Transgene to Present Preclinical Data on Novel TG-MVA Prophylactic Vaccine Against mpox at the World Congress on Infectious Diseases

TG-MVA builds on Transgene’s expertise in MVA (Modified Vaccinia Ankara) viral vectors, which are well established in smallpox vaccines development

Extensive data with TG-MVACEF and TG-MVACL demonstrate protection against Monkeypox virus (MPXV) infections across several models

Alongside its focus on advancing its myvac® platform for therapeutic cancer vaccines, Transgene is evaluating options to further develop TG-MVA and maximize its value

Strasbourg, France, May 26, 2026, 8:00 a.m. CET – Transgene (Euronext Paris: TNG), a biotech company that designs and develops virus-based immunotherapies for the treatment of cancer, today announced an oral presentation of new preclinical data highlighting the potential of TG￾MVA its Modified Vaccinia Ankara (MVA)-based prophylactic vaccine candidates against mpox produced on chicken embryo fibroblasts (TG-MVACEF) and Cell Line (TG-MVACL).

Transgene’s MVA viral vectoris derived from a virus originally developed for smallpox vaccination. Its strong safety profile and its classification within the Orthopoxvirus¹ family make it a particularly suitable vector for the development of mpox vaccines.

The oral presentation will take place at the World Congress on Infectious Diseases (WCID), held from June 25 to 27, 2026, in Barcelona, Spain.

Well-known for its Individualized Neoantigen Therapeutic Vaccines myvac® platform, which leverages MVA based viral vector technologies to stimulate the human immune system against cancer, Transgene is now applying its deep expertise in viral-vector engineering to further explore applications in acute infectious diseases. The development of TG-MVA targeting Orthopoxvirus￾related diseases results from an assessment of a significant potential biosecurity need for preparedness against potential biological threats, such as pandemics or bioterrorism.

1 Orthopoxvirus: a group of related viruses (Poxviridae family) including smallpox and monkeypox.

P R E S S R E L E A S E

With the global population largely naïve to Orthopoxviruses and vaccine supply currently dependent on a limited number of available vaccines, supply vulnerability poses a security risk. Transgene’s program aims to ensure continuous vaccine availability in both pandemic and interpandemic settings. It includes the development of a novel generation of prophylactic MVA￾based mpox vaccine (TG-MVACL) which is produced using an easily scalable and transposable cell line-based manufacturing process designed to ensure reliable vaccine supply and enable a rapid response to public health needs and biosecurity priorities.

“Our preclinical results with TG-MVACEF and TG-MVACL demonstrate its potential to offer fast￾acting protection against Monkeypox, and, more broadly, Orthopoxviruses infections. We are currently evaluating options to advance the program. TG-MVACL is considered the preferred candidate for further development in humans. It enables a high-volume solution; it is easily scalable and transposable, potentially overcoming the current industrial capacity constraints of CEF manufacturing to address public health and biosecurity needs. Although we are assessing options to continue developing this candidate, our strategy remains firmly centered on our myvac® platform, where we continue to focus on our core development efforts.” said Alessandro Riva, MD, Chairman and CEO of Transgene.

“In parallel, our business model is to generate robust proof-of-principle and proof-of-concept data to highlight the value of our innovative technologies, including TG-MVA, and enable partnerships or collaborative development. This approach allows us to maximize the impact of our assets while continuing to advance new treatment options for patients worldwide.”

At the World Congress on Infectious Diseases, Transgene will present new preclinical data evaluating the efficacy and safety of TG-MVA in mice and non-human primates (NHP). The findings demonstrate protective effects in vaccinated animals subsequently challenged with MPXV and support the continued development of TG-MVA.

The oral presentation will highlight comparative results across treatment groups, including:

• Survival outcomes following MPXV challenge
• Protective immune responses observed in animals (mice and non-human primates) vaccinated with TG‑MVA
• Safety and tolerability of the regimen in both species
• Comparability of TG-MVA produced on primary chicken embryo fibroblasts (TG-MVACEF) TG-MVA produced on a cell line (TG-MVACL) and against the current market-leading vaccine, MVA-BN®

About the Presentation:

• Title: “Robust Protection Against Monkeypox Virus Mediated by a Novel Cell‑Line–Derived MVA Vaccine (TG-MVACL)”
• Speaker: Nathalie Silvestre, Head of Vectorology Laboratory, Transgene
• Session: Vaccine development and immunization

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Contacts

Transgene:
Media:
Caroline Tosch
Corporate and Scientific Communications Manager
+33 (0)3 68 33 27 38
communication@transgene.fr

MEDiSTRAVA
Frazer Hall/Sylvie Berrebi
+ 44 (0)203 928 6900
transgene@medistrava.com

Investors & Analysts:
Lucie Larguier
Chief Financial Officer (CFO)
Nadege Bartoli
Investor Relations Analyst
and Financial Communications Officer
+33 (0)3 88 27 91 00/03
investorrelations@transgene.fr

About Transgene

Transgene (Euronext: TNG) is a biotechnology company focused on designing and developing targeted immunotherapies for the treatment of cancer. The Company’s clinical-stage programs consist of a portfolio of viral vector-based immunotherapeutics. TG4050, the first individualized therapeutic vaccine based on the myvac® platform is the Company’s lead asset, with demonstrated proof of principle in patients in the adjuvant treatment of head and neck cancers. The Company has other viral vector-based assets, including BT-001, an oncolytic virus based on the Invir.IO® viral backbone, which is in clinical development. The Company also conducts innovative discovery and preclinical work, aimed at developing novel viral vector-based modalities.

With Transgene’s myvac® platform, therapeutic vaccination enters the field of precision medicine with a novel immunotherapy that is fully tailored to each individual. The myvac® approach allows the generation of a virus-based immunotherapy that encodes patient-specific mutations, identified and selected through advanced Artificial Intelligence technologies.

With its proprietary platform Invir.IO®, Transgene is building on its viral vector engineering expertise to design a new generation of multifunctional oncolytic viruses.

Additional information about Transgene is available at: www.transgene.com
Follow us on social media: LinkedIn: @Transgene — X: @TransgeneSA — Bluesky: @Transgene

About TG-MVA

TG-MVA is Transgene’s Modified Vaccinia Ankara (MVA)-based vaccine candidate targeting Orthopoxvirus-related diseases, including mpox and smallpox. TG-MVACL is a highly attenuated, non-replicating MVA vaccine candidate designed to induce a rapid and robust antiviral immune response in individuals at risk of smallpox or mpox. It is manufactured using avian suspension cell lines, enabling rapid and scalable production, simplified industrial scale￾up, and reliable supply for large-scale and urgent medical needs. By contrast, TG-MVACEF is produced using traditional chicken embryo fibroblast (CEF) manufacturing methods.

Disclaimer

This press release contains forward-looking statements, which are subject to numerous risks and uncertainties, which could cause actual results to differ materially from those anticipated. The occurrence of any of these risks could have a significant negative outcome for the Company’s activities, perspectives, financial situation, results, regulatory authorities’ agreement with development phases, and development. The Company’s ability to commercialize its products depends on but is not limited to the following factors: positive pre-clinical data may not be predictive of human clinical results, the success of clinical studies, the ability to obtain financing and/or partnerships for product manufacturing, development and commercialization, and marketing approval by government regulatory authorities. For a discussion of risks and uncertainties which could cause the Company’s actual results, financial condition, performance or achievements to differ from those contained in the forward-looking statements, please refer to the Risk Factors (“Facteurs de Risque”) section of the Universal Registration Document, available on the AMF website (http://www.amf-france.org) or on Transgene’s website (www.transgene.com). Forward-looking statements speak only as of the date on which they are made, and Transgene undertakes no obligation to update these forward-looking statements, even if new information becomes available in the future.

Notes

1. Orthopoxvirus: a group of related viruses (Poxviridae family) including smallpox and monkeypox.