Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2020

Summary of Option Activity under 2018 Plan, 2013 Plan and 2010 Plan

A summary of option activity under the 2018 Plan, 2013 Plan, and 2010 Plan for the nine months ended September 30, 2020, is as follows:

Year-to-Date Activity	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (in millions)
Options outstanding at December 31, 2019		1,313,475		$	12.28		8.7
Granted		133,500			3.61
Cancelled/forfeited		(89,812	)		11.92
Options outstanding at September 30, 2020		1,357,163			11.46		7.7		—
Options exercisable at September 30, 2020		535,848		$	15.21		6.1		—

Summary of Restricted Stock Unit Activity under 2018 Plan

A summary of restricted stock unit activity under the 2018 Plan for the nine months ended September 30, 2020, is as follows:

Year-to-Date Activity	Number of Shares			Weighted Average Grant Date Fair Value Per Share		Aggregate Intrinsic Value (in millions)
Non-vested outstanding at December 31, 2019		9,000		$	23.60
Granted		—			—
Vested/settled		(5,858	)
Cancelled/forfeited		(3,142	)
Non-vested outstanding at September 30, 2020		—			—		—

Summary of Stock-Based Compensation Expense

The amount of stock-based compensation expense recorded to research and development expenses and to general and administrative expenses is detailed in table below:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Stock-based compensation
Research and development	$	115,817	$	166,289	$	606,470	$	785,423
General and administrative		371,586		397,735		1,151,845		1,165,894
	$	487,403	$	564,024	$	1,758,315	$	1,951,317