CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net loss	$ (34,360)	$ (16,538)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	567	497
Equity-based compensation	3,057	689
Amortization of deferred rent	190	(155)
Deferred payroll tax credit	199
Other	95	35
Change in operating assets and liabilities:
Prepaid expenses and other current assets	(1,108)	(1,704)
Accounts payable	294	1,656
Accrued expenses	543	(159)
Net cash used in operating activities	(30,523)	(15,679)
Cash flows from investing activities:
Purchase of property and equipment	(791)	(247)
Sales and maturities of marketable securities	1,499	12,014
Net cash provided by investing activities	708	11,767
Cash flows from financing activities:
Principal payments on loan payable	(500)	(500)
Proceeds from initial public offering of common stock, net of issuance costs	77,839
Payment of capital lease obligation	(2)
Proceeds from stock option exercises	3
Proceeds from issuance of Series B convertible preferred units		4,285
Net cash provided by financing activities	77,340	3,785
Net increase (decrease) in cash and cash equivalents and restricted cash	47,525	(127)
Cash and cash equivalents and restricted cash, beginning of period	56,666	10,238
Cash and cash equivalents and restricted cash, end of period	104,191	10,111
Supplemental disclosure of non‑cash items:
Property and equipment purchases in accounts payable and accrued liabilities	177	59
Supplemental cash flow information:
Cash paid for interest	27	$ 41
Purchase under capital lease	$ 44