CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Cash flows from operating activities:
Net loss	$ (85,549)	$ (151,656)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	10,077	8,344
Net amortization of premiums and accretion of discounts on marketable securities	(4,564)	194
Amortization of operating lease right-of-use assets	763	211
Depreciation expense	241	9
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(6,630)	18,825
Other non-current assets	(100)	2,998
Accounts payable	2,629	8,449
Accrued expenses	5,334	(3,653)
Operating lease liabilities	(767)	(214)
Other current liabilities	(6)	58
Other non-current liabilities	0	(6)
Net cash used in operating activities	(78,572)	(116,441)
Cash flows from investing activities:
Purchase of marketable securities	(91,202)	0
Maturities of marketable securities	199,448	49,000
Purchases of property and equipment	(615)	(17)
Net cash provided by investing activities	107,631	48,983
Cash flows from financing activities:
Proceeds from exercises of stock options	674	123
Proceeds from issuance of common stock under the employee stock purchase plan	139	0
Payments for repurchases of unvested restricted common stock	(1)	(4)
Net cash provided by financing activities	812	119
Net increase (decrease) in cash and cash equivalents	29,871	(67,339)
Cash and cash equivalents at beginning of period	92,076	542,224
Cash and cash equivalents at end of period	121,947	474,885
Supplemental disclosure of cash flow information
Operating lease right-of-use asset recognized upon adoption of ASC 842	0	1,728
Operating lease right-of-use asset recognized	$ 0	$ 1,344