CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities:
Net loss	$ (58,215)	$ (57,398)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	129	101
Accretion and amortization on investments, net	304	778
Amortization of debt issuance costs/debt discount	704	374
Gain on sales of equity investment		(1,233)
Stock-based compensation for services by non-employees	28	48
Stock-based compensation for employees and directors	3,750	3,767
Amortization of right-of-use assets	285	266
Changes in assets and liabilities:
Current and noncurrent assets	(5,507)	(3,042)
Current and noncurrent liabilities	(4,094)	5,791
Net cash used in operating activities	(62,616)	(50,548)
Cash flows from investing activities:
Purchases of property and equipment	(120)	(10)
Purchases of marketable securities	(57,049)	(82,430)
Proceeds from maturities of marketable securities	90,406	149,834
Proceeds from sales of equity investment		1,594
Net cash provided by investing activities	33,237	68,988
Cash flows from financing activities:
Proceeds from issuances of common stock from equity plans	761	204
Proceeds from issuance of common stock and warrants in public offering, net of paid issuance costs	69,916
Proceeds from issuances of common stock from at market offerings, net of paid issuance costs		16,234
Proceeds from exercise of warrants		2,479
Proceeds from debt financing		10,000
Debt discount and issuance costs for debt financing	(114)
Net cash provided by financing activities	70,563	28,917
Net effect of unrealized losses and exchange rates on cash, cash equivalents and restricted cash	2
Net change in cash, cash equivalents and restricted cash	41,186	47,357
Cash, cash equivalents and restricted cash at the beginning of the period	35,235	10,288
Cash, cash equivalents and restricted cash at the end of the period	$ 76,421	$ 57,645