Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2017

Summary of Stock-based Compensation Expense Recognized

During the three and six months ended June 30, 2017 and 2016, the Company recognized the following stock-based compensation expense:

	Three Months Ended June 30,				Six Months Ended June 30,
	2017		2016		2017		2016
Stock-based compensation expense by type of award:
Stock options	$	150,246	$	237,285	$	374,957	$	607,858
Restricted stock and restricted stock units		178,119		243,036		341,242		486,029
Employee stock purchase plan		12,893		9,924		27,298		20,912
Total stock-based compensation expense included    in expenses	$	341,258	$	490,245	$	743,497	$	1,114,799
Stock-based compensation expense by line item:
Research and development expenses	$	100,579	$	176,609	$	217,358	$	368,769
General and administrative expenses		240,679		313,636		526,139		746,030
Total stock-based compensation expense included    in expenses	$	341,258	$	490,245	$	743,497	$	1,114,799

Schedule of Unrecognized Stock-based Compensation Expense, Net of Estimated Forfeitures, by Type of Award and Weighted-average Recognition Period

The following table sets forth the Company’s unrecognized stock-based compensation expense, net of estimated forfeitures, by type of award and the weighted-average period over which that expense is expected to be recognized:

	As of  June 30, 2017
	Unrecognized Expense, Net of Estimated Forfeitures		Weighted- average Recognition Period (in years)
Type of award:
Stock options	$	1,129,690		2.57
Restricted stock and restricted stock units	$	744,249		1.22

Summary of Stock Option Activity

The following table summarizes stock option activity during the six months ended June 30, 2017:

	Shares Subject to Stock Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)
Options outstanding at December 31, 2016		883,837		$	4.28
Granted		809,534		$	1.23
Exercised		—		$	—
Cancelled		(98,477	)	$	5.29
Options outstanding at June 30, 2017		1,594,894		$	2.67		9.06
Options exercisable at June 30, 2017		594,069		$	4.14		8.66

Schedule of Weighted Average Assumptions using Black-Scholes Option Pricing Model

the fair value of each employee option grant during the six months ended June 30, 2017 was estimated on the date of grant using the Black-Scholes option pricing model with the following weighted average assumptions:

	Six months ended June 30, 2017
Expected volatility		85.32	%
Expected term (in years)		5.93
Risk-free interest rate		1.97	%
Expected dividend yield		0	%

Restricted stock [Member]

Summary of Stock Activity

The following table is a summary of restricted stock activity during the six months ended June 30, 2017:

	Shares of Restricted Stock			Weighted- Average Grant Date Fair Value
Unvested at December 31, 2016		307,096		$	3.93
Granted		—		$	—
Vested		(62,000	)	$	9.49
Forfeited		—		$	—
Repurchased		—		$	—
Unvested at June 30, 2017		245,096		$	2.53

Restricted stock units [Member]

Summary of Stock Activity

The following table summarizes restricted stock unit activity during the six months ended June 30, 2017:

	Shares Subject to Restricted Stock Units			Weighted- Average Grant Date Value
Unvested at December 31, 2016		80,625		$	5.72
Granted		—		$	—
Vested		(12,625	)	$	8.87
Forfeited		(11,250	)	$	7.08
Repurchased		—		$	—
Unvested June 30, 2017		56,750		$	4.75