Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Cash flows from operating activities:
Net loss		$ (8,458)	$ (20,898)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization		44	75
Amortization of operating lease right-of-use assets		197
Loss on impairment of fixed assets			48
Derivatives loss	$ 1,967		12,165
Gain on lease assignment			(603)
Non-cash interest expense		1	2
Common stock issued to 401(k) plan			6
Share-based compensation expense		203	541
Changes in operating assets and liabilities:
Prepaid expenses and other assets		(72)	(961)
Accounts payable		6	291
Operating lease liability		(74)
Accrued expenses and other liabilities		(272)	9
Net cash used in operating activities		(8,425)	(9,325)
Cash flows from investing activities:
Purchases of property and equipment			(65)
Net cash used in investing activities			(65)
Cash flows from financing activities:
Proceeds from issuance of stock under ESPP		1	4
Proceeds from exercise of warrants			55
Repayment of loan payable		(100)	(636)
Repurchase of warrants			(14)
Proceeds from issuance of common stock and warrants, net of commissions and issuance costs			16,511
Net cash (used in) provided by financing activities		(99)	15,920
Decrease in cash and cash equivalents and restricted cash		(8,524)	6,530
Cash, cash equivalents and restricted cash at beginning of period		16,774	13,271	$ 13,271
Cash, cash equivalents and restricted cash at end of period	$ 19,801	8,250	19,801	$ 16,774
Supplemental disclosure of cash flow information and non-cash investing and financing activities:
Cash paid for interest		1	35
Right-of-use assets and lease liability recorded upon adoption of ASC 842		$ 1,475
Fair value of derivative warrant liability reclassified to additional paid-in capital			25,326
Non-cash issuance of common stock for warrants			$ 287