Stock-Based Awards (Tables)

6 Months Ended

Jun. 30, 2017

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

Valuation Assumptions of Stock Options Granted

The assumptions that the Company used to determine the grant-date fair value of the stock options granted to employees and directors during the six months ended June 30, 2017 and 2016 were as follows, presented on a weighted average basis:

	Six Months Ended June 30, 2017			Six Months Ended June 30, 2016
Risk-free interest rate		2.19	%		1.37	%
Expected term (in years)		6.1			6.1
Expected volatility		80.2	%		80.5	%
Expected dividend yield		0	%		0	%

Summary of Stock Option Activity

The following table summarizes the Company’s stock option activity since January 1, 2017:

	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)
Outstanding at December 31, 2016		920,731		$	4.36		6.4	$	1,297
Granted		588,701			8.08
Exercised		(18,524	)		4.33
Forfeited		(46,594	)		5.14
Outstanding at June 30, 2017		1,444,314		$	5.85		7.7	$	8,220
Options exercisable at June 30, 2017		636,409		$	4.00		5.8	$	4,550
Options vested and expected to vest at June 30, 2017		1,408,747		$	5.81		7.6	$	8,063
Options exercisable at December 31, 2016		585,959		$	3.78		5.2	$	1,136
Options vested and expected to vest at December 31, 2016		904,010		$	4.37		6.3	$	1,289

Summary of Stock Based Compensation Expense

The Company recorded stock-based compensation expense related to stock options in the following expense categories of its statements of operations and comprehensive loss:

	Three Months Ended June 30,				Six Months Ended June 30,
	2017		2016		2017		2016
Research and development expenses	$	131	$	53	$	205	$	104
General and administrative expenses		142		114		264		226
	$	273	$	167	$	469	$	330