Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES
Consolidated net loss	$ (51,116)	$ (35,156)
Adjustments to reconcile net loss to net cash used in operating activities:
Non-cash stock compensation expense	11,068	1,882
Depreciation and amortization	30	23
Amortization of premium on investment securities	(44)	(75)
Amortization of debt issuance costs	231	77
Amortization of leasehold interest	54	46
Non-cash change in lease liability and right-of-use asset	2,001	373
Change in fair value of notes payable	(20)	66
Changes in assets and liabilities:
Increase in other current assets	(1,057)	(2,454)
Increase in accrued interest receivable	40	14
(Decrease) increase in accounts payable and accrued expenses	(1,567)	2,240
Decrease in lease liabilities	(1,967)	(339)
(Decrease) increase in interest payable	(832)	549
Decrease in other liabilities	(18,898)	(559)
Decrease in deferred revenue	(38)	(38)
Net cash used in operating activities	(62,115)	(33,351)
CASH FLOWS FROM INVESTING ACTIVITIES
Proceeds from maturity of short-term securities	9,000	7,050
Investment in held-to-maturity securities	(7,482)	(8,171)
Purchases of equipment	(68)	(14)
Net cash provided by (used in) investing activities	1,450	(1,135)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from sale of common stock, net		27,678
Proceeds from exercise of options	81
Proceeds from debt financings		29,740
Financing costs paid		(538)
Net cash provided by financing activities	81	56,880
NET (DECREASE) INCREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(60,584)	22,394
CASH, CASH EQUIVALENTS AND RESTRICTED CASH AT BEGINNING OF PERIOD	113,887	43,199
CASH, CASH EQUIVALENTS AND RESTRICTED CASH AT END OF PERIOD	$ 53,303	$ 65,593