CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 47,777	$ 33,406
Prepaid expenses and other current assets	2,686	2,063
Total current assets	50,463	35,469
Property and equipment, net	173	106
Right-of-use lease asset	1,181	1,227
Total assets	51,817	36,802
Current liabilities:
Accounts payable	871	514
Accrued and other current liabilities	1,901	1,972
Total current liabilities	2,772	2,486
Lease liability	996	1,057
Total liabilities	3,768	3,543
Stockholders' equity:
Common stock, $0.001 par value; 100,000,000 shares authorized at December 31, 2020 and March 31, 2021; 6,246,896 and 9,234,110 shares issued and outstanding at December 31, 2020 and March 31, 2021	9	6
Additional paid-in capital	418,320	400,071
Accumulated other comprehensive loss	(730)	(746)
Accumulated deficit	(369,550)	(366,072)
Total stockholders' equity	48,049	33,259
Total liabilities and stockholders' equity	51,817	36,802
6% Convertible Exchangeable Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value
Series A Convertible Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value
Series B Convertible Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value

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).

Name:	us-gaap_AccountsPayableCurrent
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).