STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating activities
Net loss	$ (39,247)	$ (23,846)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	174	105
Stock-based compensation	1,421	332
Non-cash interest expense	500	3,664
Change in fair value warrant liability	0	(11)
Change in fair value derivative liability	0	676
Changes in operating assets and liabilities:
Other receivables	(1,000)	(233)
Prepaid expenses and other assets	(1,954)	(1,017)
Accounts payable	802	1,337
Accrued expenses	(327)	1,923
Deferred rent	37	17
Net cash used in operating activities	(39,594)	(17,053)
Investing activities
Purchases of property and equipment	(960)	(119)
Net cash used in investing activities	(960)	(119)
Financing activities
Proceeds from issuance of common stock, net	46,277	42,974
Payments of deferred stock offering costs	(145)	0
Proceeds from issuance of redeemable convertible preferred stock, net	0	17,712
Long-term borrowings, net	8,089	3,995
Proceeds from exercise of stock options	245	92
Proceeds from exercise of warrants	0	24
Repayments of long-term debt	(938)	0
Net cash provided by financing activities	53,528	64,797
Net increase in cash and cash equivalents	12,974	47,625
Cash, cash equivalents and restricted cash at the beginning of the year	61,051	13,426
Cash, cash equivalents and restricted cash at the end of the year	74,025	61,051
Supplemental disclosure for cash flow
Cash paid for interest	576	260
Supplemental disclosure of cash flow information
Accrued interest on term loan refinanced to principal	308	0
Debt refinanced through new term loan	6,563	0
Right-of-use asset and lease liabilities recorded upon adoption of ASC 842	1,991
Conversion of redeemable convertible preferred stock into common stock	0	125,609
Conversion of convertible promissory notes into redeemable convertible preferred stock	0	19,778
Warrant liability converted to redeemable convertible preferred stock upon the exercise of warrants	0	4,297
Issuance of warrants in conjunction with debt	355	2,822
Conversion of redeemable convertible preferred stock warrants into common stock warrants	0	3,346
Accretion of redeemable convertible preferred stock	0	95
Deferred stock offering costs in accounts payable	110	0
Purchases of property and equipment included in accounts payable and accrued expenses	$ 823	$ 39