Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Summary of Share-based Compensation Expense

The total share-based compensation expense recognized is reflected in the statements of operations and comprehensive loss as follows (in thousands):

	Year Ended December 31,
	2019		2018		2017
Research and development	$	1,379	$	1,766	$	1,348
General and administrative		2,728		3,004		1,988
Total	$	4,107	$	4,770	$	3,336

Weighted Average Assumptions Used in Black-Scholes Option Pricing Model to Calculate Fair Value of Underlying Common Stock

The following table sets forth the weighted average assumptions utilized in the Black-Scholes option pricing model to calculate the fair value of the underlying common stock for the years ended December 31, 2019, 2018 and 2017.

	Year Ended December 31,
	2019			2018			2017
Expected term (years)		7.00			7.00			7.00
Expected stock price volatility		109.49	%		93.08	%		96.85	%
Risk-free interest rate		2.49	%		2.87	%		2.20	%
Expected dividend yield		0.00	%		0.00	%		0.00	%

Summary of Activity Related to Stock Options

The following table summarizes the activity related to stock options during the year ended December 31, 2019:

				Weighted
	Number of			Average
	Shares			Exercise Price
Options outstanding at December 31, 2018		3,463,096		$	6.62
Granted		1,920,100			1.23
Exercised		(16,362	)		0.40
Cancelled/Forfeited		(1,262,384	)		5.01
Options outstanding at December 31, 2019		4,104,450			4.63
Options exercisable at December 31, 2018		1,583,749			5.63
Options exercisable at December 31, 2019		2,452,764			5.44

Additional Information about the Stock Option Outstanding and Exercisable

The following table provides additional information about the Company’s stock options that were outstanding and exercisable at December 31, 2019 (aggregate intrinsic values in thousands):

							Weighted								Weighted
			Weighted				Average				Weighted				Average
			Average		Aggregate		Remaining				Average		Aggregate		Remaining
Exercise	Options		Exercise		Intrinsic		Contractual		Options		Exercise		Intrinsic		Contractual
Price	Outstanding		Price		Value		Life (Years)		Exercisable		Price		Value		Life (Years)
$0.00 - $2.99		1,759,903						7.40		716,893					4.87
$3.00 - $6.99		1,465,336					5.41			1,012,211					4.06
$7.00 - $8.99		677,433					5.05			568,759					4.61
$9.00 - $20.84		201,778						7.76		154,901					7.76
		4,104,450	$	4.63	$	3,191	6.32			2,452,764	$	5.44	$	1,472	4.66

2016 Employee Stock Purchase Plan

Summary of Share-based Compensation Expense

The share-based compensation expense recognized for the 2016 ESPP is reflected in the statements of operations and comprehensive loss as follows (in thousands):

	Year Ended December 31,
	2019		2018		2017
Research and development	$	11	$	5	$	7
General and administrative		9		10		21
Total	$	20	$	15	$	28

Restricted Stock Units (RSUs)

Summary of the Activity Related to RSUs

The following table summarizes the activity related to RSUs during the year ended December 31, 2019:

				Weighted Average
	Number of			Grant Date
	Shares			Fair Value
Non-vested RSUs outstanding at December 31, 2018		—		$	—
Granted		1,339,300			0.88
Vested		(70,000	)		1.09
Non-vested RSUs outstanding at December 31, 2019		1,269,300			0.87