CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net loss	$ (32,179)	$ (24,298)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	60	26
Accretion and amortization on investments, net	(34)	(958)
Gain on sale of available for sale securities	(19)
Change in fair value of equity investment, including foreign currency translation	(279)	3
Stock-based compensation for services by non-employees	32	33
Stock-based compensation for employees and directors	3,275	2,860
Amortization related to 401(k) contributions		9
Amortization of right-of-use assets	580	334
Changes in assets and liabilities:
Current and noncurrent assets	389	(386)
Amount due to Janssen Biotech, Inc.	(14,269)	(1,034)
Other current and noncurrent liabilities	3,855	1,928
Net cash used in operating activities	(38,589)	(21,483)
Cash flows from investing activities:
Purchases of property and equipment	(386)	(67)
Purchases of marketable securities	(182,355)	(66,408)
Proceeds from sales of securities available for sale	7,681
Proceeds from maturities of marketable securities	78,012	94,851
Net cash (used in) provided by investing activities	(97,048)	28,376
Cash flows from financing activities:
Proceeds from issuance of common stock from equity plans	82
Proceeds from issuance of common stock and warrants in public offering, net of paid issuance costs	140,794
Proceeds from issuances of common stock from at market offerings, net of paid issuance costs	4,075	243
Net cash provided by financing activities	144,951	243
Net increase in cash, cash equivalents and restricted cash	9,314	7,136
Cash, cash equivalents and restricted cash at the beginning of the period	13,914	10,844
Cash, cash equivalents and restricted cash at the end of the period	$ 23,228	$ 17,980