Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities
Net loss	$ (13,534)	$ (5,247)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	126	121
Stock-based compensation	2,584	186
Change in operating lease right-of-use assets	6
Fair value adjustment for preferred stock tranche rights liability		(1,265)
Deferred rent		(12)
Changes in operating assets and liabilities:
Grants receivable	(1,149)	5,070
Research and development tax credits receivable	191	(184)
Prepaid expenses and other current assets	493	(440)
Accounts payable	2,348	3,349
Accrued expenses and other liabilities	(2,115)	(973)
Deferred income	(3,740)	(84)
Net cash (used in) provided by operating activities	(14,790)	521
Cash flows from investing activities
Purchase of property and equipment	(88)	(27)
Purchase of other assets	(3)	(10)
Net cash used in investing activities	(91)	(37)
Cash flows from financing activities
Proceeds from issuance of common stock upon exercise of options	667
Proceeds from grants repayable		2,713
Net cash provided by financing activities	667	127,739
Effects of exchange rate changes on cash, cash equivalents and restricted cash	(717)	(360)
Net (decrease) increase in cash, cash equivalents and restricted cash	(14,931)	127,863
Cash, cash equivalents and restricted cash at beginning of period	336,454	19,990
Cash, cash equivalents and restricted cash at end of period	321,523	147,853
Non-cash investing and financing activities
Accretion of Series B and B-2 Preferred Stock to redemption value		1,195
Operating lease liabilities arising from obtaining right-of-use assets	$ 3,206
Supplemental disclosure of cash flows
Cash paid for taxes		2
Series B-2 Preferred Stock
Cash flows from financing activities
Proceeds from issuance of Preferred Stock		125,358
Payment of issuance costs on Series B-2 Preferred Stock		$ (332)