Condensed Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash Flows from Operating Activities
Net loss	$ (52,753)	$ (52,450)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,719	1,764
Amortization of operating right-of-use asset	785
Loss on disposal of property and equipment		11
Stock-based compensation	9,824	8,282
Amortization of discount or premium on available-for-sale securities	118	936
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(2,995)	(1,477)
Accounts payable	(1,298)	392
Accrued expenses	(3,692)	(1,763)
Other current liabilities	(59)	(730)
Deferred rent		16,274
Operating lease liabilities	(1,577)
Net cash used in operating activities	(48,928)	(28,761)
Cash Flows from Investing Activities
Purchase of property and equipment	(496)	(28,961)
Purchase of investments	(51,585)	(14,921)
Proceeds from maturities of investments	28,951	104,531
Net cash provided by (used in) investing activities	(23,130)	60,649
Cash Flows from Financing Activities
Proceeds from the issuance of common stock under the Employee Stock Purchase Plan	177	484
Proceeds from exercise of stock options	76	272
Proceeds from issuance of common shares in "at-the-market" equity offering, net of issuance costs	3,509
Principal payments on capital lease obligations	(4)	(24)
Net cash provided by financing activities	3,758	732
Net change in cash, cash equivalents and restricted cash	(68,300)	32,620
Cash, cash equivalents and restricted cash, beginning of period	96,204	62,441
Cash, cash equivalents and restricted cash, end of period	27,904	95,061
Supplemental Disclosure of Cash Flow Information
Cash paid for interest		1
Cash paid for income taxes		1
Supplemental Schedule of Non-Cash Investing and Financing Activities
Purchases of property and equipment included in accounts payable and accrued liabilities	$ 42	$ 5,394