CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (9,222)	$ (8,234)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	6	21
Accretion of discount on marketable securities	25	0
Change in fair value of derivative liability	0	11
Change in fair value of warrant liability	0	(223)
Amortization of discounts and financing costs	0	551
Stock-based compensation	856	683
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	512	(165)
Accounts payable	(1,679)	3,053
Accrued liabilities	(135)	865
Deferred revenue	(1,653)	(6,064)
Net cash used in operating activities	(11,290)	(9,502)
CASH FLOWS FROM INVESTING ACTIVITIES:
Maturities of marketable securities	4,500	0
Capital expenditures	0	(4)
Net cash provided by (used in) investing activities	4,500	(4)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from the issuance of common stock and warrants	20,669	0
Proceeds from the issuance of note payable	437	0
Proceeds from the exercise of warrants	22	0
Proceeds from issuance of convertible promissory notes	0	5,127
Payments of principal of note payable	0	(1,609)
Net cash provided by financing activities	21,128	3,518
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	14,338	(5,988)
CASH AND CASH EQUIVALENTS—BEGINNING	7,232	8,067
CASH AND CASH EQUIVALENTS—ENDING	21,570	2,079
Supplement Disclosure of Cash Flow Information:
Interest paid	0	234
Supplement Disclosure of Non-Cash Investing and Financing Activities:
Reduction of redeemable convertible preferred stock to redemption value	0	(10,376)
Warrants to purchase common stock issued with convertible promissory notes	0	1,029
Derivative liability issued with convertible promissory notes	0	996
Deferred financing costs included in accrued liabilities	0	154
Accretion of redeemable convertible preferred stock issuance costs	$ 0	$ 20