Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net loss	$ (29,681)	$ (22,105)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	338	283
Stock-based compensation expense	2,010	1,658
Share of loss from equity method investment	951	40
Change in fair value of preferred stock warrants		(1,632)
Changes in operating assets and liabilities:
Accounts receivable	1,660	(1,660)
Other receivables	25
Prepaid expenses and other current assets	(1,433)	(2,207)
Contract costs	(1,576)
Other assets	438	(648)
Accounts payable	(469)	1,297
Accrued liabilities	(2)	800
Deferred revenue	19,580	(97)
Net cash used in operating activities	(8,159)	(24,271)
Cash flows from investing activities:
Purchase of equity method investment	(174)	(677)
Purchase of property and equipment		(1,000)
Net cash used in investing activities	(174)	(1,677)
Cash flows from financing activities:
Proceeds from issuance of common stock, net	4,958	25,079
Proceeds from stock option exercises	35	10
Net cash provided by financing activities	4,993	25,089
Net decrease in cash and cash equivalents	(3,340)	(859)
Cash and cash equivalents at:
Beginning of period	24,237	25,096
End of period	20,897	24,237
Supplemental cash flow disclosures:
Cash paid for taxes	2	2
Supplemental noncash investing and financing activities:
Preferred stock dividends accrued		1,357
Reclassification of warrant liability into equity		10,236
Property and equipment additions	$ 13	$ 120