Nature of the Business - Additional Information (Details) $ / shares in Units, $ in Thousands		6 Months Ended
	Feb. 09, 2021 USD ($) shares	Jun. 30, 2021 USD ($)	Jun. 30, 2022 £ / shares	Jun. 30, 2022 USD ($)	Dec. 31, 2021 £ / shares	Dec. 31, 2021 USD ($)	Feb. 09, 2021 £ / shares	Feb. 09, 2021 $ / shares
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Nominal value of shares issued and sold | £ / shares			£ 0.10		£ 0.10
Placement agent fees		$ 6,355
Accumulated deficit				$ 845,436		$ 750,224
Cash, cash equivalents and marketable securities				$ 170,900
Securities Purchase Agreement
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Net proceeds from private placement	$ 143,600
Securities Purchase Agreement | Private Placement
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of ordinary shares issued and sold | shares	20,900,321
Nominal value of shares issued and sold | £ / shares							£ 0.10
Purchase price per share | $ / shares								$ 6.22
Closing price of share date	Feb. 04, 2021
Placement agent fees	$ 6,000
Other issuance costs	$ 400
Private placement, transaction date	Feb. 04, 2021
Securities Purchase Agreement | Private Placement | Non-voting Ordinary Shares
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of ordinary shares issued and sold | shares	3,215,434
Nominal value of shares issued and sold | £ / shares							£ 0.10