Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2019

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, 2019, 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, 2018		781,725		$	16.34		9.0
Granted		1,063,150			13.84
Exercised		(7,813	)		11.81
Cancelled/forfeited		(451,398	)		22.95
Options outstanding at September 30, 2019		1,385,664			12.12		8.9	$	0.1
Options exercisable at September 30, 2019		328,707		$	11.34		7.2	$	0.1

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, 2019, 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, 2018		—			—
Granted		15,000		$	23.60
Cancelled/forfeited		(6,000	)
Non-vested outstanding at September 30, 2019		9,000		$	23.60	$	0.0

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,
	2019		2018		2019		2018
Stock-based compensation
Research and development	$	166,289	$	179,930	$	785,423	$	515,584
General and administrative		397,735		172,786		1,165,894		415,933
	$	564,024	$	352,716	$	1,951,317	$	931,517