Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (17,895)	$ (14,470)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	117	112
Amortization of debt discount		284
Net amortization of premiums and discounts on marketable securities	(45)
Stock-based compensation	173	88
Change in fair value of derivative liabilities		(338)
Loss on extinguishment of related party convertible promissory note		2,180
Changes in operating assets and liabilities:
Accounts receivable	(232)	(235)
Prepaid expenses and other current assets	645	(160)
Accounts payable	3,126	1,014
Accrued expenses	(311)	1,220
Deferred revenue		(194)
Net cash used in operating activities	(14,422)	(10,499)
CASH FLOWS FROM INVESTING ACTIVITIES:
Sales and maturities of marketable securities	14,150
Purchase of property and equipment	(67)	(61)
Net cash provided by (used in) investing activities	14,083	(61)
CASH FLOWS FROM FINANCING ACTIVITIES:
Payments of initial public offering costs		(327)
Repayment of convertible promissory note, related party		(4,000)
Proceeds from capital contribution		12,000
Proceeds from exercise of stock options		5
Net cash provided by financing activities		7,678
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(339)	(2,882)
CASH AND CASH EQUIVALENTS–Beginning of period	5,618	4,180
CASH AND CASH EQUIVALENTS–End of period	$ 5,279
SUPPLEMENTAL DISCLOSURES OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Deferred offering costs in accounts payable and accrued expenses		$ 1,360