Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2019

Schedule of weighted-average assumptions estimated at the date of grant using the Black-Scholes option pricing model

	2019				2018
Expected stock price volatility	104.7	-	118.87	%	106.64	-	113.19	%
Expected term of options	5.16	-	6.1	years	5.2	-	6.1	years
Risk‑free interest rate	1.51	-	2.59	%	2.32	-	3.1	%
Expected annual dividend yield			0	%			0	%

Schedule of unrecognized compensation expense expected to be recognized in future years

That expense is expected to be recognized over the next four years as follows, in thousands:

2020	$	3,981
2021		2,941
2022		1,065
2023		304
	$	8,291

Stock options

Schedule of total compensation cost recognized in the statement of operations

Total compensation cost recognized for all stock option awards in the statements of operations is as follows (in thousands):

	Year Ended December 31,
	2019		2018
Research and development	$	2,563	$	1,712
General and administrative		3,070		2,995
Total	$	5,633	$	4,707

Summary of activity for all options

A summary of activity for the years ended December 31, 2019 and 2018 is presented below (in thousand, except share and per share amounts):

		Weighted‑
		Average		Aggregate
		Exercise Price		Intrinsic
	Shares	Per Share		Value
Outstanding—December 31, 2017	3,754,320	$	5.22
Granted	1,372,000		6.60
Exercised	(12,308)		1.18
Forfeited	(162,603)		5.00
Outstanding—December 31, 2018	4,951,409		5.62
Granted	4,703,000		2.31
Exercised	(80,020)		1.22
Forfeited	(916,205)		4.21
Expired	(117,903)		8.23
Outstanding—December 31, 2019	8,540,281	$	3.95	$	3,774
Exercisable—December 31, 2019	4,431,560	$	5.04	$	1,447
Exercisable and expected to vest—December 31, 2019	8,540,281	$	3.95	$	3,774

Restricted stock

Schedule of total compensation cost recognized in the statement of operations

Total compensation cost recognized for all restricted stock awards in the statements of operations for the years ended December 31, 2019 and 2018 is as follows (in thousands):

	Year Ended
	December 31,
	2019		2018
Research and development	$	19	$	19
General and administrative		20		62
Total	$	39	$	81

Summary of activity for all restricted stock

A summary of activity for the years ended December 31, 2019 and 2018 is presented below:

		Weighted‑average
		Grant Date
	Shares	Fair Value per Share
Outstanding—December 31, 2017	239,800	$	1.21
Vested	(120,600)		1.21
Forfeited	(14,000)		1.21
Outstanding—December 31, 2018	105,200		1.21
Vested	(52,600)		1.21
Forfeited	(20,200)		1.21
Outstanding—December 31, 2019	32,400	$	1.21
Expected to vest—December 31, 2019	32,400	$	1.21