Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 47,480	$ 8,253
Prepaid expenses and other current assets	729	579
Total current assets	48,209	8,832
Other	258	174
Total assets	48,467	9,006
Current liabilities:
Accounts payable	1,661	297
Accrued expenses and other	1,093	1,512
Accrued dividends payable	66	299
Total current liabilities	2,820	2,108
Other liabilities	52
Total liabilities	2,872	2,108
Commitments and contingencies (Note 10)
Stockholders' equity:
Undesignated stock, $0.01 par value; 20,000,000 shares authorized at December 31, 2019 and 2018, 20,000,000 shares designated at December 31, 2019 and 2018, respectively
Common stock, $0.001 par value; 100,000,000 shares authorized at December 31, 2019 and 2018, 56,894,642 and 41,190,905 issued and outstanding at December 31, 2019 and 2018, respectively	56	41
Additional paid-in capital	259,673	194,130
Retained deficit	(216,394)	(196,215)
Total stockholders' equity	43,872	5,175
Total liabilities, redeemable convertible preferred stock and stockholders' equity	48,467	9,006
Series C 6% super dividend redeemable convertible preferred stock
Current liabilities:
Convertible preferred stock, value	1,723	1,723
Series A 12% convertible preferred stock
Stockholders' equity:
Convertible preferred stock, value	$ 537	537
Series B-1 12% convertible preferred stock
Stockholders' equity:
Convertible preferred stock, value		1,761
Series B-2 12% convertible preferred stock
Stockholders' equity:
Convertible preferred stock, value		3,697
Series B-3 8% convertible preferred stock
Stockholders' equity:
Convertible preferred stock, value		$ 1,224