Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Operating activities
Net loss		$ (25,480)	$ (39,961)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation		15,902	8,539
Depreciation of property and equipment		402	413
Non-cash lease expense		1,402	803
Non-cash interest expense (income), net		822	(1,394)
Changes in assets and liabilities:
Accounts receivable, other		132	0
Accounts receivable due from related party		(58)	2,058
Prepaids and other current assets		(770)	756
Other assets		(5)	116
Accounts payable		213	(29)
Operating lease liabilities		6,255	(801)
Other liabilities		(701)	3,460
Deferred revenue from related party		(60,033)	(23,853)
Net cash used in operating activities		(61,919)	(49,893)
Investing activities
Purchases of property and equipment, net		(6,136)	(465)
Purchases of investments		(391,942)	(189,404)
Sales of investments		0	4,967
Maturities of investments		124,220	165,770
Net cash used in investing activities		(273,858)	(19,132)
Financing activities
Proceeds from issuance of common stock		325,654	73,276
Proceeds from exercise of stock options and employee stock purchase plan		26,472	5,837
Employees' tax withheld and paid for restricted stock units		(3,709)	(1,174)
Borrowings under credit facility agreement, net of issuance costs		4,358	0
Net cash provided by financing activities		352,775	77,939
Net increase in cash, cash equivalents and restricted cash		16,998	8,914
Cash, cash equivalents and restricted cash at beginning of period		40,259	28,088
Cash, cash equivalents and restricted cash at end of period		57,257	37,002
Supplemental disclosures of cash flow information
Cash paid for interest		1,433	1,317
Right-of-use assets obtained in exchange for lease obligations	[1]	27,365	2,796
Purchases of property and equipment, net recorded in accounts payable and accrued liabilities		$ 7,175	$ 0

[1] Amount for the nine months ended September 30, 2019 includes the transition adjustment of $1,301 for the adoption of Accounting Standards Update (ASU) No. 2016-02, Leases (Topic 842).