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	$ (26,282)	$ (24,256)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	1,786	695
Depreciation and amortization expense	102	44
Non-cash lease expense	320	244
Accretion of debt discount	252	369
Loss on extinguishment of debt	162	0
Change in fair value of preferred stock warrant liability	0	288
Change in fair value of derivative liability	0	(183)
Other	(31)	0
Changes in operating assets and liabilities:
Prepaid expenses, other current assets and research and development incentive receivable	(4,201)	13
Accounts payable	(211)	(1,702)
Accrued expenses	1,542	(1,157)
Lease liabilities	(425)	(397)
Net cash used in operating activities	(26,986)	(26,042)
Cash flows from investing activities:
Cash, cash equivalents and restricted cash acquired in connection with the Merger	0	26,406
Acquisition of property, equipment and intangible assets	(564)	(10)
Net cash (used in) provided by investing activities	(564)	26,396
Cash flows from financing activities:
Proceeds from exercise of stock options and warrants	175	565
Employee taxes paid related to net share settlement of vested restricted stock units	(14)	0
Proceeds from borrowings under loan and security agreements, net of issuance costs	4,888	9,849
Proceeds from sale of common stock and warrants, net of issuance costs	0	79,291
Repayments of borrowings under loan and security agreement	0	(2,914)
Net cash provided by financing activities	5,049	86,791
Effect of exchange rate changes on cash, cash equivalents and restricted cash	60	(2)
Net (decrease) increase in cash, cash equivalents and restricted cash	(22,441)	87,143
Cash, cash equivalents and restricted cash at beginning of period	128,086	8,498
Cash, cash equivalents and restricted cash at end of period	105,645	95,641
Supplemental disclosure of non-cash investing and financing activities:
Issuance costs not yet paid	0	354
Conversion of convertible preferred stock into common stock	0	64,675
Conversion of redeemable common stock into common stock	0	734
Conversion of convertible preferred stock warrants into common stock warrants	0	5,235
Fair value of net assets acquired in the Merger	$ 0	$ 46,358