Condensed Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating activities
Net loss	$ (39,075)	$ (35,219)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	387	218
Accretion of premiums and discounts on investments	(97)	(140)
Non-cash interest expense related to the revenue interest liability	13,739	3,996
Stock-based compensation expense	21,712	19,526
Changes in assets and liabilities:
Prepaids and other assets	(7,989)	(1,802)
Deferred revenue	(490)	2,618
Inventories	(9,061)	0
Other long-term liabilities	1,710	0
Accounts payable	(11,326)	(21,158)
Other accrued liabilities	13,863	11,614
Net cash used in operating activities	(16,627)	(20,347)
Investing activities
Purchases of investments	(4,420)	(26,630)
Proceeds from sales/maturities of investments	39,145	94,510
Purchase of property and equipment	(693)	(781)
Net cash provided by investing activities	34,032	67,099
Financing activities
Proceeds from revenue interest liability	25,000	124,424
Proceeds from exercise of common stock options	6,395	4,757
Payments on revenue interest liability	(110)	0
Net cash provided by financing activities	31,285	129,181
Net increase in cash and cash equivalents	48,690	175,933
Cash, cash equivalents and restricted cash at beginning of period	167,058	36,973
Cash, cash equivalents and restricted cash at end of period	215,748	212,906
Supplemental disclosure of cash flow information:
Purchase of property and equipment not yet paid	148	74
Non cash right of use asset	$ 3	$ 31