Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Taxes

Schedule of U.S. and foreign loss before income taxes

	Year ended December 31,
	2019		2018		2017
United States	$	(26,052,255)	$	(34,308,847)	$	(27,051,148)
Foreign		(6,891,328)		(5,602,328)		(4,961,156)
Total	$	(32,943,583)	$	(39,911,175)	$	(32,012,304)

Schedule of components of the net deferred income tax asset

	December 31, 2019		December 31, 2018
Deferred tax assets:
Net operating loss carry forwards	$	27,661,926	$	24,399,299
Research and development credit carry forwards		2,666,036		2,291,226
Stock-based compensation		6,046,848		4,575,617
Other		650,018		706,745
Gross deferred tax assets		37,024,828		31,972,887
Deferred tax liabilities:
Property and equipment		(28,926)		(59,524)
Gross deferred tax liabilities		(28,926)		(59,524)
Less valuation allowance		(36,995,902)		(31,913,363)
Net deferred tax asset	$	—	$	—

Reconciliation of income tax expense (benefit) at the statutory federal income tax rate and income taxes

	Year ended December 31,
	2019		2018		2017
Federal income tax benefit at statutory rate	21.0	%	21.0	%	34.0	%
State income tax, net of federal benefit	4.2		6.8		6.5
Foreign tax rate differential	0.1		0.3		—
Nondeductible research and development expenses	(4.3)		(2.2)		(5.1)
Other permanent differences	—		—		(0.1)
Research and development credit benefit	1.0		1.4		1.3
Adjustment of prior years' income taxes	(6.6)		—		—
Rate change from 2017 Tax Cuts and Jobs Act	—		0.3		(27.3)
Change in valuation allowance	(15.4)		(27.6)		(9.3)
Effective income tax rate	—	%	—	%	—	%