Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating activities
Net loss	$ (212,001)	$ (181,976)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	880	851
Amortization of debt issuance costs and imputed interest	5,322	5,850
Non-cash interest expense on liability related to sale of future royalty	34,312	11,077
Stock-based compensation expense	41,580	45,684
Loss on extinguishment of debt	0	11,183
Gain on lease termination	0	(816)
Changes in operating assets and liabilities:
Income tax receivable and payable	22,228	(22,203)
Prepaid expenses, other current assets and other assets	(1,471)	150
Accounts payable	(3,117)	7,033
Accrued direct research, other current and long-term liabilities	1,625	(514)
Payable to collaborators	0	(150,000)
Deferred revenue	(2,127)	(3,519)
Net cash used in operating activities	(112,769)	(277,200)
Investing activities
Purchases of property and equipment	(1,136)	(539)
Net cash used in investing activities	(1,136)	(539)
Financing activities
Proceeds from issuance of common stock, net	0	55,398
Payments on long-term debt	0	(167,170)
Exercise of options	8,967	9,879
Proceeds from sale of future royalties, net	0	293,571
Net cash provided by financing activities	8,967	191,678
Net decrease in cash and cash equivalents	(104,938)	(86,061)
Cash and cash equivalents at beginning of year	818,150	664,324
Cash and cash equivalents at end of period	713,212	578,263
Supplemental disclosures
Cash paid for interest	0	8,021
Non-cash activity:
Purchases of equipment in accounts payable, accrued direct research, other current, and long-term liabilities	$ 4,239	$ 2,282