Note 8 - Net Loss Per Share (Tables)

9 Months Ended

Sep. 30, 2019

Notes Tables

Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]

	Three Months Ended September 30,						Nine Months Ended September 30,
	2019			2018			2019			2018
Numerator
Net loss	$	(3,285,914	)	$	(3,309,866	)	$	(14,621,750	)	$	(9,326,825	)
Deemed dividend attributable to preferred stock		-			-			-			(11,479,308	)
Net loss attributable to common shareholders	$	(3,285,914	)	$	(3,309,866	)	$	(14,621,750	)	$	(20,806,133	)
Denominator
Weighted average common shares outstanding used to compute net loss per share, basic and diluted		9,130,057			5,183,492			8,283,302			3,645,682
Net loss per share of common stock, basic and diluted:	$	(0.36	)	$	(0.64	)	$	(1.77	)	$	(5.71	)

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]

	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Options to purchase common stock		4,348,383		783,794		2,572,413		388,377
Series B convertible preferred stock		191,543		1,338,916		281,015		751,332
Warrants to purchase common stock		1,070,028		4,716,935		1,828,085		2,644,946
		5,609,954		6,839,645		4,681,513		3,784,655