Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Cash Flows From Operating Activities:
Net loss for the year	$ (29,047)	$ (106,908)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	19,691	12,829
Depreciation expense	1,978	1,471
Non-cash lease expense	2,206	1,873
Loss on disposal of property and equipment	0	24
Foreign exchange loss (gain)	(298)	12
Net (accretion)/amortization of marketable securities	(2,233)	113
Deferred tax asset	3,620	(2,208)
Changes in operating assets and liabilities:
Prepaid expenses	593	(32)
Research and development tax credits receivable	1,287	(556)
Collaboration revenue receivable	(1,525)	0
Other receivables	(1,147)	3,554
Other non-current assets	89	(298)
Accounts payable	(1,348)	152
Accrued expenses and other current liabilities	3,020	11,166
Operating lease liabilities, current portion	615	98
Income tax payable	717	505
Operating lease liabilities, net of current portion	(2,146)	(1,118)
Deferred revenue	4,250	(6,473)
Net cash provided by (used in) operating activities	322	(85,796)
Cash Flows From Investing Activities:
Purchase of property and equipment	(602)	(1,690)
Proceeds on disposal of property and equipment	0	40
Proceeds from maturities of marketable securities	81,400	7,450
Purchase of marketable securities	(256,576)	(7,476)
Net cash used in investing activities	(175,778)	(1,676)
Cash Flows From Financing Activities:
Proceeds from exercise of stock options	447	986
Proceeds from issuance of common shares under the 2020 Employee Share Purchase Plan	433	283
Net proceeds from issuance of common shares in follow-on offering	0	94,288
Net cash provided by financing activities	880	95,557
Effect of exchange rate fluctuations on cash held	(330)	(54)
Net (Decrease) Increase In Cash And Cash Equivalents	(174,906)	8,031
Cash and cash equivalents cash at beginning of year	334,427	326,396
Cash and cash equivalents at end of year	159,521	334,427
Supplemental Disclosure Of Cash Flow Information:
Cash interest received	1,966	240
Cash taxes paid, net	10,810	25
Property and equipment purchases incurred but not yet paid	0	1,719
Right-of-use assets obtained in exchange for new operating lease liability	$ 86	$ 4,690