Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating activities
Net loss	$ (45,525)	$ (20,637)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	8,548	3,393
Depreciation and amortization	916	578
Amortization of operating lease right-of-use assets	730	784
Loss on disposal of property and equipment	0	180
Write-off of right-of-use asset upon lease termination	0	113
Changes in operating assets and liabilities:
Other current assets and other non-current assets	36	(5,026)
Accounts payable and accrued liabilities	332	5,125
Operating lease right-of-use assets	0	(169)
Operating lease liabilities	(427)	313
Net cash used in operating activities	(35,390)	(15,346)
Investing activities
Purchase of property and equipment	(2,867)	(1,566)
Net cash used in investing activities	(2,867)	(1,566)
Financing activities
Proceeds from issuance of common stock and pre-funded warrants, net of commissions of $4.6 million	0	71,675
Payment of offering costs	0	(355)
Proceeds from exercise of stock options	408	4,576
Proceeds from the issuance of common stock under Employee Stock Purchase Plan	219	0
Payment on finance lease obligations	(2)	(49)
Net cash provided by financing activities	625	75,847
Net change in cash, cash equivalents, and restricted cash during the period	(37,632)	58,935
Cash, cash equivalents, and restricted cash, beginning of period	193,434	143,093
Cash, cash equivalents, and restricted cash, end of period	155,802	202,028
Supplemental disclosure of non-cash investing and financing activities:
Operating lease liabilities arising from obtaining ROU asset	1,584	10,618
Purchases of property and equipment unpaid at period-end	$ 297	$ 271