CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net loss	$ (51,830)	$ (39,478)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	109	35
Accretion and amortization on investments, net	387	(1,283)
Gain on sales of available for sale securities	(19)
Net gain on exchange and sales of equity investment	(148)
Change in fair value of equity investment, including foreign currency translation	(187)	212
Stock-based compensation for services by non-employees	54	50
Stock-based compensation for employees and directors	5,043	4,429
Amortization related to 401(k) contributions		9
Amortization of right-of-use assets	647	504
Changes in assets and liabilities:
Current and noncurrent assets	(2,563)	(1,399)
Amount due to Janssen Biotech, Inc.	(14,269)	(1,403)
Other current and noncurrent liabilities	8,738	4,861
Net cash used in operating activities	(54,038)	(33,463)
Cash flows from investing activities:
Purchases of property and equipment	(390)	(324)
Purchases of marketable securities	(220,066)	(102,276)
Proceeds from sales of securities available for sale	7,681
Proceeds from maturities of marketable securities	128,952	137,013
Proceeds from sales of equity investment	339
Net cash (used in) provided by investing activities	(83,484)	34,413
Cash flows from financing activities:
Proceeds from issuances of common stock from equity plans	97	167
Proceeds from issuance of common stock and warrants in public offering, net of paid issuance costs	140,184
Proceeds from issuances of common stock from at market offerings, net of paid issuance costs	4,075	9,060
Proceeds from exercise of warrants	16
Proceeds from debt financing, net of paid debt issuance costs and debt discounts	24,555
Net cash provided by financing activities	168,927	9,227
Net increase in cash, cash equivalents and restricted cash	31,405	10,177
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	$ 45,319	$ 21,021