Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating Activities
Net loss	$ (59,115)	$ (41,381)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and other expense	108	123
Amortization of premium and discounts on investment securities	115	0
Gain on sale of property and equipment	0	(150)
Deferred income taxes	0	0
Share-based compensation	6,044	6,803
Changes in operating assets and liabilities:
Income tax receivable	0	1,635
Prepaid expense and other assets	542	979
Accrued interest receivable	(112)	0
Accrued research and development expenses	6,007	(2,387)
Accounts payable and accrued expenses	1,383	(2,203)
Net cash used in operating activities	(45,028)	(36,581)
Investing Activities
Purchase of marketable securities	(108,305)	0
Proceeds from sale of assets	0	150
Net cash (used in) provided by investing activities	(108,305)	150
Financing Activities
Proceeds from employee stock plan purchases	333	81
Net cash provided by financing activities	150,453	81
Net change in cash and cash equivalents	(2,880)	(36,350)
Cash and cash equivalents
Beginning of period	125,699	131,201
End of period	122,819	94,851
Supplemental disclosure of cash paid
Income tax refunds received	3,327	1,765
Underwritten Offering
Financing Activities
Proceeds from issuance of common stock	116,883	0
Private Placement
Financing Activities
Proceeds from issuance of common stock	$ 33,237	$ 0