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CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss	$ (10,873)	$ (7,367)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	262	128
Depreciation expense	20	26
Non-cash lease expense	119
Non-cash interest expense	153	27
Change in fair value of preferred stock warrant liability	288	592
Change in fair value of derivative liability	(183)	565
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(595)	170
Accounts payable	1,332	(563)
Accrued expenses	(2,072)	240
Operating lease liabilities	(201)
Net cash used in operating activities	(11,750)	(6,182)
Cash flows from investing activities:
Cash and restricted cash acquired in connection with the Merger	26,406
Net cash provided by investing activities	26,406
Cash flows from financing activities:
Proceeds from exercise of stock options	113
Repurchase of Series Seed convertible preferred stock		(1,126)
Repayments of borrowings under loan and security agreement		(500)
Payments of issuance costs of convertible preferred stock		(34)
Net cash provided by (used in) financing activities	113	(1,660)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(21)
Net increase (decrease) in cash, cash equivalents and restricted cash	14,748	(7,842)
Cash, cash equivalents and restricted cash at beginning of period	8,498	27,048
Cash, cash equivalents and restricted cash at end of period	23,246	19,206
Supplemental disclosure of cash flow information:
Cash paid for interest	243	$ 146
Supplemental disclosure of non-cash investing and financing activities:
Conversion of convertible preferred stock into common stock	64,675
Conversion of redeemable common stock into common stock	734
Conversion of convertible preferred stock warrants into common stock warrants	5,235
Fair value of net assets acquired in Merger	$ 46,358

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