BT-001 Demonstrates Sustained antitumoral Activity in Refractory Tumors When Combined with pembrolizumab

Strasbourg,France,and Lund,Sweden,October 20,2025 – Transgene (Euronext Paris: TNG),a biotech company specializing in virus-based immunotherapies for cancer,and BioInvent International AB (“BioInvent”) (Nasdaq stockholm: BINV),a biotech company focused on novel antibody advancement for cancer immunotherapy,today presented updated clinical results at the 2025 European Society for Medical Oncology (ESMO) Annual Meeting,showcasing positive antitumoral activity of BT-001 in patients with advanced refractory tumors.

The data demonstrate that intra-tumoral (IT) injection of BT-001, in combination with intravenous (IV) anti-PD-1 therapy KEYTRUDA® (pembrolizumab) from MSD (Merck & Co., Inc., Rahway, NJ, USA), was well tolerated and induced positive local, abscopal, and sustained antitumoral activity in both injected and non-injected lesions.

Translational analyses revealed increased T cell chemoattractants in the blood and infiltration of activated CD8+ T cells and macrophages in tumors following treatment with BT-001 combined with pembrolizumab. Significant tumor shrinkage (≥30% decrease in longest diameter) was observed in five of 16 injected lesions (in three melanoma patients and one sarcoma patient). Furthermore, four patients experienced tumor shrinkage in non-injected lesions.

Long-lasting partial responses (PRs) were observed in a patient with melanoma resistant to anti-PD-1/anti-CTLA-4 combination therapy and in a heavily pre-treated, PD-L1 negative leiomyosarcoma patient.

these immune-mediated tumor shrinkages align with the hypothesis that BT-001, when combined with pembrolizumab, converts “cold” tumors into immunologically active ones. The overall data support continued development of BT-001 across a range of solid tumors to enhance responses to cancer immunotherapies.

Prof.Celeste Lebbé,Dermatologist and Venereologist,Head of Dermatology Department at Hospital Saint-Louis,Paris,commented: “Many cancer patients fail to respond to existing treatments,emphasizing the urgent need for new approaches. BT-001 represents a promising new class of immunotherapy, capable of inducing a potent local immune response through the expression of GM-CSF and an anti-CTLA-4 antibody.These clinical data provide compelling proof of concept, highlighting the relevance of this oncolytic virus in transforming cold tumors into immunologically active ones. Whether administered alone or in combination with pembrolizumab, BT-001 offers the potential to expand treatment options with a favorable safety profile across multiple tumor types.“

Dr. Alessandro Riva, Chairman and CEO of Transgene, said: “We are pleased to jointly present these clinical data on BT-001 at ESMO 2025, demonstrating encouraging antitumor activity in patients with solid, refractory solid tumors. These updated results confirm BT-001’s mechanism of action as a single agent administered via intra-tumoral injection and show“

“`html

Transgene: A Leader in Oncolytic Viruses and personalized Immunotherapy

Transgene is a clinical-stage biotechnology company dedicated to developing innovative immunotherapies using viral vectors. The company focuses on two core platforms: myvac®, a personalized therapeutic vaccine, and Invir.IO®, a platform for creating next-generation oncolytic viruses. Founded in 1998, Transgene is headquartered in Illkirch-Graffenstaden, France, and listed on Euronext Paris (Euronext Paris).

The myvac® Platform: Personalized Cancer Vaccination

myvac® represents a significant advancement in precision medicine for cancer treatment. This therapeutic vaccination platform leverages Artificial Intelligence (AI) capabilities provided by its partner, NEC, to identify and select patient-specific mutations within their tumor. These mutations are then encoded into a customized viral vector, creating an immunotherapy uniquely tailored to each individual’s cancer. This personalized approach aims to stimulate a robust immune response specifically targeting the patient’s tumor cells.

Traditional cancer vaccines often target common antigens, which may not be present in all patients or may lead to immune evasion. myvac® overcomes these limitations by focusing on neoantigens – unique mutations arising within the tumor – making it a highly personalized and possibly more effective treatment option.Learn more about the myvac® pipeline.

invir.IO®: Next-Generation Oncolytic Viruses

Oncolytic viruses are engineered viruses that selectively infect and destroy cancer cells. Transgene’s Invir.IO® platform builds upon the company’s extensive expertise in viral vector engineering to design a new generation of multifunctional oncolytic viruses. These viruses are designed to not only directly kill cancer cells but also to stimulate an anti-tumor immune response, enhancing the overall therapeutic effect.

the Invir.IO® platform allows for the incorporation of multiple functionalities into a single viral vector, potentially improving efficacy and reducing off-target effects. This includes the ability to express immunostimulatory genes within the tumor microenvironment, further amplifying the immune response. Currently, Transgene has an oncolytic virus based on the Invir.IO® viral backbone in clinical development. Explore the Invir.IO® platform.

Key Differences Between myvac® and Invir.IO®

While both platforms utilize viral vectors to fight cancer, they operate through different mechanisms:

• myvac®: A personalized therapeutic vaccine that stimulates the patient’s own immune system to recognize and attack cancer cells based on their unique mutations.
• Invir.IO®: An oncolytic virus that directly infects and destroys cancer cells while also triggering an immune response.

Transgene’s Commitment to Innovation

Transgene is dedicated to ongoing research and development, continually seeking to improve its viral vector-based modalities. The company’s innovative discovery and preclinical work aim to unlock the full potential of viral immunotherapies for a wide range of cancers.

Additional facts about Transgene is available at: www.transgene.com. Follow us on social media: X (formerly Twitter): https://twitter.com/Transgene.

Frequently Asked Questions (FAQ)

Q: What is a viral vector?

A: A viral vector is a modified virus used as a delivery system to introduce genetic material into cells. In Transgene’s platforms,viral vectors are engineered to be safe and effective for therapeutic purposes.