Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		71 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (46,205)	$ (31,806)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,591	1,541
Equity-based compensation	6,424	4,157
Amortization/accretion of investment premiums/discounts	1,209	(200)
Changes in operating assets and liabilities:
Accounts receivable	1,177	(8,748)
Prepaid expenses and other current assets	(5,448)	(448)
Operating right-of-use assets	1,596	1,566
Other assets	(255)	97
Accounts payable	(917)	(370)
Accrued expenses	(4,588)	177
Deferred revenue	(5,558)	(3,151)
Operating lease liabilities	(1,402)	(1,360)
Net cash used in operating activities	(52,376)	(38,545)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(2,412)	(845)
Purchases of marketable securities	(148,330)	(31,207)
Maturities of marketable securities	125,200	89,500
Net cash (used in) provided by investing activities	(25,542)	57,448
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock through at-the-market offerings, net of issuance costs			$ 1,165,300
Proceeds from options exercised	13,340	336
Net cash provided by financing activities	58,595	4,864
Net (decrease) increase in cash and cash equivalents and restricted cash and cash equivalents	(19,323)	23,767
Cash and cash equivalents and restricted cash and cash equivalents, beginning of period	164,606	57,226
Cash and cash equivalents and restricted cash and cash equivalents, end of period	145,283	80,993	145,283
Reconciliation of cash and cash equivalents and restricted cash and cash equivalents to condensed consolidated balance sheet:
Cash and cash equivalents	141,538	80,993	141,538
Restricted cash and cash equivalents, included in prepaids and other current assets and other assets	3,745		3,745
Cash and cash equivalents and restricted cash and cash equivalents, end of period	145,283	80,993	145,283
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Purchases of property and equipment unpaid at period end	901	750
Right-of-use assets acquired under operating leases	40,394	7,347
Proceeds from at-the-market offerings unpaid at period end		551
At The Market Offerings [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock through at-the-market offerings, net of issuance costs	$ 45,255	$ 4,528	$ 196,500