Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net loss	$ (16,510)	$ (24,033)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	252	253
Stock-based compensation expense	1,562	1,521
Share of loss from equity method investment	9	910
Changes in operating assets and liabilities:
Accounts receivable	0	1,660
Other receivables	263	(162)
Prepaid expenses	702	(1,605)
Contract costs	(488)	0
Other assets	(30)	(547)
Accounts payable	(522)	394
Accrued liabilities and other	(619)	200
Deferred revenue	0	9,580
Net cash used in operating activities	(15,381)	(11,829)
Cash flows from investing activities:
Purchase of property and equipment	(33)	(53)
Net cash used in investing activities	(33)	(53)
Cash flows from financing activities:
Proceeds from issuance of common stock, net	0	4,958
Proceeds from note payable	715	0
Proceeds from stock option exercises	14	17
Net cash provided by financing activities	729	4,975
Net decrease in cash and cash equivalents	(14,685)	(6,907)
Cash and cash equivalents at:
Beginning of period	20,897	24,237
End of period	6,212	17,330
Supplemental cash flow disclosures:
Cash paid for taxes	$ 2	$ 2