Equity-based Compensation and Equity Incentive Plans (Tables)

9 Months Ended

Sep. 30, 2020

Schedule of Restricted Common Stock Activity

The following table shows restricted stock activity during the nine months ended September 30, 2020:

	Restricted stock awards
				Grant date
	Number of			fair value
	shares			(per share)
Unvested at December 31, 2019		586,929		$	2.97
Granted		226,335			1.70
Vested		(24,041	)		13.55
Forfeited		(164,371	)		2.36
Unvested at September 30, 2020		624,852		$	2.26

Schedule of Equity-based Compensation Expenses

The following table summarizes equity‑based compensation expense within the Company’s consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2020 and 2019 (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Research and development	$	422	$	353	$	1,349	$	986
General and administrative		513		716	$	1,756		2,108
	$	935	$	1,069	$	3,105	$	3,094

Schedule of Equity-based Compensation Expenses by Award Type

The following table summarizes equity‑based compensation expense by type of award for the three and nine months ended September 30, 2020 and 2019 (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Stock options	$	764	$	1,026	$	2,529	$	2,999
Restricted stock awards		165		43	$	558		95
Employee stock purchase plan		6		—	$	18		—
	$	935	$	1,069	$	3,105	$	3,094

2015 and 2017 Plan

Schedule of Stock Option Activity

The following table summarizes stock option activity during the nine months ended September 30, 2020 under the 2015 Plan and the 2017 Plan.

	Stock options outstanding
						Weighted
				Weighted		average		Aggregate
				average		remaining		Intrinsic
	Number of			exercise		contractual		value (a)
	options			price		term (in years)		(in thousands)
Outstanding at December 31, 2019		2,286,419		$	9.24		8.7	$	43
Granted		1,554,904			1.89
Exercised		(724	)		1.70				—
Forfeited		(440,645	)		7.94
Outstanding at September 30, 2020		3,399,954			6.05		8.6	$	286
Vested or expected to vest at September 30, 2020		3,399,954			6.05		8.6		286
Exercisable at September 30, 2020		1,267,259			9.51		7.8	$	25

(a) The aggregate intrinsic value is calculated as the difference between the exercise price of the options and the fair market value of the underlying common stock for the options that were in the money at September 30, 2020 and December 31, 2019.