Share-Based Payments (Tables)

6 Months Ended

Jun. 30, 2017

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



	Three Months Ended June 30,				Six Months Ended June 30,
	2017		2016		2017		2016
Stock options	$	268	$	444	$	455	$	879
Restricted stock	51		51		102		105
Restricted stock units	—		106		3		198
Performance stock options	—		14		—		14
Employee stock purchase plan	3		6		6		11
	$	322	$	621	$	566	$	1,207

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



	Three Months Ended June 30,				Six Months Ended June 30,
	2017		2016		2017		2016
Research and development expense	$	83	$	226	$	123	$	447
General and administrative expense	239		395		$	443	760
	$	322	$	621	$	566	$	1,207

A summary of the stock option activity is presented below:



	Shares		Weighted-Average Exercise Price
Outstanding at December 31, 2016	2,024,468		$	4.41
Granted	248,025		1.85
Exercised	(140,400	)	0.28
Cancelled or forfeited	(166,887	)	9.85
Outstanding at June 30, 2017	1,965,206		$	3.92
Exercisable at June 30, 2017	942,661		$	4.76
Vested and expected to vest at June 30, 2017⁽¹⁾	1,965,206		$	3.92


⁽¹⁾	Represents the number of vested options, plus the number of unvested options expected to vest. The Company adopted ASU 2016-09 as of January 1, 2017 and elected an accounting policy to record forfeitures as they occur.

A summary of the restricted stock is presented below:



	Restricted Stock		Weighted-Average Grant Date Fair Value
Unvested at December 31, 2016	22,150		$	11.43
Vested	(8,860	)	11.43
Unvested at June 30, 2017	13,290		$	11.43

A summary of the restricted stock units is presented below:



	Restricted Stock Units		Weighted-Average Grant Date Fair Value
Unvested at December 31, 2016	3,333		$	4.09
Vested	(3,333	)	4.09
Unvested at June 30, 2017	—		$	—