Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities:
Net (loss) income	$ (13,745)	$ 2,616
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation	867	861
Depreciation and amortization	33	30
Accretion on marketable securities	1,133	40
Changes in operating assets and liabilities:
Prepaid and other current assets	(1,232)	(920)
Other assets	166	308
Accounts payable, accrued liabilities and other liabilities	176	(2,673)
Net cash (used in) provided by operating activities	(12,602)	262
Cash flows from investing activities:
Purchase of marketable securities	(105,792)	(8,235)
Sale of marketable securities	29,558	11,104
Purchase of property and equipment	(60)	(14)
Net cash (used in) provided by investing activities	(76,294)	2,855
Cash flows from financing activities:
Proceeds from exercise of options	24	0
Tax withholding payments on net share settlement equity awards	(184)	(148)
Net proceeds from issuance of common stock	85,479	9,683
Net cash provided by financing activities	85,319	9,535
Net (decrease) increase in cash and cash equivalents	(3,577)	12,652
Cash and cash equivalents at beginning of period	16,512	14,032
Cash and cash equivalents at end of period	$ 12,935	$ 26,684