CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss	$ (10,308)	$ (22,502)
Adjustments to reconcile net loss to net cash from operating activities:
Stock-based compensation expense	2,273	1,750
Non-cash interest expense	135	67
Depreciation and amortization expense	1,386	1,028
Accretion of investments		(40)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	273	3,154
Operating right-of-use assets	236	502
Accounts payable	270	(920)
Accrued expenses	(1,696)	(4,315)
Deferred revenue	(12,345)	(134)
Operating lease liabilities	139	2,421
Net cash used in operating activities	(19,637)	(18,989)
Cash flows from investing activities:
Purchases of property and equipment	(1,526)	(14,065)
Maturities of investments		70,562
Net cash (used in) provided by investing activities	(1,526)	56,497
Cash flows from financing activities:
Proceeds from exercise of common stock options	316	18
Proceeds from public offering of common stock, net of issuance costs	62,204
Net cash provided by financing activities	62,520	18
Net Increase in cash, cash equivalents and restricted cash	41,357	37,526
Cash, cash equivalents and restricted cash, beginning of period	93,085	14,852
Cash, cash equivalents and restricted cash, end of period	134,442	52,378
Supplemental disclosures:
Cash paid for interest	563	228
Non-cash investing and financing activities:
Purchases of property and equipment included in accounts payable and accrued expenses	457	3,136
Deferred offering costs included in accrued expenses	336
Accretion of redeemable convertible preferred stock to redemption value		3,372
Operating right-of-use assets obtained in exchange for operating lease liabilities		23,186
Reconciliation to amounts within the condensed consolidated balance sheets
Cash and cash equivalents	130,272	47,842
Restricted cash		366
Restricted cash, net of current portion	4,170	4,170
Cash, cash equivalents and restricted cash at end of period	$ 134,442	$ 52,378