Note 10 - Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2019

Notes Tables

Schedule of Common Stock Reserved for Issuance [Table Text Block]

	September 30, 2019		December 31, 2018
Options issued and outstanding		1,862,002		865,163
Available for future grants of equity awards		351,428		223,377
Common stock warrants		45,401,562		10,914
Total		47,614,992		1,099,454

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

Securities into which warrants are convertible	Warrants outstanding		Exercise Price		Expiration Date
Common Stock		1,433,333	$	0.10	September 2024
Common Stock		30,666,667	$	0.30	September 2024
Common Stock		2,115,738	$	0.375	September 2024
Common Stock		10,454,546	$	1.10	April 2024
Common Stock		636,364	$	1.375	April 2024
Common Stock		84,000	$	3.125	March 2024
Common Stock		10,914	$	22.99	December 2026
Total		45,401,562