Unaudited Condensed Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net loss	$ (7,904)	$ (18,485)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	2,034	3,664
Non-cash interest expense	3,583	988
Amortization of debt issuance costs and debt discount	1,723	981
Depreciation and amortization expense	207	229
Fair value adjustment related to derivative and warrant liability	65	(1,783)
Change in estimated deferred offering costs	130	10
Loss on sublease and disposal of property and equipment	251
Consulting fees paid in stock	131
Change in assets and liabilities:
Accounts and other receivables	(337)	(1,498)
Prepaid expenses and other assets	537	1,420
Operating lease right-of-use assets	121	(1,649)
Accounts payable and accrued expenses	(1,299)	(6,073)
Operating lease liabilities	(194)	2,345
Other liabilities	72	(788)
Net cash used in operating activities	(880)	(20,639)
Cash flows from investing activities:
Purchases of property and equipment	(7)	(21)
Maturities of marketable securities		3,260
Net cash (used in) provided by investing activities	(7)	3,239
Cash flows from financing activities:
Proceeds from equity line of credit	2,303	5,446
Proceeds from Payment Protection Program loan	781
Payment of deferred offering costs	(97)
Repayment of principal on finance lease liabilities	(168)	(157)
Payment of debt issuance costs	(34)
Net cash provided by financing activities	2,785	5,289
Net increase (decrease) in cash, cash equivalents and restricted cash	1,898	(12,111)
Cash, cash equivalents and restricted cash, beginning of period	3,555	19,119
Cash, cash equivalents and restricted cash, end of period	5,453	7,008
Supplemental cash flow information:
Cash paid for interest	71	4,602
Commitment shares issued in connection with equity line of credit included in deferred offering costs	121
Property and equipment included in accounts payable and accrued expenses	4
Deferred offering costs included in accounts payable and accrued expenses		105
Change in fair value of embedded conversion feature recorded as debt discount in connection with debt modification		2,311
The 2019 Notes Converted to Common Stock [Member]
Supplemental cash flow information:
2019 Notes principal converted to common stock	15,863
The 2021 Notes Converted to Common Stock [Member]
Supplemental cash flow information:
2019 Notes principal converted to common stock		1,424
The 2021 Notes Converted to Preferred Stock [Member]
Supplemental cash flow information:
2019 Notes principal converted to common stock		$ 1,576