Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2020

Share-based Payment Arrangement [Abstract]

Schedule of Allocated Stock-Based Compensation Expense

The Company recorded stock-based compensation expense related to stock options and shares issued under the Company's 2017 Employee Stock Purchase Plan (2017 Plan) in the following expense categories of its accompanying consolidated statements of operations for the three months ended March 31, 2020 and 2019:

	Three Months Ended March 31,
	2020		2019
Cost of product sales	$	54	$	21
Research and development	257		243
General and administrative	2,149		2,158
	$	2,460	$	2,422

Schedule of Stock Option Activity

The following table summarizes the activity related to stock option grants to employees and nonemployees for the three months ended March 31, 2020:

	Shares	Weighted average exercise price per share		Weighted average remaining contractual life
Outstanding at December 31, 2019	7,399,217	$	9.81	6.37
Granted	1,146,258	5.65
Exercised	—	—
Expired	—	—
Forfeited	(172,435)	10.57
Outstanding at March 31, 2020	8,373,040	$	9.22	6.59
Exercisable at March 31, 2020	4,844,852	$	9.41	4.90
Vested and expected to vest at March 31, 2020	8,373,040	$	9.22	6.59

Schedule of Fair Value Options using Black-Scholes Pricing Model

The grant date fair value of each stock option grant was estimated at the time of grant using the Black-Scholes option-pricing model using the following weighted average assumptions:

	Three Months Ended March 31,
	2020			2019
Risk free interest rate	0.75		%	2.57		%
Expected term (in years)	6.08			6.08
Expected volatility	68.34		%	67.14		%
Annual dividend yield	0.00		%	0.00		%
Fair value of common stock	$	5.65		$	7.49

The Company calculated the fair value of each option grant and the shares issued under the 2017 Plan on the respective dates of grant using the following weighted average assumptions:

	Three Months Ended March 31,
	2020		2019
Risk free interest rate	1.57	%	2.51	%
Expected term (in years)	0.5		0.5
Expected volatility	79.59	%	82.20	%
Annual dividend yield	0.00	%	0.00	%

Schedule of Nonvested Restricted Stock Units Activity

The following table summarizes the activity related to RSUs granted to employees for the three months ended March 31, 2020:

	Shares
Balance at December 31, 2019	—
Granted	1,290,203
Vested and settled	—
Expired/ forfeited/ canceled	(2,217)
Balance at March 31, 2020	1,287,986
Expected to vest at March 31, 2020	1,287,986