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Item 1. Business

2025-03-31 compared with 2024-03-21 · 251 added, 296 removed, 624 unchanged (47% of the section changed)

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Our legacy CAART, or Chimeric AutoAntibody Receptor T cells, approach is designed to engineer T cells to selectively engage and eliminate only disease-causing B cells.

We believe our CABA platform has the potential to enable complete and durable responses for a broad range of autoimmune diseases.

The CARTA strategy is designed to achieve transient and complete depletion of all B cells following a single treatment by using T cells engineered to express an antibody fragment that recognizes a B cell receptor expressed on the surface of all B cells.

The construct is designed to allow for the complete elimination of all B cells, including all B cells that contribute to disease, with subsequent repopulation by healthy naïve B cells.

We believe our CABA ® platform has the potential to safely enable complete and durable responses for a broad range of autoimmune diseases and that it has potential applicability across dozens of autoimmune diseases that we have identified, evaluated and prioritized.

Resecabtagene autoleucel (rese-cel, formerly referred to as CABA-201) is a 4-1BB co-stimulatory domain-containing fully human CD19-CAR T construct designed to treat patients with a broad range of autoimmune diseases and our lead product candidate within the CARTA strategy.

Rese-cel is designed to achieve transient and deep depletion of all B cells following a single treatment by using T cells engineered to express an antibody fragment that recognizes a B cell receptor expressed on the surface of all B cells.

The construct is designed to allow for the deep elimination of all B cells, including all B cells that contribute to disease, with subsequent repopulation by healthy naïve B cells.

This approach has the potential to reset the immune system, providing meaningful durable and complete clinical responses to patients off immunosuppressive therapies.

The legacy CAART strategy is designed to selectively engage and eliminate only the pathogenic B cells responsible for driving disease by using T cells engineered to express disease specific targeting domains which are designed to mimic the antigen that is the subject of attack in an autoimmune disease.

Our CAARs differ from chimeric antigen receptors, or CARs, in the use of the autoantigen rather than an antibody fragment, which may enable the CAAR T cells to serve as a “decoy” for specific autoreactive B cell receptors expressed on the surface of B cells, engaging them and resulting in their elimination.

We believe our CABA platform has potential applicability across dozens of autoimmune diseases that we have identified, evaluated and prioritized.

CABA-201, our lead product candidate and the first product candidate from our CARTA platform, is a 4-1BB co-stimulatory domain-containing fully human CD19-CAR T construct designed to treat patients with a broad range of autoimmune diseases.

CABA-201 was designed for use in autoimmune patients to closely replicate the design of a CD19-CAR T construct employed in academic reports published in journals including Nature Medicine , Lancet Rheumatology , and the Journal of the American Medical Association .

These studies have employed a CD19-CAR T cell therapy incorporating a 4-1BB co-stimulatory domain following standard lymphodepletion with fludarabine and cyclophosphamide.

According to reports to date, in patients with systemic lupus erythematosus, anti-synthetase syndrome, and systemic sclerosis, the 4-1BB containing CD19-CAR T cell therapy has led to robust improvement in clinical disease activity within three months of treatment through rapid and deep depletion of CD19-expressing B cells followed by return of healthy B cells within seven months of treatment.

Follow-up is ongoing, with the clinical responses in systemic lupus erythematosus, or SLE, maintained off immunosuppressive therapies with up to 2.5 years of follow-up, as of February 2024 (Müller F, et al.

“CD19 CAR T-Cell Therapy in Autoimmune Disease - A Case Series with Follow-up.” The New England Journal of Medicine (2024):

The fully human CD19 binder in CABA-201, which was exclusively licensed from Nanjing IASO Biotherapeutics Co., Ltd., or IASO, was designed to be a fully human equivalent of the murine FMC63 CD19 binder that was used in the academic clinical reports referenced above.

T cells expressing a 4-1BB-containing CAR with our fully human binder have been demonstrated to possess similar biologic activity in vitro and in vivo when compared to T cells expressing a 4-1BB-containing CAR utilizing the murine FMC63 CD19 binder employed in the academic studies (Dai, Zhenyu, et al.

“Development and functional characterization of novel fully human anti-CD19 chimeric antigen receptors for T-cell therapy.” Journal of Cellular Physiology 236.8 (2021):

The fully human binder has been clinically evaluated in a dual-CD19xCD22 CAR T candidate under development for B cell leukemia and lymphoma in an investigator-initiated trial in China in approximately 20 patients, and IASO has reported a tolerability profile that we believe is favorable for development in autoimmune diseases.

In March 2023, the United States Food and Drug Administration, or the FDA, granted clearance of our CABA-201 Investigational New Drug, or IND, application for treatment of SLE in patients with active lupus nephritis, or LN, or active SLE without renal involvement.

In March 2023, the United States Food and Drug Administration, or the FDA, granted clearance of our rese-cel Investigational New Drug, or IND, application for treatment of SLE in patients with active lupus nephritis, or LN, or active SLE without renal involvement.

SLE is a chronic, potentially severe, autoimmune disease, most commonly impacting young women between the ages of 15 and 40 with higher frequency and more severity in people of color, where the immune system attacks healthy tissue throughout the body.

SLE affects an estimated 160,000-320,000 patients in the U.S, with LN as the most common end-organ manifestation, affecting approximately 40% of SLE patients.

In May 2023, we announced the FDA granted Fast Track Designation for CABA-201, designed to deplete CD19-positive B cells and improve disease activity in patients with SLE and LN.

The RESET-SLE TM Phase 1/2 clinical trial of CABA-201, which is actively enrolling patients, is designed to treat six SLE patients with active

LN, and in a separate parallel cohort, six patients with active SLE without renal involvement, with an initial dose, 1.0 x 10 6 cells/kg, that is equivalent to the dose used in the academic reports of a 4-1BB containing CD19-CAR T construct evaluated in patients with SLE.

Enrollment in the Phase 1/2 RESET-SLE TM trial has initiated and is ongoing across multiple active sites in the U.S.

In March 2024, Health Canada issued a No Objection Letter, or NOL, in response to a Clinical Trial Application for the RESET-SLE TM trial submitted by us.

The NOL allows us to begin the process to activate clinical trial sites and pursue patient enrollment for the RESET-SLE TM trial in Canada.

In May 2023, the FDA granted clearance of our CABA-201 IND application for treatment of active idiopathic inflammatory myopathy, or myositis.

SLE affects an estimated up to 320,000 patients in the U.S., and 150,000 patients in Europe, with LN as the most common end-organ manifestation, affecting approximately 40% of SLE patients.

In May 2023, we announced the FDA granted Fast Track Designation for rese-cel, designed to deplete CD19-positive B cells and improve disease activity in patients with SLE and LN.

The RESET-SLE TM Phase 1/2 clinical trial of rese-cel is designed to treat six SLE patients with active LN, and in a separate parallel cohort, six patients with active SLE without renal involvement, with a single weight-based dose of 1.0 x 10 6 cells/kg.

In March 2024, Health Canada issued a No Objection Letter in response to a Clinical Trial Application, or CTA, for the RESET-SLE TM trial submitted by Cabaletta, enabling us to begin the process to activate clinical trial sites and pursue patient enrollment for the RESET-SLE TM trial in Canada.

In October 2024, the European Medicines Agency allowed a CTA submitted by Cabaletta for the RESET-SLE TM trial to proceed, enabling us to begin the process of activating clinical trial sites and pursuing patient enrollment for the RESET-SLE TM trial.

The trial is open for enrollment across multiple sites in the United States and one site in the European Union.

In May 2023, the FDA granted clearance of our rese-cel IND application for treatment of idiopathic inflammatory myopathies, or IIM, or myositis.

Myositis refers to a group of autoimmune diseases characterized by inflammation and muscle weakness.

The three myositis subtypes being evaluated in the RESET-Myositis TM Phase 1/2 trial of CABA-201 affect approximately 66,000 patients in the U.S.

and typically affect middle-aged individuals, particularly women.

The three myositis subtypes being evaluated in the RESET-Myositis TM Phase 1/2 clinical trial of rese-cel affect approximately 70,000 patients in the U.S.

and approximately 85,000 patients in Europe and typically affect middle-aged individuals, particularly women.

The RESET-Myositis TM clinical trial, which is actively enrolling patients, is designed to treat six patients with dermatomyositis, six patients with anti-synthetase syndrome, and six patients with immune-mediated necrotizing myopathy, all in separate parallel cohorts.

The initial dose for the trial is equivalent to the dose administered to patients with myositis in the academic reports referenced above.

The first patient has been dosed in the RESET-Myositis TM trial with no cytokine release syndrome, or CRS, or Immune Effector Cell-Associated Neurotoxicity Syndrome, or ICANS, of any grade observed for the first 21 days of a 28-day dose-limiting toxicity observation window following administration.

The trial is open for enrollment across multiple active sites in the United States.

We announced the FDA granted Fast Track Designation for CABA-201 for the treatment of patients with dermatomyositis to improve disease activity and Orphan Drug Designation for CABA-201 for the treatment of myositis in January and February 2024, respectively.

In March 2024, we announced the FDA granted Rare Pediatric Disease designation for CABA-201 for juvenile dermatomyositis.

In October 2023, we announced that the FDA granted clearance of our CABA-201 IND application for treatment of systemic sclerosis, or SSc.

We announced the FDA granted Fast Track Designation for rese-cel for the treatment of patients with dermatomyositis to improve disease activity and Orphan Drug Designation for rese-cel for the treatment of myositis in January and February 2024, respectively.

In March 2024, we announced the FDA granted Rare Pediatric Disease designation for rese-cel for juvenile dermatomyositis.

The trial is open for enrollment across multiple sites in the United States and one site in the United Kingdom.

In October 2023, we announced that the FDA granted clearance of our rese-cel IND application for treatment of systemic sclerosis, or SSc.

SSc is a rare and potentially fatal chronic autoimmune disease characterized by progressive skin and internal organ fibrosis that can be life-threatening, including interstitial lung disease, pulmonary hypertension, and scleroderma renal crisis.

SSc affects approximately 88,000 patients in the U.S., typically middle-aged individuals, particularly women.

The RESET-SSc TM Phase 1/2 clinical trial of CABA-201 is designed to treat six patients with severe skin manifestations and six patients with severe organ involvement associated with SSc.

The initial dose for the trial is equivalent to the dose administered to patients with severe, diffuse SSc in the academic studies referenced above involving a 4-1BB containing CD19-CAR T construct.

We announced the FDA granted Fast Track Designation for CABA-201 for the treatment of patients with SSc to improve associated organ dysfunction and Orphan Drug Designation for CABA-201 for the treatment of systemic sclerosis in January and March 2024, respectively.

In November 2023, the FDA granted clearance of our CABA-201 IND application for treatment of generalized myasthenia gravis, or gMG, a subset of patients with myasthenia gravis, or MG.

SSc affects approximately 90,000 patients in the U.S.

and approximately 60,000 patients in Europe, typically middle-aged individuals, particularly women.

The RESET-SSc TM Phase 1/2 clinical trial of rese-cel is designed to treat six patients with severe skin manifestations and six patients with severe organ involvement associated with SSc.

We announced the FDA granted Fast Track Designation for rese-cel for the treatment of patients with SSc to improve associated organ dysfunction and Orphan Drug Designation

for rese-cel for the treatment of systemic sclerosis in January and March 2024, respectively.

The trial is open for enrollment across multiple sites in the United States.

In November 2023, the FDA granted clearance of our rese-cel IND application for treatment of generalized myasthenia gravis, or gMG, a subset of patients with myasthenia gravis, or MG.

MG is a rare autoimmune disease characterized by autoantibodies that interfere with signaling at the neuromuscular junction, or NMJ, leading to potentially life-threatening muscle weakness.

The majority of patients with MG have autoantibodies known to be pathogenic based on their interference with proteins in the NMJ, of which the majority target AChR.

gMG affects approximately 85% of the between 50,000 and 80,000 estimated MG patients in the U.S.

gMG affects approximately 55,000 patients in the U.S.

and approximately 100,000 patients in Europe.

Symptoms of gMG include profound muscle weakness throughout the body, disabling fatigue, and potential shortness of breath due to respiratory muscle weakness, with risk for episodes of respiratory failure.

Standard of care therapies include cholinesterase inhibitors, steroids, immunomodulators, and biologics, which typically require chronic administration, increasing the risk of serious long-term side effects.

The RESET-MG TM Phase 1/2 clinical trial of CABA-201 is designed to treat six patients with AChR-positive gMG and six patients with AChR-negative gMG, each in separate parallel cohorts.

The initial dose for the trial is identical to that which will be employed in our RESET TM Phase 1/2 trials in SLE, myositis and SSc.

In addition to a product candidate that we have specifically designed for use in autoimmune patients, we maintain an exclusive translational research partnership with Dr.

Georg Schett, who is a pioneer and global leader in the application of CD19-targeting cell therapies in autoimmunity and the senior author on the Nature Medicine and Lancet Rheumatology papers cited above.

The collaboration enables Dr.

Schett to share his patient samples with us, and for us to generate translational data to understand the outcomes in his CD19-CAR T cell therapy-treated patients.

Initial data from the collaboration was presented in May 2023 at the American Society for Gene and Cell Therapy 26th Annual Meeting, and in September 2023, Cabaletta scientists published “Cytokine and reactivity profiles in SLE patients following anti-CD19 CART therapy” in Molecular Therapy:

Methods and Clinical Development , highlighting studies performed on serum samples from the first six SLE patients treated with CD19-CAR T by Dr.

The RESET-MG TM Phase 1/2 clinical trial of rese-cel is designed to treat six patients with AChR-positive gMG and six patients with AChR-negative gMG, each in separate parallel cohorts.

The trial is open for enrollment across multiple sites in the United States.

In May 2024, we announced that we are working with active clinical sites to incorporate the RESET-PV TM trial as a sub-study within the Phase 1 DesCAARTes TM trial following the submission of a protocol amendment.

The RESET-PV TM trial will evaluate rese-cel as a monotherapy without preconditioning in patients with mucosal pemphigus vulgaris, or mPV, and mucocutaneous pemphigus vulgaris, or mcPV.

Approximately 15,000 patients in the U.S.

and approximately 20,000 patients in Europe are affected by PV.

The trial is open for enrollment across multiple sites in the United States.

In June 2024, we announced the initial clinical data from each of the first two patients dosed with rese-cel in the RESET-SLE TM and RESET-Myositis TM trials.

In both of these patients, no cytokine release syndrome, or CRS, immune effector cell-associated neurotoxicity syndrome, or ICANS, infections or serious adverse events were observed through data cut-off of May 28, 2024.

Rese-cel exhibited the anticipated profile of CAR T cell expansion and contraction with complete B cell depletion observed in both patients by day 15 post-infusion.

Improvements in both patients’ specific disease measures were observed, consistent with academic experience of a similar 4-1BB CD19-CAR T.

In late June 2024, a lupus nephritis patient with very active, refractory disease was dosed with rese-cel and experienced Grade 1 CRS and a protocol-defined dose-limiting toxicity of Grade 4 ICANS.

The ICANS resolved rapidly following standard management.

The study’s Independent Data Monitoring Committee reviewed data from the patient, and recommended that the study proceed as designed, without delay, at the current dose.

We recommended protocol modifications designed to improve patient safety, including enhanced monitoring for fever and neurologic symptoms along with seizure prophylaxis for all patients, in line with the practice at many academic sites including at Erlangen University, the site of the CD19-CAR T studies led by Dr.

Georg Schett.

The publication reports that in the three months following infusion, cytokine markers of systemic inflammation resolved, autoantibody titers declined, and humoral immunity was maintained.

The translational data generated by Cabaletta coupled with insights into the clinical data generated by Dr.

Schett has enabled insights and a deeper understanding of the immunologic mechanisms of response from ongoing and continued clinical studies in multiple autoimmune diseases.

With CABA-201 informed by insights from this scientific collaboration, we believe we can potentially address a broad range of autoimmune diseases in which B cells have a role in initiating or maintaining disease.

Within the legacy CAART strategy, our initial therapeutic focus has been on mucosal pemphigus vulgaris, or mPV, a chronic, autoimmune blistering skin disease that affects the mucous membranes and is caused by autoantibodies against the cell adhesion protein desmoglein 3, or DSG3.

Despite a current standard of care that includes corticosteroids and adjunctive immunosuppressive agents, pemphigus vulgaris, or PV, remains associated with frequent recurrences as well as substantial morbidity and mortality.

Our DSG3-CAART product candidate is being evaluated for the treatment of mPV, a subtype of PV that affects the epithelium of the mucous membranes, in the Phase 1 DesCAARTes TM trial.

Based on the data observed from prior cohorts, including a modest increase in DSG3-CAART persistence seen in the first combination cohort, which incorporates a pre-treatment regimen of intravenous immunoglobulin, or IVIg, and cyclophosphamide, we have underway an additional combination cohort which incorporates fludarabine into the pre-treatment regimen.

Our MuSK-CAART product candidate is designed to treat a subset of patients with MG, targeting autoreactive B cells that differentiate into antibody secreting cells that produce autoantibodies against a transmembrane protein, muscle-specific kinase, or MuSK, and is being developed for the treatment of muscle-specific kinase myasthenia gravis, or MuSK MG.

Approximately 6% to 7.5% of patients with MG have autoantibodies against MuSK.

We initiated the Phase 1 MusCAARTes TM trial in November 2022.

Our manufacturing strategy is comprised of two stages, designed to initially leverage the extensive early-stage manufacturing expertise of our academic partners and partner with contract development and manufacturing organizations, or CDMOs, and ultimately aiming to achieve full manufacturing independence through expanded CDMO relationships, establishment of our own manufacturing facilities, and/or through strategic partnership(s).

The early phase leverages the expertise in cell and vector manufacturing of our partners at the Children’s Hospital of Philadelphia, or CHOP, and the University of Pennsylvania, or Penn.

This stage included early development work, IND support and cell and vector product manufacturing for CABA-201 and DSG3-CAART.

While these partnerships and use of these established facilities have allowed us to move efficiently and reliably into clinical trials as planned, we are engaging CDMOs who are positioned for manufacturing of vectors and cell processing at commercial grade and scale.

In January 2021, we initiated a collaboration with WuXi Advanced Therapies, Inc., or WuXi, to serve as an additional cell processing manufacturing partner for our MusCAARTes TM trial and entered into a Development and Manufacturing Services Agreement, or the WuXi Agreement, with WuXi.

In August 2023, we expanded the WuXi Agreement, enabling WuXi to serve as one of our cell processing manufacturing partners for the planned global clinical development of CABA-201 in multiple indications, including potential late-stage clinical trials and commercial readiness activities.

In December 2021, we entered into a License and Supply Agreement, or LSA, with Oxford Biomedica (UK) Limited, or Oxford, to supply lentiviral vector for the clinical and commercial development of our DSG3-CAART candidate.

In May 2023, we amended the LSA with Oxford to expand the license to include our CABA-201 program.

In August 2023, we entered into a vector supply agreement with Oxford, and a related second amendment to the LSA, for CABA-201.

In November 2023, we partnered with Cellares Corp., or Cellares, to evaluate Cellares’ automated manufacturing platform, the Cell Shuttle, through Cellares’ Technology Adoption Partnership, or TAP, program.

As part of the collaboration, the companies have agreed on a proof-of-concept technology transfer process for the manufacture of CABA-201, which is progressing.

In July 2024, we provided standard notice to the FDA and communicated details of the event and proposed protocol changes to all active clinical sites within the RESET TM clinical trial program, including the requirement that the investigator promptly discuss the appropriateness and timing of infusion with the trial’s Medical Monitor.

In November 2024, we announced updated clinical data at the American College of Rheumatology Convergence 2024 conference in the first 8 patients dosed across the lupus, myositis and systemic sclerosis clinical trials.

Clinical data from these patients in the RESET-SLE TM , RESET-Myositis TM trial and RESET-SSC TM trial were presented in oral and poster presentations where compelling clinical responses were observed in lupus and myositis patients with up to six months of follow-up, and the first SSc patient demonstrated an emerging, drug-free clinical response.

In January 2025, we announced the FDA granted clearance of our rese-cel IND application for treatment of multiple sclerosis, or MS.

In addition, we announced the FDA granted Fast Track Designation for rese-cel for the treatment of relapsing and progressive forms of MS.

The RESET-MS TM trial is a Phase 1/2 open-label, dose escalation study of rese-cel in subjects with relapsing and progressive forms of MS, evaluated in separate cohorts.

Approximately 750,000 patients in the U.S.

and approximately 550,000 patients in Europe are affected by MS.

In February 2025, we announced updated clinical and translational data from the first 10 patients in the RESET TM clinical trial program, with a data cut off of January 8, 2025.

Overall, clinical responses continued to deepen over three SLE patients in DORIS remission, the first LN patient achieving complete renal response, and the first dermatomyositis patient maintaining a major total improvement score, or TIS improvement.

Each of these patients discontinued all immunosuppressants and were off or tapering steroids as of January 8, 2025.

The safety profile continued to suggest a favorable risk-benefit in the first 10 patients dosed with 90% of patients having experienced either no CRS or Grade 1 CRS and 90% of patients having experienced no ICANS.

In March 2025, we learned of an important protocol deviation in the RESET-SSc TM trial.

In this case, the patient reported a fever three days prior to infusion.

The Cabaletta Medical Monitor was not notified by the investigator prior to the site infusing the patient.

Nine days following rese-cel infusion, the patient experienced a dose-limiting toxicity of grade 3 immune effector

cell-associated neurotoxicity syndrome (ICANS) based on a transient period of confusion.

There was no cerebral edema, seizures or motor dysfunction associated with the ICANS event, and the patient was arousable throughout.

The ICANS resolved rapidly following treatment with dexamethasone, and the patient was discharged without further symptoms.

After data review, the Independent Data Monitoring Committee recommended that the trial proceed at the current dose without delay and endorsed our proposal to require investigators to affirmatively confirm in writing to the company the absence of fevers or evidence of infection.

As of March 14, 2025, 56 clinical sites across the U.S.

and Europe were actively recruiting with 33 patients enrolled across the RESET TM clinical trial program.

Our manufacturing strategy is comprised of two stages.

The initial stage is designed to leverage the extensive early-stage manufacturing expertise of our academic partners and contract development and manufacturing organizations, or CDMOs, for rapid early development and clinical supply, and in parallel partner with commercially compliant CDMOs capable of supporting late-stage clinical studies and commercial production.

Our aim is to achieve full manufacturing readiness through expanded CDMO relationships, establishment of our own manufacturing facilities, and/or through strategic partnership(s).

We are leveraging the expertise in cell and vector manufacturing of our partners at the Children’s Hospital of Philadelphia, or CHOP, and the University of Pennsylvania, or Penn.

For supply of lentiviral vector for the late-stage clinical and commercial manufacturing of rese-cel, we are working with Oxford Biomedica (UK) Limited, or Oxford.

We have also collaborated with WuXi Advanced Therapies, Inc., or WuXi, to serve as an additional and commercially compliant cell manufacturing partner for our MusCAARTes TM and RESET TM clinical trials to meet planned capacity and international supply requirements.

In July 2024, we entered into a new technology transfer agreement with Lonza Houston Inc., or Lonza, another commercially compliant CDMO, to execute a technology transfer of our expected commercial manufacturing process for rese-cel.

In December 2024, we entered into a Development and Manufacturing Services Agreement, or the Lonza Agreement, with Lonza to serve as one of our manufacturing partners for the global clinical development of rese-cel in multiple indications, including potential late-stage clinical trials and preparations for commercial readiness.

This improved process is nearly fully closed, semi-automated, and more easily scaled than the current process.

Transfer of this updated process will be performed from Cabaletta to Lonza in anticipation of being able to supply rese-cel drug product for any of Cabaletta’s ongoing and planned RESET TM clinical trials.

We plan to secure commercial, scalable manufacturing capabilities through multiple potential strategies, including expanding existing or establishing new CDMO relationships, leasing, building, qualifying and operating our own manufacturing facility, and/or establishing a strategic partnership to rapidly and reliably scale manufacturing by leveraging the partner’s manufacturing expertise.

We believe this later stage will enable control of product development and commercial supply for products arising from our CABA platform, enabling us to achieve continuous improvement of our product candidates.

Our Chief Executive Officer and our President, Science and Technology, have both, in prior roles, built and led organizations that have constructed and commissioned cell therapy facilities, which we believe will enable us to build our own manufacturing organizations and facilities, if desirable.

We plan to build upon our first mover advantage in the field of engineered T cell therapy for autoimmune diseases and further advance the discovery, development, and commercialization of our product candidate portfolio.

Our preclinical, regulatory and clinical development experience have enabled the successful clearance of six cell therapy INDs for studies in patients with autoimmune diseases within the routine review period.

We have a track record of successful manufacturing and timely clinical trial execution, with robust capabilities in clinical operations and manufacturing in order to manage the complex logistics and to implement clinical trials of engineered T cell therapy in autoimmune diseases involving oncologists and medical specialists, such as dermatologists, rheumatologists and neurologists, across a dozen sites in the United States, requiring coordination of multiple stakeholders across therapeutic areas.

We believe this experience has the potential to be a significant operating advantage.

Our scientific founders are leading experts in autoimmune diseases and CAR T technology, and we have assembled a Scientific Advisory Board with relevant experience in discovery, clinical and regulatory science for autoimmunity and cell and gene therapy.

We are led by a team with deep expertise and demonstrated success in discovering, developing, manufacturing and evaluating novel cell therapy product candidates in clinical trials.

Multiple members of our team have previously built and led organizations that have constructed and commissioned cell therapy facilities, which we believe will enable us to build our own manufacturing organizations and facilities, if desirable.

As part of our innovative manufacturing strategy where we intend to increase scale, reduce cost of goods and improve patient experience, in November 2023, we partnered with Cellares Corp., or Cellares, to evaluate their automated manufacturing platform, the Cell Shuttle TM , through the Cellares Technology Adoption Program, or TAP.

As part of the collaboration, the companies have agreed on a proof-of-concept technology transfer process for the automated manufacture and release testing of rese-cel.

In August 2024, we expanded our partnership with Cellares to facilitate the potential to incorporate the Cellares manufacturing platform to support the RESET TM clinical program.

In March 2025, we and Cellares announced the successful conclusion of the Technology Adoption Program on Cellares’ automated cell therapy manufacturing Cell Shuttle, facilitating the potential integration of the Cell Shuttle TM into our clinical and commercial, if approved, manufacturing strategy for rese-cel.

We are also evaluating pathways to improve patient experience and scalability of collection through the removal of the requirement for apheresis.

Data were published at the American Society of Cell and Gene Therapy conference in May 2024 illustrating the feasibility of this approach.

Our History and Team

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Milone is a renowned scientist in CAR T therapy and was a co-inventor of and a key driver in the preclinical discovery and development efforts that yielded Kymriah®, the first FDA-approved CAR T therapy for the treatment of B cell cancers.

Payne’s laboratory surmised that by incorporating an antigen instead of an antibody fragment as the extracellular domain of the CAAR, specific pathogenic B cells could be targeted.

This resulted in a collaboration between the two investigators to apply the scientific foundation of CAR T technology as it has been advanced by Drs.

Payne and Milone in order to address B cell-mediated autoimmune diseases.

Their first scientific publication, “Reengineering chimeric antigen receptor T cells for targeted therapy of autoimmune disease” ( Science , July 2016), attracted the attention of a colleague, Steven Nichtberger, M.D., who is an adjunct professor at the Wharton School at the University of Pennsylvania, teaching a class on biotech company formation, financing and leadership in the Vagelos Life Sciences & Management Program.

Additionally, Dr.

Nichtberger has experience creating and building companies, including a novel cellular therapy company, which required transferring the technology from an academic institution, establishing a research and development organization, hiring of manufacturing and quality teams, creating novel manufacturing processes, reaching agreement with the FDA on novel clinical development pathways and constructing a commercial-scale Good Manufacturing Practices, or GMP, facility that manufactured autologous cell therapy products for clinical trials.

In 2017, based on over a year of interaction and discussions regarding the optimal strategy to advance the scientific opportunity into a commercially developed product portfolio that could offer potentially curative treatment options to patients, Drs.

Their research attracted the attention of a colleague Steven Nichtberger, M.D., an adjunct professor at the Wharton School at the University of Pennsylvania, and in 2017, based on over a year of interaction and discussions regarding the optimal strategy to advance the scientific opportunity into a commercially developed product portfolio that could offer potentially curative treatment options to patients, Drs.

Payne, Milone and Nichtberger decided to launch Cabaletta Bio.

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Chang completed his fellowship in Rheumatology and was a faculty member in the Division of Rheumatology at the Perelman School of Medicine at the University of Pennsylvania prior to his transition to the biopharmaceutical industry.

Our initial CAART platform has yielded two clinical-stage cell therapy programs in mPV and MuSK MG, which have required collaborations between specialists – dermatologists and neurologists – and oncologists who are responsible for administering the cell therapy at each site.

Our legacy CAART platform has yielded two clinical-stage cell therapy programs in mPV and MuSK MG, which have required collaborations between specialists – dermatologists and neurologists – and oncologists who are responsible for administering the cell therapy at each site.

Given our track record of timely clinical trial implementation with CAART cell therapy in autoimmune diseases over the past five years at over a dozen sites across the United States, we believe that our team’s successful management of the complicated planning and logistics involved with implementation of these clinical trials has the potential to be an operating advantage.

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These findings demonstrate the potential for CD19-CAR T cell therapy to “reset the immune system,” eliminating the cause of autoimmune disease with restoration of the healthy immune system.

Building on these results, we announced in October 2022 the development of CABA-201, a 4-1BB-containing CD19-CAR T investigational therapy, for the treatment of severe autoimmune diseases.

Building on these results, we announced in October 2022 the development of rese-cel, a 4-1BB-containing CD19-CAR T investigational therapy, for the treatment of severe autoimmune diseases.

Prompted by the initial case report in the New England Journal of Medicine , we conducted a global search to identify the optimally designed product candidate for patients with autoimmune diseases to be highly similar to the construct used by Dr.

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The publication reports that in the three months following infusion, cytokine markers of systemic inflammation resolved, autoantibody titers declined, and humoral immunity was maintained.

Since announcing CABA-201 in October 2022, Cabaletta has had four IND applications cleared within the routine 30-day period for the RESET TM Phase 1/2 clinical trials in SLE, myositis, SSc, and gMG.

With our RESET-SLE TM and RESET-Myositis TM Phase 1/2 trials currently enrolling patients, initial clinical data from each of the first patients in the RESET-Myositis TM and RESET-SLE TM clinical trials is anticipated in the first half of 2024 with longer term follow-up on these and additional patients to be reported in the second half of 2024.

Initial clinical data with CABA-201 in the SSc and gMG trials is anticipated to be reported in the second half of 2024.

Accelerated by our team’s deep expertise in cell therapy in autoimmunity, demonstrated track record of strong clinical execution, positive regulatory interaction since 2018, and our successful cell therapy manufacturing, we are uniquely positioned to advance CD19-targeting cell therapy candidates to further our mission to develop therapies that deliver deep, durable and potentially curative responses for patients in a broad range of autoimmune diseases.

Our Research and Manufacturing Collaboration with Penn

Our CABA platform has already produced multiple product candidates through our sponsored research agreements, or SRAs, with Penn for the laboratories of our scientific co-founders, Drs.

Payne and Milone.

Our continuing relationship with our scientific co-founders provides important advice and insights to us.

Our contractual relationship with Penn through ongoing licensing and research arrangements also provides important services around manufacturing supply.

In May 2020 and October 2021, we amended and restated our worldwide license agreement with Penn to develop our CAAR T technology to treat B cell-mediated autoimmune and alloimmune diseases.

This license agreement provides us with access to multiple patent families covering CAAR T therapy as applied to the field of B cell-mediated autoimmune and alloimmune diseases and to the robust intellectual property portfolio created by Penn under these SRAs in this field.

See “Our Material Agreements -Amended and Restated License Agreement with Penn.”

Our ongoing collaboration with Penn is also based on a Master Translational Research Services Agreement, or the Services Agreement, that we entered into in October 2018, along with multiple additional agreements under the Services Agreement to engage and partner in individual Penn entities, including cell product manufacturing, correlative research, vector manufacturing, clinical trial operations and protocol development.

In February 2023, we entered into a second Master Translational Services Agreement with Penn, or the CARTA Services Agreement, pursuant to which Penn agreed to perform certain research, development and manufacturing activities.

The services encompassed by the CARTA Services Agreement are performed by different organizations at Penn pursuant to certain addenda to the CARTA Services Agreement.

In addition to the Services Agreement, we have agreements in place with various functional areas and centers that provide additional resources to Penn as well as contractual commitments from Penn with the goal of providing the capacity to manufacture certain of our product candidates.

Penn has also agreed to manufacture vector product for use in our clinical trials.

Penn’s obligations are subject to certain limitations and termination rights.

See “Our Material Agreements - Master Translational Research Services Agreement with Penn”.

We believe Penn is uniquely suited to be our partner in our efforts to develop product candidates leveraging our CAR T and CAAR T technology based on a decade of experience, including manufacturing and clinical support for approximately a dozen active cell therapy clinical trials.

The original manufacturing process for the first FDA-approved CAR T therapy was developed at Penn before being transferred to Novartis Pharmaceuticals Corporation during late-stage clinical trials.

We are leveraging Penn’s experience, validated standard operating procedures, manufacturing facilities and staffing to accelerate development efforts for our lead product candidate.

Our goal is to build upon our deep expertise in engineered T cell therapies for autoimmune diseases enhanced by our exclusive translational research partnership with Dr.

Georg Schett to accelerate the discovery, development and commercialization of our product candidates.

Since announcing rese-cel in October 2022, Cabaletta has had five IND applications cleared within the routine 30-day period for the RESET TM Phase 1/2 clinical trials in SLE, myositis, SSc, gMG and MS, in addition to the RESET-PV TM trial that is evaluating rese-cel without preconditioning.

Accelerated by the emerging clinical data with rese-cel, our team’s deep expertise in cell therapy in autoimmunity, demonstrated track record of strong clinical execution, positive regulatory interaction since 2018, and our successful cell therapy manufacturing, we are uniquely positioned to advance CD19-targeting cell therapy candidates to further our mission to develop therapies that deliver deep, durable and potentially curative responses for patients in a broad range of autoimmune diseases.

Our goal is to build upon our deep expertise in engineered T cell therapies for autoimmune diseases to accelerate the discovery, development and commercialization of our product candidates.

We believe achieving this goal could result in potentially curative therapies for patients with unmet medical needs who suffer from a broad range of autoimmune diseases with B cell involvement.

To achieve this goal, key elements of our strategy include:

• Achieving clinical proof-of-concept for our lead product candidate, CABA-201, across multiple autoimmune diseases driven by B cells.

• Achieving compelling clinical responses and a favorable safety profile for our lead product candidate, rese-cel, across multiple autoimmune diseases driven by B cells.

Academic clinical data published in Nature Medicine in September 2022 and in NEJM in February 2024, demonstrated that a CD19-CAR T cell therapy with a 4-1BB co-stimulatory domain following lymphodepletion with fludarabine and cyclophosphamide induced complete clinical responses in five out of five patients with moderate to severe, refractory SLE, with up to 2.5 years of follow up, as of February 2024.

Since then, academic clinical data has demonstrated the same 4-1BB co-stimulatory domain-containing CD19-CAR T cell therapy at the same dose following a similar preconditioning regimen resulted in robust clinical improvement in 15 patients with SLE, idiopathic inflammatory myositis, and systemic sclerosis.

The published safety data to date reported 11 out of 15 patients experienced CRS with 10 out of the 11 patients with fever, a Grade 1 event;

there was one CRS event more severe than fever, a Grade 2 event, in a myositis patient with pre-existing lung disease.

There was also a single Grade 1 ICANS event reported out of the 15 patients.

Our exclusive translational partnership with Dr.

Schett, the lead investigator of the study, is focused on generation of additional translational data to gain a deeper understanding of the immunologic mechanisms of response and clinical insights from ongoing and continued clinical studies in multiple autoimmune disease indications.

Due to the purposeful design of CABA-201 to have a high level of functional and structural similarity to the construct used in these academic studies and engineered specifically for the use in autoimmune patients, we believe CABA-201 may have the potential to transform the treatment of a broad range of autoimmune diseases.

We have four IND applications cleared for the RESET TM Phase 1/2 clinical trials in systemic lupus erythematosus, myositis, systemic sclerosis, and generalized myasthenia gravis and the RESET-SLE TM and RESET-Myositis TM Phase 1/2 trials are currently recruiting patients.

Initial clinical data from each of the first patients in the RESET-Myositis TM and RESET-SLE TM trials is anticipated in the first half of 2024 with longer term follow-up on these and additional patients to be reported in the second half of 2024.

Initial clinical data in the RESET-SSc and RESET-MG trials is anticipated to be reported in the second half of 2024.

As the academic data published to date showed T cell expansion and B cell depletion within the first month post-infusion enabled robust clinical improvement by three months with up to 2.5 years of follow-up in autoimmune patients, and given the similarity of CABA-201 to the academic construct, we expect our initial clinical and translational data to provide insights that may predict longer-term outcomes.

Due to the purposeful design of rese-cel to have a high level of functional and structural similarity to the construct used in these academic studies and engineered specifically for the use in autoimmune patients, we believe rese-cel may have the potential to transform the treatment of a broad range of autoimmune diseases.

We have five IND applications cleared for the RESET TM Phase 1/2 clinical trials in systemic lupus erythematosus, myositis, systemic sclerosis, generalized myasthenia gravis and multiple sclerosis in addition to the RESET-PV TM trial, which is evaluating rese-cel without preconditioning.

All of these clinical trials are currently recruiting patients.

As the academic data published to date showed robust clinical improvement with multiple years of follow-up in autoimmune patients, and given the similarity of rese-cel to the academic construct, we expect our initial clinical and translational data to provide insights that may predict longer-term outcomes.

• Utilizing our expertise in autoimmune cell therapy to enable a novel clinical strategy and efficient study design.

The RESET TM Phase 1/2 clinical trials are comprised of independent cohorts with well-defined disease sub-types, each comprised of 6 patients, which can enroll and dose patients in parallel.

The trials are initiating at a cell dose that is equivalent to the dose of the 4-1BB-containing CD19-CAR T cell therapy used in the academic publications (1.0 x 10 6 cells/kg) with the same preconditioning regimen of fludarabine and cyclophosphamide.

The first four RESET TM Phase 1/2 clinical trials – RESET-SLE, RESET-Myositis, RESET-SSc and RESET-MG – are comprised of independent cohorts with well-defined disease sub-types, each comprised of 6 patients, which can enroll and dose patients in parallel.

These trials are initiating at a weight-based cell dose that is equivalent to the weight-based dose of the 4-1BB-containing CD19-CAR T cell therapy used as was done in the academic publications (1.0 x 10 6 cells/kg) with the same preconditioning regimen of fludarabine and cyclophosphamide.

Each 6-patient cohort treated with an identical dose – without dose escalation requirement – is designed to inform discussions with the FDA on a registrational path for each indication, following the completion of any cohort.

Our clinical strategy enables broad investigation of CABA-201 across nine cohorts with well-defined patient populations in four RESET TM Phase 1/2 clinical trials with the same dose and similar design.

We have also received FDA Fast Track Designation for CABA-201 in SLE, lupus nephritis, dermatomyositis, and systemic sclerosis.

Our clinical strategy enables broad investigation of rese-cel across ten cohorts with well-defined patient populations in these four RESET TM Phase 1/2 clinical trials with the same dose and similar design.

In addition, the RESET-PV TM trial is evaluating weight-based dosing of rese-cel without preconditioning.

We have also received FDA Fast Track Designation for rese-cel in SLE, lupus nephritis, dermatomyositis, systemic sclerosis and multiple sclerosis.

• Leveraging our cellular therapy knowledge and experience in addition to development efficiencies gained through our longstanding Penn collaboration to rapidly build fully integrated internal infrastructure.

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Our management team has expertise in conducting complex, interdisciplinary autoimmune-focused cell therapy clinical trials with a track record of positive regulatory interactions to support cell therapies in autoimmune diseases since 2018.

We have had six INDs for autoimmune cell therapies, each cleared within the routine 30-day period with five Fast Track Designations granted to date.

We have had seven INDs for autoimmune cell therapies, each cleared within the routine 30-day period with six Fast Track Designations granted to date.

In addition, we have a successful track record of manufacturing novel cell therapy product candidates with academic and industry partners.

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We are focused on developing the first potentially curative targeted cellular therapies for patients with autoimmune diseases.

We plan to expand development of CABA-201 to a broad range of autoimmune diseases where the biologic opportunity for cure or treatment may be possible, addressing significant unmet patient need and plan to file INDs in additional indications for CABA-201 in 2024, with the goal of broadening the portfolio to aim to realize the potential of CABA-201.

We plan to expand development of rese-cel to a broad range of autoimmune diseases where the biologic opportunity for cure or treatment may be possible, addressing significant unmet patient need across multiple indications for rese-cel, with the goal of realizing the potential of rese-cel.

While potentially serving a broad range of patients, we are committed to advancing to optimize the patient experience through minimizing the requirement for inpatient stay, optimizing the preconditioning regimen, reducing the burden of apheresis, and/or innovating to address scale in autoimmune disease.

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CD19 serves as a B cell marker from the pro B cell phase until differentiation to plasma cells, while CD20 is a surface marker expressed in a narrower range of the B cell maturation process.

CABA-201 is directed to the CD19 B cell marker.

Rese-cel is directed to the CD19 B cell marker.

CAAR T product candidates are designed to eliminate antigen specific B cells in each targeted disease, preventing their further development to antibody secreting plasma cells.

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We believe the ideal therapy in autoimmune diseases with B cell involvement would completely and specifically eliminate the pathogenic B cells with restoration of the normal immune system, enabling an “immune reset,” restoring the body’s immune system to its normal function of fighting foreign invaders, not healthy tissues.

Our proprietary CABA platform encompasses two strategies.

The CARTA approach is designed to achieve transient but complete depletion of all B cells following a single infusion, allowing for the elimination of disease-causing B cells and subsequent repopulation by healthy B cells.

This strategy may be able to reset the immune system, providing potentially meaningful clinical responses to patients off immunosuppressive therapies.

The legacy CAART approach is designed to engineer T cells to express CAARs that selectively engage and eliminate only disease-causing B cells.

We believe our CABA platform has the potential to enable complete and durable responses for a broad range of autoimmune diseases.

Our CARTA Strategy

Engineered T cell therapy is a type of immunotherapy in which human T cells are genetically modified to express specific receptors, enabling the T cells to recognize and eliminate pathogenic cells.

A key application of engineered cell therapy involves the use of CARs, which are engineered molecules that enable T cells to identify specific antigens present on the surface of diseased cells.

When expressed on the patient’s T cells, the CAR directs the T cells to kill cells that express a particular antigen.

CAR T technology has been used to develop treatments for B cell cancers, which have led to regulatory approvals for 6 cell therapies for certain types of leukemias and lymphomas.

In these B cell cancers, CAR T therapy has resulted in complete remission of disease in many patients, even in patients with severe, refractory cancer.

Academic clinical data published in Nature Medicine in September 2022 and in NEJM in February 2024 demonstrated that a CD19-CAR T cell therapy with a 4-1BB co-stimulatory domain following lymphodepletion with standard doses of fludarabine and cyclophosphamide induced complete clinical responses in five out of five patients with moderate to severe, refractory SLE, with up to 2.5 years of follow up in the first treated patient, as of February 2024.

The published safety data to date reported 11 out of 15 patients experienced CRS including 10 out of the 11 patients with fever, a Grade 1 event;

there was one CRS event more severe than fever, a Grade 2 event, in a myositis patient with pre-existing lung disease.

There was also a single transient episode of dizziness, graded as a Grade 1 ICANS event, reported out of the 15 patients.

New naïve B cells repopulated within two - five months of CAR T infusion in all patients, with no evidence of recurrence of disease or autoantibodies following repopulation.

In summary, the data suggests the potential for a reset of the immune system in these patients.

Our exclusively licensed fully human CD19 binder has been designed to be highly similar to the construct used in the Nature Medicine paper.

The fully human binder has been clinically evaluated in a dual-CD19xCD22 CAR T candidate under development for B cell leukemia and lymphoma in an investigator-initiated trial in China in approximately 20 patients, where IASO has reported a tolerability profile that we believe is favorable for development in autoimmune diseases.

The activity of T cells expressing a 4-1BB-containing CAR with our fully human binder was evaluated against T cells expressing a 4-1BB-containing CAR utilizing the murine CD19 binder employed in the Nature Medicine study cited above, FMC63-CART, as a benchmark.

Compared to FMC63-CART, CABA-201 exhibited comparable biologic activity in vitro and in vivo (Dai, Zhenyu, et al).

Given its similarity to the CD19-CAR T construct employed in the trial conducted by Dr.

Georg Schett and his colleagues, including incorporation of the same 4-1BB co-stimulatory domain, our RESET TM Phase 1/2 trials are initiating at same dose as the dose used in the academic publications (1.0 x 10 6 cells/kg).

Our CAART Strategy

We believe our CAAR T cells have the potential to eliminate the reactive, antibody-producing B cells that are ultimately responsible for disease through precise targeting of cells that contain autoantibodies on their surface, while sparing normal B cells.

Our CAART strategy builds upon the scientific foundation of CARs to enable targeted B cell elimination in an autoimmune setting, which may lead to complete and durable remission of disease while sparing all other B cell populations that can provide beneficial immunity from infection.

The co-stimulatory domain and the signaling domain of both a CAR T cell and CAAR T cell carry out the same activation and cytotoxic functions once the engineered cell therapy engages its relevant target expressed on a B cell.

CAAR T cells differ from CAR T cells primarily in their extracellular targeting domain.

Rather than containing an antibody fragment, the CAAR domain incorporates the relevant components of the autoantigen that is subject to attack in a certain autoimmune disease.

Our Pipeline and Product Candidates

We are a clinical-stage biotechnology company focused on the discovery and development of engineered T cell therapies that have the potential to provide a deep and durable, perhaps curative, treatment for patients with autoimmune diseases.

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Our current product candidate pipeline is illustrated below.

FTD – FDA Fast Track Designation received in dermatomyositis, SLE and lupus nephritis, systemic sclerosis, mucosal pemphigus vulgaris, and MuSK-Ab positive MG.

Currently being evaluated in a Phase 1 trial.

Our Product Candidates

CABA-201 for multiple autoimmune indications

Our lead product candidate for the CARTA strategy, CABA-201, is designed to achieve transient but complete depletion of all B cells following a single infusion, allowing for the elimination disease-causing B cells with subsequent repopulation by naïve healthy B cells.

FTD – FDA Fast Track Designation received in dermatomyositis, SLE and lupus nephritis, systemic sclerosis, and multiple sclerosis.

Additional pipeline candidate includes MuSK-CAART for MuSK-Ab positive MG, currently being evaluated in a Phase 1 trial.

Rese-cel for multiple autoimmune indications

Rese-cel is designed to achieve transient but deep depletion of all B cells following a single infusion, allowing for the elimination disease-causing B cells with subsequent repopulation by translational naïve healthy B cells.

This strategy may be able to reset the immune system, providing potentially meaningful clinical responses to patients off immunosuppressive therapies.

Cabaletta is advancing four RESET TM Phase 1/2 clinical trials in SLE, myositis, SSc and gMG, with potential application in a broad range of other autoimmune diseases.

CABA-201 is comprised of a fully human anti-CD19 binder, which is the extracellular targeting domain.

Cabaletta is advancing six RESET TM Phase 1/2 clinical trials in SLE, myositis, SSc, gMG, PV and MS, with potential application in a broad range of other autoimmune diseases.

Rese-cel is comprised of a fully human anti-CD19 binder, which is the extracellular targeting domain.

In addition, it contains a 4-1BB costimulatory domain and a CD3-zeta signaling domain, as shown in the figure below:

Image showing the design of CABA-201, with a fully human anti-CD19 binder, the 4-1BB costimulatory domain and the CD3-Zeta signaling domain.

Image showing the design of rese-cel, with a fully human anti-CD19 binder, the 4-1BB costimulatory domain and the CD3-Zeta signaling domain.

The costimulatory and signaling domain are identical to the construct used in the academic clinical studies published in Nature Medicine and Lancet Rheumatology that were evaluated in SLE and myositis, respectively.

Academic clinical data published in Nature Medicine in September 2022 and in NEJM in February 2024 demonstrated that a CD19-CAR T cell therapy with a 4-1BB co-stimulatory domain following lymphodepletion with fludarabine and cyclophosphamide induced complete clinical responses in five out of five patients with moderate to severe, refractory SLE, with up to 2.5 years of follow up in the first treated patient off immunosuppressive therapies, as of February 2024.

Since then, academic clinical data has demonstrated the same 4-1BB co-stimulatory domain-containing CD19-CAR T cell therapy at the same dose following a similar preconditioning regimen has led to robust improvement in clinical disease activity within three months of treatment through rapid and deep depletion of CD19-expressing B cells followed by return of healthy B cells within seven months of treatment.

The published safety data to date reported 11 out of 15 patients experienced CRS with 10 out of the 11 patients with fever, a Grade 1 event;

there was one CRS event more severe than fever, a Grade 2 event, in a myositis patient with pre-existing lung disease.

There was also a single Grade 1 ICANS events reported out of the 15 patients.

In summary, the data suggests the potential for a reset of the immune system in these patients.

Our exclusively licensed fully human CD19 binder has been clinically evaluated in a dual-CD19xCD22 CAR T candidate under development for B cell leukemia and lymphoma in an investigator-initiated trial in China in approximately 20 patients, where IASO has reported a tolerability profile that we believe is favorable for development in autoimmune diseases.

The activity of T cells expressing a 4-1BB-containing CAR with our fully human binder was evaluated against T cells expressing a 4-1BB containing CAR utilizing the murine CD19 binder employed in the Nature Medicine study cited above, FMC63-CART, as a benchmark.

to FMC63-CART, CABA-201 exhibits comparable biologic activity in vitro and in vivo, as shown in the figure below (Dai, Zhenyu, et al).

In vitro (top) and in vivo (bottom) data illustrating the binding affinity and body weight effects of a CD19-CAR T with the FMC63 binder vs.

the binder utilized in CABA-201 (clone 78).

Binding affinities and body weight impact are most similar between the FMC63 binder and Clone 78, which is the binder in CABA-201.

Given its structural and functional similarity to the CD19-CAR T construct employed in the academic clinical study published in Nature Medicine , including incorporation of a 4-1BB co-stimulatory domain, we believe CABA-201 may have the potential to reset the immune system and transform treatment of a broad range of autoimmune diseases with high unmet need.

Compared to FMC63-CART, rese-cel exhibits comparable biologic activity in vitro and in vivo (Peng, et al).

Given its structural and functional similarity to the CD19-CAR T construct employed in the academic clinical study published in Nature Medicine , including incorporation of a 4-1BB co-stimulatory domain, we believe rese-cel may have the potential to reset the immune system and transform treatment of a broad range of autoimmune diseases with high unmet need.

Disease Backgrounds

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It is results in a range of clinical manifestations, including end organ damage and an increased risk of death.

SLE affects up to 320,000 patients in the U.S.

SLE affects an estimated up to 320,000 patients in the U.S., and 150,000 patients in Europe.

Lupus nephritis is the most common end-organ manifestation of SLE, affecting approximately 40% of SLE patients.

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Myositis is classified into several subtypes based on the underlying immune mechanisms and clinical characteristics.

Although the pathogenesis of myositis is not well understood, there are several subtypes thought to be driven by B cells, including dermatomyositis, or DM, anti-synthetase syndrome, or ASyS, and immune-mediated necrotizing myopathy, or IMNM.

Although the pathogenesis of myositis is not well understood, there are several subtypes thought to be driven by B cells, including

dermatomyositis, or DM, anti-synthetase syndrome, or ASyS, and immune-mediated necrotizing myopathy, or IMNM.

All three subtypes can lead to severe functional impairment and may be life-threatening.

Nearly 66,000 patients are affected by these three subtypes in the U.S.

Including juvenile myositis, or JIIM, patients, approximately 70,000 patients are affected by these subtypes in the U.S.

and approximately 85,000 patients in Europe.

Current standard of care typically involves medications to suppress the immune system and/or chronic intensive therapies such as intravenous immunoglobulin, or IVIg.

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Systemic sclerosis is a rare and potentially fatal chronic autoimmune disease characterized by progressive fibrosis and scarring of the skin and internal organs that can lead to life-threatening conditions, including interstitial lung disease, pulmonary hypertension, and scleroderma renal crisis.

Although the etiology of SSc is not well understood, the pathogenic role of autoantibodies and B cells

in SSc provides a rationale for studying CAR T therapy in this population.

Although the etiology of SSc is not well understood, the pathogenic role of autoantibodies and B cells in SSc provides a rationale for studying CAR T therapy in this population.

Approximately 90,000 patients in the U.S.

are affected by SSc, commonly middle-aged women.

and 60,000 patients in Europe are affected by SSc, commonly middle-aged women.

Current treatments, which have modest effects, include generalized immunosuppression or drugs targeted to specific symptomatic manifestations.

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The majority of patients with MG have autoantibodies known to be pathogenic based on their interference with proteins in the NMJ, of which the majority target AChR.

Generalized MG affects approximately 85% of the between 50,000 and 80,000 estimated MG patients in the United States.

Generalized MG affects approximately 55,000 patients in the U.S.

and 100,000 patients in Europe.

Symptoms of gMG include profound muscle weakness throughout the body, disabling fatigue, shortness of breath due to respiratory muscle weakness and risk for episodes of respiratory failure.

Standard of care therapies include cholinesterase inhibitors, steroids, immunomodulators, and biologics, which often require chronic administration, increasing the risk of serious long-term side effects.

Pemphigus vulgaris is an autoimmune disease that occurs when the immune system produces antibodies that attack a protein called desmoglein, or DSG.

DSG normally enables skin cells and the cells lining the inside of your mouth, nose, throat, and eyelids to bind tightly together.

Disruption by the antibodies directed to DSG can cause extensive, painful blistering and life-threatening wounds characteristic of PV.

Approximately 15,000 patients in the U.S.

and approximately 20,000 patients in Europe are affected by PV.

Current therapies do not adequately control the underlying autoimmune process, and PV management often involves long-term immunosuppression, with high-dose steroids used in initial treatment and for relapses.

The risk of mortality among patients with PV has been reported to be 2- to 3-fold higher than in the general population.

Multiple sclerosis is an autoimmune-mediated demyelinating disease of the central nervous system (CNS), affecting approximately 750,000 people in the U.S.

and approximately 550,000 patients in Europe.

The disease is more common in women than men, with onset of symptoms frequently between the ages of 20 and 40.

The immune system attack on nerves within the brain and spinal cord impairs nerve electrical conduction, resulting in a wide range of symptoms including muscle weakness, sensory loss, visual impairment, incoordination, memory loss, fatigue, and walking difficulty.

MS is classified into relapsing or progressive forms based on the pattern of clinical symptoms over time, with 85-90% experiencing a fluctuating (relapsing) course, and 10-15% steadily accumulating neurologic disability from disease onset (progressive).

The pathogenesis of MS is multifactorial, with autoreactive B cells increasingly being recognized as a major driver of disease.

Current standard of care therapies require chronic administration, which can be associated increased long-term risk of serious side effects.

Clinical Development Plan

With four IND applications cleared, Cabaletta is advancing RESET TM Phase 1/2 clinical trials in SLE, myositis, SSc and gMG, with potential application in a broad range of other autoimmune diseases.

Our CABA-201 Phase 1/2 RESET-SLE TM and RESET-Myositis TM trials are currently enrolling patients.

The RESET TM Phase 1/2 clinical trials are comprised of independent cohorts with specific objectively defined disease sub-types, which can enroll and dose patients in parallel, and each cohort is expected to be comprised of 6 patients.

The trials are initiating at a dose, which is equivalent to the dose of the 4-1BB CD19-CAR T used in the academic publications (1.0 x 10 6 cells/kg) with the same preconditioning regimen of fludarabine and cyclophosphamide.

We plan to file for INDs in additional indications for CABA-201 in 2024, broadening the portfolio to realize the potential of CABA-201.

We have also received FDA Fast Track Designation for CABA-201 in SLE, lupus nephritis, dermatomyositis, and systemic sclerosis.

Initial clinical data from the RESET-SSc TM and RESET-MG TM trials is anticipated to be reported in the second half of 2024.

As the academic data published through February 2024 showed T cell expansion and B cell depletion within the first 10 days post-infusion enabled robust clinical improvement by three months with up to 2.5 years of follow-up in autoimmune patients, and given the similarity of CABA-201 to the academic construct, we expect our initial clinical and translational data to provide insights that may predict longer-term outcomes.

Cabaletta is advancing RESET TM Phase 1/2 clinical trials in SLE, myositis, SSc, gMG, PV and MS, with potential application in a broad range of other autoimmune diseases.

Our rese-cel Phase 1/2 RESET-SLE TM , RESET-Myositis TM , RESET-SSc TM , RESET-MG TM and RESET-PV TM trials are currently enrolling patients.

These five RESET TM Phase 1/2 clinical trials are comprised of independent cohorts with specific objectively defined disease sub-types, which can enroll and dose patients in parallel, and each cohort is expected to be comprised of 6 patients.

The trials are initiating at a weight-based dose, which is equivalent to the dose of the 4-1BB CD19-CAR T used in the academic publications (1.0 x 10 6 cells/kg) with the same preconditioning regimen of fludarabine and cyclophosphamide, with the exception of the RESET-PV TM trial, which is evaluating rese-cel without preconditioning.

Our clinical strategy enables broad investigation of rese-cel across cohorts with well-defined patient populations in our Phase 1/2 clinical trials with the same dose and similar design.

We have also received FDA Fast Track Designation for rese-cel in SLE, lupus nephritis, dermatomyositis, systemic sclerosis and multiple sclerosis.

DSG3-CAART for Mucosal PV

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and (2) mcPV, which is caused by DSG3 and DSG1 autoantibodies, affecting both the mucous membranes and the skin.

PV affects 11,000-19,000 prevalent patients in the United States, of which approximately 25% have mPV and 75% have mcPV.

PV affects approximately 15,000 prevalent patients in the U.S., of which approximately 25% have mPV and 75% have mcPV.

Like most autoimmune diseases, the current standard of care for PV relies on general immune suppression, which is often transiently effective but can lead to severe infection, potentially resulting in hospitalization and death.

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The DesCAARTes TM trial is an open-label trial to assess the safety and tolerability of various dosing regimens of DSG3-CAART in the treatment of subjects with active mPV.

The primary objective of the trial is to evaluate the safety of DSG3-CAART cells, and secondary objectives include evaluating the initial signs of target engagement.

The FDA granted DSG3-CAART Orphan Drug Designation for the treatment of PV in January 2020 and Fast Track Designation for improving healing of mucosal blisters in patients with mPV in May 2020.

While we initiated the DesCAARTes TM trial without a preconditioning regimen, we have now implemented cohorts with a preconditioning regimen where certain subjects are pre-treated with IVIg and cyclophosphamide, and other patients are pre-treated with IVIg, cyclophosphamide, and fludarabine prior to DSG3-CAART infusion.

The DesCAARTes TM trial is no longer dosing patients for treatment with DSG3-CAART after evaluation of clinical and translational data from the combination cohort, where patients were pre-treated with IVIg, cyclophosphamide and fludarabine prior to DSG3-CAART infusion.

In October 2024, we presented data in an oral presentation at the European Society of Gene and Cell Therapy, or ESGCT, 31st Annual Congress showing that the use of preconditioning with DSG3-CAART did not provide serologic or clinical improvement and did not deeply deplete B-cell levels in patients with mPV.

MuSK-CAART for MuSK Myasthenia Gravis

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The MusCAARTes TM trial is an open-label trial to assess the safety and tolerability of various dosing regimens of MuSK-CAART in the treatment of subjects with active MuSK MG.

The primary objective of the trial is to evaluate the safety of MuSK-CAART cells, and a key secondary objective is to evaluate the initial signs of biologic activity.

The primary endpoint of the study is the incidence of adverse events within three months of MuSK-CAART infusion, including dose limiting toxicity defined as occurring within 28 days of infusion.

In February 2022, MuSK-CAART received Fast Track Designation from the FDA to improve activities of daily living and muscle strength in patients with MuSK antibody-positive myasthenia gravis.

We are currently evaluating clinical and translational data from the A1 and A2 cohorts in the MusCAARTes TM trial, where patients were treated with MuSK-CAART without preconditioning .

Manufacturing

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We believe this allows us to make one change in our supply partners during an early period of clinical development to facilitate in vitro comparability testing and clinical validation, prior to controlled clinical studies.

As part of this strategy, in January 2021, we initiated our strategy to partner with multiple CDMOs to supply our product candidates.

At that time, we initiated a collaboration with WuXi to serve as an additional cell processing manufacturing partner for our MusCAARTes TM trial.

In December 2021, we entered into the LSA with Oxford to supply lentiviral vector for the clinical and commercial development of our DSG3-CAART candidate.

In May 2023, we amended the LSA with Oxford to expand the license to include our CABA-201 program.

In August 2023, we entered into a vector supply agreement with Oxford, and a related second amendment to the LSA, for CABA-201.

In November 2023, Cabaletta partnered with Cellares to evaluate Cellares’ automated manufacturing platform, the Cell Shuttle, through Cellares’ Technology Adoption Partnership program.

As part of the collaboration, the companies have agreed on a proof-of-concept technology transfer process for the manufacture of CABA-201, which is progressing.

• After the early phase, and contingent on supportive clinical data from our product candidates, we are planning to advance the late phase of our manufacturing strategy.

During the late phase, we plan to expand our CDMO relationships, lease, build, qualify and run our own manufacturing facility, or establish a strategic partnership to leverage the partner’s manufacturing expertise, with a focus on innovations to address scale.

Preparations are currently ongoing to implement commercial-ready process in advance of pivotal studies for CABA-201.

We believe this later stage will enable full control of continuous improvement, product development and commercial supply for products arising from our CABA platform.

Vector Manufacturing

The lentiviral vector that we have used in the initial subjects in our DesCAARTes TM trial was manufactured at CHOP.

The lentiviral vector that we plan to use in the initial subjects in our MusCAARTes TM trial was manufactured at Penn.

In parallel, we have engaged in development work with multiple CDMOs to secure production slots for vector for our CABA-201 and DSG3-CAART clinical trials.

• As part of this strategy, in January 2021 and as amended in August 2022, we entered into an agreement with WuXi to serve as an additional cell processing manufacturing partner for our MusCAARTes TM trial and have since completed enabling engineering and patient production runs.

In August 2023, as amended in August 2024, we entered into an agreement with WuXi to serve as one of our manufacturing partners for the global clinical development of rese-cel in multiple indications, including potential late-stage clinical trials and commercial readiness activities for rese-cel.

• In order to expand our clinical supply to address the increasing pace of enrollment in our clinical trials as well as to prepare for registrational trial(s) across the RESET clinical development program while expanding our manufacturing options for rese-cel, Cabaletta has expanded its CDMO agreements with Lonza to supply rese-cel clinical product under current Good Manufacturing Practices as soon as the second half of 2025.

• In December 2021, we entered into the LSA with Oxford to supply lentiviral vector for the clinical and commercial development of our DSG3-CAART candidate.

In May 2023, we amended the LSA with Oxford to expand the license to include our CABA-201 program and in August 2023, we entered into a vector supply agreement with Oxford, and a related second amendment to the LSA, for CABA-201.

In February 2024, we and Oxford entered into a third amendment of the LSA to update the patent schedule.

In May 2023, we amended the LSA with Oxford to expand the license to include our rese-cel program.

In August 2023, we entered into a vector supply agreement with Oxford, and a related second amendment to the LSA, for rese-cel.

In February 2024, we and Oxford entered into a third amendment to the LSA to update the patent schedule.

In June 2024, we and Oxford entered into a fourth amendment to the LSA eliminating royalties on net sales of products that incorporate the Oxford technology if Oxford manufactures the vector.

We believe these efforts will provide us with sufficient clinical-grade vector to move forward with our anticipated clinical trials.

• In conjunction with our efforts to secure commercial supply for rese-cel, we plan to advance innovative manufacturing strategies in order to increase scale, reduce cost of goods and improve the patient experience.

To this end, in November 2023, Cabaletta partnered with Cellares to evaluate Cellares’ automated manufacturing platform, the Cell Shuttle, through Cellares’ Technology Adoption Program.

As part of the collaboration, the companies have agreed on a proof-of-concept technology transfer process for the manufacture of rese-cel.

In August 2024, we expanded our partnership with Cellares to facilitate the potential to incorporate the Cellares manufacturing platform to support the RESET TM clinical program.

Cell Manufacturing

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CVPF is accredited by the Foundation for the Accreditation of Cellular Therapy and is capable of and experienced at supporting manufacture for early-phase clinical trials of novel cell therapy products in first-in-man clinical trials.

We expect to rely upon CVPF as one of our manufacturing partners to provide initial Phase 1 clinical trial drug supply for CABA-201 and DSG3-CAART.

Penn’s manufacturing process for DSG3-CAART is directly related to the process developed at Penn for early clinical trials of CD19-CAR T, which subsequently became known commercially as Kymriah.

We rely upon CVPF as one of our manufacturing partners to provide initial Phase 1 clinical trial drug supply for rese-cel.

Penn’s manufacturing process for rese-cel is directly related to the process developed at Penn for early clinical trials of CD19-CAR T, which subsequently became known commercially as Kymriah.

The process was later transferred to Novartis Pharmaceuticals Corporation and further modified for the Kymriah program.

As we scale our manufacturing for our product candidates to meet our expected needs for further clinical trials, we may or may not rely on Penn, but we also expect to rely on CDMOs and other third parties for the manufacturing and processing of our clinical trial materials.

As we scale our manufacturing for our product candidates to meet our expected needs for further clinical trials, and while we continue to utilize Penn for Phase 1/2 studies in the US, we have brought on board commercial CDMOs capable of global and fully GMP compliant manufacturing, as well as other third parties for the manufacturing and processing of our clinical trial materials.

Any CDMO that we select will be subject to cGMP requirements.

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We have also initiated development work with certain contractors for cGMP and commercial vector production.

We expect third-party manufacturers will be capable of providing

and processing sufficient quantities of our product candidates to meet anticipated clinical trial demands and commercial need.

In January 2021, we initiated a collaboration with WuXi to serve as an additional cell processing manufacturing partner for our ongoing MusCAARTes TM trial, which collaboration was amended in August 2022.

In August 2023, we entered into new work orders under the WuXi Agreement for WuXi to serve as one of our cell processing manufacturing partners for the planned global clinical development of CABA-201 in multiple indications, including potential late-stage clinical trials and commercial readiness activities for CABA-201.

We expect third-party manufacturers will be capable of providing and processing sufficient quantities of our product candidates to meet anticipated clinical trial demands and commercial need.

In January 2021 and as amended in August 2022, we entered into an agreement with WuXi to serve as an additional cell processing manufacturing partner for our MusCAARTes TM trial and have since completed enabling engineering and patient production runs.

In August 2023, as

amended in August 2024, we entered into an agreement with WuXi to serve as one of our manufacturing partners for the global clinical development of rese-cel in multiple indications, including potential late-stage clinical trials for rese-cel.

In order to expand our clinical supply to address the increasing pace of enrollment in our clinical trials as well as to prepare for registrational trial(s) across the RESET clinical development program while expanding our manufacturing options for rese-cel, Cabaletta has expanded its CDMO agreements with Lonza, a leading CDMO, to supply rese-cel clinical product under current Good Manufacturing Practices as soon as the second half of 2025.

Commercialization

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The product candidates from our CABA platform are designed to address autoimmune indications where there is a compelling opportunity to improve clinical outcomes in comparison with the current standard of care.

Our lead CARTA product candidate, CABA-201, is under development for autoimmune diseases with serious unmet medical need.

Rese-cel is under development for autoimmune diseases with serious unmet medical need.

Based on the differentiated expertise of Cabaletta’s team members and our years of experience in conducting cell therapy clinical trials in autoimmunity, we are focused on being the first company to launch a cell therapy product for patients with autoimmune diseases, while continuing to innovate on next-generation approaches and differentiation strategies to deliver an optimal product candidate profile.

Our CAART product candidates are focused on rare disease populations where we believe there is potential to commercialize independently due to the concentration of treatment paradigms and limited but easily identified patient populations.

We aim to achieve full manufacturing independence through expanding our CDMO relationships, establishment of our own manufacturing facilities, and/or through a strategic partnership.

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Any therapeutic candidates we successfully develop and commercialize will compete with the existing standard of care as well as any novel therapies that may gain regulatory approval in the future.

There are multiple companies with marketed CAR T therapies for the treatment of hematologic cancers, including Novartis Pharmaceuticals Corporation, Gilead Sciences, Inc., Bristol Myers Squibb, Johnson and Johnson, Inc.

and Legend Biotech Corporation.

A subset of these companies along with other biopharmaceutical companies have announced CD19-targeting therapies and other methods of engineering T cells in development for the treatment of autoimmune diseases with B cell involvement, including SLE, MG, among others.

There are also a number of companies with leading autoimmune franchises but without disclosed cell therapy platforms who may become competitors.

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We strive to protect the proprietary technologies that we believe are important to our business, including pursuing and maintaining patent protection intended to cover our product candidates and their use, as well as other inventions that are important to our business.

In addition to patent protection, we also rely on know-how, confidentiality agreements, invention assignment agreements and trade secrets to protect aspects of our business that are not amenable to, or that we do not consider appropriate for, patent protection, to develop and maintain our proprietary position.

patent protection, to develop and maintain our proprietary position.

The confidentiality agreements are designed to protect our proprietary information and the invention assignment agreements are designed to grant us ownership of technologies that are developed for us by our employees, consultants or certain other third parties.

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Any patents that we hold may be challenged, circumvented or invalidated by third parties.

As of March 1, 2024, our in-licensed patent estate included seven issued U.S.

patents, four granted foreign patents, seven pending U.S.

As of March 1, 2025, our in-licensed patent estate included seven granted U.S.

patents, seven granted foreign patents, seven pending U.S.

patent applications, and 50 pending foreign patent applications.

See “Our Material Agreements - IASO Agreement” and “Our Material Agreements - Amended and Restated License Agreement with the Trustees of the University of Pennsylvania and the Children’s Hospital of Philadelphia.” As of March 1, 2024, our Cabaletta-owned patent estate included two U.S.

provisional patent applications.

With regard to our CABA-201 product candidate, under the IASO Agreement, we have in-licensed one patent family which is directed to a CD19 specific chimeric antigen receptor and a CD19-specific antibody binding site, and contains one pending U.S.

patent application and counterpart patent applications pending in Australia, Canada, China, Europe, Hong Kong and Japan.

See “Our Material Agreements - IASO Agreement” and “Our Material Agreements - Amended and Restated License Agreement with the Trustees of the University of Pennsylvania and the Children’s Hospital of Philadelphia.” As of March 1, 2025, our Cabaletta-owned patent estate included three U.S.

provisional patent applications and two pending international patent applications.

With regard to our rese-cel product candidate, under the IASO Agreement, we have in-licensed one patent family which is directed to a CD19-specific chimeric antigen receptor and a CD19-specific antibody and contains one pending U.S.

patent application and counterpart patent applications pending in Australia, Canada, China, Europe, and Hong Kong.

These patent applications, if issued, would be expected to expire in 2040.

The family also contains one granted Chinese patent, which is scheduled to expire in 2040.

The family also contains granted patents in China and Japan, which are scheduled to expire in 2040.

This patent family is owned by IASO and is exclusively licensed to us in the field of the license.

We also own two provisional U.S.

patent applications drawn to methods of treating autoimmune diseases with a chimeric antigen receptor, including a CD19-specific chimeric antigen receptor.

We also own two international patent applications drawn to methods of treating autoimmune diseases with a chimeric antigen receptor, including a CD19-specific chimeric antigen receptor.

Any granted patents claiming priority to these applications would be expected to expire in 2044.

With regard to our DSG3-CAART product candidate, under the Amended and Restated License Agreement with Penn, we have in-licensed one patent family containing five issued U.S.

patents with claims directed to a CAAR containing an extracellular domain containing DSG3, DSG1 or fragments thereof, nucleic acids encoding the CAAR, genetically modified cells comprising the CAAR, and methods of treatment using the same.

These patents are scheduled to expire between 2035 and 2037, without taking potential patent term extensions into account.

The family also contains counterpart patents granted in Europe, Canada, and China, which are scheduled to expire in 2035, and counterpart patent applications pending in the U.S., China, Europe and Hong Kong.

This patent family is owned by Penn and exclusively licensed to us in the field of the license.

We also own one U.S.

provisional patent application drawn to methods of treating autoimmune diseases with a chimeric antigen receptor, including a CD19-specific chimeric antigen receptor;

provisional patent application drawn to CD19-binding antibodies and CD19-specific chimeric antigen receptors;

provisional patent application drawn to methods of manufacturing cell-therapy compositions.

Any granted patents claiming priority to these applications would be expected to expire in 2045.

With regard to our MuSK-CAAR T cell product candidate, under the Amended and Restated License Agreement with Penn, we have in-licensed one patent family containing one issued U.S.

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This patent is scheduled to expire in 2039, without taking potential patent term extensions into account.

The family also contains one pending U.S.

patent application and counterpart patent applications pending in Australia, Canada, China, Europe, Hong Kong, Israel, Japan, Korea, Mexico and New Zealand, which if issued, would be expected to expire in 2039.

This family also contains a counterpart patent granted in Japan which is scheduled to expire in 2039, and counterpart patent applications pending in the U.S., Australia, Canada, China, Europe, Hong Kong, Israel, Japan, Korea, Mexico and New Zealand, which if issued, would be expected to expire in 2039.

This patent family is owned by Penn and exclusively licensed to us in the field of the license.

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IASO may also terminate the IASO Agreement if we fail to achieve certain specified diligence milestones in a timely manner and/or if we commence any patent challenges with respect to the patents and patent applications relating to the licensed sequence, in each case upon advance written notice.

A milestone payment of $1.5 million was paid to IASO in the first quarter of 2024 after the first patient in a CABA-201 trial was dosed.

A milestone payment of $1.5 million was paid to IASO in the first quarter of 2024 after the first patient in a rese-cel trial was dosed.

Oxford Biomedica

In December 2021, we entered into a Licence and Supply agreement, or LSA, with Oxford Biomedica, or Oxford, wherein the LSA grants us a non-exclusive license to Oxford's LentiVector® platform for its application in our DSG3-CAART program and puts in place a multi-year vector supply agreement.

Under the terms of the agreement, we were required to pay Oxford an upfront fee, as well as costs associated with initial vector manufacturing activities for a total cost of up to approximately $4.0 million.

In December 2021, we entered into a Licence and Supply agreement, or LSA, with Oxford wherein the LSA grants us a non-exclusive license to Oxford’s LentiVector® platform for its application in our DSG3-CAART program and puts in place a multi-year vector supply agreement.

Under the terms of the agreement, we were required to pay Oxford an upfront fee, as well as costs associated with initial vector manufacturing activities.

Oxford, is eligible to receive regulatory and sales milestones in the low tens of millions and royalties in the low single digits on net sales of products that incorporate the Oxford technology.

We can terminate the agreement at will upon advance written notice and subject to certain manufacturing slot cancellation fees.

In May 2023, we amended the LSA with Oxford to expand the license to include our CABA-201 program for an upfront fee of $0.5 million and in August 2023, we entered into a vector supply agreement with Oxford, and a related second amendment to the LSA, for CABA-201 with a total cost of up to approximately $5.0 million under the vector supply agreement.

In February 2024, we and Oxford entered into a third amendment of the LSA to update the patent schedule.

In May 2023, we amended the LSA with Oxford to expand the license to include our rese-cel program for an upfront fee of $0.5 million and in August 2023, we entered into a vector supply agreement with Oxford, and a related second amendment to the LSA, for rese-cel with a total cost of up to approximately $5.0 million under the vector supply agreement.

In February 2024, we and Oxford entered into a third amendment to the LSA to update the patent schedule.

In June 2024, we and Oxford entered into a fourth amendment to the LSA eliminating royalties on net sales of products that incorporate the Oxford technology if Oxford manufactures the vector.

In December 2024, the Company and Oxford entered into a work order for certain process characterization activities as part of commercial readiness activities.

The Company can terminate the LSA or any work order under the LSA at will upon advance written notice and subject to certain cancellation fees.

WuXi Manufacturing Agreement

In January 2021, we entered into the WuXi Agreement with WuXi to serve as an additional cell processing manufacturing partner for the MuSK-CAART Phase 1 clinical trial, or MusCAARTes TM trial.

The WuXi Agreement is scheduled to expire upon completion of WuXi’s services related to MuSK-CAART and CABA-201.

Under the August 2023 work orders, WuXi will convert our non-dedicated suite to a dedicated suite for GMP manufacturing for our CABA-201 and MuSK-CAART programs, or the Dedicated Suite, for an initial term of 18 months with two 18 month extensions at our sole option on six months’ notice prior to the end of the term.

In January 2021, we entered into a Development and Manufacturing Services Agreement, or the WuXi Agreement, with WuXi to serve as an additional cell processing manufacturing partner for the MuSK-CAART Phase 1 clinical trial, or MusCAARTes TM trial.

The WuXi Agreement is scheduled to expire upon completion of WuXi’s services related to MuSK-CAART and rese-cel.

Under the August 2023 work orders, WuXi converted our non-dedicated suite to a dedicated suite for GMP manufacturing for our rese-cel and MuSK-CAART programs, or the Dedicated Suite, for an initial term of 18 months with two 18 month extensions at our sole option on six months' notice prior to the end of the term.

In August 2024, we notified WuXi that we would extend the initial term by 18 months through August 2026.

In addition, we agreed to certain monthly minimum runs.

In lieu of the original $1.5 million termination fee under the terms of the WuXi Agreement, we would incur a $1.08 million termination fee if we terminate both the CABA-201 and MuSK-CAART work orders for any reason.

We may terminate for convenience the WuXi Agreement or any work order with six months’ prior written notice, however, we may not terminate the Dedicated Suite without terminating both the MuSK-CAART and CABA-201 GMP run work orders.

WuXi may terminate for convenience the WuXi Agreement or any work order on 18 months’ prior written notice, but such notice may not be effective prior to February 2028.

In August 2024, the 2023 work order related to GMP manufacturing was amended to reduce the minimum monthly runs through the end of 2024.

In lieu of the original $1.5 million termination fee under the terms of the WuXi Agreement, we would

incur up to a $1.08 million termination fee if we terminate both the rese-cel and MuSK-CAART work orders for any reason.

We may terminate for convenience the WuXi Agreement or any work order with six months' prior written notice, however, we may not terminate the Dedicated Suite without terminating both the MuSK-CAART and rese-cel GMP run work orders.

WuXi may terminate the WuXi Agreement or any work order for convenience on 18 months' prior written notice, but such notice may not be effective prior to February 2028.

Amended and Restated License Agreement with the Trustees of the University of Pennsylvania and the Children’s Hospital of Philadelphia

In August 2018, we entered into a license agreement with Penn, which was amended and restated in July 2019 to include the Children’s Hospital of Philadelphia, or CHOP, collectively, the Institutions, and collectively with such amendment, as amended in May 2020 and October 2021, the License Agreement, pursuant to which we obtained (a) a non-exclusive, non-sublicensable, worldwide research license to make, have made and use products in two subfields of use, (b) effective as of October 2018, an exclusive, worldwide, royalty-bearing license, with the right to sublicense, under certain of the Institutions’ intellectual property to make, use, sell, offer for sale and import products in the same two subfields of use, and (c) effective as of October 2018, a non-exclusive, worldwide, royalty-bearing license, with limited rights to sublicense, under certain of Penn’s know-how to make, have made, use, sell, offer for sale, import and have imported products in the same two subfields of use.

In August 2018, we entered into a license agreement with Penn, which was amended and restated in July 2019 to include CHOP, collectively, the Institutions, and collectively with such amendment, as amended in May 2020 and October 2021, the License Agreement, pursuant to which we obtained (a) a non-exclusive, non-sublicensable, worldwide research license to make, have made and use products in two subfields of use, (b) effective as of October 2018, an exclusive, worldwide, royalty-bearing license, with the right to sublicense, under certain of the Institutions’ intellectual property to make, use, sell, offer for sale and import products in the same two subfields of use, and (c) effective as of October 2018, a non-exclusive, worldwide, royalty-bearing license, with limited rights to sublicense, under certain of Penn’s know-how to make, have made, use, sell, offer for sale, import and have imported products in the same two subfields of use.

Our rights are subject to the rights of the U.S.

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The CARTA Services Agreement will expire on the later of (i) February 9, 2026 or (ii) completion of the services for which we have engaged Penn under the CARTA Services Agreement.

Either party may terminate the agreement with or without cause upon a certain number of days’ prior written notice.

Either party may terminate this agreement with or without cause upon a certain number of days’ prior written notice.

The services encompassed by the CARTA Services Agreement are performed by different organizations at Penn pursuant to certain addenda to the CARTA Services Agreement.

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Our products are considered more than minimally manipulated and will require evaluation in clinical trials and the submission and approval of a BLA before we can market them.

Government authorities in the United States (at the federal, state and local level) and in other countries extensively regulate, among other things, the research, development, testing, manufacturing, quality control, approval, labeling, packaging, storage, record-keeping, promotion, advertising, distribution, post-approval monitoring and reporting, marketing and export and import of biopharmaceutical products such as those we are developing.

biopharmaceutical products such as those we are developing.

Our product candidates must be approved by the FDA before they may be legally marketed in the United States and by the appropriate foreign regulatory agency before they may be legally marketed in foreign countries.

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Additionally, some significant aspects of regulation in Europe are addressed in a centralized way, but country-specific regulation remains essential in many respects.

The process for

obtaining regulatory marketing approvals and the subsequent compliance with appropriate federal, state, local and foreign statutes and regulations require the expenditure of substantial time and financial resources.

The process for obtaining regulatory marketing approvals and the subsequent compliance with appropriate federal, state, local and foreign statutes and regulations require the expenditure of substantial time and financial resources.

Biological Product Development

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The central focus of an IND submission is on the general investigational plan and the protocol(s) for human trials.

The IND automatically becomes effective 30 days after receipt by the FDA, unless the FDA raises concerns or questions regarding the proposed clinical trials and places the IND on clinical hold within that 30-day time period.

The IND automatically becomes effective 30 days after receipt by the FDA, unless the FDA raises concerns or questions regarding the

proposed clinical trials and places the IND on clinical hold within that 30-day time period.

In such a case, the IND sponsor and the FDA must resolve any outstanding concerns before the clinical trial can begin.

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Accordingly, we cannot be sure that submission of an IND will result in the FDA allowing clinical trials to begin, or that, once begun, issues will not arise that could cause the trial to be suspended or terminated.

or IBCs, as set forth in the NIH Guidelines for Research Involving Recombinant or Synthetic Nucleic Acid Molecules, or NIH Guidelines.

In addition to the submission of an IND to the FDA before initiation of a clinical trial in the United States, certain human clinical trials involving recombinant or synthetic nucleic acid molecules are subject to oversight of institutional biosafety committees, or IBCs, as set forth in the NIH Guidelines for Research Involving Recombinant or Synthetic Nucleic Acid Molecules, or NIH Guidelines.

Under the NIH Guidelines, recombinant and synthetic nucleic acids are defined as:

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Failure to exhibit due diligence with regard to conducting Phase 4 clinical trials could result in withdrawal of approval for products.

Progress reports detailing the results of the clinical trials, among other information, must be submitted at least annually to the FDA, and written IND safety reports must be submitted to the FDA and the investigators for serious and unexpected suspected adverse events, findings from other studies suggesting a significant risk to humans exposed to the biologic, findings from animal or in vitro testing that suggest a significant risk for human subjects, and any clinically important increase in the rate of a serious suspected adverse reaction over that listed in the protocol or investigator brochure.

in vitro testing that suggest a significant risk for human subjects, and any clinically important increase in the rate of a serious suspected adverse reaction over that listed in the protocol or investigator brochure.

Phase 1, Phase 2 and Phase 3 clinical trials may not be completed successfully within any specified period, if at all.

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Additionally, some clinical trials are overseen by an independent group of qualified experts organized by the clinical trial sponsor, known as a data safety monitoring board or committee.

there is an unacceptable safety risk for subjects or other grounds, such as interim data suggesting a lack of efficacy.

This group provides authorization for whether or not a trial may move forward at designated intervals based on access to certain data from the trial and may halt the clinical trial if it determines that there is an unacceptable safety risk for subjects or other grounds, such as interim data suggesting a lack of efficacy.

We may also suspend or terminate a clinical trial based on evolving business objectives and/or competitive climate.

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Before approving a BLA, the FDA will conduct a pre-approval inspection of the manufacturing facilities for the new product to determine whether the facilities comply with cGMPs.

The FDA will not approve the product unless it determines that the manufacturing processes and facilities are in compliance with cGMP requirements and adequate to assure consistent production of the product within required specifications.

The FDA will not approve the product unless it determines that the manufacturing processes and facilities are in compliance with cGMP requirements and adequate to assure consistent production of

the product within required specifications.

In addition, before approving a BLA, the FDA may also audit data from clinical trials to ensure compliance with GCP requirements.

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A Complete Response Letter usually describes all of the specific deficiencies in the BLA identified by the FDA.

The Complete Response Letter may require additional clinical data and/or an additional pivotal Phase 3 clinical trial(s), and/or other significant and time-consuming requirements related

to clinical trials, preclinical studies or manufacturing.

The Complete Response Letter may require additional clinical data and/or an additional pivotal Phase 3 clinical trial(s), and/or other significant and time-consuming requirements related to clinical trials, preclinical studies or manufacturing.

If a Complete Response Letter is issued, the applicant may either resubmit the BLA, addressing all of the deficiencies identified in the letter, withdraw the application or request a hearing.

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The FDA has a Fast Track program that is intended to expedite or facilitate the process for reviewing new drugs and biological products that meet certain criteria.

Specifically, new drugs and biological products are eligible for Fast Track Designation if they are intended to treat a serious or life-threatening condition and nonclinical or clinical data demonstrate the potential to address unmet medical needs for the condition.

Specifically, new drugs and biological products are eligible for Fast Track Designation if they are

intended to treat a serious or life-threatening condition and nonclinical or clinical data demonstrate the potential to address unmet medical needs for the condition.

Fast Track Designation applies to the combination of the product and the specific indication for which it is being studied.

The sponsor of a new drug or biologic may request the FDA to designate the drug or biologic as a Fast Track product concurrently with, or at any time after, submission of an IND, and the FDA must determine if the product qualifies for Fast Track Designation within 60 days of receipt of the sponsor’s request.

Under the Fast Track Designation, the FDA may

consider for review sections of the marketing application on a rolling basis before the complete application is submitted, if the sponsor provides a schedule for the submission of the sections of the application, the FDA agrees to accept sections of the application and determines that the schedule is acceptable, and the sponsor pays any required user fees upon submission of the first section of the application.

Under the Fast Track Designation, the FDA may consider for review sections of the marketing application on a rolling basis before the complete application is submitted, if the sponsor provides a schedule for the submission of the sections of the application, the FDA agrees to accept sections of the application and determines that the schedule is acceptable, and the sponsor pays any required user fees upon submission of the first section of the application.

Any product submitted to the FDA for marketing, including under a Fast Track program, may be eligible for other types of FDA programs intended to expedite development and review, such as priority review and accelerated approval.

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Prohibitions or restrictions on sales or withdrawal of future products marketed by us could materially affect our business in an adverse way.

From time to time, legislation is drafted, introduced, passed in Congress and signed into law that could significantly change the statutory provisions governing the approval, manufacturing, and marketing of products regulated by the FDA.

In addition to new legislation, FDA regulations, guidances, and policies are often revised or reinterpreted by the agency in ways that may significantly affect the manner in which pharmaceutical products are regulated and marketed.

Changes in regulations, statutes or the interpretation of existing regulations could impact our business in the future by requiring, for example:

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Interchangeability requires that a biological product be biosimilar to the reference product and that the product can be expected to produce the same clinical results as the reference product in any given patient and, for products administered multiple times, that the product and the reference product may be switched after one has been previously administered without increasing safety risks or risks of diminished efficacy relative to exclusive use of the reference biological product.

However, complexities associated with the larger, and often more complex, structure of biological products as compared to small molecule drugs, as well as the processes by which such products are manufactured, pose significant hurdles to implementation that are still being worked out by the FDA.

However, complexities associated with the larger, and often more complex,

structure of biological products as compared to small molecule drugs, as well as the processes by which such products are manufactured, pose significant hurdles to implementation that are still being worked out by the FDA.

A reference biological product is granted twelve years of exclusivity from the time of first licensure of the product, and the FDA will not accept an application for a biosimilar or interchangeable product based on the reference biological product until four years after first licensure.

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The containment of healthcare costs has become a priority of federal and state governments, and the prices of drugs, including biologics, have been a focus in this effort.

government, state legislatures and foreign governments have shown significant interest in implementing cost-containment programs, including price controls, restrictions on reimbursement and requirements for substitution of generic products.

substitution of generic products.

In many countries, the prices of drug products are subject to varying price control mechanisms as part of national health systems.

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Some countries may require the completion of additional studies that compare the cost effectiveness of a particular therapy to currently available therapies or so-called health technology assessments, in order to obtain reimbursement or pricing approval.

Other countries may allow companies to fix their own

prices for products, but monitor and control product volumes and issue guidance to physicians to limit prescriptions.

Other countries may allow companies to fix their own prices for products but monitor and control product volumes and issue guidance to physicians to limit prescriptions.

Efforts to control prices and utilization of pharmaceutical products will likely continue as countries attempt to manage healthcare expenditures.

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Some states also impose requirements on manufacturers and distributors to establish the pedigree of product in the chain of distribution, including some states that require manufacturers and others to adopt new technology capable of tracking and tracing product as it moves through the distribution chain.

Several states have enacted legislation requiring pharmaceutical and biotechnology companies to establish marketing compliance programs, file periodic reports with the state, make periodic public disclosures on sales, marketing, pricing, clinical trials and other activities, and/or register their sales representatives, as well as to prohibit pharmacies and other healthcare entities from providing certain physician prescribing data to pharmaceutical and biotechnology companies for use in sales and marketing, and to prohibit certain other sales and marketing practices.

and marketing, and to prohibit certain other sales and marketing practices.

All of our activities are potentially subject to federal and state consumer protection and unfair competition laws.

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Among the provisions of the ACA of greatest importance to the pharmaceutical industry are that the ACA:

, new formulations, such as extended release formulations) of solid oral dosage forms of branded products, as well as potentially impacting their rebate liability by modifying the statutory definition of AMP;

• made several changes to the Medicaid Drug Rebate Program, including increasing pharmaceutical manufacturers’ rebate liability by raising the minimum basic Medicaid rebate on average manufacturer price, or AMP, on most branded prescription drugs and adding a new rebate calculation for “line extensions” (i.e., new formulations, such as extended release formulations) of solid oral dosage forms of branded products, as well as potentially impacting their rebate liability by modifying the statutory definition of AMP;

• imposed a requirement on manufacturers of branded drugs to provide a 70% point-of-sale discount as a condition for a manufacturer’s outpatient drugs being covered under Medicare Part D;

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• The Budget Control Act of 2011 and subsequence legislation, among other things, created measures for spending reductions by Congress that include aggregate reductions of Medicare payments to providers of 2% per fiscal year, which remain in effect through 2031.

Due to the Statutory Pay-As-You-Go Act of 2010, estimated budget deficit increases resulting from the American Rescue Plan Act of 2021, and subsequent legislation, Medicare payments to providers will be further reduced starting in 2025 absent further legislation.

however, legislation has been introduced in the U.S.

Congress that would, if enacted, reverse these payment reductions.

In addition to provider payment cuts under Medicare, the American Rescue Plan Act of 2021 also eliminated the statutory Medicaid drug rebate cap, previously set at 100% of a drug’s average manufacturer price, for single source and innovator multiple source drugs, effective January 1, 2024.

These laws and regulations may result in additional reductions in Medicare and other healthcare funding available for healthcare providers and may otherwise affect the prices we may obtain for any of our product candidates for which we may obtain regulatory approval or the frequency with which any such product candidate is prescribed or used.

• The American Taxpayer Relief Act of 2012, which, among other things, further reduced Medicare payments to several providers and increased the statute of limitations period for the government to recover overpayments to providers from three to five years.

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Congressional inquiries and proposed and enacted federal and state legislation designed to, among other things, bring more transparency to drug pricing, review the relationship between pricing and manufacturer patient assistance programs, and reform government program reimbursement methodologies for drugs.

President Biden has issued multiple executive orders that have sought to reduce prescription drug costs.

In February 2023, HHS issued a proposal in response to an October 2022 executive order from President Biden that includes a proposed prescription drug pricing model that will test whether targeted Medicare payment adjustments will sufficiently incentivize manufacturers to complete confirmatory trials for drugs approved through FDA’s accelerated approval pathway.

Although a number of these and other proposed measures may require authorization through additional legislation to become effective, and the Biden administration may reverse or otherwise change these measures, both the Biden administration and Congress have indicated that they will continue to seek new legislative measures to control drug costs.

The Inflation Reduction Act of 2022, or IRA includes several provisions that may impact our business to varying degrees, including provisions that reduce the out-of-pocket spending cap for Medicare Part D beneficiaries from $7,050 to $2,000 starting in 2025, thereby effectively eliminating the coverage gap;

At a federal level, President Trump reversed some of President Biden’s executive orders including rescinding Executive Order 14087 entitled “Lowering Prescription Drug Costs for Americans." President Trump may issue new executive orders designed to impact drug pricing.

A number of these and other proposed measures may require authorization through additional legislation to become effective.

Congress and the Trump administration have indicated that they will continue to seek new legislative measures to control drug costs.

The Inflation Reduction Act of 2022, or IRA includes several provisions that may impact our business to varying degrees, including provisions that reduce the out-of-pocket spending cap for Medicare Part D beneficiaries from $7,050 to $2,000 which became effective in 2025, thereby effectively eliminating the coverage gap;

impose new manufacturer financial liability on certain drugs under Medicare Part D, allow the U.S.

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Individual states in the United States have also become increasingly active in passing legislation and implementing regulations designed to control pharmaceutical and biological product pricing, including price or patient reimbursement constraints, discounts, restrictions on certain drug access and marketing cost disclosure and transparency measures, and designed to encourage importation from other countries and bulk purchasing.

Legally mandated price controls on payment amounts by third-party payors or other restrictions could harm our business, financial condition, results of operations and prospects.

Legally mandated price controls on payment amounts by third-party payors or other

restrictions could harm our business, financial condition, results of operations and prospects.

In addition, regional healthcare authorities and individual hospitals are increasingly using bidding procedures to determine what pharmaceutical products and which suppliers will be included in their prescription drug and other healthcare programs.

This could reduce the ultimate demand for our

drugs or put pressure on our drug pricing, which could negatively affect our business, financial condition, results of operations and prospects.

This could reduce the ultimate demand for our drugs or put pressure on our drug pricing, which could negatively affect our business, financial condition, results of operations and prospects.

We cannot predict what healthcare reform initiatives may be adopted in the future.

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In addition to EU regulations related to the approval and commercialization of our products, we may be subject to the EU’s General Data Protection Regulation, or GDPR.

The GDPR imposes stringent requirements for controllers and processors of personal

data of persons in the EU, including, for example, ensuring an appropriate legal basis or condition applies to the processing of personal data, more robust disclosures to individuals and a strengthened individual data rights regime, shortened timelines for data breach notifications, limitations on retention of information, increased requirements pertaining to special categories of data, such as health data, and additional obligations when we contract with third-party processors in connection with the processing of the personal data.

The GDPR imposes stringent requirements for controllers and processors of personal data of persons in the EU, including, for example, ensuring an appropriate legal basis or condition applies to the processing of personal data, more robust disclosures to individuals and a strengthened individual data rights regime, shortened timelines for data breach notifications, limitations on retention of information, increased requirements pertaining to special categories of data, such as health data, and additional obligations when we contract with third-party processors in connection with the processing of the personal data.

The GDPR also imposes strict rules on the transfer of personal data out of the European Union to the United States and other third countries.

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Human Capital Resources

As of December 31, 2023, we had 103 employees, 101 of whom were full-time and two who were part-time.

As of December 31, 2024, we had 164 employees, 161 of whom were full-time and 3 whom were part-time.

Of those, 135 were engaged in research and development activities.

All company employees are located in the United States.

Two full-time employees are located in Switzerland.

We do not have any employees that are represented by a labor union or covered under a collective bargaining agreement.

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In August 2018, our corporate name was changed to Cabaletta Bio, Inc.

Our principal executive offices are located at 2929 Arch Street, Suite 600, Philadelphia, PA 19104 and our telephone number is (267) 759-3100.

Our website address is www.cabalettabio.com.

We have two subsidiaries, Cabaletta Bio GmbH, incorporated in Switzerland and Cabaletta Bio (Germany) GmbH, incorporated in Germany.

Our principal executive offices are located at 2929 Arch Street, Suite 600, Philadelphia, PA 19104, and we have limited corporate and research operations in Germany and Switzerland.

Our telephone number is (267) 759-3100, and our website address is www.cabalettabio.com.

We do not incorporate the information on or accessible through our website into this Annual Report on Form 10-K, and you should not consider any information on, or that can be accessed through, our website to be part of this Annual Report on Form 10-K.

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All of the Company's tangible assets are held in the United States.

Refer to Note 2, Summary of Significant Accounting Policies, to our financial statements appearing elsewhere in this Annual Report on Form 10-K for additional information.

Refer to Note 8, Segment Information, to our consolidated financial statements appearing elsewhere in this Annual Report on Form 10-K for additional information.

We own or have rights to various trademarks, service marks and trade names that we use in connection with the operation of our business.

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These reports are also available at the SEC’s Internet website at www.sec.gov.

Investors and others should note that we announce material information to our investors using our investor relations website (https:// https://www.cabalettabio.com/investors), SEC filings, press releases, public conference calls and webcasts.

We use these channels as well as social media, including LinkedIn and X (formerly Twitter) (@CabalettaBio), to communicate with the public about our company, our business, our product candidates and other matters.

It is possible that the information we post on social media could be deemed to be material information.

Therefore, we encourage investors, the media, and others interested in our company to review the information we post on the social media channels listed on our investor relations website.

Information that is contained in and can be accessed through our website or our social media posts are not incorporated into, and does not form a part of, this Annual Report on Form 10-K.

A copy of our Corporate Governance Guidelines, Code of Conduct and Business Ethics and the charters of the Audit Committee, Compensation Committee and Nominating and Corporate Governance Committee are posted on our website, www.cabalettabio.com, under the heading “Investors & Media.”

Compared sentence by sentence after normalising whitespace, quotation marks, case and digits, so re-formatting and restated figures do not read as changed language. Wording changes appear as one removal and one addition. The current filing and the prior one are authoritative.

What changed 10-K

Item 1. Business