Note 10 - Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2020

Notes Tables

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

	September 30, 2020		December 31, 2019
Options issued and outstanding		6,320,530		1,811,652
PRSUs issued and outstanding		411,000		—
Available for future grants of equity awards		1,554,328		295,180
Common stock warrants		1,244,974		43,370,162
Total		9,530,832		45,476,994

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		5,000	$	0.30	September 2024
Common Stock		224,797	$	0.375	September 2024
Common Stock		225,966	$	1.10	April 2024
Common Stock		111,931	$	1.375	April 2024
Common Stock		316,584	$	2.50	March 2025
Common Stock		269,496	$	3.125	February 2025
Common Stock		80,286	$	3.125	March 2024
Common Stock		10,914	$	22.99	December 2026
Total		1,244,974