CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net loss	$ (26,419)	$ (65,821)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	594	471
Share-based compensation expense	4,209	2,893
Class A common shares issued or to be issued as consideration for Primatope, including milestone payments		7,000
Non-cash lease expense	300	334
Accretion of discounts on short-term investments	(228)	(846)
Deferred income taxes	(1,038)	(240)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(598)	(1,544)
Accounts payable	(1,197)	(3,343)
Accrued expenses and other liabilities	(7,061)	(376)
Accrued milestones		(2,000)
Operating lease liabilities	(413)	(293)
Other long-term liabilities	55	509
Net cash used in operating activities	(31,796)	(63,256)
Cash flows from investing activities:
Purchases of property and equipment	(223)	(1,561)
Purchases of short-term investments	(26,187)	(181,807)
Proceeds from the maturities of short-term investments	115,200	174,090
Net cash provided by (used in) investing activities	88,790	(9,278)
Cash flows from financing activities:
Payments of offering costs		(100)
Proceeds from exercise of options and employee share purchase plan	2,414	181
Net cash provided by financing activities	2,414	83,187
Net increase in cash, cash equivalents and restricted cash	59,408	10,653
Cash, cash equivalents and restricted cash at beginning of period	47,138	72,186
Cash, cash equivalents and restricted cash at end of period	$ 106,546	82,839
Supplemental disclosure of non-cash investing and financing activities:
Deferred offering costs included in accrued expenses and accounts payable		19
Property and equipment included in accrued expenses and accounts payable		37
Follow-On Offering | Class A common shares
Cash flows from financing activities:
Proceeds from issuance of common shares, net of underwriting commissions and discounts		48,595
Private Placement | Class A1 common shares
Cash flows from financing activities:
Proceeds from issuance of common shares from private placement, net of underwriting commissions and discounts		$ 34,511