Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2020

Stock-based Compensation

Schedule of stock-based compensation expense

Total compensation cost recognized for all stock-based compensation awards in the condensed consolidated statements of operations was as follows (in thousands):

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2020		2019		2020		2019
Research and development	$	2,673	$	3,853	$	5,730	$	7,235
General and administrative		2,744		2,640		5,907		7,113
Total stock-based compensation expense	$	5,417	$	6,493	$	11,637	$	14,348

Schedule of changes in unvested restricted stock

The following is a summary of restricted stock and restricted stock unit awards activity for the six months ended June 30, 2020:

		Weighted
		Average
		Grant Date
		Fair Value
	Shares	Per Share
Unvested restricted stock and restricted stock unit awards as of December 31, 2019	581,408	$	24.03
Issued	283,319	$	27.91
Vested	(243,587)	$	22.65
Forfeited	(105,009)	$	24.07
Unvested restricted stock and restricted stock unit awards as of June, 30 2020	516,131	$	26.60

Schedule of stock option activity

The following is a summary of stock option activity for the six months ended June 30, 2020:

		Weighted Average		Remaining	Aggregate Intrinsic
	Shares	Exercise Price		Contractual Life (years)	Value (in thousands)
Outstanding at December 31, 2019	4,358,291	$	25.40	7.4	$	26,060
Granted	1,228,749	$	27.84
Exercised	(589,020)	$	16.78
Cancelled	(1,018,295)	$	30.83
Outstanding at June 30, 2020	3,979,725	$	26.04	8.0	$	17,695
Exercisable at June 30, 2020	1,367,908	$	23.94	6.7	$	10,035