CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating activities:
Net loss	$ (36,206)	$ (22,830)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	1,850	1,623
Right-of-use asset (accretion) amortization	70	103
Stock-based compensation	3,895	3,916
Other non-cash transactions	26	(293)
Changes in operating assets and liabilities	33,789	(14,792)
Net cash provided by (used in) operating activities	3,284	(32,479)
Investing activities:
Purchases of property and equipment	(607)	(2,148)
Proceeds from maturity of investments	0	67,687
Purchases of investments	0	(41,178)
Net cash (used in) provided by investing activities	(607)	24,361
Financing activities:
Proceeds from exercise of stock options	858	271
Proceeds from exercise of warrants	837	0
Proceeds from employee stock purchase plan	96	145
Proceeds from issuance of common stock from private placement, net of issuance costs	18,913	0
Proceeds from issuance of common stock resulting from ATM sales, net of $1.2M in transaction costs and $1.8M in proceeds receivable	33,522	9,624
Net cash provided by financing activities	54,226	10,040
Effect of exchange rate change on cash and cash equivalents	(2,287)	2,708
Net increase in cash and cash equivalents	54,616	4,630
Cash and cash equivalents at beginning of period	70,436	62,260
Cash and cash equivalents at end of period	125,052	66,890
Supplemental cash flow disclosures:
Net unrealized loss on investments	0	(319)
Property and equipment included in accounts payable	$ 0	$ 370