Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating activities:
Net loss	$ (117,391)	$ (68,498)
Reconciliation of net loss to net cash and restricted cash used in operating activities:
Depreciation and amortization	2,574	2,218
Equity-based compensation	21,960	11,894
Unrealized foreign currency remeasurement loss		(9)
Loss from equity method investment	3,256	1,310
Expense related to ViaCyte transaction	15,109
Other income, non-cash	(169)
Changes in:
Accounts receivable	2,074	(54)
Prepaid expenses and other assets	(2,502)	(304)
Accounts payable and accrued expenses	7,982	(2,979)
Deferred revenue	(270)	2,043
Deferred rent	(528)	(903)
Other liabilities, net	38	31
Net cash and restricted cash (used in) operating activities	(67,867)	(55,251)
Investing activities:
Purchase of property and equipment	(1,773)	(7,609)
Purchase of available for sale debt security		(500)
Net cash and restricted cash (used in) investing activities	(1,773)	(8,109)
Financing activities:
Proceeds from issuance of common shares, net of issuance costs	309,019
Proceeds from exercise of options	8,241	1,324
Repurchase of common shares	(57)
Net cash provided by financing activities	317,203	1,324
Effect of exchange rate changes on cash	(15)	39
Increase (decrease) in cash and restricted cash	247,548	(61,997)
Cash and restricted cash, beginning of period	242,912	318,670
Cash and restricted cash, end of period	490,460	256,673
Supplemental disclosure of non-cash investing and financing activities
Costs for supplemental offering in accounts payable and accrued expenses	$ 1,980
Property and equipment purchases in accounts payable and accrued expenses		$ 118