Cabaletta Bio (NASDAQ: CABA) prices $150M equity raise to fund rese-cel

Rhea-AI Filing Summary

Cabaletta Bio, Inc. is selling 51,725,000 shares of common stock at $2.90 per share in an underwritten public offering. Gross proceeds are expected to be about $150 million, with estimated net proceeds of approximately $141 million after underwriting discounts and expenses.

As of March 31, 2026, Cabaletta held about $117 million in cash and cash equivalents. The company plans to use the new capital with existing cash mainly to expand clinical development and manufacturing for its CD19 CAR-T candidate rese-cel, and now believes it can fund operations into mid‑2027.

Insights

Biotech equity analyst

$150M equity raise strengthens Cabaletta’s cash runway but adds dilution.

Cabaletta Bio is issuing 51,725,000 new common shares at $2.90, for about $150M in gross proceeds and roughly $141M in estimated net proceeds. This is a primary offering, so cash goes to the company rather than existing holders.

Management reports about $117M in cash and cash equivalents as of March 31, 2026, and now expects total liquidity to fund operations into mid‑2027. Stated priorities include clinical expansion and commercial readiness for rese‑cel, particularly in myositis, lupus, systemic sclerosis and pemphigus vulgaris, plus manufacturing scale‑up.

For shareholders, the raise materially boosts balance‑sheet strength but increases the share count. The overall impact on value depends on how efficiently Cabaletta converts this capital into pivotal data, regulatory progress and eventual commercialization for rese‑cel, as future filings and trial readouts clarify.

8-K Event Classification

4 items: 1.01, 2.02, 8.01, 9.01

4 items

Item 1.01 Entry into a Material Definitive Agreement Business

The company signed a significant contract such as a merger agreement, credit facility, or major partnership.

Item 2.02 Results of Operations and Financial Condition Financial

Disclosure of earnings results, typically an earnings press release or preliminary financials.

Item 8.01 Other Events Other

Voluntary disclosure of events the company deems important to shareholders but not covered by other items.

Item 9.01 Financial Statements and Exhibits Exhibits

Financial statements, pro forma financial information, and exhibit attachments filed with this report.

Key Figures

Shares offered: 51,725,000 shares Offering price: $2.90 per share Underwriter purchase price: $2.726 per share +3 more

6 metrics

Shares offered 51,725,000 shares Underwritten public offering of common stock

Offering price $2.90 per share Public offering price to investors

Underwriter purchase price $2.726 per share Price paid by underwriters, 6.0% discount

Gross proceeds $150 million Approximate aggregate gross proceeds from offering

Estimated net proceeds $141 million After underwriting discounts and offering expenses

Cash and cash equivalents $117 million Balance as of March 31, 2026

Key Terms

underwritten offering, shelf registration statement, net proceeds, clinical-stage biotechnology company, +2 more

6 terms

underwritten offering financial

"announced today the pricing of an underwritten offering of 51,725,000 shares of common stock"

An underwritten offering is when a bank or group of banks agrees to buy all of a company's new shares or bonds and then resell them to outside investors, guaranteeing the company will raise a specific amount of money. It matters to investors because it adds certainty that the funding will close while increasing the number of shares or debt in the market, which can lower the price per share and change each existing owner's ownership percentage—think of a wholesaler buying an entire shipment from a maker before it reaches stores.

shelf registration statement regulatory

"pursuant to a shelf registration statement on Form S-3-ASR (File No. 333-278126)"

A shelf registration statement is a document a company files with regulators that allows it to sell shares or bonds quickly when it’s a good time to raise money. It’s like having a pre-approved plan ready so the company can act fast without going through lengthy paperwork each time they want to sell, making fundraising more flexible.

net proceeds financial

"The Company estimates that the net proceeds from the Offering will be approximately $141 million"

The amount of money a company actually keeps from a sale or fundraising after paying all direct costs and fees, similar to take-home pay after taxes and deductions. Investors care because net proceeds determine how much cash is available for things that affect value—paying debt, funding projects, buying assets, or returning money to shareholders—so it influences future growth potential and financial health.

clinical-stage biotechnology company financial

"a clinical-stage biotechnology company focused on developing and launching curative targeted cell therapies"

CD19-CAR T cell technical

"a 4-1BB-containing fully human CD19-CAR T cell investigational therapy"

preconditioning medical

"expanded clinical development of rese-cel in multiple indications with and/or without preconditioning"

Preconditioning is a deliberate, controlled treatment or brief exposure to mild stress applied to cells, tissues, organs, or patients before a main medical procedure or therapy to make them more resistant to injury and improve the therapy’s effectiveness. For investors, evidence that a treatment benefits from preconditioning can signal higher chances of safer, more effective outcomes, smoother regulatory review, and a stronger commercial case—like a warm-up improving performance and reducing injury risk.

Offering Details

primary

Offering

Offering Type primary

Price Range $2.90 per share

Use of Proceeds Fund expanded clinical development and manufacturing for rese-cel, plus working capital and general corporate purposes

Understanding 8-K Material Events →

false 0001759138 0001759138 2026-05-04 2026-05-04

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): May 4, 2026

CABALETTA BIO, INC.

(Exact name of Registrant as Specified in Its Charter)

Delaware		001-39103		82-1685768
(State or Other Jurisdiction of Incorporation)		(Commission File Number)		(IRS Employer Identification No.)

2929 Arch Street Suite 600
Philadelphia, Pennsylvania		19104
(Address of Principal Executive Offices)		(Zip Code)

Registrant’s Telephone Number, Including Area Code: (267) 759-3100

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading Symbol(s)		Name of each exchange on which registered
Common Stock, par value $0.00001 per share		CABA		The Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 1.01 Entry into a Material Definitive Agreement.

On May 4, 2026, Cabaletta Bio, Inc. (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with TD Securities (USA) LLC, Guggenheim Securities, LLC and Cantor Fitzgerald & Co. (collectively, the “Underwriters”), relating to an underwritten registered direct offering (the “Offering”) of 51,725,000 shares (the “Shares”) of the Company’s common stock, $0.00001 par value per share (the “Common Stock”). The Shares are being sold at a price of $2.90 per share. The purchase price to be paid by the Underwriters to the Company will be $2.726 per Share, representing a discount to the Underwriters of 6.0%. The Offering is expected to close on May 5, 2026.

The Company estimates that the net proceeds from the Offering will be approximately $141 million, after deducting underwriting discounts and commissions and estimated offering expenses payable by the Company.

The Shares were issued pursuant to a shelf registration statement on Form S-3 (File No. 333-278126), as amended by that certain Post-Effective Amendment No. 1 to Form S-3 (No. 333-278126) and that certain Post-Effective Amendment No. 2 to Form S-3 (No. 333-278126), as filed with the U.S. Securities and Exchange Commission (“SEC”) on March 31, 2025 and declared effective on March 31, 2025. A prospectus supplement dated May 4, 2026 relating to the Offering has been filed with the SEC.

The Underwriting Agreement contains customary representations, warranties, covenants, indemnification obligations of the Company and the Underwriters, including for liabilities under the Securities Act of 1933, as amended, and other obligations of the parties. The representations, warranties and covenants contained in the Underwriting Agreement were made only for purposes of such agreement and as of specific dates, were solely for the benefit of the parties to such agreement, and may be subject to limitations agreed upon by the contracting parties. The foregoing is only a brief description of the terms of the Underwriting Agreement, does not purport to be a complete statement of the rights and obligations of the parties under the Underwriting Agreement and the transactions contemplated thereby, and is qualified in its entirety by reference to the Underwriting Agreement, which is filed as Exhibit 1.1 to this Current Report on Form 8-K and is incorporated herein by reference.

A copy of the legal opinion of Goodwin Procter LLP relating to the issuance and sale of the Shares in the Offering is filed as Exhibit 5.1 to this Current Report on Form 8-K and is filed with reference to, and is hereby incorporated by reference into, the Registration Statement.

Item 2.02 Results of Operations and Financial Condition.

As of March 31, 2026, the Company had approximately $117 million in cash and cash equivalents. This preliminary financial information is subject to completion, and is the responsibility of management and has been prepared in good faith on a consistent basis with prior periods. However, the Company has not reported its financial results for the three months ended March 31, 2026, and its actual results could be materially different from this preliminary financial information.

The information in this Item 2.02 shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.

Item 8.01 Other Events.

The full text of the press release announcing the pricing of the underwritten offering on May 4, 2026 is attached as Exhibit 99.1 hereto and is incorporated herein by reference.

The Company currently intends to use the net proceeds from this offering together with its existing cash and cash equivalents, primarily to fund the expanded clinical development of rese-cel in multiple indications with and/or without preconditioning, including the ongoing myositis registrational study and initiation of additional potentially registrational studies, and to further advance its manufacturing capabilities in preparation for commercial readiness

of rese-cel, in addition to working capital and general corporate purposes. Based upon the Company’s current operating plan, the Company believes that the net proceeds from this offering, together with its existing cash and cash equivalents, will enable it to fund its operating expenses and capital expenditure requirements into mid-2027.

On May 4, 2026, the Company posted to the “Investors & Media” section of the Company’s website at www.cabalettabio.com an updated corporate presentation (the “Corporate Presentation”). A copy of the Corporate Presentation is attached hereto as Exhibit 99.2 and is incorporated herein by reference.

Forward-Looking Statements

This Report contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended. These statements may be identified by words such as “may,” “might,” “will,” “could,” “would,” “should,” “plan,” “anticipate,” “intend,” “believe,” “expect,” “estimate,” “seek,” “predict,” “future,” “project,” “potential,” “continue,” “target” and similar words or expressions, or the negative thereof, are intended to identify forward-looking statements, although not all contain identifying words. Any statements in this Report that are not statements of historical fact may be deemed to be forward-looking statements. These forward-looking statements include, without limitation, the Company’s strategy and business plans, express or implied statements regarding the anticipated net proceeds from the Offering and the anticipated use of proceeds from the Offering. Any forward-looking statements in this Report are based on management’s current expectations and beliefs and are subject to a number of risks and uncertainties that are difficult to predict. Factors that could cause actual results to differ include, but are not limited to, risks and uncertainties related to uncertainties inherent in the development of product candidates, including the conduct of research activities and the conduct of clinical trials; uncertainties as to the availability and timing of results and data from clinical trials; whether results from prior preclinical studies, preliminary or interim data from earlier stage clinical trials will be predictive of the results of subsequent preclinical studies and clinical trials; regulatory developments in the United States and foreign countries; whether the Company’s cash resources will be sufficient to fund its foreseeable and unforeseeable operating expenses and capital expenditure requirements; as well as the risks and uncertainties identified in the Company’s filings with the SEC, including its Annual Report on Form 10-K for the year ended December 31, 2025 and any subsequent filings the Company makes with the SEC. In addition, any forward-looking statements represent the Company’s views only as of the date of this Report and should not be relied upon as representing its views as of any subsequent date. The Company explicitly disclaims any obligation to update any forward-looking statements. No representations or warranties (expressed or implied) are made about the accuracy of any such forward-looking statements.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits

1.1*		Underwriting Agreement, dated May 4, 2026, between Cabaletta Bio, Inc. and TD Securities (USA) LLC, Guggenheim Securities, LLC and Cantor Fitzgerald & Co. as representatives of the several underwriters named therein.
5.1		Opinion of Goodwin Procter LLP.
23.1		Consent of Goodwin Procter LLP (included in Exhibit 5.1).
99.1		Press Release dated May 4, 2026.
99.2		Cabaletta Bio, Inc. Corporate Presentation, dated May 2026, filed herewith.
104		Cover Page Interactive Data File (embedded within the Inline XBRL Document).

* Schedules and exhibits have been omitted pursuant to Item 601(a)(5) of Regulation S-K. A copy of any omitted schedule and/or exhibit will be furnished to the SEC upon request.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

				CABALETTA BIO, INC.
Date: May 4, 2026				By:		/s/ Steven Nichtberger
						Steven Nichtberger
						Chief Executive Officer and President (Principal Executive Officer)

Exhibit 99.1

Cabaletta Bio Announces Pricing of $150 Million Underwritten Offering

PHILADELPHIA, May 4, 2026 (GLOBE NEWSWIRE) — Cabaletta Bio, Inc. (“Cabaletta” or the “Company”) (Nasdaq: CABA), a clinical-stage biotechnology company focused on developing and launching curative targeted cell therapies designed specifically for patients with autoimmune diseases, announced today the pricing of an underwritten offering of 51,725,000 shares of common stock. The aggregate gross proceeds from the offering, before deducting underwriting discounts and commissions and offering expenses, are expected to be approximately $150 million. The offering is expected to close on or about May 5, 2026, subject to the satisfaction of customary closing conditions. The financing included participation from Bain Capital Life Sciences, Adage Capital Management, Cormorant Asset Management and other existing investors, multiple new mutual and sovereign wealth funds and Eli Lilly and Company.

The purchase price for the common stock is $2.90 per share, which represents the at-the-market price under Nasdaq rules. All of the shares in the offering are being sold by Cabaletta.

TD Cowen, Guggenheim Securities, and Cantor are acting as joint book-running managers for the offering. H.C. Wainwright & Co. is acting as lead manager for the offering.

The shares of common stock are being offered by Cabaletta pursuant to a shelf registration statement on Form S-3-ASR (File No. 333-278126), as amended by that certain Post-Effective Amendment No. 1 to Form S-3 (No. 333-278126) and that certain Post-Effective Amendment No. 2 to Form S-3 (No. 333-278126), which was declared effective by the U.S. Securities and Exchange Commission (SEC) on March 31, 2025. The prospectus supplement and accompanying prospectus relating to the offering will be filed with the SEC and will be available on the SEC’s website at www.sec.gov. Copies of the prospectus supplement and accompanying prospectus may also be obtained, when available, by contacting: TD Securities (USA) LLC, c/o Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, NY 11717, or by email at TDManualrequest@broadridge.com; Guggenheim Securities, LLC, by mail at Attention: Equity Syndicate Department, 330 Madison Avenue, 8^th Floor, New York, NY 10017, by telephone at (212) 518-9544 or by email at GSEquityProspectusDelivery@guggenheimpartners.com; or Cantor Fitzgerald & Co. by mail at Attention: Capital Markets, 110 East 59th Street, 6th Floor, New York 10022 or by email at prospectus@cantor.com.

This press release shall not constitute an offer to sell or the solicitation of an offer to buy these securities, nor shall there be any sale of these securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.

About Cabaletta Bio

Cabaletta Bio (Nasdaq: CABA) is a late clinical-stage biotechnology company focused on developing and launching curative targeted cell therapies designed specifically for patients with autoimmune diseases. The CABA^™ platform encompasses two complementary strategies which aim to advance the discovery and development of engineered T cell therapies with the potential to become deep and durable, perhaps curative, treatments for a broad range of autoimmune

diseases. The lead CARTA (Chimeric Antigen Receptor T cells for Autoimmunity) strategy is prioritizing the development of rese-cel, a 4-1BB-containing fully human CD19-CAR T cell investigational therapy. Rese-cel is currently being evaluated in the RESET^™ (REstoring SElf-Tolerance) clinical development program spanning multiple therapeutic areas, including rheumatology, neurology and dermatology. 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: the satisfaction of customary closing conditions related to the offering and sale of securities; the Company’s ability to complete the offering; and use of capital, expenses, future accumulated deficit and other financial results in the future.

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 related to completion of the public offering on the anticipated terms, or at all, include, but are not limited to, market conditions and the satisfaction of customary closing conditions related to the public offering. 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 filed on March 23, 2026 and our subsequent quarterly reports on Form 10-Q filed with the SEC, as well as discussions of potential risks, uncertainties, and other important factors in Cabaletta’s other filings with the SEC, including those contained or incorporated by reference in the preliminary prospectus supplement related to the public offering to be filed with the SEC.

Contacts:

Anup Marda

Chief Financial Officer

investors@cabalettabio.com

Corporate Presentation May 2026 Exhibit 99.2

Disclaimer This 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 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 may contain “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995 relating to our business, operations, and financial condition, 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 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, 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 timing, clinical significance and impact of clinical data read-outs, including the progress, results and clinical data from each of the patients dosed with rese-cel in the Phase 1/2 RESET-Myositis, RESET-SLE, RESET-SSc, RESET-MG and RESET-PV trials and our other planned activities with respect to rese-cel; our belief that rese-cel has the potential to provide drug-free, durable transformative clinical responses, through an immune reset; the Company's advancement of separate Phase 1/2 clinical trials of rese-cel and advancement of the RESET-PV and RESET-MS trials, with and without preconditioning, as applicable, 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 of any planned regulatory filings for our development programs, including IND applications and interactions with regulatory authorities, including such authorities' review of safety information from our ongoing clinical trials and discussions with regulatory agencies on potential registrational pathway for rese-cel in various indications, and the timing of trial design related thereto; our ability to successfully complete our preclinical and clinical studies for our product candidates, including our ability to progress the trial; our plans and expectations regarding automated scalable manufacturing and no preconditioning and its potential to expand and accelerate access; our expectations that automation and elimination of preconditioning and apheresis will enhance patient experience; our expectation and timing for clinical manufacturing data with Cellares' automated manufacturing process and its ability to confirm GMP readiness, including supply chain logistics, as well as its potential to provide scalability for thousands of patients per year and to facilitate post-approval expansion; 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 regulatory designations and the anticipated initiation of registrational cohorts and potential BLA submission; our expectation and timing for completion of dosing of most disease-specific cohorts; our expectations regarding opportunities based on market research; our ability to accelerate our pipeline to approval and launch and to develop transformative therapies for patients, including in collaboration with academic and industry partners and the ability to optimize such collaborations on, including timing thereof, our development programs; our ability to contract with third-party suppliers and manufacturers; 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; our expectations regarding the potential commercial and economic benefits of preconditioning elimination and automated manufacturing, including its potential to reduce costs of goods, minimize capital investment requirements, and support efficient global expansion of rese-cel. 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 development activities and clinical trials, risks related to our ability to demonstrate sufficient evidence of safety, efficacy and tolerability in our clinical trials, the risk that the results observed with the similarly-designed construct, including, but not limited 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, risks related to clinical trial site activation or enrollment rates that are lower than expected, 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 regulatory 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, risks related to volatile market and economic conditions and our ability to fund operations and continue as a going concern. 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 and quarterly report on Form 10-Q, as well as discussions of potential risks, uncertainties, and other important factors in our other 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 rights thereto.

Develop and launch the first curative targeted cellular therapies for patients with autoimmune diseases

Preconditioning (PC) free clinical data & automated manufacturing data anticipated throughout 2026 Rese-cel1: Delivering on the promise of CD19-CAR T in autoimmunity BLA – biologics license application; f/u – follow-up; PV – pemphigus vulgaris; SLE – systemic lupus erythematosus; TIS – total improvement score. resecabtagene autoleucel; CABA-201 Solimani, Farzan, et al. "Clinical progress of engineered cellular immunotherapies for autoimmunity." Nature Biotechnology (2026): 1-16. Low dose steroids is defined as 50% reduction from baseline or ≤7.5 mg/day. As of data cut-off on September 11, 2025. As of data cut-off on October 30, 2025 Autologous CAR T has delivered reliable, durable, transformative outcomes for autoimmune patients2 Rese-cel data: immunomodulator-free efficacy with a favorable safety profile using a single weight-based dose Complete phase 1/2 data expected in systemic sclerosis and lupus in 1H26; myasthenia gravis data presented at AAN Primary endpoint: moderate TIS off immunomodulators & on no or low dose steroids3 at 16 weeks All phase 1/2 patients with sufficient f/u who would have met inclusion criteria met the registrational primary endpoint4 Myositis: 17 patient single-arm study with planned 2027 BLA submission including potential for outpatient infusion $150mn raise extends runway into mid-27 including 2026 advances in PC free program, automated scalable manufacturing, progress to BLA submission in myositis next year and initiation of second pivotal indication PC free lowest dose data: 2 of 4 refractory PV patients off all medicines with compelling responses thru 6 mo f/u Safety profile in first 40 patients dosed with preconditioning (PC) supports outpatient administration4 95% - No CRS (~67%) or Grade 1 CRS (~28% - fever); 95% - No ICANS5 Data at ASGCT (May 14); next higher dose in RESET-PV and initial dose in RESET-SLE anticipated throughout 2026 Automated manufacturing by Cellares offers potential scale to thousands of patients with minimal capital investment Initial translational data at ASGCT (May 14); commercial supply agreement includes among lowest COGS in industry

Removing PC should expand access while automated manufacturing should reduce COGS & increase scale Transformative value proposition with PC elimination & automation PV: PC free rese-cel data including longer-term follow up at the initial dose SLE: PC free rese-cel data including early data at the initial dose Initial clinical experience with rese-cel manufactured by Cellares Transformative Value Proposition Elimination of PC Automated Manufacturing Expands the market Catalyzes outpatient use Reduces resource utilization Improves patient and provider experience Differentiated product profile Typical ‘biologic’ margins Potential to address larger autoimmune indications including T1D, UC and RA Minimal capital investment Scalability to produce thousands of patient runs per year Substantially reduced COGS Facilitates global expansion Longer-term PC free rese-cel data from the PV & SLE dose cohorts and from patients receiving rese-cel manufactured by Cellares 1H26 2H26 COGS – Cost of goods sold; PC – Preconditioning; PV – Pemphigus vulgaris; SLE – Systemic lupus erythematosus; RA – Rheumatoid arthritis; T1D – Type 1 diabetes; UC – Ulcerative colitis.

SLE registrational design in hand; SSc pivotal design anticipated 1H26 and MG anticipated mid-2026 Innovative clinical strategy to support accelerated regulatory path Program Trial Preclinical Phase 1/2 Registrational 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-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 Rheumatology1 Neurology Dermatology FTD Pemphigus vulgaris Contains cohort(s) without preconditioning Juvenile Myositis Pediatric Indication RESET™ – REstoring SElf-Tolerance; Ab – Antibody; AChR – Acetylcholine receptor; gMG – Generalized myasthenia gravis; PV – Pemphigus vulgaris; SLE – Systemic lupus erythematosus; SSc – Systemic sclerosis Myositis patients can also be treated by neurologists or dermatologists; lupus nephritis patients can also be treated by nephrologists. FDA Fast Track Designation received in dermatomyositis, SLE and lupus nephritis, systemic sclerosis, generalized myasthenia gravis and multiple sclerosis. FDA Regenerative Medicine Advanced Therapy (RMAT) received in myositis, SLE, LN and systemic sclerosis. RMAT RMAT RMAT Complete Phase 1/2 data expected in SLE/LN and SSc 1H26

Rese-cel: Clinical Profile and Commercial Opportunity

Broad portfolio of trials designed to address high unmet need and realize the potential of rese-cel RESET™ program advancing trials in a broad portfolio of diseases SLE – Systemic lupus erythematosus; DM – Dermatomyositis; SSc – Systemic sclerosis; gMG – Generalized myasthenia gravis; PC – Preconditioning; ESRD – End-stage renal disease; PV – pemphigus vulgaris SSc gMG PV ~90k ~100k ~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 Rheum Neuro Derm No PC only Pure autoantibody & B-cell mediated autoimmune disease Characterized by painful blisters & erosions SLE/LN ~320k Affects young women & people of color ~30-40% with lupus nephritis, which carries ~25% risk of death or ESRD within 10y > > > Myositis ~80k Typical onset middle age Only FDA-approved therapy is IVIg in DM Three-fold increased mortality due to lung & cardiac involvement > U.S. Prevalence No PC Cohorts

Rese-cel binder with similar in vitro & in vivo activity to construct used in academic studies in autoimmunity1,3 Rese-cel: CD19-CAR T specifically designed for autoimmunity Peng BJ, et al. Mol Ther Methods Clin Dev. 2024;32(2):101267. 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. Müller, 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 CD8α 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-γ production in preclinical studies. The CD8α 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 clinical and translational data5 Patients treated with rese-cel have shown compelling clinical responses with safety data that supports outpatient use for autoimmune patients6 Fully human anti-CD19 binder 4-1BB costimulatory domain CD3-z signaling domain Rese-cel4

Many of the RESET trials share common elements of preconditioning, dose, and study design RESETTM clinical trials have consistent design principles1 †Follow up period encompasses at least 15 years in total, ed to regulatory guidance for CAR T cell therapies. AE, adverse event; CABA, Cabaletta Approach to B cell Ablation; FLU, fludarabine; CY, cyclophosphamide; PBMC, peripheral blood mononuclear cell; PD, pharmacodynamics; PK, pharmacokinetics; RESET, REstoring SElf-Tolerance; SLE, systemic lupus erythematosus; SSc, systemic sclerosis. Cabaletta Bio: Data on file; 1. Peng BJ, et al. Mol Ther Methods Clin Dev. 2024;32(2):101267. Leukapheresis and rese-cel production Preconditioning Single infusion of rese-cel Weight-based dosing 1×106 cells/kg Day 1 Primary endpoint: Incidence and severity of AEs T cells isolated from patient’s own PBMCs (autologous CAR T) Day 29 Study follow-up through Year 3† Screening Additional Endpoints Clinical efficacy measuring: Drug-free responses Validated endpoints PK/PD analysis: Rese-cel expansion B cell depletion Peak BAFF levels B cell repopulation Adverse events & safety Biomarker analysis, including autoantibody levels FLU 25 mg/m2 x 3 days CY 1000 mg/m2 x 1 day (if required) Day -5 to Day -3 Discontinuation of all immunomodulatory agents

Peak rese-cel expansion and transient peripheral B cell depletion occurred within ~2 weeks post infusion​​ Rese-cel expansion & B cell kinetics across indications* *All data is as of 11 Sep, 2025, except DM-3 which includes Week 24 data as of 08 Oct 2025. **LN-1 had prolonged rese-cel detection due to TCR activation that corresponded to longer time to B cell repopulation. LN-4: follow up ongoing † DM-3 rese-cel PK at Week 20 was artifactually elevated due to low circulating lymphocyte counts. ‡ Reduced rese-cel expansion observed in AChR-pos-1 may be attributed to patient’s continued use of azathioprine, a prohibited medication, until day of infusion (Day 1). ASyS, antisynthetase syndrome; CAR, chimeric antigen receptor; DM, dermatomyositis; IMNM, immune-mediated necrotizing myopathy; LN, lupus nephritis; rese-cel, resecabtagene autoleucel; RESET, REstoring SElf-Tolerance; SLE, systemic lupus erythematosus, SSc, systemic sclerosis, TCR, T cell receptor. Cabaletta Bio: Data on file. RESET-Myositis RESET-SLE RESET-SSc Rese-cel Pharmacokinetics* Rese-cel Pharmacokinetics** Rese-cel Pharmacokinetics B Cell Kinetics B Cell Kinetics B Cell Kinetics Peripheral B cells begin repopulating ~2 to 3 months after rese-cel in patients with sufficient follow-up* † RESET-MG Rese-cel Pharmacokinetics B Cell Kinetics ‡

Across 4 RESET™ studies, 95% of patients with no CRS or Grade 1 CRS (fever) and 95% with no ICANS1 Demographics & CRS/ICANS in 1st 40 rese-cel patients by indication RESET-Myositis RESET-SLE RESET-SSc RESET-MG Number of patients 15 10 9 6 Age, years, mean (SD) 51.7 (14.6) 30.4 (7.6) 53.1 (12.3) 57.5 (9.8) Sex, % female 53.3 80.0 66.7 66.7 Duration of disease, years, mean (SD) 5.4 (3.7) 9.8 (5.0) 2.2 (1.3) 5.1 (5.3) Baseline characteristics of autoimmune disease patients treated with rese-cel Incidence, severity and onset of CRS and ICANS in the 1st 28 days in patients treated with rese-cel RESET-Myositis RESET-SLE RESET-SSc RESET-MG Total CRS‡, n (%) 5 (33.3) 3 (30.0) 4 (44.4) 1 (16.7) 13 (32.5% CRS) CRS Grade 1, n (%) 5 (33.3) 3 (30.0) 3 (33.3) 0 (0.0) 11 (27.5% G1 CRS) CRS Grade 2, n (%) – – 1 (11.1) 1 (16.7) 2 (5% G2 CRS) Time to CRS onset, days* (mean) 7.4 7.3 8.5 7.0 7.7 days CRS duration†, days (mean) 4.6 3.0 3.0 2.0 3.5 days ICANS‡ n (%) (Grade) – 1 (10) (G4) 1 (11.1) (G3) – 2 (5% ICANS) Time to ICANS onset. days (mean) – 9.0 8.0 – 8.5 days ICANS duration, days (mean) – 3.0 3.0 – 3.0 days *Days relative to rese-cel infusion. †Events occurring within 7 days of each other are considered as 1 episode. IMNM-3 CRS duration includes preceding event of fever which was consistent with CRS definition. ‡Graded per ASTCT Consensus Grading Criteria. 1. Presented at ASH 2025 with data cut-off as of October 30, 2025.

Rese-cel safety profile permits outpatient administration which could facilitate favorable reimbursement CAR T may eliminate active disease & use of expensive medications Cancer patients experience early and frequent CRS/ICANS following CAR T therapy, which increases inpatient admissions and shifts Medicare reimbursement to the DRG system. Majority of oncology patients treated with CAR T therapy experience CRS within first 5 days post-infusion1 Cancer CAR T: Safety profile often requires inpatient infusion, affecting reimbursement Rese-cel: Safety profile facilitates outpatient infusion, which could favorably impact reimbursement Many cancer patients are insured under Medicare, which has inpatient DRG-018 reimbursement Myositis & SSc patients often commercially insured (60%-75%)2,3 CRS less frequent & severe, delayed onset à potential outpatient administration Outpatient CAR T infrastructure exists at many centers RESET clinical site footprint can be leveraged to generate early adopters Outpatient administration supports viable Part B Medicare payments Ferreri, Christopher J., and Manisha Bhutani. "Mechanisms and management of CAR T toxicity." Frontiers in Oncology 14 (2024): 1396490. Smoyer-Tomic KE, et al. BMC Musculoskelet. Disord. 2012 Jun 15;13:103. doi: 10.1186/1471-2474-13-103.​ Gale, Sara L., et al. "Characterizing disease manifestations and treatment patterns among adults with systemic sclerosis: a retrospective analysis of a US healthcare claims population." Rheumatology and therapy 7.1 (2020): 89-99. Commercial

Outpatient administration reduces administrative burden and improves patient and provider accessibility RESET™ program designed for outpatient administration at launch INPATIENT MODEL OUTPATIENT MODEL Limited patient beds and resource infrastructure Increases inpatient resource pressure: ↑ total cost of care, human resource and bed space demands Reduces eligible patients treated More favorable safety profile reduces need for inpatient admission Reduces use of hospital resources; Increases throughput Reduces conflicts with cancer patient use of in-patient beds

Health status of patient population and slower disease progression improve manufacturing cost efficiency Rese-cel commercial model – manufacturing and COGM Late-stage oncology patients have high drop-off rate due to rapid disease progression and compromised T cell fitness, leading to higher manufacturing OOS rates1,2,3 Increased OOS rates; ↑ COGM + ↓ revenue since out of spec products not reimbursed In oncology, disease progress & out of specification (OOS) rates increase costs and reduce margins In autoimmunity, healthier patients & fully automated rese-cel mfg, should support lower COGM Disease progression reduces revenue capture because unused product not reimbursed Manufacturing capacity constraints à delayed commercial ramp-up Autoimmune patients are not heavily pretreated with chemotherapy à more fit immune cells that support reliable manufacture, reducing COGM Building manufacturing capacity at CDMOs to support successful launch; Cellares automation has the potential to facilitate post-approval expansion Autoimmune patients rarely progress as rapidly as cancer patients à more reliable revenue realization for manufactured product Reduced eligible patients, resulting in economies of scale not being achieved COGM – Cost of goods manufactured U.S. Food and Drug Administration. Kymriah (tisagenlecleucel) Prescribing Information. Revised 2025, U.S. Food and Drug Administration, https://www.fda.gov/media/107296/download U.S. Food and Drug Administration. Breyanzi (lisocabtagene maraleucel) Prescribing Information. Revised 2025, U.S. Food and Drug Administration, https://www.fda.gov/media/145711/download U.S. Food and Drug Administration. Yescarta (axicabtagene ciloleucel) Prescribing Information. Revised 2025, U.S. Food and Drug Administration, https://www.fda.gov/media/108377/download

Myositis: Unmet Need & Clinical Data

Highly concentrated treatment network in the US; dermatomyositis represents ~75% of this market Myositis: High rates of disability & increased risk of mortality High disease burden: disability & mortality Typical patient is a middle-aged female who experiences muscle weakness, fatigue, pain, shortness of breath and difficulty swallowing Moderate to severe disability (40% to 65%)1 Assisted walking devices (18% to 38%)1 The risk of mortality is ~3 times higher than the general population, primarily due to cancer and lung & cardiac complications2 ~20% mortality < 5 years with standard immunosuppressive treatment3 “I find it very difficult to get up from a regular chair, I need boosters or assistance from somebody else. Walking, my gait has really suffered. My stability walking has suffered as well, and I can't lift anything more than five or eight pounds. So doing stuff is difficult. Bending down is very difficult. I can't get up from the floor if I fall.” “John” 61-year-old male with ASyS4 ~10 yrs since diagnosis "It just affected every aspect of my life. Just work, family, social life, own wellbeing. It just pours into everything else with that." “Erica” 44-year-old female with DM4 ~2.5 yrs since diagnosis Opinc AH, Brzezinska OE, Makowska JS. Disability in idiopathic inflammatory myopathies: questionnaire-based study. Rheumatol Int. 2019;39(7):1213-1220. Marie I. Morbidity and mortality in adult polymyositis and dermatomyositis. Curr Rheumatol Rep. 2012;14(3):275-285. Schiopu E, Phillips K, MacDonald PM, Crofford LJ, Somers EC. Predictors of survival in a cohort of patients with polymyositis and dermatomyositis: effect of corticosteroids, methotrexate and azathioprine. Arthritis Res Ther. 2012;14(1):R22. Primary market research conducted via third-party, blinded interviews with myositis patients, conducted in 2024. Khoo 2023 6. Kronzer 2023 7. Coffey 2021 8. Dahal 2022 9. Shelley 2022 ~7,500 pts5,9 Immune-mediated necrotizing myopathy (IMNM) ~15,000 pts7,8 Anti-synthetase syndrome (ASyS) ~60,000 pts5,6 Dermatomyositis (DM) Subtype prevalence in the U.S.

IVIg is the only approved therapy (only for patients with the adult dermatomyositis subtype) Myositis: Limited treatment option​s for ~80k U.S. patients Lundberg, Ingrid E., et al. "Idiopathic inflammatory myopathies." Nature Reviews Disease Primers 7.1 (2021): 86.​ Analysis from quantitative survey of U.S. myositis-treating physicians, conducted 2Q25. N = ~240. Autoimmune disease with B cells component Limited treatment options1 Idiopathic inflammatory myopathies (IIMs, or myositis) are a group of autoimmune diseases characterized by inflammation and muscle weakness Common therapies: steroids plus an immunomodulator (i.e. methotrexate, azathioprine, mycophenolate, rituximab) IVIg (intravenous immunoglobulin), the only FDA-approved therapy, is approved in adult dermatomyositis Therapies can carry potential long-term side effects such as serious infections and organ damage Despite existing therapies, disease is often refractory Two therapies in Phase 3 development, Brepocitinib and Vyvgart®, demonstrated improvement with chronic administration added onto existing immunomodulatory medications Myositis patients with moderate to severe, refractory disease potentially eligible for rese-cel (per analysis of quantitative research with ~240 myositis-treating physicians) Eligible U.S. myositis patients2 ~16k to 20k U.S. myositis patients potentially eligible for rese-cel ~80k myositis patients

Single-arm cohort including DM/ASyS patients with a primary endpoint at 16 weeks Myositis registrational cohort – Key design elements Registrational Cohort2 ASyS DM & ASyS (n=17) Initial Phase 1/2 Cohorts1 DM (combined n ~6) TIS, total improvement score. Pediatric submission based on data available at the time of adult submission from ongoing Ph 1/2 study (no new study) to support pediatric label claim Size of myositis registrational cohort based on key statistical parameters and estimated background remission rate in myositis. Low dose steroids is defined as 50% reduction from baseline or ≤7.5 mg/day. As of October 24, 2025. Registrational trial initiated with planned 2027 BLA submission Expansion of current RESET-Myositis trial to include registrational cohort in DM / ASyS (~60k / ~15k US patients) Primary Endpoint: Moderate or Major TIS response @ Week 16 off all immunomodulators and off or on low-dose3 steroids Expanded trial to 17 patients to ensure approximately 14 DM patients can enroll based on natural U.S. prevalence estimates Confirmed current dose of 1 million cells/kg in a single infusion Safety database ~100 autoimmune patients at ≥1-month of follow-up (with at least 35 myositis patients) ~70% of the safety database already enrolled across the RESET clinical development program4 P P P P P

All patients had active, refractory disease despite multiple immunomodulatory agents, including IVIg Baseline characteristics: First 13 patients in RESET-Myositis* *As of 11 Sep, 2025. †Baseline disease activity = activity before preconditioning. ‡Reflects any exposure to RTX and IVIg prior or at time of study entry. RTX is not allowed within approximately 6 months of Screening. ASyS, antisynthetase syndrome; CDASI-A, Cutaneous Dermatomyositis Disease Area and Severity Index – Activity; CK, creatine kinase; DM, dermatomyositis; GC, glucocorticoid; HMGCR, 3-hydroxy-3-methylglutaryl-coenzyme A reductase; IM, immunomodulatory medication; IMNM, immune-mediated necrotizing myopathy; IVIg, intravenous immunoglobulin; JIIM, juvenile idiopathic inflammatory myopathy; MMT-8, manual muscle testing 8; NXP, nuclear matrix protein; N/A, not applicable; RESET, REstoring SElf-Tolerance; RTX, rituximab; SAE, small ubiquitin-like modifier activating enzyme; SRP, signal recognition particle; TIF1, transcription intermediary factor 1; U/L, units per liter. Cabaletta Bio – Data on File. DM N=4 ASyS N=2 IMNM N=6 JIIM N=1 Mean age, years (min, max) ~58 (45, 72) ~44 (39, 48) ~55 (33, 64) 14 Female, n (%) 3 (75) 1 (50) 1 (17) 1 (100) Years since diagnosis, mean (min, max) 3.0 (2.0, 3.6) 9.2 (3.6, 14.8) 4.5 (1.4, 8.8) 8.5 Myositis-specific autoantibody 50% TIF1-γ 25% NXP, 25% SAE 100% Jo-1 67% HMGCR 33% SRP NXP-2 Baseline disease activity† Mean MMT-8 Median CK, U/L Mean CDASI-A 109.6 40.0 26 129.5 311.5 N/A 122.0 2214.5 N/A 134.0 176.0 N/A Prior RTX‡ Prior IVIg‡ 75% 100% 100% 100% 50% 83% 100% 100% Therapies at Screening Systemic GCs ≤2 IMs ≥3 IMs 75% 50% 50% 100% 50% 50% 67% 100% 0% 0 0 100%

3 of 3 patients with DM with sufficient follow-up achieved major TIS responses at Week 16 DM: Efficacy data following rese-cel infusion* *As of 11 Sep, 2025. † Historical NXP-2 autoantibody, but none detected at Pre-preconditioning (Baseline) visit). ‡ At latest follow-up (Day 29). § Insufficient follow-up. ¶Reflects trend from baseline to latest timepoint. DM, dermatomyositis; FDA, Food and Drugs Administration; GC, glucocorticoids; HCQ, hydroxychloroquine; IM, immunomodulatory medication; IVIg, intravenous immunoglobulin; mg, milligrams; MMF, mycophenolate mofetil; MTX, methotrexate; N/A, not available; NXP, nuclear matrix protein; rese-cel, resecabtagene autoleucel; SAE, small ubiquitin-like modifier activating enzyme; TAC, tacrolimus; TIF1-γ, transcription intermediary factor 1 gamma; TIS, total improvement score. Cabaletta Bio: Data on File. After discontinuation of all IM medications, 3 of 3 DM patients achieved the 16-week primary endpoint for the upcoming pivotal study of at least moderate TIS response TIS Mod. Major Min. None TIS Discontinued all immunomodulators DM-1 DM-2 DM-2 DM-4 MMF, HCQ IVIg, MMF, HCQ IVIg, MTX, TAC MTX Pivotal primary endpoint: Moderate TIS off all IM therapy on no steroids or low dose (50% reduction or <7.5mg/day) Assessment at Week 16 DM Patients (baseline autoantibody) DM-1 (SAE) DM-2 (None detected† ) DM-3 (TIF1-γ) DM-4 (TIF1-γ) IM-free ü ü ü ü‡ Low dose or no GC ü ü ü ü‡ TIS Response Major Major Major N/A§ Complete and transient B cell depletion ü ü ü ü‡ Antibody trend¶ ê N/A ê N/A§ Meets pivotal primary endpoint ü ü ü N/A§ TIS (N=4)

Patient who would meet key inclusion criteria in registrational cohort achieved a major TIS response at Week 16 ASyS: Efficacy data following rese-cel infusion* *As of 11 Sep, 2025. †Reflects trend from baseline to latest timepoint antibody results are available (Week 24 for both patients). In ASyS-2, Jo-1 antibody level trended up from Week 20 to Week 24 but was lower than baseline. ‡Based on the research-based, qualified, quantitative Luminex assay. §ASyS-1 to minimal response at latest follow-up (Week 32); treated with GC bursts and obinutuzumab; ASyS-2 to no response at latest follow-up (Week 28); treated with GC burst. ASyS, antisynthetase syndrome; FDA, Food and Drugs Administration; GC, glucocorticoids; IM, immunomodulatory medication; IVIg, intravenous immunoglobulin; mg, milligrams; MMF, mycophenolate mofetil; N/A, not available; rese-cel, resecabtagene autoleucel; TAC, tacrolimus; TIS, total improvement score. 1. Cabaletta Bio: Data on File. 2. Pinal-Fernandez I, et al. Ann Rheum Dis. 2024;83(11):1549–1560. 3. Galindo-Feria AS, et al. Best Pract Res Clin Rheumatol. 2022;36(2):101767. 4. Müller, F, et al. Nat Med. 2025:31(6):1793–1797. Major TIS Assessment at Week 16 ASyS (baseline autoantibody) ASyS-1 (Jo-1) ASyS-2 (Jo-1) IM-free ü ü Low dose or no GC ü ü TIS response Major Minimal Complete and transient B cells depletion ü ü Antibody trend† ê‡ êè‡ Meets pivotal primary endpoint ü Ð Discontinued all immunomodulators§ ASyS-1 ASyS-2 IVIg, TAC IVIg, MMF, TAC ASyS-2 would not meet pivotal entry criteria based on mild muscle weakness on MMT-8. Maximum TIS score possible is 65. Jo-1 antibody increased from Week 20 to Week 24 Mod. Min. None Pivotal primary endpoint: Moderate TIS off all IM therapy on no steroids or low dose (50% reduction or ≤7.5 mg/day) TIS (N=2) Responses to CD19-CAR T among some ASyS patients may be time-limited by the recurrence or persistence of pathogenic autoantibodies1–3 from CD19-negative long-lived plasma cells despite complete B cell depletion

Rese-cel Manufacturing Strategy & Innovation

Rese-cel commercial process preliminary comparability established T cell collection Rese-cel manufacture (9 day) Rese-cel administration apheresis cell selection and activation cell expansion cell harvest preconditioning infusion Product release QC testing and QA release Reliable process with >90% manufacturing success rate in first ~70 patients1 Process A - Early clinical process Process B – Commercial-ready manufacturing process Substantially closed process reducing contamination risk Partially automated manufacturing process improving process consistency 3-fold higher capacity per facility footprint than original Process A FDA feedback received on comparability between Process A and Process B Preliminary data enables use of previously dosed patients in safety database 1. Across Process A and Process B; only 1 failure attributed to patient starting material.

Automation and elimination of preconditioning and apheresis could enhance patient experience Advancing breakthrough innovations to improve scalability and costs Stratton et al, ESGCT 2024. Poster available at https://www.cabalettabio.com/technology/posters-publications (https://d1io3yog0oux5.cloudfront.net/_cdcc45a1b07d9c1e0fc529e815f21ec3/cabalettabio/db/947/8240/pdf/Whole+Blood+Mfg+Poster+ESGCT+2024.pdf) Automation run feasibility completed under TAP program. Video on Cellares technology can be viewed here: https://vimeo.com/947203843/cd59569f16. Under evaluation in an ongoing study in Pemphigus Vulgarus (NCT004422912); presented at ESGCT Conference 2025, presentation is available at https://www.cabalettabio.com/technology/posters-publications. T cell collection Rese-cel manufacture and harvest (9 day) Rese-cel administration apheresis cell selection and activation cell expansion cell harvest preconditioning infusion Product release post-production testing and QA review CURRENT INNOVATIONS One outpatient infusion without preconditioning4 Blood draw to replace apheresis1,2 Cellares Cell Shuttle3 Fully closed, end-to-end automation Rapid & global scalability Shorter turn-around-time

Three successful engineering runs3 completed in 2025 led to IND amendment (INDa) clearance Rese-cel engineering runs with Cellares supported INDa clearance Note: Shaded areas represent historical ranges defined by tolerance intervals that covers 90% of the population with 95% confidence. Cellares used Celleca for cell count to enable automated testing, while historical Process A data were collected using NC200. Data generated in Cabaletta Analytical Development lab using NC200 showed Engineering batches are within historical ranges. Effective Concentration 50, which is a measurement of product potency in a validated luciferase-based assay, designed for potency release testing on manufactured product.  Lower EC50 indicates greater potency of product. Shaded area in the graphs indicate range of process comparability, based on historic process data. %CD45+ CD3+ (Total T cells produced) %CD3+ CAR+ (Total CAR-T cells produced) Vector copy number (Amount of vector per cell) EC 502 (Product potency) Viability1 (assesses T cell health) Process A Cellares Eng Runs PD Batches Process A Process A Process A Process A Cellares Cellares Cellares Cellares Clinical manufacturing experience with Cellares’ automated manufacturing process anticipated in 1H26 to confirm GMP readiness, including supply chain readiness, with the Cellares manufacturing platform

Rese-cel – Initial Dose Data without Preconditioning (Data in Graphs as of ESGCT 2025)

In the RESET-PV trial, 4 refractory patients received rese-cel at the lowest dose without preconditioning and had follow-up between 24 and 36 weeks as of the data cut-off 2 of 4 patients demonstrated compelling clinical activity through 6 months follow-up 3 of 4 patients remained off all immunomodulators and steroids as of the data cut-off Complete peripheral B cell elimination was observed in 3 of 4 patients CRS was observed in 1 patient (Grade 1); ICANS – none Based on the safety profile observed at the lowest dose, multiple additional patients have been enrolled at a higher dose cohort in the RESET-PV trial and durability data at the higher dose is anticipated in 2H26 In the RESET-SLE trial evaluating rese-cel without preconditioning in patients with lupus, the initial dose cohort is fully enrolled with initial data at the first dose anticipated in 1H26 After discontinuing all immunomodulators (IM), clear biologic and clinical activity observed without PC Summary of rese-cel without preconditioning (PC), initial dose cohort1 Data cut off as of April 2, 2026. Cabaletta Bio: Data on file. DATA TO BE PRESENTED AT ASGCT 2026 1H26 – PV: PC free rese-cel data at the initial dose with 6-9 month follow up (ASGCT 2026) 1H26 – SLE: PC free rese-cel, early data at the initial dose 2H26 – SLE & PV: PC free rese-cel durability data from multiple cohorts

Clear evidence of biologic and clinical activity in all three PV patients in the initial dose cohort PDAI improvements were present in all three and were compelling in two of the three patients All patients remain off all immunomodulators while GCs are being tapered from low doses Peripheral B cell elimination was observed in the two patients with the greatest clinical response BAFF induction in these two patients was at the low end of the range of rese-cel with PC Rese-cel persistence without PC was similar to patients who received rese-cel with PC Peak persistence was not impacted by absence of PC and occurred slightly later without PC IFNγ induction in non-PC patients was at the higher end of the range observed in PC patients Higher levels may be attributable to higher B cell burden in PV patients and/or absence of preconditioning Rese-cel was generally well tolerated in PV patients without PC1 Based on limited data in the first three patients without PC, CRS rate was similar in rese-cel patients with PC Early clinical activity observed without preconditioning; low dose rese-cel may be a ‘threshold’ dose Summary of rese-cel without preconditioning (PC), initial dose cohort* *As of 11 September 2025. Cabaletta Bio: Data on file. BAFF, B cell activating factor; CRS, cytokine release syndrome; GC: glucocorticoids; PDAI, pemphigus disease area index; PV, pemphigus vulgaris; rese-cel, resacabtagene autoleucel; IFNγ, interferon-gamma Standard preconditioning in RESET trials consists of fludarabine 25 mg/m2 x 3 days and cyclophosphamide 1000 mg/m2 x 1 day. AS PRESENTED AT ESGCT 2025

Similar magnitude of rese-cel expansion & B cell depletion kinetics in patients treated with and without PC Similar PK & B cell depletion in rese-cel treated patients without PC* *As of 11 September 2025. Gray vertical dotted line indicates day of rese-cel infusion (study visit Day 1). Gray shading in BAFF plot is range of median serum BAFF induction observed in PV patients following rituximab (Nagel et. al, 2009 Journal of Investigative Dermatology and Hébert et. al, 2021 Frontiers in Immunology). Cabaletta Bio: Data on file. B cell depletion CAR T cell expansion Peak BAFF levels PV-1M-2 & PV-1M-3 had 100% reduction of peripheral B cells at initial rese-cel dose BAFF levels in these two patients were at the low end of the range observed with rese-cel with PC PV-1M-1 PV-1M-2 PV-1M-3 Rese-cel with PC in non-PV indications (med±50%CI) AS PRESENTED AT ESGCT 2025

Near complete resolution of clinical symptoms and rapid reduction in autoantibodies in 2 of 3 patients Early clinical activity of rese-cel without preconditioning* *As of 11 September 2025. Cabaletta Bio: Data on file. Disease severity intervals as defined Krain RL, et al. Br J Dermatol. 2021;184(5): 975–977. Gray vertical dotted line indicates day of rese-cel infusion (study visit Day 1). Baseline Week 12 Images PV-1M-2 Images PV-1M-2 PDAI Total Activity Score Anti-DSG3 and Anti-DSG1 Titers PDAI improvements were most significant in the two patients who experienced peripheral B cell elimination; all three patients were off immunomodulators as of the data cut-off Anti-DSG3 Anti-DSG1 AS PRESENTED AT ESGCT 2025

Lupus: Unmet Need & Clinical Data

Increased mortality risk & negative impact on quality of life for patients with SLE & LN SLE & LN: Represent a high unmet clinical need ESRD, end-stage renal disease; LN, lupus nephritis; SLE, systemic lupus erythematosus. 1. Zen M, et al. Eur J Intern Med. 2023;112:45–51. 2. Rahman P, et al. Lupus. 2001;10(2):93-96. 3. Singh, R, et al. Lupus 27.10 (2018): 1577-1581.4. Murimi-Worstell, I., et al. BMJ 10.5 (2020): e031850. 5. Lichtnekert, J. Nature reviews rheumatology 20.11 (2024): 699-711. 6. Tektonidou, M. Arthritis & rheumatology 68.6 (2016): 1432-1441. 7. Results from quantitative survey of U.S. lupus-treating physicians (rheumatologists & nephrologists), conducted 2Q25. N = ~150. SLE patients with moderate to severe, refractory disease & LN patients with refractory disease potentially eligible for rese-cel (per analysis of quantitative research with ~150 lupus-treating physicians) Eligible U.S. Non-Renal SLE & LN patients7 ~40,000 U.S. non-renal SLE patients potentially eligible for rese-cel ~210k non-renal SLE patients ~50,000 U.S. LN patients potentially eligible for rese-cel ~110k LN patients SLE is a chronic autoimmune condition that can affect nearly every organ system1 Most common in women, with disease onset generally between ages of 20-40 years Common symptoms include severe fatigue, joint pain and swelling, skin rashes, ulcers & Raynaud’s phenomenon >50% of patients develop permanent widespread organ damage, caused by disease & current treatments2 Standardized mortality ratio from 2.4-4.5 for SLE patients3,4 ~30-40% of SLE patients develop LN, with inflammation & damage within the kidneys LN may present silently or with symptoms such as proteinuria, hematuria, swelling & elevated blood pressure 10-30% of patients with LN will progress to ESRD, requiring dialysis or transplantation within the first decade of their disease5,6 Market research indicates opportunity to achieve superior penetration and potentially further expand the market through introducing a no preconditioning CAR T alternative for patients

All patients had active, refractory disease and had failed multiple B cell-targeted therapies Baseline characteristics: First 9 patients in RESET-SLE* *As of 11 Sep, 2025. †Baseline disease activity = activity before preconditioning. ‡SLE medications may include biologics, anti-malarials, and immunosuppressants. §N=2 patients included in UPCR analysis: SLE-1 had pure Class V LN and extra-renal SLE disease activity and SLE-5 had Class II LN with moderate to severe chronicity and extra-renal disease activity that met inclusion criteria for the non-renal cohort. dsDNA, double-stranded DNA; GC, glucocorticoid; LN, lupus nephritis; RESET, REstoring SElf-Tolerance; SLE, systemic lupus erythematosus; SLEDAI-2K, SLE Disease Activity Index 2000; Sm, Smith; UPCR, urine protein-to-creatinine ratio. Cabaletta Bio: Data on File. Cohort​ Non-renal SLE (n=5) LN​ (n=4) Age, years, mean (min, max) ~34 (26, 44) ~26 (18, 35)​ Female, n (%) 4 (80) 3 (75) Time from diagnosis to screening, years, mean (min, max) 11.5 (6.1​, 17.3) 7.3 (2.2​, 15.7) Autoantibodies (%) dsDNA: 100% Sm: ​60% dsDNA: 75% Sm: ​75% Baseline disease activity​† SLEDAI-2K (median) 10 16 UPCR (mg/mg) (median) 1.09§ 3.45 Therapies at screening:​ Systemic GCs ≤2 SLE immunomodulators​‡ ≥3 SLE immunomodulators​‡ 80% 60% 40%​ 50% 50% 50% GC dose at screening, mg/day, mean (min, max) 13.4 (0, 30) 6.25 (0, 20)

Improvements in SLEDAI-2K over time and significant reduction in anti-dsDNA antibodies after discontinuing immunomodulators Efficacy data following rese-cel infusion* *As of 11 Sep, 2025. †Week 20 urinalysis components of the SLEDAI-2K (WBC, RBC and casts) imputed from Week 16 for total SLEDAI-2K score. ‡Assessed by ELISA at a central lab at baseline, weeks 12, 24, 36 and 52. dsDNA, double-stranded DNA; LN, lupus nephritis; rese-cel, resecabtagene autoleucel; SLE, systemic lupus erythematosus; SLEDAI-2K, Systemic Lupus Erythematosus Disease Activity Index 2000. Cabaletta Bio: Data on File. SLEDAI-2K, non-renal SLE (n=5) SLEDAI-2K Discontinued all immunomodulators SLEDAI-2K, LN (n=4) Anti-dsDNA antibody (N=9)‡ SLEDAI-2K Discontinued all immunomodulators † Clinical & translational data in lupus for rese-cel with preconditioning (PC) along with initial PC free data in PV support expansion of simplified PC free regimen into lupus; initial data anticipated in 1H26

Systemic Sclerosis: Unmet Need & Clinical Data

Associated with progressive morbidity and high mortality1,2 Systemic sclerosis: Profound unmet need & limited options AHSCT, autologous hematopoietic stem cell transplantation; ILD, interstitial lung disease; SSc, systemic sclerosis. 1. Allanore Y, et al. Nat Rev Dis Primers. 2015;1:15002. 2. Denton CP, et al. Lancet. 2017;390(10103):1685–1699. 3. Thoreau B, et al. Front Immunol. 2022;13:933468. 4. Truchetet ME, et al. Clin Rev Allergy Immunol. 2023;64(3):262–283. 5. Pope JE, et al. Nat Rev Rheumatol. 2023;19(4):212–226. 6. Results from quantitative survey of U.S. SSc-treating physicians (rheumatologists), conducted 3Q25. N = ~100. Rare, potentially life-threatening autoimmune disease1 Typically, middle age onset and more common in females​1 Highest mortality of all rheumatological diseases & significant burden from persistent skin & organ manifestations4,5 Mean survival is ~12 years from diagnosis Need for disease-modifying therapies across all SSc subsets5 FDA-approved agents for SSc-ILD slow but do not stabilize or improve lung progression Approved based on 1-year primary endpoints No existing treatments capable of halting SSc pathology other than AHSCT, which carries high risk​ Patients experience a progressive & often fatal course​ SSc patients with early, active disease potentially eligible for rese-cel (per quantitative research with ~100 SSc-treating physicians) Eligible U.S. SSc patients6 ~12,000-15,000 U.S. SSc patients potentially eligible for rese-cel ~90k SSc patients (~40% with clinically significant ILD) Characterized by progressive skin & internal organ fibrosis1 Deep, tissue-level B cell-driven autoimmunity, with activated B cells & autoantibodies, promotes inflammation & organ damage3

All patients had active, refractory disease and were on 1 to 3 disease-specific therapies at screening Baseline characteristics: First 6 Patients in RESET-SSc* *As of 11 Sep, 2025; primary endpoint is incidence and severity of adverse events through Day 29 †Baseline disease activity = activity before preconditioning. ‡Per patient history and HRCT. DLCO, % predicted diffusing capacity for carbon monoxide; FVC, forced vital capacity; GC, glucocorticoid; HAQ-DI, Health Assessment Questionnaire Disability Index; HCQ, hydroxychloroquine; HRCT, high-resolution computed tomography; ILD, interstitial lung disease; IVIg, intravenous immune globulin; MMF, mycophenolate mofetil; MPA, mycophenoloic acid; mRSS, modified Rodnan skin score; NIN, nintedanib; SAE, serious adverse event; PFT, pulmonary function test; RESET, REstoring SElf-Tolerance; RNA Pol III, ribonucleic acid polymerase III; Scl-70, anti–topoisomerase I antibody; SSc, systemic sclerosis; TOC, tocilizumab; y, years. Cabaletta Bio: Data on File. Severe Skin Cohort Organ Cohort Patient / Cohort SSc-Skin-1 SSc-Skin-2 SSc-Skin-3 SSc-Organ-1 SSc-Organ-2 SSc-Organ-3 Age, sex 66 F 55 F 59 M 70 M 43 F 60 F Disease duration (y) ~2 ~0.5 ~2 ~5 ~2 ~1 Autoantibodies RNA Pol III Scl-70 RNA Pol III ‒ Scl-70 Scl-70 Baseline† mRSS 42 38 45 12 9 24 Baseline† HAQ-DI 2.25 2.125 2.875 0.75 0.50 2.50 Baseline† PFTs (% predicted) FVC: 91 DLCO: 70 FVC: 93 DLCO: 58 FVC: 50 DLCO: 89 FVC: 69 DLCO: 58 FVC: 76 DLCO: 66 FVC: 83 DLCO: 78 ILD presence‡ ü ‒ ‒ ü ü ü Therapies at Screening MMF GC, MPA MMF MMF, TOC, NIN GC, TOC MMF, IVIg, HCQ

As of the data cut-off, 4 of 4 SSc patients with ≥12 weeks follow-up had FVC stabilization or improvement SSc: Efficacy data following rese-cel infusion* *As of 11 Sep, 2025; primary endpoint is incidence and severity of adverse events through Day 29. †Reflects trend from baseline to latest available timepoint. ‡Revised CRISS is evaluated at Weeks 12, 24, 36, and 52. PFTs from Week 24 are carried forward for Week 36 evaluation. §Revised CRISS-50 met at Weeks 12 and 36. Not met at Week 24. ¶DLCO and FVC are evaluated at Weeks 12 and 24. **Based on the research-based, qualified, quantitative Luminex assay. ‡‡Tapering GC. CRISS, Composite Response Index in Systemic Sclerosis; DLCO, % predicted diffusing capacity for carbon monoxide; FVC, forced vital capacity; GC, glucocorticoid; IM, immunomodulatory medication; mRSS, modified Rodnan Skin Score (measure of skin thickness in SSc across 17 body areas, with a maximum score of 51); N/A, not applicable; rese-cel, resecabtagene autoleucel; RNA Pol III/RP11, ribonucleic acid polymerase III; Scl-70, anti–topoisomerase I antibody; SSc, systemic sclerosis. Cabaletta Bio: Data on File. Severe Skin Cohort Organ Cohort Patient / Cohort SSc-Skin-1 SSc-Skin-2 SSc-Skin-3 SSc-Organ-1 SSc-Organ-2 SSc-Organ-3 Latest follow-up Week 48 Week 24 Day 29 Week 16 Week 12 Day 29 GC-free ü ü ü ü ü –‡‡ IM-free ü ü ü ü ü ü Antibody and trend† RNA Pol III ê Scl-70 ê** RNA Pol III; too early None detected Scl-70 ê Scl-70; too early Revised CRISS-25‡ (time to response) ü Week 12 ü Week 24 N/A ü Week 12 ü Week 12 N/A Revised CRISS-50‡ (time to response) ü Week 12§ ü Week 24 N/A – ü Week 12 N/A mRSS (baseline to latest follow-up) 42→23 38→27 45→32 12→6 9→4 24→22 FVC¶ [%] (baseline to latest follow-up) 91→105 93→100 N/A 69→72 76→77 N/A DLCO¶ [%] (baseline to latest follow-up) 70→81 58→75 N/A 58→58 66→75 N/A SSc patients were able to achieve meaningful clinical responses off all immunomodulators and off or tapering steroids

Myasthenia Gravis: Unmet Need & Clinical Data

High impact of disease due to patient symptoms & cost burden, particularly for refractory patients Myasthenia gravis: Significant disease & treatment burden Gilhus NE, et al. Eur J Neurol. 2024 2. Dresser L, et al. J Clin Med. May 2021. 3. Results from quantitative survey of U.S. MG-treating physicians (neurologists), conducted 3Q25. N = ~100. Generalized MG patients with refractory disease potentially eligible for rese-cel (per quantitative research with ~100 MG-treating physicians) Eligible U.S. MG patients3 ~35,000 U.S. MG patients potentially eligible for rese-cel ~100k MG patients Serious, chronic autoimmune neuromuscular disorder1 Available therapeutic options focus on specific symptoms and can be associated with serious long-term side effects Mainstays include steroids, immunosuppressants (e.g., mycophenolate), FcRn antagonists, complement inhibitors and rituximab MG represents a significant healthcare cost burden in the US, particularly for patients whose disease is inadequately controlled Treatments have transient effect & involve long-term broad immunosuppression1 Characterized by defective transmission at the neuromuscular junction, resulting in weakness of the skeletal muscles Typically associated with autoantibodies (e.g. AChR, MuSK, LRP4) Symptoms range from ocular involvement, including double vision and ptosis, to severe weakness of the limb, bulbar, trunk, and respiratory muscles, which is worsened with exertion Mortality rate estimated to be 5-9%, primarily driven by myasthenic crises, or respiratory crises requiring ventilation2

All patients had active, refractory disease despite multiple immunomodulatory agents Baseline Characteristics: 13 RESET-MG Patients* AChR Positive (n=7) AChR Negative (n=6) Age, years, mean (min, max) 54.0 (41, 65) 53.3 (37, 70) Female, n (%) 3 (42.9%) 6 (100.0%) Time from diagnosis to screening, years, mean (min, max) 7.10 (1.4, 19.1) 6.83 (0.6, 16.2) Autoantibodies (%) AChR: 100% Seronegative: 50% MuSK: 33.3% LRP4: 16.7% Baseline disease activity​† MG-ADL (mean) 12.3 12.8 QMG (mean) 14.1 16.8 Prior MG therapies (excluding GCs), mean (min, max) 4.6 (0, 8) 3.5 (1, 6) Therapies at screening:​ Systemic GCs ≤2 MG therapies​‡ ≥3 MG therapies​‡ 57% 71% 29% 50% 83% 17% GC dose at screening§, mg/day, mean (min, max) 10 (0, 25) 10.8 (0, 30) *As of 6 March, 2026. †Baseline disease activity = activity before preconditioning. ‡MG therapies include acetylcholinesterase inhibitors, FcRn inhibitors, biologics, IVIg, and immunosuppressants. §GC dose = glucocorticoid dose expressed in equivalent dose of prednisone (mg/day). AChR, acetylcholine receptor; FcRn, neonatal Fc receptor; GC, glucocorticoid; IVIg, intravenous immunoglobulin; LRP4, low-density lipoprotein receptor-related protein 4; MG, myasthenia gravis; MG-ADL, MG – Activities of Daily Living; MuSK, muscle-specific tyrosine kinase; QMG, Quantitative Myasthenia Gravis Score; RESET, REstoring SElf-Tolerance; rese-cel, resecabtagene autoleucel. Cabaletta Bio – Data on File.

No CRS was observed in 11 of 13 patients; CRS was mild and resolved with no sequelae; no ICANS observed Incidence of Relevant and Related Serious Adverse Events* Cohort AChR Positive AChR Negative Patient AChR-pos-1 AChR-pos-2 AChR-pos-3 AChR-pos-4 AChR-pos-5 AChR-pos-6 AChR-pos-7 AChR-neg-1 AChR-neg-2 AChR-neg-3 AChR-neg-4 AChR-neg-5 AChR-neg-6 CRS† None Grade 2‡ None None None None Grade 1‡ None None None None None None ICANS† None None None None None None None None None None None None None Serious infections§ None None None None None None None None None None None None None Related SAEs¶ (Grade) (Excluding CRS/ICANS) None Physical deconditioning, anorexia (3) None None None None None None None None None Neutropenic fever (3) None *As of 6 March, 2026; (N=13 dosed); primary endpoint is incidence and severity of adverse events through Day 29. †Graded per ASTCT Consensus Grading Criteria. ‡The median time to onset of observed CRS was 5 days (range 2–8 days) relative to the rese-cel infusion (events occurring within 7 days of each other were considered a single event). §Coded in System Organ Class of Infections and Infestations and meets seriousness criteria. ¶As assessed per US Food and Drug Administration guidelines. AChR, acetylcholine receptor; AE, adverse event; ASTCT, American Society for Transplantation and Cellular Therapy; CRS, cytokine release syndrome; ICANS, immune effector cell-associated neurotoxicity syndrome; SAE, serious adverse event. Cabaletta Bio – Data on File.

After discontinuation of all immunomodulators Efficacy data in AChR-positive patients following rese-cel infusion1* *As of 6 March, 2026. †Baseline disease activity = activity before preconditioning. ‡Mean and n numbers are based on dosed patients not receiving rescue medication for MG. §AChR-pos-1: AZA, a prohibited medication, was continued until the day of infusion (Day 1). IVIg was stopped prior to rese-cel infusion and restarted 4 weeks after infusion for continued MG symptoms; patient discontinued study at Week 20 due to visit refusal. AChR-pos-1, Day 29 visit data unavailable. ¶AChR-pos-4 missed Week 16 visit. **AChR-pos-7 received rescue IVIg due to MG exacerbation 3 days post rese-cel infusion; IVIg rescue therapy ongoing. AChEI, acetylcholinesterase inhibitors (i.e PYR); AChR, acetylcholine receptor; AZA, azathioprine; EFG, efgartigimod; GC, glucocorticoid; IM, immunomodulatory medication; IVIg, intravenous immunoglobulin; MG, myasthenia gravis; MG-ADL, MG – Activities of Daily Living; MMF, mycophenolate mofetil; PYR, pyridostigmine; QMG, Quantitative Myasthenia Gravis Score; rese-cel, resecabtagene autoleucel. 1. Cabaletta Bio – Data on File. 2. Muppidi S, et al. Muscle Nerve. 2022;65(6):630–639. 3. EMA. Available at: www.ema.europa.eu/en/documents/overview/soliris-epar-medicine-overview_en.pdf (accessed April 2026). 4. Barnett C, et al. Neurol Clin. 2018;36(2):339–353. After discontinuation of all immunodulators, 5 of 7 AChR-positive patients showed clinically meaningful improvements on the MG-ADL scale Cabaletta anticipates announcing registrational plans and trial design in mid-26 AChR-pos-1§ AChR-pos-2 AChR-pos-3 AChR-pos-4 AChR-pos-5 AChR-pos-6 AChR-pos-7** MG medications (screening visit) AZA, IVIg, GC, PYR EFG, PYR EFG, MMF, GC EFG, MMF, GC, PYR PYR GC, PYR IVIg GC-free (latest follow-up) Taper ü Taper ü ü Taper ü AChEI-free (latest follow-up) Ongoing ü ü ü Taper ü ü MG-ADL response Received IVIg ü ü ü ü ü Received IVIg MG-ADL point change from baseline† Clinically meaningful improvement threshold2,3 MG-ADL QMG Clinically meaningful improvement threshold4 Discontinued all immunomodulators ≥2 QMG point change from baseline† n‡ 5 5 5 5 3¶ 3 2 1 n‡ 5 5 5 5 3¶ 3 2 1 ≥3 Discontinued all immunomodulators AChR-pos-1 not evaluable due to continued use of a prohibited medication, azathioprine, until the day of infusion. AChR-pos-1 not evaluable due to continued use of a prohibited medication, azathioprine, until the day of infusion.

After discontinuation of all immunomodulators Efficacy data in AChR-negative patients following rese-cel infusion1* *As of 6 March, 2026. †Baseline disease activity = activity before preconditioning. ‡Mean and n numbers are based on dosed patients not receiving rescue medication for MG. §AChR-neg-1, no Week 44 QMG performed (unrelated AE prevented assessment being completed); AChR-neg-2, no Week 28 visit data available (missed visit). ¶AChR-neg-1 receiving low dose IVIg for ongoing hypogammaglobinemia every 2 months from Week 8; AChR-neg-2 received rescue EFG from Week 13 through Week 16 and IVIg every 3 weeks from Week 24 visit due to MG symptoms; AChR-neg-3 receiving chronic GC for adrenal insufficiency. AChEI, acetylcholinesterase inhibitors (i.e PYR); AChR, acetylcholine receptor; AZA, azathioprine; EFG, efgartigimod; GC, glucocorticoid; IM, immunomodulatory medication; IVIg, intravenous immunoglobulin; LRP4, low-density lipoprotein receptor-related protein 4; MG, myasthenia gravis; MG-ADL, MG – Activities of Daily Living; MMF, mycophenolate mofetil; MuSK, muscle-specific tyrosine kinase; PLA, plasmapheresis; PYR, pyridostigmine; QMG, Quantitative Myasthenia Gravis Score; rese-cel, resecabtagene autoleucel; ROZ, rozanolixizumab, 1. Cabaletta Bio – Data on File. 2. Muppidi S, et al. Muscle Nerve. 2022;65(6):630–639. 3. EMA. Available at: www.ema.europa.eu/en/documents/overview/soliris-epar-medicine-overview_en.pdf (accessed April 2026). 4. Barnett C, et al. Neurol Clin. 2018;36(2):339–353. After discontinuation of all immunomodulators, 5 of 6 AChR-negative patients showed clinically meaningful improvements on the MG-ADL scale; Cabaletta anticipates announcing registrational plans and trial design in mid-26 AChR-neg-1¶ (seronegative) AChR-neg-2¶ (seronegative) AChR-neg-3 (MuSK) AChR-neg-4 (MuSK) AChR-neg-5 (LRP4) AChR-neg-6 (seronegative) MG medications (screening visit) PLA, GC, PYR MMF, ROZ, PYR PLA,GC AZA EFG EFG, GC, PYR GC-free (latest follow-up) ü ü No¶ ü ü Taper AChEI-free (latest follow-up) ü ü ü ü ü Taper MG-ADL response ü Received EFG and IVIg ü ü ü ü MG-ADL point change from baseline† Clinically meaningful improvement threshold2,3 MG-ADL Discontinued all immunomodulators QMG Clinically meaningful improvement threshold4 QMG point change from baseline† Discontinued all immunomodulators ≥2 n‡ 6 6 6 6 3 3 2 1 1 1 1 1 Seronegative MuSK LRP4 Seronegative MuSK LRP4 ≥3 n‡ 6 6 6 6 3 3 2 1 1 1 1

Corporate Summary

Track record of operational success evaluating & developing novel cell therapy candidates in autoimmunity Cabaletta Bio leadership LEADERSHIP TEAM Anup Marda Chief Financial Officer Nicolette Sherman Chief HR Officer Michael Gerard General Counsel Steven Nichtberger, M.D. President, CEO & Chairman Heather Harte-Hall Chief Compliance Officer Gwendolyn Binder, Ph.D. President, Science & Technology SCIENTIFIC ADVISORY BOARD Aimee Payne, M.D., Ph.D. Co-Founder and Co-Chair Michael C. Milone, M.D., Ph.D. Co-Founder and Co-Chair Carl June, M.D. Jay Siegel, M.D. Iain McInnes, Ph.D., FRCP, FRSE, FMedSci Georg Schett, M.D. David J. Chang, M.D., M.P.H., FACR Chief Medical Officer Samik Basu, M.D. Chief Scientific Officer Arun Das, M.D. Chief Business Officer Sarah Yuan Chief Technology Officer Steve Gavel Chief Commercial Officer Francisco Ramírez-Valle, M.D., Ph.D.,

Removing PC should expand access while automated manufacturing should reduce COGS & increase scale Transformative value proposition with PC elimination & automation PV: PC free rese-cel data including longer-term follow up at the initial dose SLE: PC free rese-cel data including early data at the initial dose Initial clinical experience with rese-cel manufactured by Cellares Transformative Value Proposition Elimination of PC Automated Manufacturing Expands the market Catalyzes outpatient use Reduces resource utilization Improves patient and provider experience Differentiated product profile Typical ‘biologic’ margins Potential to address larger autoimmune indications including T1D, UC and RA Minimal capital investment Scalability to produce thousands of patient runs per year Substantially reduced COGS Facilitates global expansion Longer-term PC free rese-cel data from the PV & SLE dose cohorts and from patients receiving rese-cel manufactured by Cellares 1H26 2H26 COGS – Cost of goods sold; PC – Preconditioning; PV – Pemphigus vulgaris; SLE – Systemic lupus erythematosus; RA – Rheumatoid arthritis; T1D – Type 1 diabetes; UC – Ulcerative colitis.

Appendix

TIS is a composite tool measuring a patient’s relative improvement from their baseline Myositis outcomes captured through validated composite endpoint Major Total Improvement Score 100 80 0 Minimal Moderate 60 40 20 Week 24 Baseline Week 12 None Extramuscular Activity 20 max achievable score Manual Muscle Testing (MMT8) 32.5 max achievable score Patient Global Activity 10 max achievable score Physician Global Activity 20 max achievable score Health Assessment  Questionnaire (HAQ) 10 max achievable score Muscle Enzymes 7.5 max achievable score Total improvement score (TIS) components TIS developed via conjoint analysis based continuous model using absolute percentage change in 6 core set measures (CSM): MMT8, Extramuscular Activity, Physician Global Activity, Health Assessment Questionnaire, Patient Global Activity, and Muscle Enzymes  TIS is the sum of improvement scores in the 6 CSMs, with ceiling of potential effect likely higher in DM and ASyS than in IMNM given minimal extramuscular involvement Illustrative patient-specific TIS ceiling for milder disease Illustrative patient-specific TIS ceiling for more severe disease ASyS – antisynthetase syndrome; CSM – core set measure; DM – dermatomyositis; IMNM – immune-mediated necrotizing myopathy; IVIg – intravenous immunoglobulin. Aggarwal R et al. NEJM. 2022;387(14):1264-1278.

Corporate Presentation May 2026

FAQ

What did Cabaletta Bio (CABA) announce in its latest 8-K?

Cabaletta Bio announced the pricing of an underwritten public offering of 51,725,000 shares of common stock at $2.90 per share, raising about $150 million in gross proceeds to support development and commercialization of its autoimmune cell therapy candidate rese-cel.

How large is Cabaletta Bio’s new stock offering and at what price?

The offering covers 51,725,000 shares of Cabaletta Bio common stock, each priced at $2.90. Underwriters will pay $2.726 per share, reflecting a 6.0% discount. All shares are being sold by the company, making this a primary capital raise for Cabaletta.

How much cash will Cabaletta Bio receive from the offering and how will it be used?

Cabaletta Bio expects approximately $141 million in net proceeds from the offering. Together with existing cash, funds are intended mainly to expand clinical development of rese-cel, enhance manufacturing capabilities for potential commercialization, and support working capital and general corporate purposes.

What is Cabaletta Bio’s cash position and runway after this financing?

Cabaletta reported about $117 million in cash and cash equivalents as of March 31, 2026. With net proceeds of roughly $141 million from the stock sale, management believes it can fund operating expenses and capital needs into mid‑2027 under its current operating plan.

When is Cabaletta Bio’s underwritten offering expected to close?

The offering is expected to close on or about May 5, 2026, subject to customary closing conditions. Joint book-running managers include TD Securities (USA) LLC, Guggenheim Securities, LLC, and Cantor, with H.C. Wainwright & Co. acting as lead manager for the transaction.

What is rese-cel, the program Cabaletta plans to fund with this raise?

Rese-cel is Cabaletta Bio’s fully human CD19-directed CAR T cell therapy candidate for autoimmune diseases. It is being evaluated in the RESET clinical program across multiple indications, including myositis, systemic lupus erythematosus, systemic sclerosis, myasthenia gravis, and pemphigus vulgaris.

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