CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss	$ (27,824)	$ (16,355)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	48	27
Accretion and amortization on investments, net	416	(124)
Amortization of debt issuance costs/debt discount	180
Gain on sales of equity investment	(1,233)
Change in fair value of equity investment, including foreign currency translation		220
Stock-based compensation for services by non-employees	25	16
Stock-based compensation for employees and directors	1,794	1,568
Amortization of right-of-use assets	132	244
Changes in assets and liabilities:
Current and noncurrent assets	(3,757)	249
Current and noncurrent liabilities	(2,515)	(12,039)
Net cash used in operating activities	(32,734)	(26,194)
Cash flows from investing activities:
Purchases of property and equipment	(10)	(191)
Purchases of marketable securities	(25,122)	(6,913)
Proceeds from maturities of marketable securities	61,621	39,262
Proceeds from sales of equity investment	1,594
Net cash provided by investing activities	38,083	32,158
Cash flows from financing activities:
Proceeds from issuances of common stock from equity plans	17
Proceeds from issuances of common stock from at market offerings, net of paid issuance costs	16,234	686
Proceeds from exercise of warrants	12
Net cash provided by financing activities	16,263	686
Net increase in cash, cash equivalents and restricted cash	21,612	6,650
Cash, cash equivalents and restricted cash at the beginning of the period	10,288	13,914
Cash, cash equivalents and restricted cash at the end of the period	$ 31,900	$ 20,564