Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net loss	$ (402,266)	$ (223,485)	$ (100,077)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,156	2,577	1,800
Stock-based compensation expense	48,760	23,650	10,729
Non-cash payments for acquired manufacturing rights	0	7,995	0
Loss on disposal of assets	0	44	97
Asset impairment charges	0	213	0
Amortization of operating right-of-use assets	7,015	6,619	1,657
Net amortization (accretion) of premium (discounts) on investments	(34,775)	(947)	1,406
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	17,870	433	(7,369)
Operating lease right-of-use assets	(16,724)	0	0
Other assets	(33,007)	(465)	(3,539)
Operating lease liabilities	11,284	1,151	(12,856)
Accounts payable	11,225	2,896	(12,470)
Accrued compensation	9,876	(2,275)	3,170
Accrued manufacturing expenses	44,501	3,826	(8,572)
Accrued expenses	36,295	7,171	4,631
Net cash used in operating activities	(296,790)	(170,597)	(121,393)
Cash flows from investing activities:
Purchases of property and equipment	(16,062)	(5,848)	(6,555)
Purchases of investments	(1,329,896)	(102,745)	(336,341)
Manufacturing facility and equipment construction-in-progress	(51,815)	0	0
Maturities of investments	611,876	168,691	100,500
Sales of investments	12,586	14,480	30,062
Proceeds from sales of property and equipment	0	7	26
Net cash (used in) provided by investing activities	(773,311)	74,585	(212,308)
Cash flows from financing activities:
Proceeds from issuance of common stock and pre-funded warrants from follow-on offerings, net of issuance costs	545,302	759,181	0
Proceeds from issuance of common stock under ATM Sales Program, net of issuance costs	90,741	97,299	13,896
Proceeds from exercise of common stock options	5,608	4,895	3,012
Proceeds from issuance of common stock under Employee Stock Purchase Plan	2,038	1,033	888
Release of restricted stock units	(3,876)	(861)	0
Net cash provided by financing activities	639,813	861,547	17,796
Effect of exchange rate changes on cash and cash equivalents	(6,686)	137	(439)
Net (decrease) increase in cash, cash equivalents and restricted cash	(436,974)	765,672	(316,344)
Cash, cash equivalents and restricted cash, beginning of period	835,528	69,856	386,200
Cash, cash equivalents and restricted cash, end of period	398,554	835,528	69,856
Supplemental disclosure of cash flow information:
Cash paid for interest	0	2	7
Supplemental disclosures of non-cash investing and financing activities:
Purchases of property and equipment recorded in accounts payable and accrued expenses	8,510	110	766
Issuance of common stock for acquired manufacturing rights	0	7,995	0
Stock issued for payment of accounts payable	$ 0	$ 0	$ 10,000