Stockholders' Equity (Tables)

9 Months Ended

Sep. 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 nine months ended September 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 thousands)
Options outstanding at December 31, 2020		1,240,354		$	11.16		7.8
Granted		687,500		$	3.48
Cancelled/forfeited		(18,879	)	$	20.37
Options outstanding at September 30, 2021		1,908,975		$	8.30		8.0	$	12
Options exercisable at September 30, 2021		858,426		$	11.70		6.9	$	1

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,
	2021		2020		2021		2020
Stock-based compensation
Research and development	$	183,805	$	115,817	$	528,385	$	606,470
General and administrative		416,508		371,586		1,226,027		1,151,845
	$	600,313	$	487,403	$	1,754,412	$	1,758,315