CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018		0	440,529
Beginning balance at Dec. 31, 2018	$ 5,245	$ 0	$ 1	$ 87,099	$ (81,855)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock and common stock warrants, net of issuance costs (in shares)			527,344
Issuance of common stock and common stock warrants, net of issuance costs	13,416			13,416
Issuance of common stock for exercise of warrants, net of offering costs (in shares)			2,095,949
Issuance of common stock for exercise of warrants, net of offering costs	3,658		$ 2	3,656
Issuance of common stock upon exercise of pre-funded warrants (in shares)			1,485,156
Issuance of common stock upon exercise of pre-funded warrants	8		$ 2	6
Issuance of common stock upon vesting of restricted stock units (in shares)			230
Issuance of common stock upon vesting of restricted stock units	0
Stock-based compensation	426			426
Impact of anti-dilution protection on liability-classified warrants	(243)			(243)
Net loss	(11,873)				(11,873)
Ending balance (in shares) at Sep. 30, 2019		0	4,549,208
Ending balance at Sep. 30, 2019	10,637	$ 0	$ 5	104,360	(93,728)
Beginning balance (in shares) at Jun. 30, 2019		0	2,002,702
Beginning balance at Jun. 30, 2019	14,338	$ 0	$ 2	103,862	(89,526)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock and common stock warrants, net of issuance costs (in shares)			2,032,950
Issuance of common stock and common stock warrants, net of issuance costs	383		$ 2	381
Issuance of common stock upon exercise of pre-funded warrants (in shares)			513,326
Issuance of common stock upon exercise of pre-funded warrants	3		$ 1	2
Issuance of common stock upon vesting of restricted stock units (in shares)			230
Issuance of common stock upon vesting of restricted stock units	0
Stock-based compensation	115			115
Net loss	(4,202)				(4,202)
Ending balance (in shares) at Sep. 30, 2019		0	4,549,208
Ending balance at Sep. 30, 2019	10,637	$ 0	$ 5	104,360	(93,728)
Beginning balance (in shares) at Dec. 31, 2019		0	5,080,100
Beginning balance at Dec. 31, 2019	6,093	$ 0	$ 5	107,235	(101,147)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock and common stock warrants, net of issuance costs (in shares)			3,933,078
Issuance of common stock and common stock warrants, net of issuance costs	14,455		$ 4	14,451
Issuance of common stock upon exercise of pre-funded warrants (in shares)			448,800
Issuance of common stock upon exercise of pre-funded warrants	4		$ 1	3
Stock-based compensation	437			437
Exercise of stock options	0
Net loss	(13,041)				(13,041)
Ending balance (in shares) at Sep. 30, 2020		0	9,461,978
Ending balance at Sep. 30, 2020	7,948	$ 0	$ 10	122,126	(114,188)
Beginning balance (in shares) at Jun. 30, 2020		0	6,717,900
Beginning balance at Jun. 30, 2020	3,783	$ 0	$ 7	113,491	(109,715)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock and common stock warrants, net of issuance costs (in shares)			2,744,078
Issuance of common stock and common stock warrants, net of issuance costs	8,492		$ 3	8,489
Stock-based compensation	146			146
Net loss	(4,473)				(4,473)
Ending balance (in shares) at Sep. 30, 2020		0	9,461,978
Ending balance at Sep. 30, 2020	$ 7,948	$ 0	$ 10	$ 122,126	$ (114,188)