Medigene AG: Medigene presents first preclinical data on mKRAS G12V combined with a PD1-41BB costimulatory switch protein

Planegg/Martinsried (pta011/23.10.2023/09:00 UTC+2)

Medigene AG (Medigene, the "Company", FSE: MDG1, Prime Standard) an immuno-oncology platform company focusing on the discovery and development of T cell immunotherapies for solid tumors, presents data showing significantly enhanced T cell activity when combining the PD1-41BB costimulatory switch protein (CSP) with recombinant T cell receptors (rTCR) not only when directed at the cancer-testis antigen (CTA) New York esophageal squamous cell carcinoma-1 (NY-ESO-1)/L Antigen Family Member-1a (LAGE-1a), but also, presented here for the first time, against the neoantigen mutant Kirsten rat sarcoma virus (mKRAS) G12V at the ESMO Congress 2023 held October 20-24, 2023, in Madrid, Spain.

The poster with the title "Mitigation of Tumor Microenvironment-Mediated Immunosuppression Using a PD1-41BB Switch Protein with Optimal Affinity TCRs for First-In-Class, 3rd Generation TCR-T Therapies" will be available on Monday, October 23, 2023, following the conference presentation on Medigene's website: https://medigene.com/science/abstracts/

"The immunosuppressive tumor microenvironment remains a major challenge for many T cells, including engineered T cells when applied against solid tumors. We are pleased to report encouraging pre-clinical data showing significantly enhanced T cell functionality by engaging our PD1-41BB CSP with different optimal affinity TCRs not only targeting CTAs like NY-ESO-1/LAGE-1a, but also against the neoantigen mKRAS G12V," said Prof. Dolores Schendel, Chief Scientific Officer at Medigene. "Armoring and enhancing our optimal affinity TCRs with the PD1-41BB costimulatory switch protein has the potential to overcome an immunosuppressive tumor microenvironment, leading to TCR-T therapies that improve safety, efficacy and durability outcomes for patients."

Within the solid tumor microenvironment (TME) T cell functionality is strongly impaired by the expression of the programmed cell death 1 ligand 1 (PD-L1) on tumor cells. The engagement of PD-L1 on tumor cells with PD-1 on T cells prevents specific killing of tumor cells. Moreover, PD-L1 signalling to T cells via the PD-1 receptor limits proliferation, cytokine secretion and cytotoxic response, while exhaustion is induced by repetitive TCR signalling in the absence of T cell costimulation.

The presented data showed that by combining optimal affinity TCRs with a PD1-41BB CSP, not only is the PD-1/PD-L1 axis blocked, but also T cell proliferation, cytokine secretion and cytotoxic response are increased through positive 4-1BB signaling, resulting in mitigation of the immunosuppressive TME through enhanced T cell functionality.

Robust expression of rTCR directed against NY-ESO-1/LAGE-1a and/or the neoantigen mKRAS G12V as well as the PD1-41BB CSP was demonstrated in TCR-T cells. The combination of NY-ESO-1/LAGE-1a or mKRAS G12V-specific rTCRs with PD1-41BB CSP displayed elevated polyfunctionality by increased levels of effector, stimulatory and chemoattractive cytokines as compared to TCR-T cells without PD1-41BB CSP in melanoma and pancreatic tumor cell lines.

Interferon-gamma (IFNγ) release measured in several tumor cell lines of different origin was enhanced in TCR-T cells co-expressing the rTCR and PD1-41BB CSP as compared to TCR-T cells lacking PD1-41BB CSP. The co-stimulatory effects of PD1-41BB were highly dependent on the rTCR-mediated recognition of the specific tumor-antigen NY-ESO-1/LAGE-1a or mKRAS G12V, respectively, and on the expression of the inhibitory ligand PD-L1 on tumor cells.

Elevated and sustained killing of 3D tumor spheroids was observed with TCR-T cells co-expressing the rTCR targeting mKRAS G12V and PD1-41BB CSP compared to TCR-T cells without the PD1-41BB CSP.

Additional data on Medigene's library of KRAS mutation-specific TCRs will be presented at the Society of Immunotherapy of Cancer (SITC) 38th Annual Meeting held in San Diego, November 1 to 5, 2023.

SITC 2023 Presentation Details:

Title: A novel library of optimal affinity KRAS mutation-specific T cell receptors associated with multiple HLAs, in combination with a PD1-41BB armoring and enhancement costimulatory switch receptor

Authors: Dolores Schendel, Giulia Longinotti, Mario Catarinella, Melanie Salvermoser, Julia Bittmann, Kirsty Crame, Kathrin Davari

Presenter: Selwyn Ho

Abstract number: 388

Date/ time: Saturday, November 4, 2023; Poster lunch session (11:55 am to 1:25 pm) and poster reception (7:00 pm to 8:30 pm); poster will be on display from 9:00 am to 8:30 pm (all times PDT)

Location: Poster Hall, San Diego Convention Center

The abstract will be available on the SITC website on October 31, 2023 at 9 am EDT, and the poster will be available on Medigene's website following the presentation.

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About Medigene AG

Medigene AG (FSE: MDG1) is an immuno-oncology platform company dedicated to developing T cell therapies to effectively eliminate cancer. Its End-to-End Platform, built on multiple proprietary and exclusive TCR generation and optimization, as well as product enhancement technologies, allows Medigene to create best-in-class, differentiated T cell receptor engineered T cell (TCR-T) therapies for multiple solid tumor indications that are optimized for safety, efficacy and durability. This platform provides product candidates for both its in-house therapeutics pipeline and partnering. For more information, please visit www.medigene.com

About Medigene's MDG1015 Program

MDG1015 is a 3rd generation T cell receptor engineered T cell (TCR-T) therapy targeting NY-ESO-1 / LAGE-1a, a well-recognized and validated cancer testis antigen which is expressed in multiple tumor types. MDG1015 contains our high-avidity, NY-ESO-1 /LAGE-1a TCR combined with our proprietary PD1-41BB costimulatory switch protein that blocks the PD1/PD-L1 inhibitory axis while simultaneously activating the T cell through the well described -41BB pathway further enhancing the activity and persistence of the TCR-T cell in the hostile tumor microenvironment (TME). MDG1015 is currently undergoing IND/CTA enabling studies.

About Medigene's PD1-41BB Costimulatory Switch Protein

Checkpoint inhibition via PD-1/PD-L1 pathway:

Cells of solid tumors are sensitive to killing by activated T cells but can escape this killing activity by producing inhibitory molecules known as 'checkpoint proteins', such as the Programmed Death Ligand 1 (PD-L1), on their surface. When this occurs, activated T cells which express PD-1, the natural receptor for PD-L1, are inactivated. The expression of PD-L1 is an adaptive immune resistance mechanism for tumors that can help them survive and grow.

The 4-1BB (CD137) costimulatory signaling pathway:

Effective T cell immune responses to antigens typically require both a primary antigenic stimulation via the T cell receptor (TCR) and costimulatory signals. The intracellular signaling domains of the 4-1BB protein offer a well-characterized pathway to costimulation and enhanced T cell responses.

Medigene's PD1-41BB switch receptor turns the tumor's attempted self-defense mechanism against the tumor by substituting the inhibitory signaling domain of PD-1 with the activating signaling domain of 4-1BB. Therefore, instead of inactivating T cells, the switch receptor delivers an activating signal to TCR-T cells. PD1-41BB-modified TCR-T cells proliferate strongly in the presence of PD-L1-positive tumor cells and kill more tumor cells upon repeated exposure. Additionally, switch receptor signals enable TCR-T cells to function better with low levels of glucose or high levels of TGFß, two conditions characteristic of strongly hostile tumor microenvironments.

About KRAS

KRAS (Kirsten rat sarcoma viral oncogene homologue) belongs to the group of small so-called Guanosine-5′-triphosphate (GTP)-binding proteins, known as RAS-like GTPases. Under physiological conditions KRAS tightly regulates cell proliferation and survival.

In cancer, KRAS is found frequently altered, in a wide variety of often fatal solid cancer types like pancreatic ductal adenocarcinoma, non-small-cell lung cancer, and colorectal cancer. Mutations in the KRAS gene result in the creation of neoantigens which drive uncontrolled proliferation of cancer cells. These mutations within the KRAS gene are unique to cancer cells and absent in healthy normal tissue, making KRAS an attractive target for TCR-T therapies. T cell receptor engineered T cell therapies offer a promising approach to targeting these mutations and addressing the challenges posed by solid tumors. Unlike CAR-T cells, which require surface antigens for recognition and may have limitations in target accessibility, TCR-T cells recognize a broader range of targets including intracellular proteins like neoantigens. This unique ability makes TCR-T therapies particularly well-suited for targeting KRAS mutations and other challenging neoantigens.

This press release contains forward-looking statements representing the opinion of Medigene as of the date of this release. The actual results achieved by Medigene may differ significantly from the forward-looking statements made herein. Medigene is not bound to update any of these forward-looking statements. Medigene® is a registered trademark of Medigene AG. This trademark may be owned or licensed in select locations only.

Medigene AG

Pamela Keck
Phone: +49 89 2000 3333 01
E-mail: investor@medigene.com

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