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 April 2021

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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

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Develop and launch the first curative

targeted cellular therapies for patients with autoimmune diseases

Cabaletta overview Developing highly

specific CAAR T products to treat B cell-mediated autoimmune diseases Where there is a biologic opportunity for deep and durable, perhaps curative, responses Leveraging a clinically validated CAR T product design and manufacturing process through

Penn alliance Preclinical pipeline led by MuSK-CAART for myasthenia gravis - IND filing planned in 2H211 Product portfolio2 currently targeting diseases that affect over 80,000 patients in the US Issued U.S. patent on lead clinical program with

emerging differentiated IP portfolio First issued CAAR T product patent covers all or any part of the relevant human antigens (DSG3 and DSG1) Phase 1 DesCAARTesTM trial ongoing for patients with mucosal pemphigus vulgaris (mPV) Acute safety data

from initial cohort of the DesCAARTes trial expected in 1H21 followed by additional cohort data in 2H211 First patient dosed without observing any dose limiting toxicity (DLT) Cash runway through at least 3Q22 with $109M in cash and

investments as of December 31, 2020 Assumes no future impact due to COVID-19. Includes four disclosed product candidates and three undisclosed disease targets in our pipeline through expansion of our Sponsored Research Agreement with the University

2020 progress and anticipated 2021

milestones Validate MuSK-CAART manufacturing process with CMO partner DSG3-CAART Multiple U.S. sites open for enrollment Dosing initiated in DesCAARTes clinical trial Acute safety data from first cohort 1H211 In vivo target engagement data

presented at AAN MuSK-CAART Fast Track and Orphan Drug Designation IND-enabling studies initiated IND filing 2H211 1. Assumes no future impact due to COVID-19. Additional topline data on completed dose cohort(s) 2H211

Our scientific platform leverages

clinically validated CAR T technology CAR T Therapy Chimeric Antigen Receptor T cell Kymriah CAAR T product candidates are designed for selective and specific elimination of the pathogenic B cells CAAR T Therapy Chimeric AutoAntibody Receptor T cell

CABA CAAR T AUTOANTIGEN (e.g. DSG3, MuSK ) CD137 (4-1BB) Costimulatory Domain CD3-Zeta Signaling Domain HEALTHY B CELL

CABA (Cabaletta Approach for

Selective B cell Ablation) platform Epitope mapping to determine regions targeted by autoantibodies Optimize CAAR construct / design with the goal of selectively ablating reactive B cells Preclinical in vitro and in vivo testing to evaluate efficacy

and safety Scientific, clinical and commercial assessment to inform product candidate development Vector & Clinical Cell manufacturing Clinical trials DSG3-CAART MuSK-CAART

Therapeutic Area Indication Program

Discovery2 Preclinical Phase 1 Phase 2/3 Dermatology Mucosal Pemphigus Vulgaris DSG3-CAART Mucocutaneous Pemphigus Vulgaris DSG3/1-CAART Neurology MuSK Myasthenia Gravis MuSK-CAART Hematology Hemophilia A w/ FVIII Alloantibodies FVIII-CAART

Pipeline1 includes multiple disease targets where cure is possible Three additional undisclosed disease targets added to our pipeline portfolio through expansion of our Sponsored Research Agreement with the University of Pennsylvania are not shown.

In our discovery stage, we perform epitope mapping and optimize CAAR construct and design. Current pipeline includes 7 programs targeting diseases affecting >80,000 patients in the US

DSG3-CAART for patients with mucosal

DSG3 antibodies are widely

considered to be necessary and sufficient to cause PV1 PV is an optimal lead indication for CAAR T therapy Spindler, Volker, et al. "Mechanisms causing loss of keratinocyte cohesion in pemphigus." Journal of Investigative Dermatology 138.1 (2018):

32-37. Schmidt, Enno, et al. "Novel ELISA systems for antibodies to desmoglein 1 and 3." Experimental dermatology 19.5 (2010): 458-463. Joly, Pascal, et al. "First-line rituximab combined with short-term prednisone versus prednisone alone for the

treatment of pemphigus (Ritux 3): a prospective, multicentre, parallel-group, open-label randomised trial." The Lancet 389.10083 (2017): 2031-2040. Mouquet, Hugo, et al. "B-cell depletion immunotherapy in pemphigus: effects on cellular and humoral

immune responses." Journal of Investigative Dermatology 128.12 (2008): 2859-2869. Hammers, Christoph M., et al. "Persistence of anti-desmoglein 3 IgG+ B-cell clones in pemphigus patients over years." Journal of Investigative Dermatology 135.3

(2015): 742-749. Ohyama, Bungo, et al. "Epitope spreading is rarely found in pemphigus vulgaris by large-scale longitudinal study using desmoglein 2-based swapped molecules." Journal of investigative dermatology 132.4 (2012): 1158-1168.

Ellebrecht, Christoph T., et al. "Reengineering chimeric antigen receptor T cells for targeted therapy of autoimmune disease." Science 353.6295 (2016): 179-184. Serum anti-DSG3 antibodies are 98 - 100% sensitive and specific2 1 The DSG3 CAAR has

published animal model proof-of-concept validation7 5 Depletion of B cells by rituximab3 or antibody by plasmapheresis transiently improves clinical disease 2 The B cell repertoire and antigenic epitopes on DSG1/3 are well understood6, and formed

the basis for DSG3 and DSG1 CAAR designs 4 Incomplete B cell depletion by rituximab leads to PV recurrences, with identical disease-causing B cell clones4,5 3 anti- dsg anti- dsg

Current treatments require broad

immunosuppression associated with safety risks and transient efficacy Overview of Pemphigus Vulgaris Image credit: D@nderm. Rituximab label, 08/2020 revision. Joly, Pascal, et al. "First-line rituximab combined with short-term prednisone versus

prednisone alone for the treatment of pemphigus (Ritux 3): a prospective, multicentre, parallel-group, open-label randomised trial." The Lancet 389.10083 (2017): 2031-2040. Kushner, Carolyn J., et al. "Factors Associated With Complete

Remission After Rituximab Therapy for Pemphigus." JAMA dermatology (2019). Tony, Hans-Peter, et al. "Safety and clinical outcomes of rituximab therapy in patients with different autoimmune diseases: experience from a national registry

(GRAID)." Arthritis research & therapy 13.3 (2011): 1-14. Current Treatment Landscape Broad immunosuppression3,4 Modestly effective Poorly tolerated Rituximab plus steroids (~2,800mg/yr)2 Response: ~40% of patients achieved a 16-week period with

no lesions or medicines during 1 yr2 5-9%2,3 annual risk of severe infection in PV Real world data indicate: Transient remission ~ 70% CROT4: ~30% relapse in 1 year4 >50% relapse within 2 years4 ~30% never achieve CROT4 ~1.9% lifetime risk of

fatal infection5 CROT = 8+ weeks without lesions while off systemic therapy http://www.danderm-pdv.is.kkh.dk/atlas/3-157.html http://www.dermis.net/bilder/CD008/550px/img0042.jpg Mucosal PV1 25% of U.S. pemphigus vulgaris Mucocutaneous PV1 75% of

U.S. pemphigus vulgaris Associated Antibody Anti-DSG3 Anti-DSG3 + Anti-DSG1 Clinical Signs Painful blisters of the mucous membranes (mouth, nose, larynx, esophagus, eyes, genitalia, rectum) Blisters on orifices and skin US Disease Prevalence 3,250

to 4,750 9,750 to 14,250

DSG3-CAART encompasses all known

pathogenic epitopes Ohyama, Bungo, et al. "Epitope spreading is rarely found in pemphigus vulgaris by large-scale longitudinal study using desmoglein 2-based swapped molecules." Journal of investigative dermatology 132.4 (2012): 1158-1168.

Antibodies that target the specific extracellular domain are shown below each extracellular domain. EC5 directed antibodies are not known to be pathogenic DSG3-CAART Costimulatory Domains anti-EC4 P2C1, P5D4, P5B6, P3A6, P5E4 2 anti-EC3 AK18 2

anti-EC2 PVB28, AK19 2 anti-EC1 AK23, Px43, Px44, 6G2C11, F779 2 EC1 EC2 EC3 EC4 Transmembrane Domain Cytoplasmic tail % of PV sera targeting each domain1 91% 71% 51% 19% 12% EC5 EC1 EC2 EC3 EC4 CD137 CD3z DSG3 Protein

Tolerability Target Engagement No

evidence of toxicity at clinically relevant doses with selective and specific target engagement DSG3-CAART preclinical data1,2 INDICATOR RESULTS In vitro off-target toxicity No specific cytotoxicity at clinically relevant cell numbers vs

FcgR-expressing cells No confirmed interactions with human membrane proteins In vivo off-target toxicity No off-target effects detected at clinically relevant doses Anti-DSG3 autoantibody titer Serologic remission' -

dose-dependent elimination of anti-DSG3 B cells and antibodies CAAR T cell engraftment Dose-dependent increase in CAAR-positive cells observed via flow cytometry Tissue blistering Histologic remission' - no blistering of oral

mucosa Anti-DSG3 hybridoma outgrowth Significantly delayed outgrowth despite soluble anti-DSG antibodies Ellebrecht, Christoph T., et al. "Reengineering chimeric antigen receptor T cells for targeted therapy of autoimmune disease." Science 353.6295

(2016): 179-184. 2. Lee, Jinmin, et al. "Antigen-specific B-cell depletion for precision therapy of mucosal pemphigus vulgaris." The Journal of Clinical Investigation (2020).

Study Endpoint & Objectives

Primary Endpoint: Adverse Events, including Dose Limiting Toxicity (DLT) DLTs include any grade 3 or 4 CRS or neurotoxicity, or any grade 2 CRS or neurotoxicity that failed to improve to Grade 1 or baseline within 7 days Secondary

Objectives: DSG3 ELISA titer changes, rate of/time to/duration of remission, manufacturing success rate, CAAR T expansion/persistence DesCAARTes : Phase 1 clinical trial in mucosal-dominant PV (mPV) patients FDA has requested, and the Company

has agreed, that we will share data from part A to inform a discussion on the optimal design of part C. According to FDA advice, the submission of part A data is not gating to planned enrollment in part B. Open-label study to determine the maximum

tolerated dose & fractionation of DSG3-CAART Part Cohort # Subjects A - Dose Escalation Fractionated infusion at increasing dose levels A1-A4 3 (+3) per cohort B - Dose Consolidation Consolidating selected dose fractions into a

single infusion B1-B2 3 (+3) per cohort C - Expansion1 Expanded subject enrollment at final selected dose C ~12 Total ~30 (+18) Age: 18 Inadequately managed by standard immunosuppressive therapies Confirmed diagnosis Active disease

Anti-DSG3 antibody positive Rituximab recently administered Prednisone > 0.25mg/kg/day Other autoimmune disorder requiring immunosuppressive therapies Recent investigational treatment ALC < 1,000 at screening Major Inclusion Criteria Major

Exclusion Criteria SCREENING PERIOD FOLLOWED (2-4 WEEKS) TREATMENT PERIOD (1-3 WEEKS) Next Patient

Safety assessed acutely (Day 8) and

at 3 months, with ability to measure CAAR T engagement by 6 months DesCAARTes clinical trial assessments and timeframes Spindler, Volker, et al. "Mechanisms causing loss of keratinocyte cohesion in pemphigus." Journal of Investigative

Dermatology 138.1 (2018): 32-37. This information represents data that we believe can be used to inform potential efficacy endpoints in future clinical development. Dasyam, Nathaniel, Philip George, and Robert Weinkove. "Chimeric antigen receptor

T cell therapies: Optimising the dose." British journal of clinical pharmacology 86.9 (2020): 1678-1689. Raje, Noopur, et al. "Anti-BCMA CAR T-cell therapy bb2121 in relapsed or refractory multiple myeloma." New England Journal of Medicine

380.18 (2019): 1726-1737. Up to Wk -18 Wk -18 to -1 Day -7 to -3 Pre-infusion visit DSG3-CAART INFUSION Day 8 Acute safety data 3 Months Primary safety endpoint 6 Months Evidence of target engagement 3 Years Efficacy 15 Years Long-term follow-up

8-10 weeks from screening to infusion Day 8 acute safety data Monitors for key risks: CRS / neurotoxicity Impact of soluble antibody Other adverse events Target engagement to be assessed by declining anti-DSG3 titers1,2 We believe initial signal

would be evidenced by ~20% or more reduction in anti-DSG3 titers, and a more robust decline would be expected with greater target engagement Translational program evaluating potential for in vivo expansion and threshold dose effect3,4 Other key

potential efficacy measures2 Disease activity (clinical) Steroid / immunosuppressive use Primary safety endpoint at 3 months Potential for disease flare during planned steroid taper

Preclinical studies demonstrated

DSG3-CAART target engagement in the presence of soluble antibodies Soluble antibodies may alter the dynamics of DSG3-CAART proliferation Ellebrecht, Christoph T., et al. "Reengineering chimeric antigen receptor T cells for targeted therapy of

autoimmune disease." Science 353.6295 (2016): 179-184. Antibodies derived from a hybridoma model. Non-transduced T cell. CFSE (carboxyfluorescein diacetate succinimidyl ester) is a dye used in flow cytometric monitoring that reduces in

intensity as it is distributed in actively dividing cells. Non-dividing cells will retain more CFSE dye. Lee, Jinmin, et al. "Antigen-specific B-cell depletion for precision therapy of mucosal pemphigus vulgaris." The Journal of Clinical

Investigation (2020). Soluble anti-DSG3 induced CAAR T cell proliferation Inhibitory antibodies may reduce, but do not prevent, DSG3-CAART target engagement Increased target engagement Decreased target engagement EC1-4 vs. PV Ab #12 EC1-4 vs. PV Ab

#22 NTD3 vs. PV Ab #12 NTD3 vs. PV Ab #22 Cell division Increased T cell division compared to response to normal human IgG 4 Observations Additionally, in an active immune model, DSG3-CAART demonstrated in vivo target engagement in the presence of

physiologic DSG3 antibodies5

DSG3-CAART demonstrated target