Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities:
Net loss	$ (10,852)	$ (13,745)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation	1,128	867
Depreciation and amortization	14	33
Accretion on marketable securities	900	1,133
Changes in operating assets and liabilities:
Prepaid and other current assets	(744)	(1,232)
Other assets	118	166
Accounts payable, accrued liabilities and other liabilities	(1,268)	176
Net cash used in operating activities	(10,704)	(12,602)
Cash flows from investing activities:
Purchase of marketable securities	(30,291)	(105,792)
Sale of marketable securities	60,070	29,558
Purchase of property and equipment	(235)	(60)
Investment in Cend Therapeutics	(10,000)	0
Net cash provided by (used in) investing activities	19,544	(76,294)
Cash flows from financing activities:
Proceeds from exercise of options	0	24
Tax withholding payments on net share settlement equity awards	(168)	(184)
Net proceeds from issuance of common stock	29	85,479
Net cash (used in) provided by financing activities	(139)	85,319
Net increase (decrease) in cash and cash equivalents	8,701	(3,577)
Cash and cash equivalents at beginning of period	24,647	16,512
Cash and cash equivalents at end of period	$ 33,348	$ 12,935