Equity-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Equity-Based Compensation Expense

Equity-based compensation expense is classified in the condensed consolidated statements of operations and comprehensive loss as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
	(In thousands)
Research and development	$	2,096	$	2,633	$	3,879	$	5,026
General and administrative		2,308		2,268		5,117		3,982
Total	$	4,404	$	4,901	$	8,996	$	9,008

Summary of Restricted Stock Activity

The following table summarizes the Company’s restricted stock activity for the six months ended June 30, 2019:

	Number of Shares			Weighted Average Grant Date Fair Value per Share
Unvested restricted stock as of December 31, 2018		109,073		$	15.53
Granted		-			-
Vested		(36,462	)		1.34
Cancelled		-			-
Unvested restricted stock as of June 30, 2019		72,611		$	22.66

Summary of Weighted Average Assumptions Used to Compute Fair Value of Option Granted

Key assumptions used to apply this pricing model were as follows:

	Three Months Ended June 30,		Six Months Ended June 30,
	2019	2018	2019	2018
Risk-free interest rate	2.1%	2.8%	2.4%	2.6%
Expected life of options	5.5-6.0 years	5.5-6.25 years	5.5-6.0 years	5.5-6.25 years
Expected volatility of underlying stock	67.9%	87.7%	68.6%	89.0%
Expected dividend yield	0.0%	0.0%	0.0%	0.0%

Summary of Stock Option Activity

The following is a summary of stock option activity for the six months ended June 30, 2019:

	Number of Options			Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(In years)		(In thousands)
Outstanding at December 31, 2018		5,037,663		$	15.63
Granted		793,813			14.54
Exercised		(233,872	)		8.65
Forfeited		(282,108	)		18.79
Outstanding at June 30, 2019		5,315,496		$	15.61		8.14	$	14,978
Exercisable at June 30, 2019		2,165,526		$	13.43		7.01	$	10,193