CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net loss	$ (17,070)	$ (10,755)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	391	271
Equity-based compensation	2,214	1,618
Amortization/accretion of investment securities	(177)	(365)
Non-cash operating lease expense	259	244
Change in operating assets and liabilities:
Accounts receivable	25,000
Prepaid expenses and other current assets	(806)	(206)
Other assets	(732)
Accounts payable	1,089	(98)
Accrued expenses	(2,234)	(3,016)
Operating lease liabilities	(268)	(130)
Deferred revenue	(5,030)	(3,106)
Other liabilities		13
Net cash provided by (used in) operating activities	2,636	(15,530)
Cash flows from investing activities:
Purchase of property and equipment	(209)	(681)
Purchase of marketable securities	(19,400)	(77,297)
Maturities of marketable securities	75,700	45,600
Net cash provided by (used in) investing activities	56,091	(32,378)
Cash flows from financing activities:
Principal payments on loan payable		(167)
Proceeds from stock option exercises	405	13
Other	(6)	(3)
Net cash provided by (used in) financing activities	399	(157)
Net (decrease) increase in cash and cash equivalents and restricted cash	59,126	(48,065)
Cash and cash equivalents and restricted cash, beginning of period	38,806	115,274
Cash and cash equivalents and restricted cash, end of period	97,932	67,209
Supplemental disclosure of non-cash items:
Property and equipment purchases in accounts payable and accrued expenses	$ 10	483
Operating lease right-of-use asset obtained in exchange for operating lease obligation		$ 5,349