Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 23,674	$ 24,228
Marketable securities	132,581	128,233
Prepaid expenses and other current assets	2,356	1,420
Total current assets	158,611	153,881
Property and equipment, net	744	898
Operating lease, right-of-use ("ROU") asset	1,467	1,776
Other assets	320	320
Total assets	161,142	156,875
Current liabilities:
Accounts payable	854	4,090
Accrued expenses	1,815	2,514
Operating lease obligations, current portion	1,224	1,197
Total current liabilities	3,893	7,801
Operating lease obligations, long-term portion	189	536
Total liabilities	4,082	8,337
Commitments and Contingencies
Stockholders' equity:
Common stock, $0.0001 par value: 300,000 shares authorized; 137,589 and 127,668 shares issued and outstanding at March 31, 2024 and December 31, 2023, respectively	14	13
Additional paid-in-capital	483,231	463,796
Accumulated other comprehensive (loss) income	(90)	37
Accumulated deficit	(326,095)	(315,308)
Total stockholders' equity	157,060	148,538
Total liabilities and stockholders' equity	$ 161,142	$ 156,875

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).