CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating activities
Net loss	$ (16,525)	$ (11,077)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	74	54
Stock-based compensation	508	166
Non-cash interest expense	254	2,761
Change in fair value warrant liability		996
Change in fair value derivative liability		317
Changes in operating assets and liabilities:
Other receivable	(948)
Prepaid expenses and other assets	(2,019)	115
Accounts payable	1,243	(115)
Accrued expenses	(1,463)	149
Deferred rent	11	(5)
Net cash used in operating activities	(18,865)	(6,639)
Investing activities
Purchases of property and equipment	(429)	(28)
Net cash used in investing activities	(429)	(28)
Financing activities
Proceeds from issuance of common stock in public offering, net	46,308
Long-term borrowings, net	3,089	1,995
Repayments of long-term debt	(938)
Proceeds from exercise of stock options	126
Net cash provided by financing activities	48,585	1,995
Net increase (decrease) in cash and cash equivalents	29,291	(4,672)
Cash, cash equivalents and restricted cash at the beginning of the period	61,051	13,406
Cash, cash equivalents and restricted cash at the end of the period	90,342	8,734
Supplemental disclosure for cash flow
Cash paid for interest	191	90
Supplemental disclosure of non-cash investing and financing activities
Accrued interest on term loan refinanced to principal	308
Issuance of warrants in conjunction with debt	296
Debt refinanced with new term loan	6,563
Initial recognition of operating lease right-of-use assets and operating lease liabilities	1,991
Accretion of redeemable convertible preferred stock		33
Deferred stock offering costs included in accounts payable and accrued expenses	31	$ 604
Purchases of property and equipment included in accounts payable	$ 6