CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 43,639	$ 33,406
Prepaid expenses and other current assets	2,564	2,063
Total current assets	46,203	35,469
Property and equipment, net	73	106
Right-of-use lease asset	58	1,227
Total assets	46,334	36,802
Current liabilities:
Accounts payable	1,197	514
Accrued and other current liabilities	1,921	1,972
Total current liabilities	3,118	2,486
Lease liability	0	1,057
Total liabilities	3,118	3,543
Stockholders' equity:
Common stock, $0.001 par value; 100,000,000 shares authorized at December 31, 2020 and June 30, 2021; 6,246,896 and 9,234,110 shares issued and outstanding at December 31, 2020 and June 30, 2021	9	6
Additional paid-in capital	418,542	400,071
Accumulated other comprehensive loss	(658)	(746)
Accumulated deficit	(374,677)	(366,072)
Total stockholders' equity	43,216	33,259
Total liabilities and stockholders' equity	46,334	36,802
6% Convertible Exchangeable Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value	0	0
Series A Convertible Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value	0	0
Series B Convertible Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value	$ 0	$ 0

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).