Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Income Taxes

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

	Year ended December 31,
	2016		2015		2014
United States	$	(18,803,227)	$	(12,145,964)	$	(5,669,577)
Foreign		(4,612,823)		(377,843)		—
Total	$	(23,416,050)	$	(12,523,807)	$	(5,669,577)

Schedule of components of the net deferred income tax asset

	December 31, 2016		December 31, 2015
Deferred tax assets:
Net operating loss carry‑forwards	$	14,877,358	$	6,531,375
Startup costs		—		817,052
Research and development credit carry‑forwards		1,337,748		425,282
Deferred revenue		—		304,264
Stock-based compensation		1,576,280		227,093
Other		43,004		—
Gross deferred tax assets		17,834,390		8,305,066
Deferred tax liabilities:
Accumulated depreciation		(21,632)		(18,519)
Gross deferred tax liabilities		(21,632)		(18,519)
Less valuation allowance		(17,812,758)		(8,286,547)
Net deferred tax asset	$	—	$	—

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

	Year ended December 31,
	2016		2015		2014
Federal income tax benefit at statutory rate	34.0	%	34.0	%	34.0	%
State income tax, net of federal benefit	7.8	%	2.9	%	(0.3)	%
Foreign tax rate differential	(0.2)	%	(0.1)	%	—	%
Nondeductible research and development expenses	(4.7)	%	(1.1)	%	—	%
Other permanent differences	—	%	(0.1)	%	(0.7)	%
Research and development credit benefit	3.9	%	2.0	%	1.6	%
Change in valuation allowance	(40.7)	%	(37.8)	%	(34.6)	%
Effective income tax rate	0.1	%	(0.2)	%	—	%