339,125			31,720			120,000			151,720
Exercised		(97,223	)		(26,250	)		(123,473	)		(154,766	)		(24,375	)		(179,141	)
Forfeited		(23,500	)		—			(23,500	)		(102,500	)		—			(102,500	)
Outstanding as of June 30		3,295,666			130,000			3,425,666			1,691,286			182,500			1,873,786

Stock-based Compensation Expense included in Accompanying Statements of Operations and Comprehensive Loss

Stock-based compensation expense is included in the following line items in the accompanying statements of operations and comprehensive loss for the three and six months ended June 30, 2019 and 2018 (in thousands):

	Three Months Ended				Six Months Ended
	June 30, 2019		June 30, 2018		June 30, 2019		June 30, 2018
Research and development	$	545	$	145	$	996	$	373
General and administrative		602		247		1,151		431
Total stock-based compensation	$	1,147	$	392	$	2,147	$	804