Stock Based Compensation (Tables)

9 Months Ended

Sep. 30, 2020

Share-based Payment Arrangement [Abstract]

Schedule of stock based compensation expense

The Company recorded stock-based compensation expense in the following expense categories of its accompanying consolidated statements of operations and comprehensive loss for the three months ended September 30, 2020 and 2019 and nine months ended September 30, 2020 and 2019, respectively (amounts in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Research and development	$	258	$	180	$	731	$	981
General and administrative	830		1,016		2,417		2,149
Total	$	1,088	$	1,196	$	3,148	$	3,130

Summary of the activity related to stock option grants to employees and nonemployees

The following table summarizes the activity related to stock option grants to employees and nonemployees for the nine months ended September 30, 2020:

	Shares	Weighted average exercise price per share		Weighted-average remaining contractual life (years)
Outstanding at December 31, 2019	2,498,606	$	17.18	7.7
Granted	1,824,375	4.77
Exercised	(1,449)	1.08
Forfeited	(567,356)	13.81
Outstanding at September 30, 2020	3,754,176	$	11.67	8.0
Vested and exercisable at September 30, 2020	1,358,519	$	20.83	6.0
Vested and expected to vest at September 30, 2020	3,754,176	$	11.67	8.0

Summary of grant date fair value assumptions

The grant date fair value of each option grant was estimated during the three and nine months ended September 30, 2020 and 2019 using the following assumptions within the Black-Scholes option-pricing model:

	Three Months Ended September 30, 2020	Three Months Ended September 30, 2019	Nine Months Ended September 30, 2020	Nine Months Ended September 30, 2019
Expected term (in years)	6.08	6.08	5.75	6.02
Expected volatility	77%	81%	77%	80%
Risk-free interest rate	0.36%	1.51%	0.87%	2.23%
Expected dividend yield	0%	0%	0%	0%