Condensed Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
OPERATING ACTIVITIES
Net loss	$ (35,811)	$ (12,747)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	3,904	31
Amortization of operating lease right-of-use assets	1,301	470
Depreciation	553	213
Acquired in-process research and development	150	465
Net accretion on investments in marketable securities	(2,329)
Change in fair value of derivative liabilities		(6,453)
Loss on extinguishment of convertible notes		2,316
Noncash interest expense		1,604
Net change in fair value of redeemable convertible preferred stock tranche obligations		58
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(391)	969
Other non-current assets	10	(150)
Accounts payable	2,674	(2,700)
Accrued clinical and research and development expenses	3,275	2,970
Accrued expenses and other current liabilities	(3,146)	(758)
Operating lease liabilities	(336)	(351)
Net cash used in operating activities	(30,146)	(14,063)
INVESTING ACTIVITIES
Purchases of marketable securities	(292,337)
Purchase of property and equipment	(1,289)	(561)
Purchase of in-process research and development	(330)	(58)
Net cash used in investing activities	(293,956)	(619)
FINANCING ACTIVITIES
Proceeds from issuance of convertible notes, net of issuance costs - related party		2,212
Proceeds from issuance of convertible notes, net of issuance costs		1,286
Proceeds from issuance of redeemable convertible preferred stock and tranche obligations, net of issuance costs		68,077
Proceeds from exercise of stock options	26
Payment of deferred initial public offering costs	(105)
Payment of transaction costs for exchange of common stock for warrants	(25)
Net cash (used in) provided by financing activities	(104)	71,575
Net (decrease) increase in cash, cash equivalents and restricted cash	(324,206)	56,893
Cash, cash equivalents, and restricted cash at beginning of period	406,299	1,872
Cash, cash equivalents, and restricted cash at end of period	82,093	58,765
COMPONENTS OF CASH, CASH EQUIVALENTS, AND RESTRICTED CASH
Cash and cash equivalents	81,526	58,765
Restricted cash	567
Total cash, cash equivalents, and restricted cash	82,093	58,765
SUPPLEMENTAL NON-CASH INVESTING AND FINANCING ACTIVITIES
Exchange of common stock for pre-funded warrants	37,600
Conversion of convertible notes to shares of Series A-2 redeemable convertible preferred stock		35,576
Reclassification of shares of Series Seed redeemable convertible preferred stock to mezzanine equity		9,830
Purchase of property and equipment in accounts payable and accrued expenses and other current liabilities	379	1,048
In-process research and development costs in accounts payable, accrued expenses and other current liabilities, and other non-current liabilities	$ 993	$ 790