CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net loss	$ (63,888)	$ (103,012)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	1,189	979
Share-based compensation expense	9,060	6,357
Class A common shares issued or to be issued as consideration for Primatope, including milestone payments		8,800
Non-cash lease expense	603	635
Accretion of discounts on short-term investments	(313)	(2,055)
Deferred income taxes	4,372	(1,390)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(3,843)	(1,644)
Accounts payable	(3,228)	(1,663)
Accrued expenses and other liabilities	(4,146)	2,720
Accrued milestones		(15,000)
Operating lease liabilities	(833)	(602)
Other long-term liabilities	7	943
Net cash used in operating activities	(61,020)	(104,932)
Cash flows from investing activities:
Purchases of property and equipment	(223)	(767)
Purchases of short-term investments	(133,954)	(273,488)
Proceeds from the maturities of short-term investments	191,750	306,340
Net cash provided by investing activities	57,573	32,085
Cash flows from financing activities:
Payments of offering costs	(569)	(118)
Proceeds from exercise of options and employee share purchase plan	5,350	693
Net cash provided by financing activities	79,975	83,681
Net increase in cash, cash equivalents and restricted cash	76,528	10,834
Cash, cash equivalents and restricted cash at beginning of period	47,138	72,186
Cash, cash equivalents and restricted cash at end of period	123,666	83,020
Supplemental information:
Cash paid for income taxes	282	1,027
Supplemental disclosure of non-cash investing and financing activities:
Deferred offering costs included in accrued expenses and accounts payable	335
Property and equipment included in accrued expenses and accounts payable		253
Follow-On Offering | Class A common shares
Cash flows from financing activities:
Proceeds from issuance of common shares, net of underwriting discounts and commissions inclusive of the over-allotment option exercise	47,600	48,595
Private Placement | Class A1 common shares
Cash flows from financing activities:
Proceeds from issuance of common shares from private placement, net of placement agent fees	$ 27,594	$ 34,511