Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities
Net loss	$ (57,785)	$ (57,641)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	452	416
Stock-based compensation expense	10,983	8,708
In process research and development expenses	20	30
Amortization of operating lease right-of-use assets	645	858
Amortization of long-term debt discount and issuance costs	292	1,605
Amortization of premium on marketable securities, net of accretion of discounts	125	66
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(2,589)	(2,855)
Other assets	61	16
Operating lease liabilities	(683)	117
Accounts payable	(2,507)	(6,565)
Accrued expenses	52	(729)
Accrued research and development expenses	753	1,078
Accrued compensation and benefits	(5,802)	(6,500)
Accrued interest expense	2,500	2,500
Net cash used in operating activities	(53,483)	(58,896)
Cash flows from investing activities
Research and development asset acquisitions, net of cash acquired	(20)	(30)
Purchase of marketable securities	(37,403)	0
Maturities of marketable securities	46,000	12,800
Purchase of property and equipment	(157)	(802)
Net cash provided by investing activities	8,420	11,968
Cash flows from financing activities
Proceeds from the exercise of stock options	126	15
Net cash provided by financing activities	721	774
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(154)	(242)
Net decrease in cash, cash equivalents and restricted cash	(44,496)	(46,396)
Cash, cash equivalents and restricted cash, at the beginning of the period	183,467	486,620
Cash, cash equivalents and restricted cash, at the end of the period	138,971	439,982
Supplemental disclosure of cash flow information:
Cash paid for interest	675	675
Supplemental disclosure of noncash investing and financing activities:
Operating lease right-of-use asset obtained in exchange for lease liability	3,029	0
Change in unrealized loss on marketable securities, net of tax	(377)	(69)
Employee Stock Purchase Plan
Cash flows from financing activities
Purchase of shares pursuant to Employee Stock Purchase Plan	$ 595	$ 759