Disclaimer The following presentation, including any printed or electronic copy of these slides, the talks given by the presenters, the information communicated during any delivery of the presentation and any question an

Corporate Presentation FEBRUary 2025

Disclaimer The following presentation,

including any printed or electronic copy of these slides, the talks given by the presenters, the information communicated during any delivery of the presentation and any question and answer session and any document or material distributed at or in

connection with the presentation (collectively, the "Presentation") has been prepared by Cabaletta Bio, Inc. ("we," "us," "our," "Cabaletta" or the "Company") and is made for

informational purposes only. This Presentation does not purport to be a prospectus, to be complete or to contain all of the information you may desire. Statements contained herein are made as of the date of this Presentation unless stated otherwise,

and this Presentation shall not under any circumstances create an implication that the information contained herein is correct as of any time after such date or that information will be updated or revised to reflect information that subsequently

becomes available or changes occurring after the date hereof. This Presentation may contain "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995 relating to our business, operations, and

financial conditions, and include, but are not limited to, express or implied statements regarding our current beliefs, expectations and assumptions regarding: our business, future plans and strategies for our CAAR T technology; our ability to grow

our autoimmune-focused pipeline; the ability to capitalize on and potential benefits resulting from our research and translational insights; including those related to any similarly-designed constructs or dosing regimens; the anticipated market

opportunities for rese-cel in patients with autoimmune diseases; the Company's business plans and objectives; our expectations around the potential success and therapeutic and clinical benefits of rese-cel and our other product candidates, as

well as our ability to successfully complete research and further development and commercialization of our drug candidates in current or future indications, including the timing and results of our clinical trials and our ability to conduct and

complete clinical trials; expectation that clinical results will support rese-cel's safety and activity profile; our plan to leverage increasing clinical data and a unique development program for rese-cel; the clinical significance of the clinical

data read-out at upcoming medical or scientific meetings; our belief that rese-cel has the potential to provide drug-free, durable meaningful clinical responses, through an immune reset, including the potential for achieving drug-free remission in

patients with refractory myositis; the Company's advancement of separate Phase 1/2 clinical trials of rese-cel in patients with SLE, myositis, SSc and gMG and advancement of the RESET-PV and RESET-MS trials, including updates related to status,

safety data, efficiency of clinical trial design and timing of data read-outs or otherwise; our ability to leverage our experience in autoimmune cell therapy; our ability to enroll the requisite number of patients, dose each dosing cohort in the

intended manner and timing thereof, and advance the trial as planned in our Phase 1/2 clinical trials of rese-cel; the timing any planned regulatory filings for our development programs, including IND applications; the progress and results of our

MusCAARTes Phase 1 trial, and impact around reported safety and clinical and translational data of cohorts from our MusCAARTes Phase 1 trial; Cabaletta's advancement of the whole blood manufacturing program to remove the burden of

apheresis; statements regarding the timing of regulatory filings and interactions with regulatory authorities, including such authorities' review of safety information from our ongoing clinical trials and potential registrational pathway for

rese-cel; our ability to successfully complete our preclinical and clinical studies for our product candidates, including our ability to enroll the requisite number of patients, dose each dosing cohort in the intended manner, and progress the trial;

our ability to increase enrollment from our rapidly expanding clinical network in the RESET clinical trial program in the US and Europe; our ability to obtain and maintain regulatory approval of our product candidates, including our expectations

regarding the intended incentives conferred by and ability to retain Fast Track Designations for our product candidates; our ability to accelerate our pipeline to approval and launch and to develop meaningful therapies for patients, including in

collaboration with academic and industry partners and the ability to optimize such collaborations on our development programs; our ability to contract with third-party suppliers and manufacturers and retain such manufacturers, whether due to

legislative action or otherwise; to implement an enhanced manufacturing process and further develop our internal manufacturing strategy, capabilities and facilities; our ability to execute our manufacturing strategy to enable expansion of clinical

supply and efficiently scale commercial supply for rese-cel; our potential commercial opportunities, including value and addressable market, for our product candidates. Words such as, but not limited to, "look forward to,"

"believe," "expect," "anticipate," "estimate," "intend," "plan," "would," "should" and "could," and similar expressions or words, identify

forward-looking statements. Various risks, uncertainties and assumptions could cause actual results to differ materially from those anticipated or implied in our forward-looking statements. Such risks and uncertainties include, but are not limited

to, risks related to the success, cost, and timing of our product candidate development activities and preclinical studies and clinical trials, risks related to our ability to demonstrate sufficient evidence of safety, efficacy and tolerability in

our preclinical studies and clinical trials of rese-cel and MuSK-CAART, the risk that the results observed with the similarly-designed construct, including, but not limited to, due to dosing regimen, are not indicative of the results we seek to

achieve with rese-cel, the risk that signs of biologic activity or persistence may not inform long-term results, the risk that persistence observed with effective CD19-CAR T oncology studies in combination with lymphodepletion is not indicative of,

or applicable to, clinical responses in patients with mPV, risks related to clinical trial site activation or enrollment rates that are lower than expected, our ability to demonstrate sufficient evidence of safety, efficacy and tolerability in its

preclinical studies and clinical trials of rese-cel; risks that modifications to trial design or approach may not have the intended benefits and that the trial design may need to be further modified; our ability to protect and maintain our

intellectual property position, risks related to our relationships with third parties, uncertainties related to regulatory agencies' evaluation of regulatory filings and other information related to our product candidates, our ability to

retain and recognize the intended incentives conferred by any Orphan Drug Designations and Fast Track Designations, risks related to regulatory filings and potential clearance, the risk that any one or more of our product candidates will not be

successfully developed and commercialized, the risk that the results of preclinical studies or clinical studies will not be predictive of future results in connection with future studies, and risks related to volatile market and economic conditions

and public health crises. New risks and uncertainties may emerge from time to time, and it is not possible to predict all risks and uncertainties. Except as required by applicable law, we do not plan to publicly update or revise any forward-looking

statements contained herein, whether as a result of any new information, future events, changed circumstances or otherwise. Although we believe the expectations reflected in such forward-looking statements are reasonable, we can give no assurance

that such expectations will prove to be correct. Accordingly, you are cautioned not to place undue reliance on these forward-looking statements. No representations or warranties (expressed or implied) are made about the accuracy of any such

forward-looking statements. For a discussion of these and other risks and uncertainties, and other important factors, any of which could cause our actual results to differ materially from those contained in the forward-looking statements, see the

section entitled "Risk Factors" in our most recent annual report on Form 10-K, as well as discussions of potential risks, uncertainties, and other important factors in our other and subsequent filings with the Securities and Exchange Commission.

Certain information contained in this Presentation relates to or is based on studies, publications, surveys and other data obtained from third-party sources and the Company's own internal estimates and research. While the Company believes

these third-party sources to be reliable as of the date of this Presentation, it has not independently verified, and makes no representation as to the adequacy, fairness, accuracy or completeness of, any information obtained from third-party

sources. The Company is the owner of various trademarks, trade names and service marks. Certain other trademarks, trade names and service marks appearing in this Presentation are the property of third parties. Solely for convenience, the trademarks

and trade names in this Presentation are referred to without the and TM symbols, but such references should not be construed as any indicator that their respective owners will not assert, to the fullest extent under applicable law, their

Develop and launch the first curative

targeted cellular therapies for patients with autoimmune diseases

Planning to leverage increasing

clinical data and unique development program for rese-cel1 2025: Pursuing an efficient path to approval CRS, cytokine release syndrome; DM - dermatomyositis; DORIS - definition of remission in SLE; ICANS, immune effector cell-associated

neurotoxicity syndrome; LN - lupus nephritis; PK - pharmacokinetic; PD - pharmacodynamic; SLE - systemic lupus erythematosus; TIS - total improvement score. resecabtagene autoleucel; CABA-201 As of Jan 8, 2025. As of

Feb 13, 2025. Golder, et al. Lupus. 2018;27(3): 501-506 Unique development strategy designed to accelerate time to approval and launch Compelling clinical efficacy with favorable safety profile & deep B cell depletion Multiple near-term

catalysts including clarity on potential path to approval Multiple disease-specific trials with a common design allow for generation of disease-specific efficacy data with shared safety database Weight-based dose, single infusion; supported by

clinical & translational data2 Industry-leading clinical network: 50 active US and European sites 26 patients enrolled Enrolling ~1 pt/week since Nov. 20243 Deepening clinical efficacy data over-time with immunosuppressant and steroid-free

outcomes2: DORIS remission in 3 SLE patients Complete renal response in 1st LN pt Major TIS response in 1st DM patient Favorable safety profile in 1st 10 patients 90% either no CRS or Grade 1 CRS 90% no ICANS Deep systemic B cell depletion observed

in the periphery and confirmed in the tissue in scleroderma patient by lymph node biopsy Meeting scheduled with FDA to align on registrational trial designs in 1H25 for rese-cel Enroll and complete dosing in multiple disease-specific cohorts in 2025

Present clinical data on rese-cel at medical meetings throughout 2025, including data evaluating rese-cel without preconditioning Patients are seeking a drug-free, symptom-free life which is rarely achieved despite current therapies; physicians also

prioritize prevention of end-organ damage4

RESET clinical program has

disease-specific cohorts designed to evolve directly into registrational studies Innovative clinical strategy with potential for accelerated regulatory path Program1 Trial Preclinical Phase 1/2 Pivotal Rese-cel (CABA-201) 4-1BB CD19-CAR T

RESET-Myositis CARTA Chimeric Antigen Receptor T cells for Autoimmunity RESET-SLE RESET-SSc RESET-MG RESET-MS RESET-PV Dermatomyositis Antisynthetase syndrome Immune-mediated necrotizing myopathy Lupus

Nephritis Non-Renal SLE Skin + Organ Cohort AChR-Ab neg. gMG AChR-Ab pos. gMG Skin Cohort Rheumatology Neurology Dermatology FTD Mucocutaneous & mucosal pemphigus vulgaris Contains cohort(s) without preconditioning Juvenile Myositis Pediatric

Indication RESET - REstoring SElf-Tolerance; Ab - Antibody; AChR - Acetylcholine receptor; gMG - Generalized myasthenia gravis; MS - Multiple sclerosis; SLE - Systemic lupus erythematosus Additional

pipeline candidate includes MuSK-CAART for MuSK-Ab positive MG, currently being evaluated in a Phase 1 trial. FDA Fast Track Designation received in dermatomyositis, SLE and lupus nephritis, systemic sclerosis, mucosal pemphigus vulgaris, MuSK-Ab

positive MG, and multiple sclerosis. Progressive MS Relapsing MS

Chimeric Antigen Receptor T Cells for

Autoimmunity (rese-cel)

~150 autoimmune patients have been

dosed with a range of autologous CAR T constructs (industry & academia)1 Autologous CAR T is potentially transformational for autoimmunity IIM - idiopathic inflammatory myopathy; MG - Myasthenia gravis; MS - Multiple sclerosis;

SPS - Stiff person syndrome; SSc - Systemic sclerosis. Note: Other' indications includes CIDP, IgG4-related disease, ANCA-associated vasculitis, NMOSD, Lambert Eaton myasthenic syndrome, autoimmune encephalitis. 1. Data as

of November 2024 (ACR Convergence 2024) based on Cabaletta Bio literature review across industry and academia. 2. Abstract 1749: Safety and Long-term Efficacy of CD19-CAR T-cell Therapy in 30 Patients with Autoimmune Disease. ACR Convergence 2024.

Compelling immunosuppressant-free clinical responses observed across many autoimmune diseases, durable for up to 4 years Clinical recurrences observed in <5% of ~150 treated patients IIM patient relapsed after 12+ months of drug-free remission No

evidence of CD19 escape or failure Patient treated with BCMA-CAR T & now in remission2 ~150 Patients Treated (by Disease) Type of CAR T Construct Efficacy Observations1 Safety Observations1 Among ~150 autoimmune patients dosed with cell therapy,

frequency and severity of CRS/ICANS events were considerably lower than those observed in cancer patients <2% Gr 3+ CRS & Gr 3+ ICANS events observed Vaccine titers stable with CD19-CAR T mono-targeting therapy insufficient data with

CD19xBCMA-CAR T 31% 60% 8%

Cabaletta rese-cel binder with similar

in vitro & in vivo activity to construct used in academic studies1,3 Rese-cel: CD19-CAR T specifically designed for autoimmunity Peng, Binghao J, et al. "Preclinical specificity and activity of CABA-201, a fully human 4-1BB containing CD19

CAR T therapy for treatment-resistant autoimmune disease." Poster presented at: American Society Gene and Cell Therapy 26th Annual Meeting; 2023 May 19; Los Angeles, CA. 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): 5832-5847. M ller, Fabian, et al. "CD19 CAR T-Cell Therapy in Autoimmune Disease-A Case Series with Follow-up."

New England Journal of Medicine 390.8 (2024): 687-700. Maschan, Michael, et al. "Multiple site place-of-care manufactured anti-CD19 CAR-T cells induce high remission rates in B-cell malignancy patients." Nature Communications 12, 7200

(2021) Transmembrane domain in rese-cel is CD8 vs. TNFRSF19 (Troy) utilized in the academic construct. The two transmembrane domains have not been shown to have a significant difference in function or IFN- production in preclinical

studies. The CD8 transmembrane domain is employed in tisagenlecleucel. Volkov, Jenell, et al. "Case study of CD19 CAR T therapy in a subject with immune-mediate necrotizing myopathy treated in the RESET-Myositis phase I/II trial."

Molecular Therapy 32.11 (2024): 3821-3828. Abstract 1733: Safety and Efficacy of CABA-201, a Fully Human, Autologous 4-1BB Anti-CD19 CAR T Cell Therapy in Patients with Immune-Mediated Necrotizing Myopathy and Systemic Lupus Erythematosus from the

RESET-MyositisTM and RESET-SLETM Clinical Trials. ACR 2024. Rese-cel product design & clinical / translational data 4-1BB costimulatory domain with fully human binder Binder with similar affinity & biologic activity to academic FMC63 binder

while binding to the same epitopes1,2 Same weight-based dose as in academic studies Potential to provide immune reset based on initial clinical and translational data5 Initial patients treated with rese-cel have shown compelling clinical responses

with safety data that supports autoimmune development6 Fully human anti-CD19 binder 4-1BB costimulatory domain CD3- signaling domain Rese-cel4

Broad portfolio with six RESET trials

designed to address high unmet need and realize the potential of rese-cel RESET program addressing several autoimmune markets SLE - Systemic lupus erythematosus; DM - Dermatomyositis; SSc - Systemic sclerosis; gMG -

Generalized myasthenia gravis; MS - multiple sclerosis; ESRD - End-stage renal disease; PV - pemphigus vulgaris SSc gMG PV ~90k ~55k ~15k Middle age onset common Progressive skin & organ fibrosis with lung, cardiac, renal

damage Average survival of 12y Bimodal age of onset Profound weakness that can be disabling Risk for myasthenic crises, with respiratory failure Phase 1/2 Trials Rheum Neuro Derm No Flu/Cy Pure autoantibody & B-cell mediated autoimmune disease

Characterized by painful blisters & erosions SLE ~160-320k Affects young women & people of color ~40% with lupus nephritis, which carries ~25% risk of death or ESRD within 10y > > > Myositis ~70k Typical onset middle age Only

FDA-approved therapy is IVIg in DM High mortality due to lung & cardiac involvement > MS ~750k Chronic inflammation, axon loss, cognitive impairment, and irreversible neurologic damage > ~85k ~150k ~60k ~100k ~550k ~20k U.S. Prevalence EU

Designed to evaluate the safety and

tolerability of rese-cel in subjects with active, refractory disease Key inclusion and exclusion criteria in RESETTM clinical program ASyS, antisynthetase syndrome; CAR, chimeric antigen receptor; DM, dermatomyositis; HSCT, hematopoietic stem

cell transplantation; IIM, idiopathic inflammatory myopathy; JIIM, juvenile idiopathic inflammatory myopathy; LN, lupus nephritis; MAA, myositis-associated antibody; SLEDAI-2k, SLE disease activity index 2000; SSc, systemic sclerosis. 1.

ClinicalTrials.gov. Available at: www.clinicaltrials.gov/study/NCT06121297 (accessed October 2024). 2. ClinicalTrials.gov. Available at: www.clinicaltrials.gov/study/NCT06328777 (accessed October 2024). 3. ClinicalTrials.gov. Available at:

www.clinicaltrials.gov/study/NCT06154252 (accessed October 2024). RESET-SLE Diagnosis of SLE (SLE or LN) Age 18 and 65 Positive ANA or anti-dsDNA at screening SLE (non-renal): active, moderate to severe SLE, SLEDAI-2K 8;

pure class V LN eligible LN: active, biopsy-proven LN class III or IV ( class V) RESET-Myositis Diagnosis of IIM (ASyS, DM, or IMNM) Age 18 and 75 Presence of at least one myositis antibody JIIM: Age 6 and 17

with presence of at least one MSA or MAA Diagnosis of SSc limited or diffuse Age 18 and 70 Evidence of significant skin, pulmonary, renal, or cardiac involvement RESET-SSc Evidence of active disease despite prior or current

treatment with standard of care Key inclusion criteria1-3 Key exclusion criteria1-3 B cell-depleting agent within prior 3-6 months; Previous CAR T therapy and/or HSCT Presence of kidney disease other than LN Current symptoms of severe,

progressive, or uncontrolled pulmonary or cardiac disease Cancer-associated myositis Significant lung or cardiac impairment Severe lung or cardiac impairment Anticipate enrolling and completing dosing in multiple disease-specific cohorts in 2025;

similarly designed RESET-MG Phase 1/2 trial enrolling

Individual trials in myositis, SLE,