CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities
Net loss	$ (98,776)	$ (67,475)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	355	334
Amortization of debt issuance costs	549
Stock-based compensation expense	13,867	7,642
Noncash contract asset	(105)
Noncash lease expense	312	264
Noncash lease liability	309	362
Loss on fixed assets held for sale	243
Unrealized gain on foreign currency transactions	(930)
Amortization of discount on investments		3
Changes in operating assets and liabilities:
Refund Liability	22,163
Contract asset	(452)
Prepaid expenses and other current assets, non-current assets, and accounts receivable	(853)	(3,919)
Accounts payable, accrued expenses and other long term-liabilities	7,841	1,877
Net cash used in operating activities	(55,477)	(60,912)
Cash flows from investing activities
Maturities of short-term investments	1,474	8,193
Purchases of short-term investments		(8,931)
Deposit on property and equipment	(1,793)
Purchases of property and equipment	(1,096)
Net cash used in investing activities	(1,415)	(738)
Cash flows from financing activities
Proceeds from exercise of stock options	1,199	1,020
Proceeds from notes payable, net of issuance costs	40,259
Financing costs, paid	(148)
Proceeds from equity offerings, net of offering costs		108,196
Net cash provided by financing activities	41,310	109,216
Net (decrease) increase in cash and cash equivalents	(15,582)	47,566
Cash and cash equivalents-beginning of period	138,509	90,943
Cash and cash equivalents-end of period	122,927	138,509
Supplemental disclosure of cash flow information
Contractual exit fee included in notes payable	900
Property and equipment in accrued expenses	$ 43
Financing in accounts payable and accrued expenses		$ 148