Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (21,653)	$ (15,247)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	721	694
Deferred tax benefit	(14)	(23)
Stock-based compensation	4,121	2,659
Non-cash warrant inducement expense	2,688	0
Non-cash investment income	0	(1)
Non-cash patent write-off	0	19
Non-cash loss on disposal of assets	2	1
Changes in assets and liabilities, net of effects of acquisition:
Accounts receivable	6	(19)
Prepaids and other current assets	(376)	(8)
Other assets	(3)	(1)
Accounts payable	(143)	56
Accrued expenses	163	(34)
Accrued salaries and payroll related expenses	208	980
Deferred revenue	(184)	299
Deferred rent	(10)	(34)
Net cash used in operating activities	(14,474)	(10,659)
CASH FLOWS FROM INVESTING ACTIVITIES
Proceeds from sale of fixed assets	7	0
Purchases of property and equipment	(815)	(400)
Expenditures for patents and domain names	(332)	(177)
Payment for acquisition of business assets, net of acquired cash	0	(513)
Redemption of investments held-to-maturity	4,747	10,509
Purchase of investments held-to-maturity	0	(12,249)
Net cash provided by (used in) investing activities	3,607	(2,830)
CASH FLOWS FROM FINANCING ACTIVITIES
Net proceeds from the sale of common stock from private placement offerings	15,950	5,177
Net proceeds from the sale of common stock from underwritten public offering	0	10,621
Proceeds from exercise of warrants	9,272	280
Proceeds from exercise of stock options	78	0
Net cash provided by financing activities	25,300	16,078
Effects of currency translation on cash and cash equivalents	7	(6)
NET INCREASE IN CASH AND CASH EQUIVALENTS	14,440	2,583
CASH AND CASH EQUIVALENTS — Beginning of year	5,084	2,501
CASH AND CASH EQUIVALENTS — End of year	19,524	5,084
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
Taxes	1	1
SUPPLEMENTAL DISCLOSURE OF NON-CASH ACTIVITIES
Issuance of common stock in settlement of liability	119	110
Stock options issued in settlement of liability	332	0
Issuance of common stock in the acquisition of business assets	0	545
Property and equipment included in accounts payable	245	191
Property and equipment included in accrued liabilities	95	0
Patents included in accounts payable	$ 9	$ 117