CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating activities
Net loss	$ (14,905)	$ (7,293)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	54	31
Stock-based compensation	471	238
Loss from remeasurement of development derivative liability	454	0
Non-cash interest expense	132	129
Non-cash research and development expense	557	0
Other non-cash transactions	100	0
Changes in operating assets and liabilities:
Other receivable	337	(437)
Prepaid expenses and other assets	(9,602)	(91)
Accounts payable	(712)	225
Accrued expenses and other current liabilities	(713)	(1,533)
Net cash used in operating activities	(23,827)	(8,731)
Investing activities
Purchases of property and equipment	(558)	(84)
Acquisition of intellectual property rights	(100)	0
Net cash used in investing activities	(658)	(84)
Financing activities
Proceeds from development derivative liability	10,000	0
Payments of deferred stock offering costs	(116)	0
Long-term borrowings, net	0	616
Proceeds from exercise of stock options	17	0
Repayments of long-term debt	0	(938)
Net cash provided by (used in) financing activities	9,901	(322)
Net decrease in cash and cash equivalents	(14,584)	(9,137)
Cash, cash equivalents and restricted cash at the beginning of the period	74,025	61,051
Cash, cash equivalents and restricted cash at the end of the period	59,441	51,914
Supplemental disclosure for cash flow
Cash paid for interest	246	98
Supplemental disclosure of non-cash investing and financing activities
Issuance of warrants in conjunction with development derivative liability	7,925	0
Accrued interest on term loan refinanced to principal	0	308
Issuance of warrants in conjunction with debt	0	209
Debt refinanced with new term loan	0	6,563
Initial recognition of operating lease right-of-use assets and operating lease liabilities	0	1,991
Deferred stock offering costs in accounts payable	45	0
Purchases of property and equipment included in accounts payable and accrued expenses	$ 1,031	$ 11