Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities:
Net loss	$ (35,595)	$ (45,681)
Adjustments to reconcile net loss to net cash used in operating activities:
Amortization of (discount)/premium on available-for-sale securities	7	(20)
Equity-based compensation expense	6,542	6,347
Depreciation expense	1,453	2,360
Gain on disposal of property and equipment	3
Changes in operating assets and liabilities:
Prepaid expenses and other current and non-current assets	621	362
Accounts receivable - related party	(286)
Accounts payable	(318)	(3,892)
Accrued expenses and other current and non-current liabilities	(4,529)	(1,818)
Deferred revenue- related party, current and non-current	(6,364)
Net cash used in operating activities	(38,466)	(42,342)
Cash flows from investing activities:
Purchases of property and equipment	(384)	(759)
Proceeds from sale and maturities of available-for-sale securities		7,900
Purchases of available-for-sale securities	(48,368)	(401)
Net cash (used in) provided by investing activities	(48,752)	6,740
Cash flows from financing activities:
Proceeds from issuance of common stock	134,878
Proceeds from exercise of stock options	38
Net cash provided by financing activities	134,916
Net increase/(decrease) in cash, cash equivalents and restricted cash	47,698	(35,602)
Cash, cash equivalents, and restricted cash at beginning of period	155,071	76,370
Cash, cash equivalents, and restricted cash at end of period	202,769	40,768
Supplemental disclosure of non-cash investing and financing activities:
Change in unrealized loss	(11)
Decrease in right of use asset due to lease termination	(1,233)
Property and equipment included in accounts payable and accruals	$ 47	$ 27