Condensed Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating activities
Net loss	$ (15,351)	$ (14,950)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	2,446	2,420
Depreciation and amortization	411	247
Amortization of operating lease right-of-use assets	250	265
Changes in operating assets and liabilities:
Other current assets and other non-current assets	(803)	(813)
Accounts payable and accrued liabilities	(769)	(631)
Operating lease liabilities	(275)	104
Net cash used in operating activities	(14,091)	(13,358)
Investing activities
Purchase of property and equipment	(452)	(1,089)
Net cash used in investing activities	(452)	(1,089)
Financing activities
Proceeds from exercise of stock options	134	282
Payment on finance lease obligations	(1)	0
Net cash provided by financing activities	133	282
Net change in cash, cash equivalents, and restricted cash during the period	(14,410)	(14,165)
Cash, cash equivalents, and restricted cash, beginning of period	143,345	193,434
Cash, cash equivalents, and restricted cash, end of period	128,935	179,269
Supplemental disclosure of non-cash investing and financing activities:
Operating lease liabilities arising from obtaining ROU asset	0	1,584
Purchases of property and equipment unpaid at period-end	$ 91	$ 794