Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2020

Equity [Abstract]

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 three months ended March 31, 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		61,000		3.89
Options outstanding at March 31, 2020		1,374,475		11.91		8.5	$	—
Options exercisable at March 31, 2020		447,477	$	14.39		7.5	$	—

Summary of Restricted Stock Unit Activity under 2018 Plan

A summary of restricted stock unit activity under the 2018 Plan for the three months ended March 31, 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 March 31, 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 March 31,
	2020		2019
Stock-based compensation
Research and development	$	262,457	$	369,941
General and administrative		404,881		301,986
	$	667,338	$	671,927