Cabaletta Bio Reports Second Quarter 2023 Financial Results and Provides Business Update Received second IND application clearance for CABA-201 in myositis as well as Fast Track Designation in SLE and LN Strengthened bal

Cabaletta Bio Reports Second Quarter 2023 Financial

Results and Provides Business Update

Received second IND application clearance for CABA-201 in myositis as well as Fast Track

Designation in SLE and LN

Strengthened balance sheet by closing $100M public offering extending cash runway into the

fourth quarter of 2025

PHILADELPHIA, Aug. 10, 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 second quarter ended June 30, 2023, and provided a business update.

As we continue to pursue our vision of launching the first CD19 CAR-T product for patients with autoimmune

diseases, we accelerated the progress of CABA-201 in the first half of 2023 by securing FDA clearance to initiate two separate and efficiently designed Phase 1/2 clinical trials in patients with systemic lupus

erythematosus and myositis. With separate parallel cohorts in each trial, we are well positioned to rapidly evaluate and develop CABA-201 for patients with autoimmune diseases, said Steven Nichtberger,

M.D., Chief Executive Officer of Cabaletta. Backed by a strong balance sheet that we believe positions us to deliver on our milestones, we continue to expect 3-month clinical data for initial patients

treated with CABA-201 by the first half of 2024. With expanding clinical evidence in the field, we look forward to building on our momentum and advancing our mission to develop and launch the first curative

targeted cellular therapies for patients with autoimmune diseases.

Recent Operational Highlights and Upcoming Anticipated 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

to participate in the following upcoming investor conferences:

Second Quarter 2023 Financial Results

The Company expects that its cash, cash equivalents and short-term

investments as of June 30, 2023, will enable it to fund its operating plan into the fourth 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 fully human

CD19-CAR T, as the lead product candidate being evaluated in systemic lupus erythematosus and myositis, 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 is designed to develop potentially curative therapies that offer

deep and durable responses for patients with a broad range of autoimmune diseases. Cabaletta Bio s headquarters and labs 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 its expectations regarding: Cabaletta s ability to grow its autoimmune-focused pipeline; its plans around CABA-201,

including its ability to enroll the requisite number of patients, dose each dosing cohort in the intended manner and advance the separate Phase 1/2 clinical trials of CABA-201 in each indication, as well as

leverage the potential therapeutic benefits from using the initial dose used in the September 2022 Nature Medicine publication; Cabaletta s ability to retain and recognize the intended incentives conferred from the Fast Track Designation

for CABA-201; the Company s business plans and objectives; the progress and results of its DesCAARTes Phase 1 trial, including Cabaletta s

ability to enroll the requisite number of patients in the additional combination cohort, dose each dosing cohort in the intended manner, and progress the trial; expectations for the

MusCAARTes Phase 1 trial, including potential trial timelines and the therapeutic benefits of MuSK-CAART; statements regarding anticipated significance of, and timing of release of, efficacy

endpoints and tolerability data for CABA-201 and its safety and persistence data and combination sub-study cohort data for its DesCAARTes trial; 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 SLE,

mPV, MG, or other autoimmune diseases as well as expected therapeutic benefits of the Company s product candidates; 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; availability of funding for existing

programs; and ability to fund operations into the fourth quarter of 2025.

Any 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 publication, including due to the dosing regimen, 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 and public

health crises; 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

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 subsequent and 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.