Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Operating activities
Net loss	$ (3,496)	$ (2,970)	$ (9,491)	$ (11,006)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization			8	18
Stock-based compensation			803	386
Loss on disposal of fixed assets				31
Changes in operating assets and liabilities:
Prepaid expenses and other assets			(23)	(761)
Accounts payable and accrued expenses			163	(998)
Net cash used in operating activities			(8,540)	(12,330)
Investing activities
Cash received from merger transaction				23,250
Proceeds from sale of equipment				8
Net cash provided by investing activities				23,258
Financing activities
Proceeds from issuance of common stock, net			7,490	4,000
Proceeds from exercise of warrants				3,119
Proceeds from exercise of stock options			71
Net cash provided by financing activities			7,561	7,119
Net increase (decrease) in cash and restricted cash			(979)	18,047
Cash and restricted cash at beginning of period			17,303	1,117	$ 1,117
Cash at end of period	$ 16,324	$ 19,164	$ 16,324	19,164	$ 17,303
Noncash activities:
Conversion of promissory notes and interest to common stock				3,447
Conversion of contingently issuable shares to common stock				291
Issuance of common stock in merger				23,375
Conversion of preferred stock to common stock				27
Fair value of assets acquired, excluding cash and restricted cash				3,072
Fair value of liabilities assumed				(2,947)
Fair value of net assets acquired in the merger				$ 125