Share-Based Payments (Tables)

9 Months Ended

Sep. 30, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Stock-Based Compensation Expense

Stock-based compensation expense by award type was as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Stock options	$	246	$	201	$	905	$	656
Restricted stock	—		50		$	23	152
Restricted stock units	—		—		$	—	3
Employee stock purchase plan	2		2		7		8
	$	248	$	253	$	935	$	819

The Company allocated stock-based compensation expense as follows in the condensed consolidated statements of operations and comprehensive loss (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Research and development expense	$	99	$	56	$	387	$	179
General and administrative expense	149		197		$	548	$	640
	$	248	$	253	$	935	$	819

Summary of Stock Option Activity and Related Information

A summary of the stock option activity is presented below:

	Shares		Weighted-Average Exercise Price
Outstanding at December 31, 2017	2,695,796		$	3.16
Granted	3,055,900		1.72
Exercised	(71,403	)	0.79
Cancelled or forfeited	(1,111,941	)	2.40
Outstanding at September 30, 2018	4,568,352		$	2.42
Exercisable at September 30, 2018	1,868,379		$	3.35

Summary of Restricted Stock

A summary of the restricted stock is presented below:

	Restricted Stock		Weighted-Average Grant Date Fair Value
Unvested at December 31, 2017	4,430		$	11.43
Vested	(4,430	)	11.43
Unvested at September 30, 2018	—