Equity-Based Compensation (Tables)

9 Months Ended

Sep. 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 September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
	(In thousands)
Research and development	$	1,513	$	2,591	$	5,392	$	7,617
General and administrative		1,566		1,865		6,683		5,847
Total	$	3,079	$	4,456	$	12,075	$	13,464

Summary of Restricted Stock Activity

The following table summarizes the Company’s restricted stock activity for the nine months ended September 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		(37,198	)		1.34
Cancelled		-			-
Unvested restricted stock as of September 30, 2019		71,875		$	22.88

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 September 30,		Nine Months Ended September 30,
	2019	2018	2019	2018
Risk-free interest rate	1.6%	2.8%	2.2%	2.6%
Expected life of options	6.0 years	6.0 years	5.5-6.0 years	5.5-6.25 years
Expected volatility of underlying stock	67.5%	87.7%	68.3%	88.9%
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 nine months ended September 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		1,057,473			14.86
Exercised		(255,183	)		8.68
Forfeited		(431,643	)		18.45
Outstanding at September 30, 2019		5,408,310		$	15.58		7.90	$	7,172
Exercisable at September 30, 2019		2,320,649		$	13.58		6.66	$	6,609