CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net loss	$ (36,351)	$ (23,280)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	784	586
Equity-based compensation	4,609	3,432
Amortization/accretion of investment securities	(196)	(694)
Non-cash operating lease expense	523	492
Change in operating assets and liabilities:
Accounts receivable	25,000
Prepaid expenses and other current assets	(1,292)	(1,091)
Other assets	(963)
Accounts payable	1,543	(1,028)
Accrued expenses	(1,377)	(1,771)
Operating lease liabilities	(541)	(378)
Deferred revenue	(8,930)	(8,145)
Other liabilities		(59)
Net cash used in operating activities	(17,191)	(31,936)
Cash flows from investing activities:
Purchases of property and equipment	(283)	(1,279)
Purchases of marketable securities	(19,400)	(77,297)
Maturities of marketable securities	114,700	67,300
Net cash provided by (used in) investing activities	95,017	(11,276)
Cash flows from financing activities:
Principal payments on loan payable		(365)
Proceeds from sale of common stock, net of issuance costs		42,220
Proceeds from stock option exercises	1,003	92
Other	(9)	(6)
Net cash provided by financing activities	994	41,941
Net increase (decrease) in cash and cash equivalents and restricted cash	78,820	(1,271)
Cash and cash equivalents and restricted cash, beginning of period	38,806	115,274
Cash and cash equivalents and restricted cash, end of period	117,626	114,003
Supplemental disclosure of non-cash items:
Property and equipment purchases in accounts payable and accrued expenses	$ 7	27
Offering costs in accounts payable and accrued expenses		198
Operating lease right-of-use asset obtained in exchange for operating lease obligation		$ 5,349