Lexeo Therapeutics, Inc. Common Stock (LXEO) 10-Q 9 May 24 2024 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2024	May 07, 2024
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Entity Registrant Name	Lexeo Therapeutics, Inc.
Entity Central Index Key	0001907108
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity File Number	001-41855
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	85-4012572
Entity Address, Address Line One	345 Park Avenue South
Entity Address, Address Line Two	Floor 6
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10010
City Area Code	212
Local Phone Number	547-9879
Entity Small Business	true
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Title of 12(b) Security	Common Stock ($0.0001 par value)
Trading Symbol	LXEO
Security Exchange Name	NASDAQ
Document Quarterly Report	true
Document Transition Report	false
Entity Shell Company	false
Entity Interactive Data Current	Yes
Entity Common Stock, Shares Outstanding		32,945,341

Condensed Balance Sheets

Condensed Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 195,060	$ 121,466
Prepaid expenses and other current assets	3,029	2,828
Total current assets	198,089	124,294
Restricted cash	3,252	3,252
Property and equipment, net	1,044	1,056
Lease right-of-use assets - finance, net	1,700	1,763
Lease right-of-use assets - operating	9,120	9,442
Total assets	213,205	139,807
Current liabilities:
Accounts payable	4,297	3,794
Accrued expenses and other current liabilities	13,772	8,030
Accrued bonuses	950	2,810
Current portion of lease liabilities - finance	524	518
Current portion of lease liabilities - operating	2,087	2,087
Total current liabilities	21,630	17,239
Non-current liabilities
Non-current portion of lease liabilities - finance	1,154	1,247
Non-current portion of lease liabilities - operating	7,471	7,786
Total liabilities	30,255	26,272
Commitments and contingencies (Note 10)
Stockholders' and members' deficit:
Common stock, $0.0001 par value, 500,000,000 shares authorized as of March 31, 2024; 32,948,332 shares issued and 32,928,141 shares outstanding as of March 31, 2024; 500,000,000 shares authorized as of December 31, 2023; 26,668,485 shares issued and 26,646,378 shares outstanding as of December 31, 2023	3	3
Additional paid-in capital	386,469	295,372
Accumulated deficit	(203,522)	(181,840)
Total stockholders' equity	182,950	113,535
Total liabilities and stockholders' equity	$ 213,205	$ 139,807

Condensed Balance Sheets (Paren

Condensed Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2024	Dec. 31, 2023
Common stock, par value per share	$ 0.0001	$ 0.0001
Common stock, Authorized	500,000,000	500,000,000
Common Stock, Shares issued	32,948,332	26,668,485
Common stock, Outstanding	32,928,141	26,646,378

Condensed Statements of Operati

Condensed Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Operating expenses
Research and development expenses	$ 15,742	$ 16,438
General and administrative	7,549	2,852
Total operating expenses	23,291	19,290
Operating loss	(23,291)	(19,290)
Other income and expense
Other income (expense), net	(5)	(4)
Interest expense	(37)	(50)
Interest income	1,651	687
Total other income and expense	1,609	633
Loss from operations before income taxes	(21,682)	(18,657)
Net loss and comprehensive loss	$ (21,682)	$ (18,657)
Net loss per common share, basic	$ (0.77)	$ (11.58)
Net loss per common share, diluted	$ (0.77)	$ (11.58)
Weighted average number of shares outstanding used in computation of net loss per common share, basic	27,979,838	1,610,793
Weighted average number of shares outstanding used in computation of net loss per common share, diluted	27,979,838	1,610,793

Condensed Consolidated Statemen

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Deficit - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Temporary equity, balance, shares at Dec. 31, 2022		143,653,545
Temporary equity, balance, value at Dec. 31, 2022		$ 185,033
Balance, shares at Dec. 31, 2022			1,607,185
Balance, value at Dec. 31, 2022	$ (112,954)			$ 2,492	$ (115,446)
Exercise of stock options, shares			1,494
Exercise of stock options, value	12			12
Amounts reclassified from deposit liabilities upon the vesting of early-exercised stock options previously subject to repurchase, net of proceeds received from early exercise of unvested stock options subject to repurchase and recorded as deposit liabilities, share			5,325
Amounts reclassified from deposit liabilities upon the vesting of early-exercised stock options previously subject to repurchase, net of proceeds received from early exercise of unvested stock options subject to repurchase and recorded as deposit liabilities, value	21			21
Stock-based compensation expense	397			397
Net loss	(18,657)				(18,657)
Temporary equity, balance, shares at Mar. 31, 2023		143,653,545
Temporary equity, balance, value at Mar. 31, 2023		$ 185,033
Balance, shares at Mar. 31, 2023			1,614,004
Balance, value at Mar. 31, 2023	(131,181)			2,922	(134,103)
Temporary equity, balance, shares at Dec. 31, 2022		143,653,545
Temporary equity, balance, value at Dec. 31, 2022		$ 185,033
Balance, shares at Dec. 31, 2022			1,607,185
Balance, value at Dec. 31, 2022	(112,954)			2,492	(115,446)
Net loss	(66,400)
Balance, shares at Dec. 31, 2023			26,646,378
Balance, value at Dec. 31, 2023	113,535		$ 3	295,372	(181,840)
Exercise of stock options, shares			942
Exercise of stock options, value	10			10
Amounts reclassified from deposit liabilities upon the vesting of early-exercised stock options previously subject to repurchase, net of proceeds received from early exercise of unvested stock options subject to repurchase and recorded as deposit liabilities, share			1,916
Amounts reclassified from deposit liabilities upon the vesting of early-exercised stock options previously subject to repurchase, net of proceeds received from early exercise of unvested stock options subject to repurchase and recorded as deposit liabilities, value	3			3
Issuance of common stock upon private placement offering, Shares			6,278,905
Issuance of common stock upon private placement offering, Value	88,753			88,753
Stock-based compensation expense	2,331			2,331
Net loss	(21,682)				(21,682)
Balance, shares at Mar. 31, 2024			32,928,141
Balance, value at Mar. 31, 2024	$ 182,950		$ 3	$ 386,469	$ (203,522)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Deficit (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)
Commissions and Offering Costs
Net of issuance costs	$ 6,246

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Cash flows from operating activities:
Net loss	$ (21,682)	$ (18,657)
Adjustments to reconcile net loss to net cash used in operating activities:
Reduction in the carrying amount of ROU assets, operating	322	321
Reduction in the carrying amount of ROU assets, finance	85	69
Stock based compensation expense	2,331	397
Depreciation and amortization expense	69	57
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(201)	524
Accounts payable	639	1,044
Accrued expenses and other current liabilities	3,885	(1,789)
Lease liabilities, operating	(315)	(332)
Lease liabilities, finance		(8)
Net cash used in operating activities	(14,867)	(18,374)
Cash flows from investing activities:
Purchase of internal use software	(8)
Purchase of property and equipment	(185)
Net cash used in investing activities	(193)
Cash flows from financing activities:
Proceeds from exercise of stock options	10	12
Payments on finance leases	(109)	(110)
Proceeds from issuance of common stock upon private placement offering, net of commissions and offering costs	88,753
Net cash provided by (used in) financing activities	88,654	(98)
Net change in cash, cash equivalents and restricted cash	73,594	(18,472)
Cash, cash equivalents and restricted cash at beginning of period	124,718	80,588
Cash, cash equivalents and restricted cash at end of period	198,312	62,116
Supplemental disclosure of non-cash activities
Offering costs included in accounts payable and accrued expenses	4,542	180
Issuance costs related to convertible debt included in accounts payable and accrued expenses	51
(Property and equipment purchased in the prior period and paid in the current period), net of property and equipment purchased in the current period included in accounts payable and accrued expenses	(136)	12
Finance lease right-of use assets and finance lease liabilities recognized	22
Amounts reclassified from deposit liabilities upon the vesting of early-exercised stock options previously subject to repurchase, (net of proceeds received from early exercise of unvested stock options subject to repurchase and recorded as deposit liabilities)	$ 3	$ 21

Description of Business and Bas

Description of Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Basis of Presentation	1. Description of Business and Basis of Presentation Description of Business —Lexeo Therapeutics, Inc. (the “Company”) is a clinical stage genetic medicine company with a focus on hereditary and acquired diseases of high unmet need. The Company’s investigational therapies have the potential to offer gene therapy-based treatments to address many diseases that have eluded today’s existing drug delivery platforms. The Company utilizes adeno-associated viruses (“AAV”) that have been engineered to transfer genes to patients. The Company’s therapeutic investigational treatments include gene therapies primarily in the early clinical and late pre-clinical stages of research and development. The Company is located in New York, NY and was first formed on February 17, 2017, as an LLC under the laws of the State of Delaware under the legal name Lexeo Therapeutics, LLC. The Company filed and executed a certificate of conversion to corporation on November 20, 2020, to convert the LLC to Lexeo Therapeutics, Inc, a Delaware corporation. All of the Company’s tangible assets are held in the United States (“U.S.”). Basis of Presentation and Principles of Consolidation —The Company’s fiscal year ends on December 31, and its fiscal quarters end on March 31, June 30, and September 30. These unaudited condensed financial statements and accompanying notes reflect the operations of the Company that have been prepared in conformity with generally accepted accounting principles in the United States of America (“GAAP”) for interim financial information. Accordingly, they do not include all of the information and disclosures required by GAAP for complete financial statements. These unaudited condensed financial statements and accompanying notes should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto for the year ended December 31, 2023 (the “Annual Financial Statements”). The unaudited condensed consolidated balance sheet at December 31, 2023 has been derived from the audited consolidated financial statements at that date. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary to present fairly the financial position of the Company and its results of operations and cash flows for the periods presented have been included. Operating results for the three months ended March 31, 2024 are not necessarily indicative of the results that may be expected for the year ending December 31, 2024, for any other interim period, or for any other future year. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”). The Company has no unconsolidated subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Certain prior period balances have been reclassified to conform to the current period presentation. A 10.594230-for-1 reverse share split of the Company’s series A convertible preferred stock, series B convertible preferred stock, common stock, and options to purchase common stock under the Company’s 2021 Equity Incentive Plan (as defined in Note 8), as well as corresponding adjustments in the respective conversion prices of the series A convertible preferred stock and series B convertible preferred stock, was effected on October 13, 2023 as approved by the Company’s board of directors (the "Board of Directors") and its shareholders (the “Stock Split”). The Stock Split reduced the number of shares of the Company’s authorized, issued and outstanding common stock, as well as the numbers of shares reserved and available for future issuance and underlying outstanding options to purchase common stock under its 2021 Equity Incentive Plan, on a 10.594230-for-1 basis. As such, all references to series A convertible preferred stock and series B convertible preferred stock conversion ratios, conversion share and per share amounts, and post- conversion share and per share amounts, as well as common stock option, option per common share, common share and common per share amounts, in these unaudited condensed financial statements and accompanying notes have been retroactively restated to reflect the Stock Split and the Stock Split’s effect on the respective series A convertible preferred stock and series B convertible preferred stock conversion ratios for each series of convertible preferred stock. The Stock Split did not affect the par values per share. Need for Additional Capital —Since inception, the Company has incurred net losses and negative cash flows from operations, including net losses of $ 21.7 million and $ 66.4 million during the three months ended March 31, 2024 and the year ended December 31, 2023, respectively. As of March 31, 2024, the Company had cash and cash equivalents of $ 195.1 million and an accumulated deficit of $ 203.5 million and expects to incur substantial operating losses and negative cash flows from operations for the foreseeable future. During the years ended December 31, 2021 and December 31, 2020, the Company raised aggregate total net proceeds of $ 185.0 million in connection with the issuance of series A and series B convertible preferred stock. During the year ended December 31, 2023 the Company raised $ 100.3 million of total net proceeds in connection with the closing of its initial public offering ("IPO") on November 7, 2023 and subsequent partial exercise of the underwriters' option to purchase additional shares, as well $ 3.9 million of net proceeds from the issuance of a convertible Simple Agreement for Future Equity (“SAFE”) note (the "SAFE Note") in August 2023. During the three months ended March 31, 2024, the Company received total net proceeds of approximately $ 88.8 million after deducting underwriting commissions and offering expenses in a private placement offering of its common stock (see Note 7). Management estimates that the Company's current cash and cash equivalents balance is sufficient to fund its operations for at least 12 months from the issuance date of these unaudited condensed financial statements. If the Company is unable to obtain additional funding before achieving sufficient profitability and positive cash flows from operations, if ever, the Company will be forced to delay, reduce or eliminate some or all of its research and development programs, which could adversely affect its business prospects, or the Company may be unable to continue operations. Although management continues to pursue plans to obtain additional funding before achieving sufficient profitability and positive cash flows from operations, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations, if at all. Risks and Uncertainties —The Company is subject to risks and uncertainties common to early-stage companies in the biopharmaceutical industry, including, but not limited to, successful discovery and development of its product candidates, development by competitors of new technological innovations, dependence on key personnel, the ability to attract and retain qualified employees, protection of proprietary technology, compliance with governmental regulations, the ability to secure additional capital to fund operations, and commercial success of its product candidates. Any of the Company’s current product candidates and future product candidates that it may develop will require extensive nonclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel, infrastructure, and extensive compliance- reporting capabilities. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies There have been no significant changes in the Company’s accounting policies from those disclosed in its Annual Financial Statements. Use of Estimates —The preparation of the financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of income and expense during the reporting period. The most significant estimates relate to the accruals of research and development costs, including accruals of research contract costs, and assumptions used to estimate the fair value of the Company’s stock option awards and, prior to its IPO, to determine the fair value of its common stock. Management evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors, including the current economic environment, and makes adjustments when facts and circumstances dictate. These estimates are based on information available as of the date of the financial statements; therefore, actual results could differ from those estimates. Net Loss per Share— The Company follows the two-class method when computing net income (loss) per common share as the Company has issued shares that meet the definition of participating securities. The two-class method determines net income (loss) per common share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income (loss) available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed. The Company considers its convertible preferred stock to be participating securities as, in the event a dividend is paid on common stock, the holders of these securities would be entitled to receive dividends on a basis consistent with the common stockholders. The Company also considers the shares issued upon the early exercise of stock options that are subject to repurchase to be participating securities because holders of such shares have non-forfeitable dividend rights in the event a dividend is paid on common stock. There is no allocation required under the two-class method during periods of loss since the participating securities do not have a contractual obligation to share in the losses of the Company. Basic net income (loss) per common share is computed by dividing the net income (loss) per common share by the weighted-average number of common shares outstanding for the period. Diluted net income (loss) per common share is computed by adjusting net income (loss) to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net loss per common share is computed by dividing the diluted net loss by the weighted-average number of common shares outstanding for the period, including potential dilutive common shares. For the purposes of this calculation, shares of convertible preferred stock are considered potential dilutive common shares. In periods in which the Company reported a net loss, diluted net loss per common share was the same as basic net loss per common share since dilutive common shares were not assumed to have been issued if their effect was anti-dilutive. During (i) the three months ended March 31, 2023, 8,070,027 potential common shares related to the conversion of series A convertible preferred stock and 5,489,573 potential common shares related to the conversion of series B convertible preferred stock, which converted into 8,070,027 common shares and 6,386,337 common shares, respectively, in connection with the Company’s IPO on November 7, 2023, and 2,105,970 potential common shares related to the exercise of outstanding stock options (see Note 8), and (ii) the three months ended March 31, 2024, 3,538,294 total potential common shares related to the exercise of outstanding stock options and settlement of outstanding restricted stock units ("RSUs") (see Note 8), were excluded from the computation of diluted net loss per common share because including them would have had an anti-dilutive effect as the Company reported net losses for those periods. Concentrations of Credit Risk —Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents and restricted cash. The Company’s cash and restricted cash balances exceed Federal Deposit Insurance Corporation insurance limits, and the Company’s cash equivalents consist of investments in a U.S. government money market fund. The Company’s cash and cash equivalents and restricted cash is held with large financial institutions that management believes to be of high credit quality. To date, the Company has no t recognized any losses caused by uninsured balances.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The three levels of inputs that may be used to measure fair value are as follows: Level 1 —Inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2 —Inputs are observable, unadjusted quoted prices in active markets for similar assets or liabilities, unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities. Level 3 —Inputs are unobservable inputs for the asset or liability. The Company’s cash equivalents consist of investments in a U.S. government money market fund stated at carrying value, which approximates fair value and is based on quoted prices in active markets for identical securities. Cash is stated at carrying value, which approximates fair value due to its short-term nature. The carrying values of the Company’s prepaid expenses, other current assets, accounts payable and accrued expenses approximate their fair values due to their short-term nature. The following table presents information about the Company’s financial assets measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values: As of March 31, 2024: Level 1 Level 2 Level 3 Total Assets: Cash equivalents (money market) $ 175,033 $ - $ - $ 175,033 $ 175,033 $ - $ - $ 175,033 As of December 31, 2023: Level 1 Level 2 Level 3 Total Assets: Cash equivalents (money market) $ 102,484 $ - $ - $ 102,484 $ 102,484 $ - $ - $ 102,484

Property and Equipment

Property and Equipment	3 Months Ended
	Mar. 31, 2024
Property, Plant and Equipment [Abstract]
Property and Equipment	4. Property and Equipment The following is the summary of the Company’s property and equipment and related accumulated depreciation and amortization as of March 31, 2024 and December 31, 2023: Useful Life March 31, December 31, 2023 Internal use software 3 years $ 309 $ 296 Furniture and fixtures 5 years 380 380 Lab equipment 7 years 558 514 Leasehold improvements 7 years 247 247 Total property and equipment 1,494 1,437 Less: accumulated depreciation and amortization ( 450 ) ( 381 ) Total property and equipment, net $ 1,044 $ 1,056

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	3 Months Ended
	Mar. 31, 2024
Accrued Liabilities and Other Liabilities [Abstract]
Accrued Expenses and Other Current Liabilities	5. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following: March 31, December 31, 2023 Accrued research and development expenses $ 8,071 $ 6,384 Accrued general and administrative expenses and other professional fees 5,129 1,092 Accrued payroll expenses 246 242 Taxes payable 150 157 Other current liabilities 176 155 Total accrued expenses and other current liabilities $ 13,772 $ 8,030

Leases

Leases	3 Months Ended
	Mar. 31, 2024
Leases [Abstract]
Leases	6. Leases Operating Lease Right-of-Use Asset In January 2022 , the Company entered into a lease agreement for an office facility and laboratory space in New York, New York that commenced in April 2022 and ends in July 2029 with an additional five-year option to extend the lease beyond July 2029 at the then-prevailing effective market rental rate . Upon commencement of this lease, the Company recorded operating lease right-of-use assets and operating lease liabilities of $ 11.6 million based on the present value of payments over the lease term using an estimated incremental borrowing rate of 8.53 % in accordance with the provisions of ASC Topic 842, Leases (“ASC 842”). In connection with the Company’s lease of office space and laboratory space, the Company provided a security deposit to the landlord in the form of a letter of credit totaling $ 1.2 million. The cash collateralizing the letter of credit was included in long-term restricted cash in the Company’s condensed balance sheets as of March 31, 2024 and December 31, 2023. This lease was classified as an operating lease in accordance with the provisions of ASC 842. The Company did no t recognize any right-of-use assets and lease liabilities associated with the potential option to renew or extend. The Company’s operating lease agreement does not contain any significant residual value guarantees or restrictive covenants. The remaining lease terms and payment terms as of March 31, 2024 and December 31, 2023 were 5.3 years and 5.6 years, respectively. The components of this operating lease were as follows: Three Months Ended March 31, 2024 2023 Operating lease expense $ 537 $ 537 Variable lease expense 113 69 Total operating lease expense $ 650 $ 606 Cash paid for amounts included in the measurement of lease liabilities, included in operating cash flows $ 530 $ 548 The following table provides a reconciliation of the Company’s remaining undiscounted contractual rent obligations due within each year ended December 31 to the operating lease liabilities recognized as of March 31, 2024: Years ended December 31 Operating 2024 $ 1,592 2025 2,152 2026 2,206 2027 2,261 2028 2,318 Thereafter 1,372 Total lease payments 11,901 Less: present value adjustment ( 2,343 ) Total operating lease liabilities $ 9,558 Included in the balance sheet: Current portion of lease liabilities - operating 2,087 Non-current portion of lease liabilities - operating 7,471 Total operating lease liabilities $ 9,558 Equipment Finance Leases Commencing in April 2022, the Company leases certain laboratory equipment under financing arrangements accounted for as finance leases in accordance with the provision of ASC 842 that are classified in the Company’s condensed balance sheet as finance lease liabilities with related right-of-use assets recorded and depreciated on a straight-line basis over the estimated useful life of 7 years. The total gross, accumulated amortization, and net book values of equipment finance lease right-of-use assets capitalized under such finance lease arrangements at March 31, 2024 were $ 2.2 million, $ 0.5 million and $ 1.7 million, respectively. Under the terms of the equipment finance lease agreements executed through the issuance of these unaudited condensed financial statements, the principal balances plus interest for the equipment are to be repaid in full after 60 monthly installments following lease commencement, with lease commencement dates ranging from April 1, 2022 to April 1, 2023 , annual imputed interest rates ranging from 7.90 % to 9.30 %, and monthly installment payment amounts ranging from approximately $ 4,000 to $ 18,000 . As of March 31, 2024, the total aggregate monthly installment payment amount was approximately $ 49,000 for equipment finance lease agreements executed through the issuance date of these unaudited condensed financial statements. The weighted-average remaining lease payment term, weighted-average remaining amortization term, and weighted-average effective interest rate for the Company's equipment finance lease agreements as of March 31, 2024 were 3.4 years, 5.6 years, and 8.58 %, respectively. The weighted-average remaining lease payment term, weighted-average remaining amortization term, and weighted-average effective interest rate for the Company's equipment finance lease agreements as of December 31, 2023 were 3.7 years, 5.7 years, and 8.59 %, respectively. The components of the equipment finance leases were as follows: Three Months Ended March 31, 2024 2023 Reduction in the carrying amount of ROU assets, finance $ 85 $ 69 Interest on finance lease liabilities 37 50 Total finance lease expense $ 122 $ 119 Cash paid for amounts included in the measurement of lease liabilities, included in financing cash flows $ 109 $ 110 The following table provides a reconciliation of the Company’s remaining equipment finance lease obligations due within each year ending December 31 to the equipment finance lease liabilities recognized at March 31, 2024: Years ended December 31 Equipment Finance Leases 2024 $ 391 2025 587 2026 587 2027 359 2028 11 Total lease payments 1,935 Less: imputed interest ( 257 ) Total finance lease liabilities $ 1,678 Included in the balance sheet: Current portion of lease liabilities - finance 524 Non-current portion of lease liabilities - finance 1,154 Total finance lease liabilities $ 1,678

Capital Stock

Capital Stock	3 Months Ended
	Mar. 31, 2024
Equity [Abstract]
Capital Stock	7. Capital Stock As of March 31, 2024 and December 31, 2023, the Company’s amended and restated certificate of incorporation provided that the authorized capital stock of the Company was 510,000,000 shares consisting of 500,000,000 shares of common stock and 10,000,000 shares of undesignated preferred stock, both with a par value of $ 0.0001 per share. As of March 31, 2024 and December 31, 2023, 32,948,332 shares and 26,668,485 shares, respectively, of the Company's common stock authorized were issued, including 20,191 shares and 22,107 shares, respectively, that were legally issued upon the early exercise of unvested stock options and that are excluded from the number of shares outstanding until the right to repurchase subsequently lapses upon vesting. Each common share entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are entitled to receive dividends, if any, as may be declared by the Company’s Board of Directors. No cash dividends have been declared or paid by the Company. Upon the declaration of effectiveness of the Company’s IPO registration statement on November 2, 2023, the Company's outstanding convertible SAFE Note automatically converted into 411,815 shares of common stock. Upon the closing of the Company's IPO on November 7, 2023, the Company issued and sold 9,090,910 shares of its common stock, and subsequently, the underwriters partially exercised their associated 30-day option to purchase additional shares of common stock with 1,048,746 additional shares issued. The net proceeds to the Company from the IPO and subsequent partial exercise of the underwriters’ 30-day option to purchase additional shares were approximately $ 100.3 million based on the initial offering price of $ 11.00 per share, after deducting underwriting discounts, commissions and offering expenses totaling $ 11.3 million. Also upon the closing of the Company's IPO on November 7, 2023, all 85,495,722 then outstanding shares of the Company’s series A convertible preferred stock and all 58,157,823 then outstanding shares of the Company’s series B convertible preferred stock converted into 8,070,027 shares and 6,386,337 shares of common stock, respectively, including 896,764 shares of common stock issued as a result of series B convertible preferred stock antidilution provisions. On March 11, 2024, the Company entered into a common stock purchase agreement to issue and sell an aggregate of 6,278,905 shares of its common stock at a price of $ 15.13 per share, in a private placement that closed on March 13, 2024 (the "Private Placement"). The gross and net proceeds received from the Private Placement were approximately $ 95.0 million and $ 88.8 million, respectively, after deducting approximately $ 6.2 million of commissions and other offering costs. The Company had reserved the following number of shares of common stock for the exercise of outstanding stock options, settlement of outstanding RSUs, and future issuance of stock-based awards: March 31, December 31, 2023 Options to purchase shares of common stock under the 2021 Plan and 2023 Plan 3,313,349 2,415,740 RSUs subject to settlement in shares of common stock 224,945 - Shares available for issuance under the 2021 Plan and 2023 Plan 2,503,744 2,293,816 Shares available for issuance under the 2023 ESPP 505,284 238,600 Total shares of common stock reserved for future issuance 6,547,322 4,948,156

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2024
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	8. Stock-based Compensation In February 2021, the Company adopted the 2021 Equity Incentive Plan (the “2021 Plan”) for the issuance of stock options to the Company’s key directors, officers, employees and consultants, as a means to secure the benefits arising from capital stock ownership. In connection with the Company’s IPO in November 2023, the Company adopted the 2023 Equity Incentive Plan (the “2023 Plan”) and the 2023 Employee Stock Purchase Plan (the "2023 ESPP" and collectively with the 2021 Plan and 2023 Plan, the “Plans”). The purposes of the Plans are to promote the alignment of the interests of key directors, officers, employees, and consultants with the success of the Company and to provide compensation opportunities to attract, retain and motivate directors, officers, employees, and consultants of the Company. The maximum number of shares of common stock that may be issued under the 2023 Plan is 4,737,000 shares, which is approximately the sum of (i) 1,803,980 new shares, plus (ii) the 2021 Plan’s available reserve, plus (iii) the number of returning shares, if any, upon the cancellation or forfeiture of equity awards that are outstanding under the 2021 Plan. In addition, the number of shares of common stock reserved for issuance under the 2023 Plan will automatically increase on January 1 of each year, beginning on January 1, 2024, and continuing through and including January 1, 2033, by 5 % of the total number of shares of common stock outstanding on December 31 of the immediately preceding calendar year, or a lesser number of shares determined by the Company’s Board of Directors prior to the applicable January 1. The number of shares of common stock reserved for issuance under the 2023 ESPP will automatically increase on January 1 of each calendar year, beginning on January 1, 2024 and continuing through and including January 1, 2033, by the lesser of (i) 1 % of the total number of shares of capital stock outstanding on December 31 of the preceding calendar year, (ii) 477,200 shares and (iii) a number of shares determined by the Company’s Board of Directors. Shares subject to purchase rights granted under the 2023 ESPP that terminate without having been exercised in full will not reduce the number of shares available for issuance under the 2023 ESPP. On January 1, 2024, the number of shares of common stock reserved for issuance under the 2023 Plan and the 2023 ESPP automatically increased by 1,333,424 shares and 266,684 shares, respectively, to totals of 3,720,103 shares and 505,284 shares, respectively. As of March 31, 2024, 2,503,744 shares and 505,284 shares were available for future issuance under the 2023 Plan and 2023 ESPP, respectively. No shares have been issued under the 2023 ESPP through March 31, 2024. Stock option activity Stock options granted under the 2021 Plan generally (i) are subject to requisite service requirements, (ii) vest over a four-year period with 25 % of the options granted vesting after one year and the remainder vesting in equal monthly installments over the following 36 months , and (iii) allow for early exercise subject to repurchase. Stock options granted under the 2021 Plan to certain of the Company’s non-employees vest in equal monthly installments over a four-year period or vested upon the achievement of a certain milestone event. The Company has no t repurchased any shares of common stock issued pursuant to the early exercise of stock options granted under the 2021 Plan through March 31, 2024. Stock options granted under the 2023 Plan generally (i) are subject to requisite service requirements, and (ii) vest over a four-year period with 25 % of the options granted vesting after one year and the remainder vesting in equal monthly installments over the following 36 months . The following table summarizes the stock option activity under the 2021 Plan and the 2023 Plan for the three months ended March 31, 2024 (weighted-average remaining contractual term (in years) is not stated in thousands): Number of Weighted- Weighted- Weighted- Aggregate Shares (per share) (per share) (in years) Value Outstanding as of December 31, 2023 2,415,740 $ 8.32 $ 5.80 7.83 $ 13,689 Granted 985,880 15.43 11.50 Exercised ( 942 ) 11.02 8.27 5 Forfeited ( 87,179 ) 6.21 4.31 Expired ( 150 ) 15.15 10.08 Outstanding as of March 31, 2024 3,313,349 $ 10.48 $ 7.52 8.38 $ 18,241 Vested options outstanding and exercisable as of March 31, 2024 1,071,426 $ 6.10 $ 3.89 6.66 $ 10,461 Unvested options outstanding and exercisable as of March 31, 2024 1,162,401 $ 10.13 $ 7.34 8.66 $ 6,833 Unvested options outstanding and unexercisable as of March 31, 2024 1,079,522 $ 15.20 $ 11.32 9.80 $ 947 The weighted-average grant date fair value of stock options granted during the three months ended March 31, 2023 was $ 13.01 per share. The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock. The total intrinsic value of stock options exercised during the three months ended March 31, 2023 was $ 12 . The total grant date fair values of stock options vested during the three months ended March 31, 2024 and March 31, 2023 were $ 0.9 million and $ 0.5 million, respectively. The Company estimated the fair value of options granted using a Black-Scholes option pricing model with the following assumptions presented on a weighted average basis during the three months ended March 31, 2024 (not stated in thousands): Three Months Ended March 31, 2024 Weighted average risk-free interest rate 4.07 % Expected term (in years) 6.07 Expected volatility 86.03 % Expected dividend yield 0.00 % The expected dividend yields are 0.00 % as the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future. RSU activity RSUs granted under the 2023 Plan generally (i) are subject to requisite service requirements, and (ii) vest over a four-year period with 25 % of the RSUs granted vesting after approximately one year and the remainder vesting in equal quarterly installments over the following nine quarters . No RSUs were granted prior to the quarter ended March 31, 2024. The following table summarizes the RSU activity under the 2023 Plan for the three months ended March 31, 2024: Number of Weighted- Shares (per share) Unvested as of December 31, 2023 - $ - Granted 224,945 15.31 Vested - - Forfeited - - Unvested as of March 31, 2024 224,945 $ 15.31 Stock-based compensation expense Stock-based compensation expense was classified as follows in the Company’s unaudited condensed statements of operations and comprehensive loss: Three Months Ended March 31, 2024 2023 Research and development expense $ 1,084 $ 158 General and administrative expense 1,247 239 Total stock-based compensation expense $ 2,331 $ 397 As of March 31, 2024, there was $ 21.8 million of unrecognized stock-based compensation expense related to unvested stock options and RSUs estimated to be recognized over a weighted-average period of 1.60 years.

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Net Loss Per Share	9. Net Loss per Share Basic and diluted net loss per common share attributable to common stockholders was calculated as follows: Three Months Ended March 31, 2024 2023 Numerator: Net loss attributable to common stockholders $ ( 21,682 ) $ ( 18,657 ) Denominator: Weighted-average common shares outstanding, basic and diluted 27,979,838 1,610,793 Net loss per share attributable to common stockholders, basic and diluted $ ( 0.77 ) $ ( 11.58 )

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	10. Commitments and Contingencies Leases —As of March 31, 2024, the Company had entered into commitments under lease agreements to rent office space and finance equipment (see Note 6). Commitments —As of March 31, 2024, the Company had entered into commitments under license, acquisition, research collaboration and sponsored research agreements with third parties (see Note 11). In addition, the Company has entered into services agreements with third parties for pharmaceutical manufacturing and research activities in the normal course of business, which can generally be terminated by the Company with 30 - to 60 -days’ written notice, unless otherwise indicated. Further, certain of the Company’s manufacturing agreements could require early termination and wind-down payments due from the Company upon either the termination of its clinical trials or if the Company terminates such agreements for convenience. Contingencies —From time to time, the Company may have certain contingent liabilities that arise in the ordinary course of business. The Company recognizes any associated legal fees as incurred and accrues a liability for such contingent liability matters when it is probable that future expenditures will be made, and such expenditures can be reasonably estimated. For all periods presented, the Company was not a party to any pending material litigation or other material legal proceedings, except that on October 12, 2023, Rocket Pharmaceuticals, Inc. (“Rocket”) filed a lawsuit in the U.S. District Court for the Southern District of New York against the Company and two individuals claiming, among other things, misappropriation of confidential information and trade secrets. The individual defendants are a current employee and a former employee of the Company’s analytical development team, both of whom were employed at Rocket before joining the Company in 2021. The complaint alleges the individual defendants downloaded confidential Rocket company documents and other proprietary materials prior to leaving Rocket in 2021 and that the Company used this information to advance its programs. The complaint seeks unspecified damages and asks the court to enjoin the Company from competing and working in the market for gene therapy treatments targeting cardiac diseases. The Company retained legal counsel to assist with its ongoing review of the allegations in Rocket’s complaint and is confident in its defenses to the allegations. On December 7, 2023, the Company filed a motion to dismiss the complaint, which is now fully briefed and pending before the court. While it is not possible to predict the outcome with certainty and an estimate of the possible loss cannot be made, the Company currently does not expect the final outcome will have a material adverse effect on its timelines for development of its product candidates. Indemnification Agreements —In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its Board of Directors and executive officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. For all periods presented, the Company has not incurred any material costs as a result of such indemnifications.

License, Acquisition, Research

License, Acquisition, Research and Collaboration and Sponsored Research Agreements	3 Months Ended
	Mar. 31, 2024
Business Combinations [Abstract]
License, Acquisition, Research and Collaboration and Sponsored Research Agreements	11. License, Acquisition, Research and Collaboration and Sponsored Research Agreements Adverum Biotechnologies —On January 25, 2021, the Company entered into an exclusive license agreement with Adverum Biotechnologies Inc. (“Adverum”) to in-license materials and technology related to the treatment of cardiomyopathy due to Friedreich’s ataxia ("FA") (the “Adverum Agreement”). In connection with the Adverum Agreement, the Company gained access to a portfolio of inventions, patent rights, technology, and licensed methods that the Company continues to develop, and the Company will assume all development and commercialization activities worldwide. Pursuant to the Adverum Agreement, the Company paid a one-time up-front non-refundable fee of $ 7.5 million , and is obligated to pay aggregate development and regulatory milestones of up to $ 17.5 million including a $ 3.5 million development milestone that was achieved and paid in the first quarter of 2023, and aggregate sales event and commercialization milestones of up to $ 49.0 million. The Company is obligated to pay Adverum tiered royalties ranging from high single-digits to sub teens based on annual aggregate worldwide net sales of Products (as defined in the Adverum Agreement). As of March 31, 2024, there were no research and development expenses recorded by the Company or payments made to Adverum under the terms of the Adverum Agreement other than the one-time up-front non-refundable fee of $ 7.5 million and the $ 3.5 million development milestone that was achieved and paid in the first quarter of 2023. The Adverum Agreement remains in effect until termination at the date of the last royalty term to expire. The Company can terminate the Adverum Agreement with 120 days’ written notice. The Adverum Agreement can also be terminated as a result of a patent challenge, material breach of contractual terms, or insolvency by either party. Cornell University —On May 27, 2020, the Company entered into two exclusive license agreements with Cornell University (“Cornell”) (the “First Cornell License Agreement” and the “Second Cornell License Agreement,” collectively “the Cornell License Agreements”). The First Cornell License Agreement is for the in-license of technology related to portfolios for APOE-associated Alzheimer’s disease and Anti-Tau, although the Company’s license is not restricted by such indications and it includes assignment to the Company of Cornell’s IND for the use of AAVrh10.hAPOE2 vector to treat APOE4 homozygous patients who are at risk for or have Alzheimer’s disease to support development of the Company’s LX1001 program. The Second Cornell License Agreement is for the in-license of technology related to a portfolio for FA although the Company’s license is not restricted by such indications, and it includes assignment to the Company of Cornell’s IND for the use of AAVrh.10cUhCLN2 to treat children with CLN2 Batten disease to support development of the Company’s LX1004 program. Through the Cornell License Agreements, the Company gains access to a portfolio of inventions, patent rights, technology, and licensed methods that the Company continues to develop. Under the terms of the Cornell License Agreements, the Company has assumed all development and commercialization activities worldwide with respect to the licensed technology. As initial consideration for the Cornell License Agreements, the Company paid Cornell an upfront payment in cash of $ 0.3 million and issued $ 1.3 million of notes (“Notes”). In November 2020, Notes with outstanding principal of $ 1.3 million were cancelled in exchange for 1,337,610 shares of series A convertible preferred stock. As additional consideration, the Company is required to pay Cornell up to $ 8.4 million upon the achievement of specific clinical and regulatory milestones under the First Cornell License Agreement and up to $ 4.3 million in two portfolios and up to $ 0.6 million for a third portfolio upon the achievement of specific clinical and regulatory milestones under the Second Cornell License Agreement. In the second quarter of 2022, a clinical and regulatory milestone of $ 0.1 million was recognized and paid to Cornell in connection with the Second Cornell License Agreement. The Company is also required to pay Cornell a flat royalty in the mid-single-digits based on net sales of the products covered by the licenses, subject to certain adjustments. Upon expiration of the royalty term of a given licensed product in a country, the respective license becomes non-exclusive and royalty-free. In addition, each of the Cornell License Agreements may be terminated by the Company for any reason upon ninety ( 90 ) days’ advance notice to Cornell and by Cornell upon the Company’s material uncured breach, and all licenses and rights granted by either party under such agreement will concurrently terminate. During the three months ended March 31, 2023, the Company did no t incur or pay any research and development expenses in connection with the Cornell License Agreements. During the three months ended March 31, 2024, the Company incurred and paid $ 30,000 of research and development expenses to Cornell in connection with the Cornell License Agreements. Stelios Therapeutics, Inc. —Stelios Therapeutics, Inc. (“Stelios”) was an early-stage company developing novel adeno-associated AAV-based gene therapies for rare cardiac conditions including arrhythmogenic cardiomyopathy and TNNI3-associated hypertrophic cardiomyopathy. On July 16, 2021 , the Company acquired 100 % of the outstanding stock of Stelios that was accounted for as an asset acquisition pursuant FASB ASC 805, Business Combinations . The Company is required to pay up to an aggregate of $ 20.5 million to the selling shareholders of Stelios upon the achievement of certain development milestones, including a $ 2.0 million development milestone that was achieved and paid in the third quarter of 2022. Regents of the University of California, San Diego —Stelios entered into exclusive worldwide license agreements on April 23, 2020, and August 6, 2020 (the “First UCSD Agreement” and the “Second UCSD Agreement”, respectively) with the Regents of UCSD to in-license materials and intellectual property related to gene therapies for arrhythmogenic right ventricular cardiomyopathy and hypertrophic cardiomyopathy, respectively. The First UCSD Agreement and the Second UCSD Agreement relate to the Company’s development efforts for its LX2021 and LX2022 programs, respectively. In connection with the First UCSD Agreement and the Second UCSD Agreement, the Company gained access to inventions, patent rights, technology, and licensed methods that it continues to develop, and it has assumed all worldwide development and commercialization activities with respect to the licensed technologies. The First UCSD Agreement and Second UCSD Agreement required Stelios to pay one-time up-front non-refundable cash fees of $ 20,000 for each agreement and requires the Company to pay aggregate development and commercialization milestones of up to $ 4.8 million and $ 2.4 million, respectively, and low- to mid-single digit royalties and low-single digit royalties, respectively, based on aggregate net sales. The only research and development expenses incurred by Stelios or the Company and payments made to the Regents of UCSD through March 31, 2024 under the terms of the First UCSD Agreement and the Second UCSD Agreement were the one-time up-front non-refundable cash fees of $ 20,000 for each agreement. The Company has the right to terminate the First UCSD Agreement and the Second UCSD Agreement at any time upon sixty ( 60 )-days’ written notice to the Regents of UCSD. On October 4, 2021, the Company entered into an exclusive worldwide license agreement (the “Third UCSD Agreement” and collectively with the First UCSD Agreement and the Second UCSD Agreement, the “UCSD Agreements”) with the Regents of UCSD to in-license materials and intellectual property related to LX2020, a gene therapy for arrhythmogenic right ventricular cardiomyopathy. The Third UCSD Agreement relates to the Company’s development efforts for its LX2020 program. In connection with the Third UCSD Agreement, the Company gained access to inventions, patent rights, technology, and licensed methods that it continues to develop, and it has assumed all worldwide development and commercialization activities with respect to the licensed technology. The Third UCSD Agreement required the Company to pay a one-time up-front non-refundable cash fee of $ 20,000 and requires the Company to pay aggregate development and commercialization milestones of up to $ 4.0 million, and low- to mid-single digit royalties based on aggregate net sales. The only research and development expenses incurred by the Company and payments made to the Regents of UCSD under the terms of the Third UCSD Agreement were the one-time up-front non-refundable cash fee of $ 20,000 . The Company has the right to terminate the Third UCSD Agreement at any time upon sixty ( 60 )-days’ written notice to the Regents of UCSD. On December 3, 2021, the Company entered into two sponsored research agreements with the Regents of UCSD (the "First UCSD SRA", the "Second UCSD SRA", and collectively, the “UCSD SRAs”) for the Company’s LX2020, LX2021 and LX2022 programs in connection with the UCSD Agreements. Under the terms of the UCSD SRAs, the Company has the first rights to obtain non-exclusive or exclusive, sublicensable, royalty-bearing, perpetual and transferable worldwide licenses in any resulting inventions owned by the Regents of UCSD or resulting inventions jointly owned between the Company and the Regents of UCSD, and the Company retains the rights to any resulting inventions owned by the Company. The UCSD SRAs each have a two-year term and may be terminated early by the Company at any time upon the giving of thirty ( 30 ) days’ written notice to the Regents of UCSD. The total costs to be invoiced to the Company over the terms of the UCSD SRAs are $ 5.6 million, of which the Company incurred and paid $ 0.2 million of research and development expenses during the three months ended March 31, 2023. The Company did not incur or pay any research and development expenses in connection with the UCSD SRAs during the three months ended March 31, 2024. The Company has paid a cumulative total of $ 3.2 million to the Regents of UCSD as of March 31, 2024, in connection with the UCSD SRAs. Weill Cornell Medical College —On February 2, 2021, the Company entered into a Research Collaboration Agreement with Weill Cornell Medical College (“WCM” and the “WCM Agreement”) in connection with the Cornell License Agreements entered on May 27, 2020. The Company committed to fund scientific research at WCM to investigate further and potentially enhance the technology licensed to the Company pursuant to the License Agreements. Under the terms of the WCM Agreement, each WCM invention, joint invention, and related joint results for which an Improvement, as defined in the WCM Agreement, applies and the Company has made an election to amend the Cornell License Agreements, the Company has the first option to negotiate in good faith with WCM for royalty- bearing, worldwide license, under Cornell patent rights, Cornell rights, and Cornell’s interest in joint patent rights, to develop, make, have made, use, offer for sale, sell, have sold, and import derived products in the field. During the three months ended March 31, 2023 the Company incurred $ 0.7 million of research and development costs and paid $ 1.6 million in connection with the WCM Agreement. During the three months ended March 31, 2024 the Company did not incur or pay any research and development expenses in connection with the WCM Agreement. Cumulatively, the Company has incurred and paid total research and development costs of $ 9.9 million to WCM in connection with the WCM Agreement as of March 31, 2024. The WCM Agreement expired in accordance with its terms in January 2024.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2024
Subsequent Events [Abstract]
Subsequent Events	12. Subsequent Events Subsequent events have been evaluated through May 9, 2024, which is the date that these unaudited condensed financial statements were issued and were available to be issued. On April 13, 2024, the Company entered into a third sponsored research agreement with the Regents of UCSD (the “Third UCSD SRA”) for the Company’s LX2022 program in connection with the Second UCSD Agreement. Under the terms of the Third UCSD SRA, the Company has the first rights to obtain non-exclusive or exclusive, sublicensable, royalty-bearing, perpetual and transferable worldwide licenses in any resulting inventions owned by the Regents of UCSD or resulting inventions jointly owned between the Company and the Regents of UCSD, and the Company retains the rights to any resulting inventions owned by the Company. The Third UCSD SRA has a two-year term and may be terminated early by the Company at any time upon the giving of thirty ( 30 ) days’ written notice to the Regents of UCSD. The costs to be invoiced to the Company over the term of the Third UCSD SRA are $ 0.7 million, and the Company may incur additional costs of $ 0.6 million under the Third UCSD SRA if certain study objectives are met. The Company also entered into an amendment to the Second UCSD SRA for the Company’s LX2022 program that extended the term of the Second UCSD SRA to December 2024. On April 19, 2024, the Company entered into an amendment to the First UCSD SRA (as amended, the "Amended First UCSD SRA") for the Company’s LX2021 program in connection with the First UCSD Agreement. The Amended First UCSD SRA extends the term of the First UCSD SRA to December 2026 and provides for additional research and development studies and expenses. The total costs to be invoiced to the Company under the Amended First UCSD SRA are $ 0.8 million. On April 21, 2024, the Company entered into the Third License Agreement (the “Third Cornell License Agreement”) with Cornell. Pursuant to the Third Cornell License Agreement, Cornell has granted the Company an exclusive license to practice under certain patent rights generated in animal studies conducted by Cornell on behalf of the Company and a non-exclusive license to know-how concerning a gene therapy for FA cardiomyopathy and current and future data generated in an ongoing investigator-initiated Phase 1A trial of AAVrh.10hFXN to treat FA cardiomyopathy. Both licenses are worldwide and cover products with human and non-human prophylactic and therapeutic uses. Cornell has also granted the Company a right of reference to Cornell’s Investigation New Drug application for a gene therapy for FA cardiomyopathy. The Third Cornell License Agreement provides that Company will pay a license issue fee and an initial data transfer fee to Cornell totaling $ 0.6 million and thereafter pay an annual data transfer fee of $ 50,000 until data is no longer being gathered. The Company has agreed to pay annual license maintenance fees ranging from $ 2,500 to $ 25,000 until such time Company commercializes a licensed product. In addition, the Company will pay Cornell up to an aggregate of $ 2.1 million in regulatory milestones and up to an aggregate of $ 100 million in commercial milestones, plus low single digit royalties on net sales. The Third Cornell License Agreement contains other customary license terms including terms related to sublicensing, development, commercialization, milestones, royalties, intellectual property, and termination. Upon expiration of the applicable royalty term for a product in a given country, the Company shall retain a non-exclusive, royalty free license to the data and know-how, including to continue selling such product in that country. Cornell may terminate the Third Cornell License Agreement if the Company (i) breaches the Third Cornell License Agreement (subject to a cure period), (ii) participates in any proceeding challenging the validity of the licensed patents, (iii) publishes the licensed data without Cornell’s prior written consent, or (iv) does not reach certain milestones. Cornell may also terminate the Third Cornell License Agreement in part on product-by-product basis if the Company does not diligently develop and sale a product. The Company may terminate the Third Cornell License Agreement, in whole or in part with respect to the right of reference, or the licensed data, know-how, or patent rights, with 90 days’ prior written notice to Cornell.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates —The preparation of the financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of income and expense during the reporting period. The most significant estimates relate to the accruals of research and development costs, including accruals of research contract costs, and assumptions used to estimate the fair value of the Company’s stock option awards and, prior to its IPO, to determine the fair value of its common stock. Management evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors, including the current economic environment, and makes adjustments when facts and circumstances dictate. These estimates are based on information available as of the date of the financial statements; therefore, actual results could differ from those estimates.
Net Loss per Share	Net Loss per Share— The Company follows the two-class method when computing net income (loss) per common share as the Company has issued shares that meet the definition of participating securities. The two-class method determines net income (loss) per common share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income (loss) available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed. The Company considers its convertible preferred stock to be participating securities as, in the event a dividend is paid on common stock, the holders of these securities would be entitled to receive dividends on a basis consistent with the common stockholders. The Company also considers the shares issued upon the early exercise of stock options that are subject to repurchase to be participating securities because holders of such shares have non-forfeitable dividend rights in the event a dividend is paid on common stock. There is no allocation required under the two-class method during periods of loss since the participating securities do not have a contractual obligation to share in the losses of the Company. Basic net income (loss) per common share is computed by dividing the net income (loss) per common share by the weighted-average number of common shares outstanding for the period. Diluted net income (loss) per common share is computed by adjusting net income (loss) to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net loss per common share is computed by dividing the diluted net loss by the weighted-average number of common shares outstanding for the period, including potential dilutive common shares. For the purposes of this calculation, shares of convertible preferred stock are considered potential dilutive common shares. In periods in which the Company reported a net loss, diluted net loss per common share was the same as basic net loss per common share since dilutive common shares were not assumed to have been issued if their effect was anti-dilutive. During (i) the three months ended March 31, 2023, 8,070,027 potential common shares related to the conversion of series A convertible preferred stock and 5,489,573 potential common shares related to the conversion of series B convertible preferred stock, which converted into 8,070,027 common shares and 6,386,337 common shares, respectively, in connection with the Company’s IPO on November 7, 2023, and 2,105,970 potential common shares related to the exercise of outstanding stock options (see Note 8), and (ii) the three months ended March 31, 2024, 3,538,294 total potential common shares related to the exercise of outstanding stock options and settlement of outstanding restricted stock units ("RSUs") (see Note 8), were excluded from the computation of diluted net loss per common share because including them would have had an anti-dilutive effect as the Company reported net losses for those periods.
Concentrations of Credit Risk	Concentrations of Credit Risk —Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents and restricted cash. The Company’s cash and restricted cash balances exceed Federal Deposit Insurance Corporation insurance limits, and the Company’s cash equivalents consist of investments in a U.S. government money market fund. The Company’s cash and cash equivalents and restricted cash is held with large financial institutions that management believes to be of high credit quality. To date, the Company has no t recognized any losses caused by uninsured balances.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Schedule of Fair Value Hierarchy for Assets and Liabilities Measured at Fair Value on Recurring Basis	The following table presents information about the Company’s financial assets measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values: As of March 31, 2024: Level 1 Level 2 Level 3 Total Assets: Cash equivalents (money market) $ 175,033 $ - $ - $ 175,033 $ 175,033 $ - $ - $ 175,033 As of December 31, 2023: Level 1 Level 2 Level 3 Total Assets: Cash equivalents (money market) $ 102,484 $ - $ - $ 102,484 $ 102,484 $ - $ - $ 102,484

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2024
Leases [Abstract]
Components of Operating Lease	The components of this operating lease were as follows: Three Months Ended March 31, 2024 2023 Operating lease expense $ 537 $ 537 Variable lease expense 113 69 Total operating lease expense $ 650 $ 606 Cash paid for amounts included in the measurement of lease liabilities, included in operating cash flows $ 530 $ 548
Reconciliation of Remaining Undiscounted Contractual Rent Obligations	The following table provides a reconciliation of the Company’s remaining undiscounted contractual rent obligations due within each year ended December 31 to the operating lease liabilities recognized as of March 31, 2024: Years ended December 31 Operating 2024 $ 1,592 2025 2,152 2026 2,206 2027 2,261 2028 2,318 Thereafter 1,372 Total lease payments 11,901 Less: present value adjustment ( 2,343 ) Total operating lease liabilities $ 9,558 Included in the balance sheet: Current portion of lease liabilities - operating 2,087 Non-current portion of lease liabilities - operating 7,471 Total operating lease liabilities $ 9,558
Components of Equipment Finance Leases	The components of the equipment finance leases were as follows: Three Months Ended March 31, 2024 2023 Reduction in the carrying amount of ROU assets, finance $ 85 $ 69 Interest on finance lease liabilities 37 50 Total finance lease expense $ 122 $ 119 Cash paid for amounts included in the measurement of lease liabilities, included in financing cash flows $ 109 $ 110
Reconciliation of Remaining Equipment Finance Lease Obligations	The following table provides a reconciliation of the Company’s remaining equipment finance lease obligations due within each year ending December 31 to the equipment finance lease liabilities recognized at March 31, 2024: Years ended December 31 Equipment Finance Leases 2024 $ 391 2025 587 2026 587 2027 359 2028 11 Total lease payments 1,935 Less: imputed interest ( 257 ) Total finance lease liabilities $ 1,678 Included in the balance sheet: Current portion of lease liabilities - finance 524 Non-current portion of lease liabilities - finance 1,154 Total finance lease liabilities $ 1,678

Property and Equipment (Tables)

Property and Equipment (Tables)	3 Months Ended
	Mar. 31, 2024
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment, Net	The following is the summary of the Company’s property and equipment and related accumulated depreciation and amortization as of March 31, 2024 and December 31, 2023: Useful Life March 31, December 31, 2023 Internal use software 3 years $ 309 $ 296 Furniture and fixtures 5 years 380 380 Lab equipment 7 years 558 514 Leasehold improvements 7 years 247 247 Total property and equipment 1,494 1,437 Less: accumulated depreciation and amortization ( 450 ) ( 381 ) Total property and equipment, net $ 1,044 $ 1,056

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	3 Months Ended
	Mar. 31, 2024
Accrued Liabilities and Other Liabilities [Abstract]
Summary of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following: March 31, December 31, 2023 Accrued research and development expenses $ 8,071 $ 6,384 Accrued general and administrative expenses and other professional fees 5,129 1,092 Accrued payroll expenses 246 242 Taxes payable 150 157 Other current liabilities 176 155 Total accrued expenses and other current liabilities $ 13,772 $ 8,030

Capital Stock (Tables)

Capital Stock (Tables)	3 Months Ended
	Mar. 31, 2024
Equity [Abstract]
Schedule of Common Stock Reserved for Future Issuances	The Company had reserved the following number of shares of common stock for the exercise of outstanding stock options, settlement of outstanding RSUs, and future issuance of stock-based awards: March 31, December 31, 2023 Options to purchase shares of common stock under the 2021 Plan and 2023 Plan 3,313,349 2,415,740 RSUs subject to settlement in shares of common stock 224,945 - Shares available for issuance under the 2021 Plan and 2023 Plan 2,503,744 2,293,816 Shares available for issuance under the 2023 ESPP 505,284 238,600 Total shares of common stock reserved for future issuance 6,547,322 4,948,156

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2024
Share-Based Payment Arrangement [Abstract]
Summary of Stock Option Activity	The following table summarizes the stock option activity under the 2021 Plan and the 2023 Plan for the three months ended March 31, 2024 (weighted-average remaining contractual term (in years) is not stated in thousands): Number of Weighted- Weighted- Weighted- Aggregate Shares (per share) (per share) (in years) Value Outstanding as of December 31, 2023 2,415,740 $ 8.32 $ 5.80 7.83 $ 13,689 Granted 985,880 15.43 11.50 Exercised ( 942 ) 11.02 8.27 5 Forfeited ( 87,179 ) 6.21 4.31 Expired ( 150 ) 15.15 10.08 Outstanding as of March 31, 2024 3,313,349 $ 10.48 $ 7.52 8.38 $ 18,241 Vested options outstanding and exercisable as of March 31, 2024 1,071,426 $ 6.10 $ 3.89 6.66 $ 10,461 Unvested options outstanding and exercisable as of March 31, 2024 1,162,401 $ 10.13 $ 7.34 8.66 $ 6,833 Unvested options outstanding and unexercisable as of March 31, 2024 1,079,522 $ 15.20 $ 11.32 9.80 $ 947
Summary of Following Assumptions Presented on Weighted Average Basis	The Company estimated the fair value of options granted using a Black-Scholes option pricing model with the following assumptions presented on a weighted average basis during the three months ended March 31, 2024 (not stated in thousands): Three Months Ended March 31, 2024 Weighted average risk-free interest rate 4.07 % Expected term (in years) 6.07 Expected volatility 86.03 % Expected dividend yield 0.00 %
Summary of RSU activity	The following table summarizes the RSU activity under the 2023 Plan for the three months ended March 31, 2024: Number of Weighted- Shares (per share) Unvested as of December 31, 2023 - $ - Granted 224,945 15.31 Vested - - Forfeited - - Unvested as of March 31, 2024 224,945 $ 15.31
Summary of Stock-Based Compensation Expenses	Stock-based compensation expense was classified as follows in the Company’s unaudited condensed statements of operations and comprehensive loss: Three Months Ended March 31, 2024 2023 Research and development expense $ 1,084 $ 158 General and administrative expense 1,247 239 Total stock-based compensation expense $ 2,331 $ 397

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Schedule of Net Loss Per Share Attributable to Common Stockholders	Basic and diluted net loss per common share attributable to common stockholders was calculated as follows: Three Months Ended March 31, 2024 2023 Numerator: Net loss attributable to common stockholders $ ( 21,682 ) $ ( 18,657 ) Denominator: Weighted-average common shares outstanding, basic and diluted 27,979,838 1,610,793 Net loss per share attributable to common stockholders, basic and diluted $ ( 0.77 ) $ ( 11.58 )

Description of Business and B_2

Description of Business and Basis of Presentation - Additional Information (Details) - USD ($) $ in Thousands			1 Months Ended	3 Months Ended		12 Months Ended	24 Months Ended
	Nov. 07, 2023	Oct. 13, 2023	Aug. 31, 2023	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2021
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Reverse stock split		10.594230-for-1
Net Loss				$ 21,682	$ 18,657	$ 66,400
Cash and cash equivalents, including restricted cash				195,060		121,466
Accumulated deficit				(203,522)		$ (181,840)
Proceeds from issuance of common stock	$ 100,300
Series A and Series B Convertible Preferred Stock [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate total net proceeds raised with issuance of convertible preferred stock							$ 185,000
SAFE [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Net proceeds			$ 3,900
IPO [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Net proceeds	$ 100,300
Private Placement Offering [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Net proceeds				$ 88,800

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)			3 Months Ended		85 Months Ended
	Nov. 07, 2023	Nov. 02, 2023	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024
Summary of Significant Accounting Policies [Line Items]
Loss recognized from uninsured balances					$ 0
SAFE | Common Stock | IPO
Summary of Significant Accounting Policies [Line Items]
Number of common shares on conversion of debt instrument		411,815
Exercise of Outstanding Stock Options
Summary of Significant Accounting Policies [Line Items]
Antidilutive securities excluded from Computation of diluted net loss per common share				2,105,970
Exercise of Outstanding Stock Options | Restricted Stock Units [Member]
Summary of Significant Accounting Policies [Line Items]
Antidilutive securities excluded from Computation of diluted net loss per common share			3,538,294
Series A Convertible Preferred Stock
Summary of Significant Accounting Policies [Line Items]
Antidilutive securities excluded from Computation of diluted net loss per common share				8,070,027
Number of shares issued during the period upon conversion of convertible securities	8,070,027
Series A Convertible Preferred Stock | Common Stock
Summary of Significant Accounting Policies [Line Items]
Number of shares issued during the period upon conversion of convertible securities	8,070,027
Series B Convertible Preferred Stock
Summary of Significant Accounting Policies [Line Items]
Antidilutive securities excluded from Computation of diluted net loss per common share				5,489,573
Series B Convertible Preferred Stock | Common Stock
Summary of Significant Accounting Policies [Line Items]
Number of shares issued during the period upon conversion of convertible securities	6,386,337

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Fair Value Hierarchy for Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	$ 175,033	$ 102,484
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	175,033	102,484
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	175,033	102,484
Level 1 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	$ 175,033	$ 102,484

Property and Equipment - Schedu

Property and Equipment - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 1,494	$ 1,437
Less: accumulated depreciation and amortization	(450)	(381)
Total property and equipment, net	1,044	1,056
Internal Use Software
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 309	296
Useful Life	3 years
Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 380	380
Useful Life	5 years
Lab Equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 558	514
Useful Life	7 years
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 247	$ 247
Useful Life	7 years

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Accrued Liabilities and Other Liabilities [Abstract]
Accrued research and development expenses	$ 8,071	$ 6,384
Accrued general and administrative expenses and other professional fees	5,129	1,092
Accrued payroll expenses	246	242
Taxes payable	150	157
Other current liabilities	176	155
Total accrued expenses and other current liabilities	$ 13,772	$ 8,030

Leases - Additional Information

Leases - Additional Information (Details)			1 Months Ended			3 Months Ended	12 Months Ended	60 Months Ended
	Apr. 01, 2023	Apr. 01, 2022 USD ($)	Jul. 31, 2029	Apr. 30, 2022	Jan. 31, 2022	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Jul. 31, 2034	Aug. 01, 2029 USD ($)	Dec. 11, 2023 USD ($) Installment
Lessee, Lease, Description [Line Items]
Operating lease commencement date				2022-04
Operating lease right-of-use assets						$ 9,120,000	$ 9,442,000
Operating lease liabilities						9,558,000
Net book values						$ 1,700,000	$ 1,763,000
Remaining lease terms						5 years 3 months 18 days	5 years 3 months 18 days
Remaining lease payment terms						5 years 7 months 6 days	5 years 7 months 6 days
Weighted average remaining lease payment term						3 years 4 months 24 days	3 years 8 months 12 days
Weighted average remaining amortization term						5 years 7 months 6 days	5 years 8 months 12 days
Weighted average effective interest rate						8.58%	8.59%
Office Facility and Laboratory Space
Lessee, Lease, Description [Line Items]
Operating lease agreement entered date					2022-01
Operating lease end date			2029-07
Option to extend						additional five-year option to extend the lease beyond July 2029 at the then-prevailing effective market rental rate
Existence of option to extend								true
Operating lease right-of-use assets		$ 11,600,000
Operating lease liabilities		$ 11,600,000
Incremental borrowing rate		8.53%
Office Facility and Laboratory Space | Scenario Forecast
Lessee, Lease, Description [Line Items]
Renewal term									5 years
Operating lease right-of-use assets									$ 0
Operating lease liabilities									$ 0
Office Facility and Laboratory Space | Letter of Credit
Lessee, Lease, Description [Line Items]
Security deposit		$ 1,200,000
Laboratory Equipment
Lessee, Lease, Description [Line Items]
Estimated useful life						7 years
Total gross						$ 2,200,000
Accumulated amortization						500,000
Net book values						1,700,000
Number of monthly installments | Installment										60
Finance lease, commencement date range, start		Apr. 01, 2022
Finance lease, commencement date range, end	Apr. 01, 2023
Total aggregate monthly installment payment amount						$ 49,000
Laboratory Equipment | Minimum
Lessee, Lease, Description [Line Items]
Imputed interest rate										7.90%
Monthly installment payment amounts										$ 4,000
Laboratory Equipment | Maximum
Lessee, Lease, Description [Line Items]
Imputed interest rate										9.30%
Monthly installment payment amounts										$ 18,000

Leases - Components of Operatin

Leases - Components of Operating Lease (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Leases [Abstract]
Operating lease expense	$ 537	$ 537
Variable lease expense	113	69
Total operating lease expense	650	606
Cash paid for amounts included in the measurement of lease liabilities, included in operating cash flows	$ 530	$ 548

Leases - Reconciliation of Rema

Leases - Reconciliation of Remaining Undiscounted Contractual Rent Obligations (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Leases [Abstract]
2024	$ 1,592
2025	2,152
2026	2,206
2027	2,261
2028	2,318
Thereafter	1,372
Total lease payments	11,901
Less: present value adjustment	(2,343)
Total operating lease liabilities	9,558
Included in the balance sheet:
Current portion of lease liabilities - operating	2,087	$ 2,087
Non-current portion of lease liabilities - operating	$ 7,471	$ 7,786

Leases - Components of Equipmen

Leases - Components of Equipment Finance Leases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Leases [Abstract]
Reduction in the carrying amount of ROU assets, finance	$ 85	$ 69
Interest on finance lease liabilities	37	50
Total finance lease expense	122	119
Cash paid for amounts included in the measurement of lease liabilities, included in financing cash flows	$ 109	$ 110

Leases - Reconciliation of Re_2

Leases - Reconciliation of Remaining Equipment Finance Lease Obligations (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Leases [Abstract]
2024	$ 391
2025	587
2026	587
2027	359
2028	11
Total lease payments	1,935
Less: imputed interest	(257)
Total finance lease liabilities	1,678
Included in the balance sheet:
Current portion of lease liabilities - finance	524	$ 518
Non-current portion of lease liabilities - finance	$ 1,154	$ 1,247

Capital Stock - Additional Info

Capital Stock - Additional Information (Details) - USD ($)				3 Months Ended
	Mar. 11, 2024	Nov. 07, 2023	Nov. 02, 2023	Mar. 31, 2024	Dec. 31, 2023
Class of Stock [Line Items]
Authorized capital stock				510,000,000
Common stock shares authorized				500,000,000	500,000,000
Preferred stock shares authorized				10,000,000
Common stock, par value per share				$ 0.0001	$ 0.0001
Preferred stock, par value per share				$ 0.0001
Common stock, shares issued				32,948,332	26,668,485
Common stock shares issued upon early exercise of unvested stock options				20,191	22,107
Dividends, common stock, cash				$ 0
Proceeds from issuance of common stock		$ 100,300,000
Gross proceeds from private placement				$ 88,753,000
Series A Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, shares outstanding		85,495,722
Number of shares issued during the period upon conversion of convertible securities		8,070,027
Series B Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, shares outstanding		58,157,823
Series B Convertible Preferred Stock | Antidilutive Securities
Class of Stock [Line Items]
Number of shares issued during the period upon conversion of convertible securities		896,764
Common Stock
Class of Stock [Line Items]
Number of common shares issued and sold				6,278,905
Common Stock | Series A Convertible Preferred Stock
Class of Stock [Line Items]
Number of shares issued during the period upon conversion of convertible securities		8,070,027
Common Stock | Series B Convertible Preferred Stock
Class of Stock [Line Items]
Number of shares issued during the period upon conversion of convertible securities		6,386,337
IPO | Common Stock
Class of Stock [Line Items]
Number of common shares issued and sold		9,090,910
Offering price per share		$ 11
Underwriting discounts, commissions and other offering expenses		$ 11,300,000
IPO | SAFE | Common Stock
Class of Stock [Line Items]
Number of common shares on conversion of debt instrument			411,815
Over-Allotment Option | Common Stock
Class of Stock [Line Items]
Number of common shares issued and sold		1,048,746
Private Placement
Class of Stock [Line Items]
Underwriting discounts, commissions and other offering expenses	$ 6,200,000
Gross proceeds from private placement	95,000,000
Net proceeds from private placement	$ 88,800,000
Private Placement | Common Stock
Class of Stock [Line Items]
Number of common shares issued and sold	6,278,905
Offering price per share	$ 15.13

Capital Stock - Schedule of Com

Capital Stock - Schedule of Common Stock Reserved for Future Issuances (Details) - shares	Mar. 31, 2024	Dec. 31, 2023
Class of Stock [Line Items]
Total shares of common stock reserved for future issuance	6,547,322	4,948,156
2021 Plan and 2023 Plan
Class of Stock [Line Items]
Total shares of common stock reserved for future issuance	2,503,744	2,293,816
2023 ESPP
Class of Stock [Line Items]
Total shares of common stock reserved for future issuance	505,284	238,600
Restricted Stock Units [Member]
Class of Stock [Line Items]
Total shares of common stock reserved for future issuance	224,945
Common Stock | 2021 Plan and 2023 Plan
Class of Stock [Line Items]
Total shares of common stock reserved for future issuance	3,313,349	2,415,740

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)		3 Months Ended		5 Months Ended	12 Months Ended	33 Months Ended	38 Months Ended
	Nov. 07, 2023	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Dec. 31, 2023	Nov. 07, 2023	Mar. 31, 2024	Jan. 01, 2024
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock, shares reserved for issuance		6,547,322		6,547,322	4,948,156		6,547,322
Stock-based compensation expense		$ 2,331,000	$ 397,000
Unrecognized stock-based compensation expense		$ 21,800,000		$ 21,800,000			$ 21,800,000
Unrecognized compensation expense, weighted-average period of recognition		1 year 7 months 6 days
Restricted Stock Units [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock, shares reserved for issuance		224,945		224,945			224,945
Employee Stock Option
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Weighted-average grant date fair value of stock options granted			$ 13.01
Intrinsic value of stock options exercised			$ 12
Repurchase of Common stock							$ 0
Total grant date fair values of options vested		$ 900,000	$ 500,000
Expected dividend yields percentage		0%
2021 Plan | Employee Stock Option
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period							4 years
Vesting period, percentage							25%
2021 Plan | Employee Stock Option | Non-employee
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share based compensation payment description						vest over a four-year period with 25% of the options granted vesting after one year and the remainder vesting in equal monthly installments over the following 36 months
2023 Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of shares authorized	4,737,000					4,737,000
Common stock, shares reserved for issuance	1,803,980	2,503,744		2,503,744		1,803,980	2,503,744	3,720,103
Percentage of automatically increase in available shares of common stock on beginning of each calendar year	5%
Increase in aggregate number of shares of common stock reserved for issuance								1,333,424
2023 Plan | Restricted Stock Units [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period				4 years
Vesting period, percentage				25%
Number of shares, granted		224,945			0
Share based compensation payment description				vest over a four-year period with 25% of the RSUs granted vesting after approximately one year and the remainder vesting in equal quarterly installments over the following nine quarters
2023 Plan | Employee Stock Option
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period				4 years
Vesting period, percentage				25%
Share based compensation payment description				vest over a four-year period with 25% of the options granted vesting after one year and the remainder vesting in equal monthly installments over the following 36 months
2023 ESPP
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock, shares reserved for issuance		505,284		505,284			505,284	505,284
Number of shares automatically increase in available shares of common stock under plan	477,200
Increase in aggregate number of shares of common stock reserved for issuance								266,684
Number of shares available for future grants		0		0			0
2023 ESPP | Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Percentage of automatically increase in available shares of common stock on beginning of each calendar year	1%

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Details) - Employee Stock Option [Member] - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Weighted average grant date fair value, granted		$ 13.01
Aggregate intrinsic value, exercised		$ 12
2021 Plan and 2023 Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of shares outstanding, beginning	2,415,740
Granted, shares	985,880
Exercised, shares	(942)
Forfeited, shares	(87,179)
Expired, shares	(150)
Number of shares outstanding, ending	3,313,349		2,415,740
Number of shares, vested and exercisable	1,071,426
Number of shares, unvested and exercisable	1,162,401
Number of shares, unvested and unexercisable	1,079,522
Weighted average exercise price, beginning balance	$ 8.32
Weighted average exercise price, granted	15.43
Weighted average exercise price, exercised	11.02
Weighted average exercise price, forfeited	6.21
Weighted average exercise price, Expired	15.15
Weighted average exercise price, ending balance	10.48		$ 8.32
Weighted average exercise price, vested and exercisable	6.1
Weighted average exercise price, unvested and exercisable	10.13
Weighted average exercise price, unvested and unexercisable	15.2
Weighted average grant date fair value, beginning	5.8
Weighted average grant date fair value, granted	11.5
Weighted average grant date fair value, exercised	8.27
Weighted average grant date fair value, forfeited	4.31
Weighted average grant date fair value, expired	10.08
Weighted average grant date fair value, ending	7.52		$ 5.8
Weighted average grant date fair value, vested and exercisable	3.89
Weighted average grant date fair value, Unvested and exercisable	7.34
Weighted average grant date fair value, Unvested and unexercisable	$ 11.32
Weighted average remaining contractual term	8 years 4 months 17 days		7 years 9 months 29 days
Weighted average remaining contractual term, vested and exercisable	6 years 7 months 28 days
Weighted average remaining contractual term, unvested and exercisable	8 years 7 months 28 days
Weighted average remaining contractual term, unvested and unexercisable	9 years 9 months 18 days
Aggregate intrinsic value, beginning	$ 13,689,000
Aggregate intrinsic value, exercised	5,000
Aggregate intrinsic value, ending	18,241,000		$ 13,689,000
Aggregate intrinsic value, vested and exercisable	10,461,000
Aggregate intrinsic value, unvested and exercisable	6,833,000
Aggregate intrinsic value, unvested and unexercisable	$ 947,000

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Following Assumptions Presented on Weighted Average Basis (Details) - Employee Stock Option	3 Months Ended
	Mar. 31, 2024
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Weighted average risk-free interest rate	4.07%
Expected term (in years)	6 years 25 days
Expected volatility	86.03%
Expected dividend yield	0%

Stock-based Compensation - Su_3

Stock-based Compensation - Summary of RSU activity (Details) - Restricted Stock Units [Member] - 2023 Plan - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of shares, granted	224,945	0
Number of shares unvested, ending balance	224,945
Weighted average grant date fair value, granted	$ 15.31
Weighted-average grant date fair value, unvested, ending balance	$ 15.31

Stock-Based Compensation - Su_4

Stock-Based Compensation - Summary of Stock-based Compensation Expenses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 2,331	$ 397
Research and development expense
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	1,084	158
General and administrative expense
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 1,247	$ 239

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Net Loss Per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Numerator:
Net loss attributable to common stockholders	$ (21,682)	$ (18,657)	$ (66,400)
Denominator:
Weighted-average common shares outstanding, basic	27,979,838	1,610,793
Weighted-average common shares outstanding, diluted	27,979,838	1,610,793
Net loss per share attributable to common stockholders, basic	$ (0.77)	$ (11.58)
Net loss per share attributable to common stockholders, diluted	$ (0.77)	$ (11.58)

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - Third Parties for Pharmaceutical Manufacturing and Research Activities	3 Months Ended
	Mar. 31, 2024
Maximum
Loss Contingencies [Line Items]
Termination notice period (in days)	60 days
Minimum
Loss Contingencies [Line Items]
Termination notice period (in days)	30 days

License, Acquisition, Researc_2

License, Acquisition, Research and Collaboration and Sponsored Research Agreements - Additional Information (Details)

1 Months Ended

3 Months Ended

28 Months Ended

38 Months Ended

Dec. 03, 2021 USD ($) IntegerItem

Oct. 04, 2021 USD ($)

Jul. 16, 2021 USD ($)

Jan. 25, 2021 USD ($)

Aug. 06, 2020 USD ($)

May 27, 2020 USD ($) IntegerItem

Apr. 23, 2020 USD ($)

Nov. 30, 2020 USD ($) shares

Mar. 31, 2024 USD ($)

Mar. 31, 2023 USD ($)

Sep. 30, 2022 USD ($)

Jun. 30, 2022 USD ($)

Mar. 31, 2024 USD ($)

Mar. 31, 2024 USD ($)

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Research and development expenses

$ 15,742,000

$ 16,438,000

Stelios Therapeutics Inc

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Asset acquisition date of acquisition

Jul. 16, 2021

Asset acquisition percentage of outstanding stock acquisition

100%

Payment to selling shareholders

$ 2,000,000

Maximum | Stelios Therapeutics Inc

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Payment to selling shareholders

$ 20,500,000

Adverum License Agreement | Adverum Biotechnologies Inc

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

One-time up-front non-refundable fee paid

$ 7,500,000

7,500,000

Development milestone paid

3,500,000

Royalty payments description

The Company is obligated to pay Adverum tiered royalties ranging from high single-digits to sub teens based on annual aggregate worldwide net sales of Products (as defined in the Adverum Agreement).

Research and development expenses

$ 0

License agreement termination notice period

120 days

Adverum License Agreement | Adverum Biotechnologies Inc | Maximum

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Development and regulatory milestones due

$ 17,500,000

Commercialization milestones due

$ 49,000,000

Cornell License Agreements | Cornell University

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Research and development expenses

$ 30,000

0

License agreement termination notice period

90 days

Number of license agreements | IntegerItem

2

Upfront payment in cash

$ 300,000

Notes issued

1,300,000

Notes with outstanding principal exchanged

$ 1,300,000

Cornell License Agreements | Cornell University | Series A Convertible Preferred Stock

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Shares issued on debt exchanged | shares

1,337,610

First Cornell License Agreements | Cornell University | Maximum

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Specific clinical and regulatory milestones due

8,400,000

Second Cornell License Agreements | Cornell University

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Clinical and regulatory milestone paid

$ 100,000

Second Cornell License Agreements | Cornell University | Maximum | Two Portfolios

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Specific clinical and regulatory milestones due

4,300,000

Second Cornell License Agreements | Cornell University | Maximum | Third Portfolio

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Specific clinical and regulatory milestones due

$ 600,000

First UCSD License Agreement | Stelios Therapeutics Inc

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

One-time up-front non-refundable fee paid

$ 20,000

$ 20,000

License agreement termination notice period

60 days

First UCSD License Agreement | Stelios Therapeutics Inc | Research and Development Expense

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

One-time up-front non-refundable fees

$ 20,000

First UCSD License Agreement | Maximum | Stelios Therapeutics Inc

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Development and commercialization milestones due

$ 4,800,000

Second UCSD License Agreement | Stelios Therapeutics Inc

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

License agreement termination notice period

60 days

Second UCSD License Agreement | Stelios Therapeutics Inc | Research and Development Expense

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

One-time up-front non-refundable fees

$ 20,000

Second UCSD License Agreement | Maximum | Stelios Therapeutics Inc

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Development and commercialization milestones due

$ 2,400,000

Third UCSD License Agreement | Stelios Therapeutics Inc

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

One-time up-front non-refundable fee paid

$ 20,000

License agreement termination notice period

60 days

Development and commercialization milestones description

the Company to pay aggregate development and commercialization milestones of up to $4.0 million, and low- to mid-single digit royalties based on aggregate net sales.

Third UCSD License Agreement | Stelios Therapeutics Inc | Research and Development Expense

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

One-time up-front non-refundable fees

$ 20,000

Third UCSD License Agreement | Maximum | Stelios Therapeutics Inc

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Development and commercialization milestones due

$ 4,000,000

UCSD Sponsored Research Agreements | Stelios Therapeutics Inc

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Research and development expenses

200,000

Number of research agreements | IntegerItem

2

Research agreement term

2 years

Research agreement termination notice period

30 days

Costs incurred for research

$ 5,600,000

Payment to research and development

$ 3,200,000

Research Collaboration Agreement | Weill Cornell Medical College

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Research and development expenses

$ 700,000

Payment to research and development

$ 1,600,000

$ 9,900,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - Subsequent Event - USD ($)	Apr. 21, 2024	Apr. 19, 2024	Apr. 13, 2024
Third UCSD License Agreement
Subsequent Event [Line Items]
Research agreement term			2 years
Research agreement termination notice period			30 days
Costs incurred for research			$ 700,000
Additional costs incurred for research			$ 600,000
Amended First UCSD Agreement
Subsequent Event [Line Items]
Costs incurred for research		$ 800,000
Third Cornell License Agreements | Cornell University
Subsequent Event [Line Items]
License agreement termination notice period	90 days
License fee and initial data transfer fee	$ 600,000
Annual data transfer fee	50,000
Maximum | Third Cornell License Agreements | Cornell University
Subsequent Event [Line Items]
Annual license maintenance fees	25,000
Regulatory milestone to be paid	2,100,000
Commercialization milestones due	100,000,000
Minimum | Third Cornell License Agreements | Cornell University
Subsequent Event [Line Items]
Annual license maintenance fees	$ 2,500