Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2021

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 six months ended June 30, 2021, 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, 2020		1,240,354		$	11.16		7.8
Granted		530,000		$	3.75
Cancelled/forfeited		(18,879	)	$	20.37
Options outstanding at June 30, 2021		1,751,475		$	8.82		8.1		—
Options exercisable at June 30, 2021		779,148		$	11.87		7.0		—

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 June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Stock-based compensation
Research and development	$	176,534	$	228,197	$	344,580	$	490,654
General and administrative		418,129		375,377		809,519		780,258
	$	594,663	$	603,574	$	1,154,099	$	1,270,912