CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Operating activities
Net loss	$ (69,204)	$ (52,892)
Adjustments to reconcile net loss to net cash used in operating activities:
Amortization of premium on marketable securities	1,270	497
Depreciation and amortization	996	1,123
Stock-based compensation expense	9,952	8,686
Loss on disposal of capital equipment	0	0
Gain (loss) on foreign currency translation	258	(249)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(1,764)	(965)
Accounts payable, accrued expenses, and other current liabilities	933	2,390
Deferred revenue	(3,432)	959
Deferred rent, net of current portion	(35)	(40)
Net cash used in operating activities	(61,026)	(40,491)
Investing activities
Purchase of marketable securities	(164,977)	(139,334)
Proceeds from maturities of marketable securities	84,385	52,297
Proceeds from sale of equipment	0	0
Purchase of property and equipment	(755)	(398)
Net cash used in investing activities	(81,347)	(87,435)
Financing activities
Proceeds from issuances of common stock under employee stock plans	2,022	1,851
Net cash provided by financing activities	141,482	75,461
Net increase in cash and cash equivalents	(891)	(52,465)
Cash and cash equivalents at beginning of year	24,918	77,383
Cash and cash equivalents at end of year	24,027	24,918
Supplemental disclosures of cash flow information:
Cash paid for income taxes	0	990
Supplemental disclosures of non-cash investing and financing information
Offering costs included in accounts payable and accrued expenses	20	208
Public Offering
Financing activities
Proceeds from issuance of common stock, net of issuance costs	134,770	73,610
At The Market
Financing activities
Proceeds from issuance of common stock, net of issuance costs	$ 4,690	$ 0