CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities:
Net loss	$ (8,028)	$ (10,308)
Adjustments to reconcile net loss to net cash from operating activities:
Stock-based compensation expense	2,349	2,273
Non-cash interest expense	84	135
Depreciation and amortization expense	1,078	1,386
Prepaid expenses and other current assets	(193)	273
Prepaid manufacturing services	7
Operating right-of-use assets	319	236
Accounts payable	(265)	270
Accrued expenses	(2,860)	(1,696)
Deferred revenue	(12,704)	(12,345)
Operating lease liabilities	(638)	139
Net cash used in operating activities	(20,851)	(19,637)
Cash flows from investing activities:
Purchases of property and equipment	(182)	(1,526)
Net cash used in investing activities	(182)	(1,526)
Cash flows from financing activities:
Proceeds from exercise of common stock options		316
Proceeds from issuance of common stock upon at-the-market offering, net of fees	589	62,204
Net cash provided by financing activities	589	62,520
Net (decrease) increase in cash, cash equivalents and restricted cash	(20,444)	41,357
Cash, cash equivalents and restricted cash, beginning of period	81,108	93,085
Cash, cash equivalents and restricted cash, end of period	60,664	134,442
Supplemental disclosures:
Cash paid for interest	516	563
Non-cash investing and financing activities:
Purchases of property and equipment included in accounts payable and accrued expenses	24	457
Deferred offering costs included in accrued expenses	67	336
Reconciliation to amounts within the consolidated balance sheets
Cash and cash equivalents	56,494	130,272
Restricted cash	4,170	4,170
Cash, cash equivalents and restricted cash at end of period	$ 60,664	$ 134,442