Note 5 - Equity (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

Schedule of Stockholders' Equity Note, Warrants or Rights [Table Text Block]

	Number of Warrants			Weighted Avg. Exercise Price
Outstanding at January 1, 2018		748,060		$	5.17
Issued		3,166,492			1.74
Cancelled or expired		(15,385	)		—
Exercised		(34,615	)		—
Outstanding at December 31, 2018		3,864,552		$	2.36
Issued		3,611,504			0.47
Cancelled or expired		—			—
Exercised		—			—
Outstanding at December 31, 2019		7,476,056		$	1.45

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

Expected term:	10 years
Risk-free rate:	1.51% – 2.63%
Volatility:	75.98% – 79.89%
Dividend yield:	0%

Share-based Payment Arrangement, Option, Activity [Table Text Block]

	Number of Shares			Weighted Avg. Exercise Price
Outstanding at January 1, 2018		2,628,749		$	1.31
Options granted		2,034,525			6.21
Options exercised		—			—
Options expired		(127,593	)		—
Outstanding at December 31, 2018		4,535,681		$	3.31
Options granted		1,744,300			1.48
Options exercised		—			—
Options expired		(297,058	)		—
Outstanding at December 31, 2019		5,982,923		$	2.66