Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Restricted Stock Unit Activity and Related Information

	Number of Shares			Weighted Average Grant Date Fair Value
Unvested balance at December 31, 2018		163,425		$	3.20
Granted		—			—
Vested		(163,425	)		3.20
Forfeited		—			—
Unvested balance at March 31, 2019		—		$	—

Summary of Stock-Based Compensation Expense, Including Shares Issued to Nonemployee for Consulting Services

Stock-based compensation expense, including shares issued to a nonemployee for consulting services, was classified in the statements of operations as follows (in thousands):

	For the Three Months Ended March 31,
	2019		2018
Research and development	$	370	$	363
General and administrative		600		859
	$	970	$	1,222

Summary of Stock Option Activity

The following table summarizes the Company’s stock option activity for the three months ended March 31, 2019 (in thousands except share and per share amounts):

	Number of Shares			Weighted Average Exercise Price Per Share
Outstanding at December 31, 2018		3,158,676		$	5.93
Granted		1,426,500			4.23
Exercised		(2,543	)		1.09
Forfeited		(18,206	)		10.77
Outstanding at March 31, 2019		4,564,427		$	5.38
Exercisable at March 31, 2019		1,974,359		$	6.24
Vested and expected to vest at March 31, 2019		4,481,177		$	5.44