[8-K] Lexeo Therapeutics, Inc. Reports Material Event
Lexeo Therapeutics, Inc. (symbol: LXEO) is the issuer of record for a Form 8-K filing submitted to the SEC.
Rhea-AI Filing Summary
Lexeo Therapeutics, Inc. (symbol: LXEO) is the issuer of record for a Form 8-K filing submitted to the SEC.
Positive
- None.
Negative
- None.
Filing Explained
The Mantle deal would commit $5.3 million in cash and $3 million in unregistered Lexeo stock at closing, with completion still conditional.
Lexeo’s Form 8-K reports that it entered an agreement to acquire Mantle Therapeutics, with Mantle becoming a wholly owned subsidiary if the merger closes. The merger is not completed: it remains subject to conditions including stockholder approval, and the company said it expected closing in the third quarter of 2026.
At closing, the stated upfront consideration is
As of
The immediate resolution points are merger completion or termination by
Sources and calculations
- Lexeo Therapeutics Form 8-K and exhibits (2026-09-22)
- Form 8-K purpose (current)
- Dilution definition (current)
- Lexeo second-quarter 2026 fundamentals (2026-06-30)
- Available liquidity against the last reported quarterly operating outflow, in days at that rate ($92,834,000 + $118,869,000 + $22,468,000) / ($17,597,000 / 91) = 1211 days
8-K Event Classification
AI-generated analysis. How Rhea-AI works. Not financial advice.
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
FORM 8-K
CURRENT REPORT
Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934
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Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).
Emerging growth company
If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.
Item 1.01 Entry into a Material Definitive Agreement.
On September 16, 2026, Lexeo Therapeutics, Inc. (“Lexeo” or the “Company”) entered into an Agreement and Plan of Merger (the “Merger Agreement”) with Mantle Therapeutics Inc. (“Mantle”), Magma Merger Sub Inc., a Delaware corporation and a wholly-owned subsidiary of the Company (“Merger Sub”), and Shareholder Representative Services LLC, a Colorado limited liability company, solely in its capacity as representative, agent and attorney in fact of the Sellers. Pursuant to the Merger Agreement, Merger Sub will be merged with and into Mantle (the “Merger”), with Mantle continuing as the surviving corporation and wholly owned subsidiary of Lexeo. Capitalized terms used but not defined herein have the meanings ascribed to such terms in the Merger Agreement.
Effect on Capital Stock
At the effective time of the Merger (the “Effective Time”), and subject to the terms of the Merger Agreement, each outstanding share of Mantle capital stock (other than shares held by Mantle as treasury shares, shares held by Lexeo or Merger Sub, and Dissenting Shares) will be converted into the right to receive an aggregate upfront purchase price consisting of: (i) $5,300,000 in cash, subject to certain adjustments; and (ii) $3,000,000 in shares of Lexeo common stock, par value $0.0001 per share (the "Common Stock"). The Common Stock issued at the Effective Time will not be registered under the Securities Act of 1933, as amended (the "Securities Act"), or any state securities laws, and will be issued in reliance on the exemption from registration provided by Section 4(a)(2) under the Securities Act and/or Regulation D promulgated thereunder for transactions not involving a public offering.
Immediately prior to the Effective Time, each outstanding share of Mantle restricted stock will vest in full and be cancelled in exchange for the right to receive the same consideration as each share of Mantle capital stock above, subject to withholding. Immediately prior to the Effective Time, each outstanding simple agreement for future equity ("SAFE") of Mantle will be cancelled in exchange for the applicable SAFE consideration, determined in accordance with the liquidity event provisions of each SAFE. Each outstanding convertible promissory note of Mantle will be cancelled upon payment of the payoff amount determined under the Merger Agreement.
Contingent Consideration
In addition to the consideration payable at closing, the Merger Agreement provides for the following contingent payments, none of which is guaranteed and each of which may never become payable:
Lexeo makes no guarantees that it will achieve any milestone, and the Merger Agreement does not require Lexeo to devote any particular level of resources to the development or commercialization of Mantle’s product candidates beyond the commercially reasonable efforts standard set forth in the Merger Agreement.
Conditions to the Merger
The consummation of the Merger is subject to the satisfaction or waiver of customary closing conditions, including, among others: (i) receipt of the Requisite Stockholder Approval; (ii) the accuracy of each party's representations and warranties as of the closing (subject to specified materiality standards, including a material adverse effect standard for certain representations); (iii) compliance in all material respects with each party's pre-closing covenants; (iv) the absence of any legal restraint or prohibitory order; (v) the absence of a material adverse effect; and (vi) the delivery of specified ancillary agreements.
Representatives, Warranties and Covenants
Mantle has made customary representations, warranties and covenants in the Merger Agreement, including, among others, covenants to (i) conduct the business in the ordinary course during the period between the execution of the Merger Agreement and the consummation of the Merger, except (a) as expressly contemplated or permitted by the Merger Agreement; (b) as required by applicable law; (c) as set forth on the Company Disclosure Schedule; or (d) as Lexeo has otherwise consented to in writing (such consent not to be unreasonably withheld, delayed or conditioned), and (ii) use reasonable best efforts to take all actions necessary or advisable to consummate the Merger, and to cooperate with the other parties to the Merger Agreement in connection therewith. Lexeo and Merger Sub have also made customary representations and warranties in the Merger Agreement.
Termination
The Merger Agreement contains customary termination rights, including the right of either party to terminate if: (i) the Merger has not been consummated by November 16, 2026; (ii) a final, non-appealable order or law permanently prohibiting the consummation of the Merger is in effect; or (iii) the Requisite Stockholder Approval has not been obtained within one business day after execution of the Merger Agreement. Either party may also terminate upon an uncured material breach by the other party, subject to a 10 business day cure period for curable breaches. The parties may also terminate the Merger Agreement at any time prior to the Effective Time by mutual written consent.
Support Agreements
In connection with the execution of the Merger Agreement, on September 16, 2026, certain of Mantle’s stockholders (collectively, the “Key Stockholders”) entered into a voting and support agreement (each, a “Stockholder Support Agreement” and collectively, the “Stockholder Support Agreements”) with Lexeo and Mantle. The Key Stockholders hold, collectively, approximately 76.1% of outstanding shares of Mantle capital stock, voting together as a single class on an as-converted-to-common-stock basis, and approximately 83.5% of the outstanding shares of Mantle preferred stock. Under the Stockholder Support Agreements, the Key Stockholders have agreed to vote their shares of Mantle capital stock in favor of the adoption of the Merger Agreement and certain other matters, subject to certain terms and conditions contained therein.
The foregoing description of the Merger Agreement and the transactions contemplated thereby does not purport to be complete and is qualified in its entirety by reference to the Merger Agreement, a copy of which is filed as Exhibit 2.1 hereto and is incorporated herein by reference.
Item 8.01 Other Events.
On September 22, 2026, the Company issued a press release announcing its entry into the Merger Agreement as well as other strategic collaborations entered into by the Company. As part of the press release, the Company announced that it would be hosting a conference call and webcast at 8:00 a.m. ET on September 22, 2026 to discuss said transactions and provide a business update. A copy of the press release is attached as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated by reference herein.
The corporate presentation to be used in connection with the webcast described above is attached hereto as Exhibit 99.2 and is incorporated by reference herein.
Also on September 22, 2026, the Company announced that it has 22 participants enrolled or imminently enrolling in its CLARITY-FA study.
Forward Looking Statements
This report contains certain forward-looking statements regarding the business of Lexeo that are not a description of historical facts within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements include statements regarding the expected closing of the proposed acquisition of Mantle Therapeutics Inc. and the satisfaction of the conditions thereto, and the achievement of any contingent consideration events. Words such as “may,” “might,” “will,” “objective,” “intend,” “should,” “could,” “can,” “would,” “expect,” “believe,” “design,” “estimate,” “predict,” “potential,” “develop,” “plan” or the negative of these terms, and similar expressions, or statements regarding intent, belief, or current expectations, are forward-looking statements. While Lexeo believes these forward-looking statements are reasonable, undue reliance should not be placed on any such forward-looking statements. These forward-looking statements are based upon current information available to the company as well as certain estimates and assumptions and are subject to various risks and uncertainties (including, without limitation, those set forth in Lexeo’s filings with the U.S. Securities and Exchange Commission (SEC)), many of which are beyond the company’s control and subject to change. Actual results could be materially different from those indicated by such forward-looking statements as a result of many factors, including but not limited to: risks and uncertainties related to global macroeconomic conditions and related volatility; expectations regarding the initiation, progress, and expected results of Lexeo’s preclinical studies, clinical trials and research and development programs; the unpredictable relationship between preclinical study results and clinical study results; delays in submission of regulatory filings or failure to receive regulatory approval; liquidity and capital resources; and other risks and uncertainties identified in Lexeo’s Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2026, filed with the SEC on August 12, 2026, and subsequent future filings Lexeo may make with the SEC. New risks and uncertainties may emerge from time to time, and it is not possible to predict all risks and uncertainties. Lexeo claims the protection of the Safe Harbor contained in the Private Securities Litigation Reform Act of 1995 for forward-looking statements. Lexeo expressly disclaims any obligation to update or alter any statements whether as a result of new information, future events or otherwise, except as required by law.
Item 9.01 Financial Statements and Exhibits.
(d) Exhibits
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Description |
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2.1*+ |
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Agreement and Plan of Merger, dated as of September 16, 2026 by and among Lexeo Therapeutics, Inc., Mantle Therapeutics Inc., Magma Merger Sub Inc., and Shareholder Representative Services LLC |
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Press release |
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Corporate Presentation, dated September 22, 2026 |
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Cover Page Interactive Data File (embedded within the Inline XBRL document) |
* Certain exhibits, schedules, and annexes have been omitted pursuant to Item 601(a)(5) of Regulation S-K. Lexeo agrees to furnish supplementally a copy of any omitted exhibits, schedules, and annexes to the SEC upon its request.
+ Portions of this exhibit (indicated by [***]) have been omitted because the registrant has determined that the information is both not material and is the type that the registrant treats as private or confidential.
SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.
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Lexeo Therapeutics, Inc. |
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Date: |
September 22, 2026 |
By: |
/s/ R. Nolan Townsend |
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R. Nolan Townsend, Chief Executive Officer |
Exhibit 99.1
Lexeo Therapeutics Enters Into Agreement to Acquire Mantle Therapeutics and Announces Multiple New Strategic Collaborations to Expand Leadership in Friedreich Ataxia
Acquisition of Mantle Therapeutics will add multiple new modalities designed to increase or replace frataxin in the brain
Collaborations launched to evaluate gene therapy sequential dosing following treatment with LX2006 and explore cerebellar targeting to optimize outcomes in FA associated neurological disease
SUNRISE-FA 2 pivotal study continues enrollment and remains the company’s top priority development program;topline data on track for 2H 2027
Disciplined capital allocation supports these strategic initiatives while maintaining cash runway into 2028
Company to host webcast today at 8:00 AM ET
NEW YORK – September 22, 2026 (GLOBE NEWSWIRE) – Lexeo Therapeutics, Inc. (Nasdaq: LXEO), a clinical stage company focused on reshaping the path of genetic diseases with high unmet need, today announced a series of strategic transactions to expand its presence in Friedreich ataxia (FA), including the signing of a definitive agreement to acquire Mantle Therapeutics Inc. and three new research collaborations supporting cerebellar-targeted development opportunities for frataxin gene therapy. Together, these transactions will simultaneously expand Lexeo's vision and capabilities beyond gene therapy, deepen the company’s focus on the multisystem burden of FA, and add multiple therapeutic approaches designed to increase or restore frataxin in the brain. These transactions are being pursued within Lexeo's existing balance sheet capacity, with cash runway guidance unchanged into 2028 and future investment decisions guided by predefined milestones to identify and prioritize the most compelling central nervous system (CNS) opportunities.
“Our objective is to build the best-in-class therapeutic platform for the treatment of Friedreich ataxia,” said R. Nolan Townsend, Chief Executive Officer of Lexeo Therapeutics. “LX2006 remains our highest priority as the best-in-class treatment for FA cardiomyopathy, and the addition of Mantle’s pipeline, combined with new research collaborations will broaden our technology platform with multiple complementary CNS-targeted therapeutic strategies designed to restore frataxin in the brain and further improve outcomes for individuals living with FA. Together, these initiatives will strengthen our leadership position in the disease category while supporting disciplined portfolio advancement and capital allocation.”
Acquisition of Mantle Therapeutics Will Establish Lexeo's Multimodal Friedreich Ataxia Platform
On September 16, 2026, Lexeo entered into an agreement to acquire Mantle Therapeutics Inc. (“Mantle”), a private clinical stage company focused on developing multiple therapies for the treatment of FA. The acquisition will deepen Lexeo's focus on FA and strengthen its capabilities in addressing the neurologic aspects of disease.
The acquired portfolio will include:
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Under the terms of the agreement, Lexeo will pay Mantle shareholders $8.3 million in upfront consideration, consisting of a combination of cash and equity. The agreement also provides for up to $13.0 million in success-based milestone payments, payable in a combination of cash and equity upon the achievement of future clinical and regulatory milestones, bringing the total potential consideration to $21.3 million. Subject to customary closing conditions, the transaction is expected to close in the third quarter of 2026.
Following closing, Lexeo will continue its evaluation of the acquired programs against predefined scientific, clinical, strategic and financial criteria and will prioritize investment in the opportunities demonstrating the strongest potential for clinical patient impact, regulatory success and shareholder value creation. The Company's cash runway guidance into 2028 includes plans to advance one of the acquired programs into clinical development. The Company expects to provide a program prioritization update in early 2027 and submit an IND for its next FA development candidate in 2027.
Together with LX2006, the expanded portfolio provides Lexeo with the technology to evaluate multiple biologic theses for the treatment of FA in the brain. These complementary therapies will be evaluated both as standalone treatments and in concert with LX2006, and all future clinical trials are expected to include a treatment arm for patients previously treated with LX2006.
Strategic Collaborations Supporting Sequential Dosing of CNS Targeted Frataxin Gene Therapy
Lexeo has established three collaborations to evaluate cerebellar-targeted sequential dosing of frataxin gene therapy, all designed to be complementary to systemically administered LX2006.
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Similarly, Lexeo intends to evaluate the outcomes of these research collaborations against predefined scientific, clinical and financial criteria and prioritize investment in opportunities with the greatest potential to advance into clinical development and provide FA patients with a sequential CNS-dosing option to complement prior systemic administration of LX2006.
Expanded Vision to Reflect Strategic Focus
Lexeo is introducing an expanded vision reflecting the company’s focus on the treatment of genetic diseases with high unmet need in both the cardiovascular and neurological space. The refreshed positioning aligns with Lexeo's growing Friedreich ataxia platform and expanded portfolio across multiple modalities outside of gene therapy.
Continued Advancement of LX2006
LX2006 continues to advance enrollment in the SUNRISE-FA 2 pivotal study, which remains Lexeo's highest operational and capital-allocation priority. The program remains on track to provide a topline data readout in the second half of 2027. The Company believes LX2006 has the potential to become the first disease-modifying therapy specifically targeting Friedreich ataxia cardiomyopathy.
Corporate Webcast Details
Lexeo Therapeutics will host a webcast at 8:00 AM ET today, September 22, 2026. Analysts and investors can participate by accessing the webcast live on the Events & Presentations page in the Investors section of Lexeo’s website, www.lexeotx.com. The webcast will be archived on the company’s website following the call.
About Lexeo Therapeutics
Lexeo Therapeutics is a New York City-based, clinical stage company dedicated to reshaping the path of genetic disease. By advancing pioneering science, Lexeo seeks to set a new standard in the treatment of cardiovascular and neurological genetic diseases, charting the path to patient outcomes once thought out of reach. The Company is advancing a portfolio of therapeutic candidates designed to address the underlying genetic causes of disease, including LX2006 for Friedreich ataxia (FA), LX2020 for plakophilin-2 (PKP2) arrhythmogenic cardiomyopathy, and others in devastating diseases with high unmet need.
Cautionary Note Regarding Forward-Looking Statements
Certain statements in this press release may constitute “forward-looking statements” within the meaning of the federal securities laws, including, but not limited to, Lexeo’s expectations and plans regarding its current product candidates and programs, the anticipated benefits of its current product candidates, the timing for receipt and announcement of data from its clinical trials, the timing and likelihood of potential regulatory developments, trial design changes and approval, expectations regarding the time period over which Lexeo’s capital resources will be sufficient to fund its anticipated operations and estimates regarding Lexeo’s financial condition, the expected closing of the proposed acquisition of Mantle Therapeutics Inc. and the satisfaction of the conditions thereto, the anticipated benefits of the proposed acquisition and the acquired programs, the timing and outcome of Lexeo’s evaluation of the acquired programs and research collaborations against predefined criteria, the expected timing of a program prioritization update, the expected submission of an IND for Lexeo’s next Friedreich ataxia development candidate, and the potential achievement of future clinical and regulatory milestones. Words such as “may,” “might,” “will,” “objective,” “intend,” “should,” “could,” “can,” “would,” “expect,” “believe,” “design,” “estimate,” “predict,” “potential,” “develop,” “plan” or the negative of these terms, and similar expressions, or statements regarding intent, belief, or current expectations, are forward-looking statements. While Lexeo believes these forward-looking statements are reasonable, undue reliance should not be placed on any such forward-looking statements. These forward-looking statements are based upon current information available to the company as well as certain estimates and assumptions and are subject to various risks and uncertainties (including, without limitation, those set forth in Lexeo’s filings with the U.S. Securities and Exchange Commission (SEC)), many of which are beyond the company’s control and subject to change. Actual results could be materially different from those indicated by such forward-looking statements as a result of many factors, including but not limited to: risks and uncertainties related to global macroeconomic conditions and related volatility; expectations regarding the initiation, progress, and expected results of Lexeo’s preclinical studies, clinical trials and research and development programs; the unpredictable relationship between preclinical study results and clinical study results; delays in submission of regulatory filings or failure to receive regulatory approval; liquidity and capital resources; and other risks and uncertainties identified in
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Lexeo’s Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2026, filed with the SEC on August 12, 2026, and subsequent future filings Lexeo may make with the SEC. New risks and uncertainties may emerge from time to time, and it is not possible to predict all risks and uncertainties. Lexeo claims the protection of the Safe Harbor contained in the Private Securities Litigation Reform Act of 1995 for forward-looking statements. Lexeo expressly disclaims any obligation to update or alter any statements whether as a result of new information, future events or otherwise, except as required by law.
Media Response:
Media@lexeotx.com
Investor Response:
Ashley Kaplowitz
akaplowitz@lexeotx.com
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Business Update September 22, 2026 Exhibit 99.2 1
This presentation contains “forward-looking statements” within the meaning of the federal securities laws, including, but not limited to, Lexeo’s expectations and plans regarding its current product candidates and programs, the anticipated benefits of its current product candidates, the timing for receipt and announcement of data from its clinical trials, the timing and likelihood of potential regulatory developments, trial design changes and approval, expectations regarding the time period over which Lexeo’s capital resources will be sufficient to fund its anticipated operations and estimates regarding Lexeo’s financial condition, the expected closing of the proposed acquisition of Mantle Therapeutics Inc. and the satisfaction of the conditions thereto, the anticipated benefits of the proposed acquisition and the acquired programs, the timing and outcome of Lexeo’s evaluation of the acquired programs and research collaborations against predefined criteria, the expected timing of a program prioritization update, the expected submission of an IND for Lexeo’s next Friedreich ataxia development candidate, and the potential achievement of future clinical and regulatory milestones. Words such as “may,” “might,” “will,” “objective,” “intend,” “should,” “could,” “can,” “would,” “expect,” “believe,” “design,” “estimate,” “predict,” “potential,” “develop,” “plan” or the negative of these terms, and similar expressions, or statements regarding intent, belief, or current expectations, are forward-looking statements. While Lexeo believes these forward-looking statements are reasonable, undue reliance should not be placed on any such forward-looking statements. These forward-looking statements are based upon current information available to the company as well as certain estimates and assumptions and are subject to various risks and uncertainties (including, without limitation, those set forth in Lexeo’s filings with the U.S. Securities and Exchange Commission (SEC)), many of which are beyond the company’s control and subject to change. Actual results could be materially different from those indicated by such forward-looking statements as a result of many factors, including but not limited to: the outcome of ongoing discussions with the U.S. Food and Drug Administration (FDA) regarding the design of our pivotal trial for accelerated approval pathway and the design of our confirmatory study for obtaining full approval; expectations regarding the initiation, progress, and expected results of Lexeo’s preclinical studies, clinical trials and research and development programs; the unpredictable relationship between preclinical study results and clinical study results; topline data and final results from our pivotal trial; delays in submission of regulatory filings or failure to receive regulatory approval; risks and uncertainties related to global macroeconomic conditions and related volatility; liquidity and capital resources; and other risks and uncertainties identified in Lexeo’s Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2026, filed with the SEC on August 12, 2026, and subsequent future filings Lexeo may make with the SEC. New risks and uncertainties may emerge from time to time, and it is not possible to predict all risks and uncertainties. Lexeo claims the protection of the Safe Harbor contained in the Private Securities Litigation Reform Act of 1995 for forward-looking statements. Lexeo expressly disclaims any obligation to update or alter any statements whether as a result of new information, future events or otherwise, except as required by law. Forward-looking statements 2
Reshaping the path of genetic disease Our vision: To set a new standard in the treatment of genetic diseases with high unmet need, charting the path to patient outcomes once thought out of reach Genetic disease expertise with cardiovascular and neurological focus Proven experience in the clinic Platform designed for safety and scalability 3 Individuals and families impacted by Friedreich ataxia 3
Building a best-in-class FA platform Expanding beyond FA-CM to address full burden of FA through complementary modalities, while maintaining financial and executional discipline The combination of these approaches will advance Lexeo’s objective of building a best-in-class, multimodal therapeutic platform for FA Entrench Leadership in FA-CM LX2006 has potential to be the first disease-modifying gene therapy for FA cardiomyopathy (FA-CM) LX2006 to become backbone treatment for complementary FA modalities SUNRISE-FA 2 pivotal study remains Lexeo’s highest priority Broaden FA Opportunity Mantle acquisition and three new research collaborations Complementary modalities with potential standalone, sequential or combined use with LX2006 Potential to address patients across full spectrum of FA, regardless of cardiomyopathy status or stage Disciplined portfolio advancement Programs to continue to be evaluated against predefined criteria Cash runway guidance into 2028 includes plans to advance one acquired program into clinical development Program prioritization update expected in early 2027, with an IND for the next FA development candidate planned in 2027 FA = Friedreich ataxia; FA-CM = Friedreich ataxia cardiomyopathy 4
Friedreich Ataxia is a progressive multisystem disease with significant unmet need 5 Cardiac complications are the leading driver of mortality, while neurological decline drives substantial lifelong disability; a leading FA platform must address both. Neurological Burden Progressive ataxia, impaired coordination and peripheral nervous system involvement can materially reduce independence and quality of life Cardiac Burden Cardiac complications account for up to 80% of deaths in those with FA, with an average life expectancy of 35–40 years1,2 There is no approved treatment specifically for FA cardiomyopathy ~5,000 individuals affected by FA in the U.S.2 ~15,000 individuals affected by FA worldwide2
Expanding the FA platform while maintaining strategic and financial discipline Mantle Acquisition 1 What Lexeo will acquire: 1 Clinical-stage program 2 Preclinical fast followers 1 Discovery program Small molecules Protein replacement RNA-based Three CNS-Targeted Gene Therapy Research Collaborations 2 Cerebellar-targeted gene therapy Strategies intended to address the neurological manifestations of FA through targeted CNS delivery. Sequential dosing of LX2006 Evaluation of CNS-targeted gene therapy following systemic administration of LX2006. Enabling delivery and repeat administration Novel delivery and immune-suppression strategies intended to support CNS targeting and potential repeat gene therapy administration. Upon closing, the acquired complementary therapies will continue to be evaluated both as standalone treatments and in concert with LX2006. Future clinical trials are expected to include a treatment arm for patients previously treated with LX2006. $8.3M up to $13M Upfront consideration (cash + equity) Success-based milestones (cash + equity) 6
Mantle acquisition will add four differentiated approaches to increasing or replacing frataxin Plan to prioritize investment on the opportunities with the strongest potential for clinical patient impact, regulatory success and shareholder value creation Program Therapeutic approach Stage Route Role in FA platform LX3010 (MTL-104) Oral combination designed to increase frataxin through complementary mechanisms Clinical Oral Potential complementary oral approach LX3030 (MTL-707) Third-generation benzamide HDAC inhibitor designed to increase production of endogenous frataxin Preclinical Oral Potential differentiated oral approach LX3050 (MTL-501) TfR1-targeted frataxin-replacement fusion protein Preclinical IV Potential tissue-directed protein replacement LX3070 (MTL-801) TfR1-targeted antisense oligonucleotide for FXN mRNA stabilization Discovery IV Potential CNS-directed RNA approach HDAC = histone deacetylase; FXN = frataxin, TfR1 = transferrin receptor 1; mFARS = modified Friedreich Ataxia Rating Scale 7
Program highlights: differentiated oral approaches to increase frataxin Differentiated oral profile combining robust frataxin upregulation with CNS exposure LX3030 Third-generation oral small molecule (sub-500Da) designed to increase production of endogenous frataxin in the CNS Builds on prior scientific validation of the HDAC target class Designed to enhance frataxin upregulation and central nervous system exposure Preclinical studies demonstrated robust increases in frataxin Potential differentiated oral approach to addressing the neurological manifestations of FA Early functional and biological signals support the potential for a differentiated oral approach LX3010 Clinical-stage, oral combination designed to increase frataxin through complementary mechanisms Approximately six-point improvement in mFARS scores at 16 weeks Mean nine-fold increase in frataxin protein levels from baseline in muscle biopsies across 11 FA patients Convenient oral formulation designed with the needs of individuals with FA in mind Potential differentiated approach supported by both an early functional signal and evidence of increased FXN protein levels 8
Program highlights: complementary approaches to restore frataxin Direct protein replacement diversifies the platform beyond approaches that rely on endogenous frataxin production LX3050 Preclinical recombinant human frataxin fused to a proprietary anti-TfR1 Fab, designed to directly replace deficient frataxin and increase delivery to the brain Directly replaces deficient frataxin rather than depending on increased endogenous production TfR1 brain shuttle supports delivery across the blood-brain barrier and into multiple disease-relevant tissues In vitro studies demonstrated dose-responsive improvements in measures of mitochondrial function CNS-directed RNA stabilization creates an additional path to increasing endogenous frataxin LX3070 Discovery-stage ASO Fab conjugate program designed to stabilize FXN mRNA and increase translation of endogenous frataxin protein Differentiated RNA mechanism designed to increase the body’s own production of frataxin Combines an RNA-targeted mechanism with a proprietary anti-TfR1 Fab In vitro studies demonstrated dose-responsive increases in frataxin Potential CNS-directed RNA approach that further diversifies Lexeo’s multimodal FA platform 9
Three new research collaborations supporting sequential dosing of CNS-targeted gene therapy Sponsored research agreement evaluating intra-cisternal administration of LX2006 following systemic dosing in large animal models. Sequential dosing Option agreement providing the opportunity to secure a license to a novel IV, BBB-crossing capsid. Blood Brain Barrier-Crossing Capsid Novel immune suppression strategies Option agreement providing the opportunity to secure an exclusive license to VTX-PID, an IgG-degrading enzyme. IgG = immunoglobulin G 10
Unlocking the full spectrum of FA LX2006 has the potential to serve as the cardiac foundation of a broader multimodal FA platform addressing both cardiac and neurological disease No cardiomyopathy Neuro-predominant disease Mild CM Diagnosed cardiac involvement Moderate CM Moderate cardiac disease Advanced CM Greater cardiac disease burden Potential disease-modifying gene therapy for FA cardiomyopathy LX2006 FA-CM Opportunity Potential label-broadening opportunity for LX2006 pending additional mFARS data Neurological burden can span the full continuum Cardiomyopathy Spectrum Future Multimodal Platform Potential Complementary modalities with potential standalone, sequential or combined use with LX2006 Small molecules Protein replacement RNA-based Neuro-targeted collaborations Gene therapy Potential reach regardless of cardiomyopathy status or stage FA = Friedreich ataxia; FA-CM = Friedreich ataxia cardiomyopathy; CM = cardiomyopathy; mFARS = modified Friedreich Ataxia Rating Scale 11
Unlocking the full spectrum of FA Multiple opportunities to address the full spectrum of FA with LX2006 as the backbone LX2006 Best-in-class treatment for FA-CM FXN Increase LX3010 – LX3030 Increase endogenous Frataxin (oral) Neurological Transgene Delivery WCM , Apertura & Vivet Collaborations Enable cerebellar targeting and sequential dosing RNA Modulation LX3070 Stabilize FXN mRNA FXN Protein Replacement LX3050 Directly replace frataxin 12
Building the leading FA platform through focus, breadth and disciplined execution These transactions will advance Lexeo's objective of building the best-in-class FA platform, with complementary therapeutic approaches that provide a breadth of opportunity unmatched in the FA landscape SUNRISE-FA 2 remains the highest operational and capital-allocation priority Execute SUNRISE-FA 2 Mantle and research collaborations add complementary approaches across cardiac and neurological FA Expand the platform Predefined development gates will determine which CNS candidates receive further investment Select strongest opportunity FA = Friedreich ataxia 13
Thank you 14