Condensed Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Operating activities
Net loss	$ (31,039)	$ (30,079)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	4,758	5,338
Depreciation and amortization	870	560
Amortization of operating lease right-of-use assets	509	494
Accretion (Amortization) of Discounts and Premiums, Investments	3	0
Changes in operating assets and liabilities:
Other current assets and other non-current assets	(537)	(1,614)
Accounts payable and accrued liabilities	614	(1,157)
Operating lease liabilities	(563)	(176)
Net cash used in operating activities	(25,385)	(26,634)
Investing activities
Purchase of property and equipment	(684)	(2,280)
Purchase of available-for-sale securities	(39,067)	0
Net cash used in investing activities	(39,751)	(2,280)
Financing activities
Proceeds from exercise of stock options	134	376
Proceeds from the issuance of common stock under Employee Stock Purchase Plan	63	219
Payment on finance lease obligations	(2)	(2)
Net cash provided by financing activities	195	593
Net change in cash, cash equivalents, and restricted cash during the period	(64,941)	(28,321)
Cash, cash equivalents, and restricted cash, beginning of period	143,345	193,434
Cash, cash equivalents, and restricted cash, end of period	78,404	165,113
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	$ 265	$ 419