Transgene to Present Preclinical Data Demonstrating Robust Protection Against Mpox with its Novel Scalable Cell Line–Derived MVA Vaccine Candidate (TG-MVATM) at WCID 2026

TG-MVATM uses a scalable cell line manufacturing process intended to strengthen and diversify global mpox and smallpox vaccine supply

TG-MVATM demonstrated efficacy, immunogenicity and safety comparable to those of the approved reference vaccine against mpox in multiple preclinical models

Transgene plans to advance TG-MVATM rapidly in the clinic

Oral presentation today at the World Congress on Infectious Diseases (WCID)

Strasbourg, France, June 25, 2026, 7:30 a.m. CET – Transgene (Euronext Paris: TNG), a biotech company that designs and develops virus-based immunotherapies for the treatment of cancer, today announces the oral presentation of positive preclinical data supporting its next￾generation Modified Vaccinia Ankara (MVA)–based vaccine candidate, TG-MVATM against mpox, at the World Congress on Infectious Diseases (WCID) 2026.

Transgene demonstrated that TG-MVATM, an innovative cell line–derived version, provides robust protection against monkeypox virus (MPXV) with efficacy, immunogenicity and safety comparable to the currently-reference MVA vaccine.

“Growing concerns over biosecurity and pandemic preparedness in Europe, the United States and across the world, combined with a substantial vaccine supply gap, have created an attractive opportunity to leverage the investment we have already made in the MVA cell-line platform used for myvac®. This enables the development of a cell-line based MVA vaccine (TG-MVATM) with scalable process to position Transgene as a potential additional supplier for mpox and smallpox vaccines in the medium term.

The promising preclinical results presented today at the World Congress on Infectious Diseases support the rapid advancement of TG-MVATM toward clinical development. We will work diligently to implement the next steps in alignment with the Health Authorities,” said Alessandro Riva, MD, Chairman and CEO of Transgene.

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

Addressing a growing global health threat with innovative and scalable cell-line manufacturing

The persistent risk of emerging poxviruses and biothreats, combined with limited manufacturing capacity, and a declining population immunity following the cessation of routine smallpox vaccination, highlights the need for additional, scalable vaccine solutions, alongside currently approved reference MVA-based mpox and smallpox1 vaccines.

Current mpox and smallpox vaccine supply relies on a limited number of manufacturers, creating vulnerabilities in global preparedness, with several regions reliant on a single approved MVA￾based vaccine.

By seeking to develop a cell-line based preventive vaccine against mpox and smallpox, Transgene is leveraging multiple manufacturing innovations initially developed to improve its myvac® platform to address an important public health need. These innovations can be applied to the prevention of mpox and other Orthopoxviruses2 infections.

TG-MVATM is a next generation vaccine candidate designed to address key supply and manufacturing challenges through:

• A non-replicating MVA backbone, similar to that of the approved reference vaccine,
• An innovative cell line–based manufacturing process, enabling scalable and reproducible production and overcoming the industrial limitations associated with CEF (Chicken Embryo Fibroblast) manufacturing,
• The potential to diversify supply and significantly expand vaccine availability to support outbreaks, stockpiling strategies and future biothreat responses.

Robust and comparable protection across established preclinical models

TG-MVATM was evaluated in mice and non-human primates (NHP) models. The candidate demonstrated comparable efficacy, immunogenicity and safety to the approved reference vaccine, and in particular:

• Protection against severe mpox morbidity and mortality, comparable to the approved reference vaccine:
  • Strong survival rates identical to the reference vaccine obtained in both mouse (100%) and primate (87%) models
  • Strong protection against disease severity, including reduced lesion formation, control of viral burden and attenuated clinical manifestations
• Induction of immune responses:
  • Level of neutralizing antibodies, comparable to those elicited by the approved reference MVA vaccine in both mice and NHPs
  • Broad humoral and cellular immune responses, including T-cell immunity, across all tested animal models, comparable to the approved reference vaccine
  • Comparable antibody kinetics and peak responses
• Similar safety profile across all vaccinated animals, with only mild and transient reactogenicity typically associated with vaccination.

Advancing toward clinical development

Supported by these compelling preclinical results as well as TG-MVATM potential to significantly contribute to addressing the future mpox and smallpox vaccine supply gaps, Transgene plans to advance rapidly TG-MVATM into clinical development, while confirming strategic focus on its individualized therapeutic vaccine platform myvac® and reiterates its financial visibility until early 2028.

About the oral keynote presentation

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

Download the oral presentation here.

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Contacts

Transgene:

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

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

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

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. TG4070, a second individualized vaccine candidate derived from the myvac® platform, is in Phase 1 clinical development in combination with nivolumab in adjuvant non-small lung cancer (NSCLC). 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-MVATM

TG-MVATM 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.

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. Both are caused by viruses from Orthopoxviruses
2. Orthopoxvirus: a group of related viruses (Poxviridae family) including smallpox and monkeypox