Condensed Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating Activities
Net loss	$ (26,795)	$ (15,076)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and other expense	13	38
Amortization of premium and discounts on investment securities	395	0
Share-based compensation	2,292	2,324
Changes in operating assets and liabilities:
Income tax receivable	0	(2,942)
Prepaid expense and other assets	(516)	(140)
Accrued interest receivable	122	0
Accrued research and development expenses	848	1,524
Accounts payable and accrued expenses	(5,816)	(3,254)
Net cash used in operating activities	(29,457)	(17,526)
Investing Activities
Purchase of marketable securities	(26,710)	0
Maturities of marketable securities	19,000	0
Net cash used in investing activities	(7,710)	0
Financing Activities
Proceeds from employee stock plan purchases	129	179
Net cash provided by financing activities	129	179
Net decrease in cash and cash equivalents	(37,038)	(17,347)
Cash and cash equivalents
Beginning of period	66,373	125,699
End of period	$ 29,335	$ 108,352