Cabaletta Bio Reports Fourth Quarter and Full Year 2022 Financial Results and Provides Business Update Company expecting Investigational New Drug (IND) clearance in the first half of 2023 for CABA-201, a 4-1BB-containing

Cabaletta Bio Reports Fourth Quarter and Full Year 2022 Financial Results and Provides Business Update

Company expecting Investigational New Drug (IND) clearance in the first half of 2023 for

CABA-201, a 4-1BB-containing fully human CD19-CAR T cell therapy, with potential to

generate initial clinical data by the first half of 2024

PHILADELPHIA, March 16, 2023 Cabaletta Bio, Inc.

(Nasdaq: CABA), a clinical-stage biotechnology company focused on developing and launching the first curative targeted cell therapies for patients with autoimmune diseases, today reported financial results for the fourth quarter and full year ended

December 31, 2022, and provided a business update.

As we seek FDA clearance for CABA-201 in the next

few months, we believe that our specifically designed product candidate for autoimmune patients, our experience with efficient autoimmune cell therapy clinical trial design coupled with timely implementation of complicated autoimmune cell therapy

trials and our exclusive translational research partnership with Georg Schett, M.D., which is currently delivering actionable clinical insights, provide us with the opportunity to deliver potentially transformative outcomes for patients with a broad

range of autoimmune diseases, said Steven Nichtberger, M.D., Chief Executive Officer and Co-founder of Cabaletta. In parallel, we continue to make progress on our pipeline of clinical-stage CAART

legacy product candidates, with 1-month safety and persistence data for the combination sub-study in the

DesCAARTes trial for DSG3-CAART anticipated in the first half of 2023 and recruitment in the MusCAARTes trial for MuSK-CAART

ongoing. Looking ahead, we are confident in our ability to advance our autoimmune-focused pipeline for patients with serious unmet need and deliver on multiple upcoming value-creating milestones.

Recent Operational Highlights and Upcoming Milestones

Chimeric Antigen Receptor T cells for Autoimmunity (CARTA) Strategy

CABA-201: Autologous, engineered T cells with a chimeric antigen receptor containing a fully human CD19

binder and a 4-1BB co-stimulatory domain as a potential treatment for a broad range of autoimmune diseases where B cells contribute to the initiation and/or maintenance

Chimeric AutoAntibody Receptor T (CAART) cells Strategy

DSG3-CAART: Desmoglein 3 chimeric autoantibody receptor T (DSG3-CAART) cells as a potential treatment for patients with mucosal pemphigus vulgaris

Muscle-specific kinase (MuSK) chimeric autoantibody receptor T (MuSK-CAART) cells as a potential treatment for patients with MuSK-associated myasthenia gravis.

Corporate Highlights

Cabaletta will participate in the upcoming 22nd Annual Needham Virtual Healthcare Conference, which is being held from April 17 20,

Fourth Quarter and Full Year 2022 Financial Results

The Company expects that its cash, cash equivalents and

investments as of December 31, 2022, will enable it to fund its operating plan into the first quarter of 2025.

Cabaletta Bio (Nasdaq: CABA) is 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. The CABA platform encompasses two strategies: the CARTA (chimeric antigen receptor

T cells for autoimmunity) strategy, with CABA-201, a 4-1BB-containing CD19-CAR T, as the

lead product candidate, and the CAART (chimeric autoantibody receptor T cells) strategy, with multiple clinical-stage candidates, including DSG3-CAART for mucosal pemphigus vulgaris and MuSK-CAART for MuSK myasthenia gravis. The expanding CABA platform may offer potentially curative therapies for patients with a broad range of autoimmune diseases. Cabaletta Bio s headquarters are located in Philadelphia, PA.

Forward-Looking Statements

This press release contains

forward-looking statements of Cabaletta Bio within the meaning of the Private Securities Litigation Reform Act of 1995, as amended, including without limitation, express or implied statements regarding expectations regarding:

Cabaletta s ability to grow its autoimmune-focused pipeline; the ability to capitalize on and potential benefits resulting from the translational research partnership with Georg Schett, M.D., and the exclusive license agreement with IASO Bio;

the company s business plans and objectives; the timing of its IND clearance for CABA-201, initiation of clinical evaluation of CABA-201 and generation of initial

clinical data for CABA-201; statements regarding anticipated significance of, and timing of release of, safety and persistence data and combination cohort data; statements regarding regulatory filings for its

development programs, including the planned timing of such regulatory filings and potential review by such regulatory authorities; the expectation that Cabaletta Bio may improve outcomes for patients suffering from mPV, MG, or other autoimmune

diseases; the progress and results of its DesCAARTes Phase 1 trial and MusCAARTes Phase 1 trial, including Cabaletta s ability

to enroll the requisite number of patients, dose each dosing cohort in the intended manner, and progress the trial; the ability to accelerate Cabaletta s pipeline and develop meaningful therapies for patients, including in collaboration with

academic and industry partners and the ability to optimize such collaborations on its development programs; use of capital, expenses, future accumulated deficit and other financial results in the future; ability to fund operations into the first

quarter of 2025; and the anticipated contribution of the members of Cabaletta s executives to the company s operations and progress.

forward-looking statements in this press release are based on management s current expectations and beliefs of future events, and are subject to a number of risks and uncertainties that could cause actual results to differ materially and

adversely from those set forth in or implied by such forward-looking statements. These risks and uncertainties include, but are not limited to: risks related to regulatory filings and potential clearance; the risk that signs of biologic activity or

persistence may not inform long-term results; Cabaletta s ability to demonstrate sufficient evidence of safety, efficacy and tolerability in its preclinical studies and clinical trials of DSG3-CAART, MuSK-CAART and CABA-201; the risk that the results observed with the similarly-designed construct employed in the recent Nature Medicine and Lancet Rheumatology publications are not indicative of the results we seek

to achieve with CABA-201; risks related to clinical trial site activation or enrollment rates that are lower than expected; risks related to unexpected safety or efficacy data observed during clinical studies;

risks related to volatile market and economic conditions; risks related to the impact of public health epidemics affecting countries or regions in which Cabaletta has operations or does business, such as

COVID-19; Cabaletta s ability to retain and recognize the intended incentives conferred by Orphan Drug Designation and Fast Track Designation for its product candidates, as applicable; risks related to

Cabaletta s ability to protect and maintain its intellectual property position; risks related to fostering and maintaining successful relationships with Cabaletta s collaboration and manufacturing partners; uncertainties related to the

initiation and conduct of studies and other development requirements for its product candidates; the risk that any one or more of Cabaletta s product candidates will not be successfully developed and/or commercialized; and the risk that the

initial or interim results of preclinical studies or clinical studies will not be predictive of future results in connection with future studies. For a discussion of these and other risks and uncertainties, and other important factors, any of which

could cause Cabaletta s actual results to differ from those contained in the forward-looking statements, see the section entitled Risk Factors in Cabaletta s most recent annual report on Form

10-K as well as discussions of potential risks, uncertainties, and other important factors in Cabaletta s other filings with the Securities and Exchange Commission. All information in this press release

is as of the date of the release, and Cabaletta undertakes no duty to update this information unless required by law.

SELECTED FINANCIAL DATA

(unaudited; in thousands, except share and per share data)

Statements of Operations

Selected Balance Sheet Data

Chief Financial Officer

Stern Investor Relations, Inc.