CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED SHARES AND SHAREHOLDERS (DEFICIT) EQUITY - USD ($) $ in Thousands	Convertible Preferred Shares (Series A, B and C)	Common Shares Initial Public Offering	Common Shares Follow-On Offering	Common Shares Private Placement	Common Shares	Additional Paid-In Capital Initial Public Offering	Additional Paid-In Capital Follow-On Offering	Additional Paid-In Capital Private Placement	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Initial Public Offering	Follow-On Offering	Private Placement	Total
Balance at the beginning of the period at Dec. 31, 2017	$ 119,770
Balance at the beginning of the period (in shares) at Dec. 31, 2017	22,885,492
Changes in temporary equity
Issuance of Series C convertible preferred shares, net of issuance costs	$ 190,822
Issuance of Series C convertible preferred shares, net of issuance costs (in shares)	12,784,601
Conversion of convertible preferred shares to common shares	$ (310,592)
Conversion of convertible preferred shares to common shares (in shares)	(35,670,093)
Balance at the beginning of the period at Dec. 31, 2017					$ 1				$ 1,289		$ (90,998)				$ (89,708)
Balance at the beginning of the period (in shares) at Dec. 31, 2017					4,288,329
Changes in equity
Conversion of convertible preferred shares into common shares					$ 8				310,584						310,592
Conversion of convertible preferred shares into common shares (in shares)					35,670,093
Issuance of common shares upon completion of offering, net of underwriting discounts and commissions and offering costs		$ 4				$ 155,532						$ 155,536
Issuance of common shares upon completion of offering, net of underwriting discounts and commissions and offering costs (in shares)		9,484,202
Exercise of options									377						377
Exercise of options (in shares)					47,023
Share-based compensation expense									5,701						5,701
Unrealized gain (loss) on short-term investments and currency translation adjustments, net of tax										$ (4)					(4)
Net loss											(103,227)				(103,227)
Balance at the end of the period at Dec. 31, 2018					$ 13				473,483	(4)	(194,225)				279,267
Balance at the end of the period (in shares) at Dec. 31, 2018					49,489,647
Changes in equity
Issuance of common shares upon completion of offering, net of underwriting discounts and commissions and offering costs			$ 2				$ 48,474	$ 34,511					$ 48,476	$ 34,511
Issuance of common shares upon completion of offering, net of underwriting discounts and commissions and offering costs (in shares)			2,816,110	2,000,000
Common shares issued or to be issued in connection with the acquisition of all issued and outstanding equity securities of Primatope Therapeutics, Inc.									7,000						7,000
Common shares issued or to be issued in connection with the acquisition of all issued and outstanding equity securities of Primatope Therapeutics, Inc. (in shares)					337,008
Common shares issued or to be issued in connection with a milestone payment due to Primatope Therapeutics, Inc.									1,800						1,800
Common shares issued or to be issued in connection with a milestone payment due to Primatope Therapeutics, Inc. (in shares)					94,284
Exercise of options									1,119						1,119
Exercise of options (in shares)					200,579
Share-based compensation expense									15,080						15,080
Unrealized gain (loss) on short-term investments and currency translation adjustments, net of tax										37					37
Net loss											(161,867)				(161,867)
Balance at the end of the period at Dec. 31, 2019					$ 15				$ 581,467	$ 33	$ (356,092)				$ 225,423
Balance at the end of the period (in shares) at Dec. 31, 2019					54,937,628