Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 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 three months ended March 31, 2019 and 2018:

	Three months ended March 31, 2019									Three months ended March 31, 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		90,000			—			90,000			10,000			120,000			130,000
Exercised		(23,593	)		(13,125	)		(36,718	)		(37,894	)		(11,250	)		(49,144	)
Forfeited		(9,844	)		—			(9,844	)		(102,500	)		—			(102,500	)
Outstanding as of March 31		3,133,827			143,125			3,276,952			1,786,438			195,625			1,982,063

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 months ended March 31, 2019 and 2018 (in thousands):

	Three Months Ended
	March 31, 2019		March 31, 2018
Research and development	$	452	$	228
General and administrative		548		184
Total stock-based compensation	$	1,000	$	412