Arenavirus based Non-lytic Viral Immune Drivers with tumor-tropic mutations as new class of amplificators of anti-tumoral T cell responses

Background: Recent understandings of anti-tumoral immune mechanisms reveal that the strong and sustainable activation of specific CD8 + T cells in the tumor is one major trigger for successful immunotherapy. Checkpoint blockade, therapeutic vaccine, bi-specific T cell engager (BiTE) and CAR-T cells have strongly contributed to such tumor-specific T cell activation, however especially for solid cancers complete remission is limited. Recently, we showed that the non-cytopathic lymphocytic choriomeningitis virus (LCMV) induces strong anti-tumor responses without directly killing tumor cells. LCMV triggers infiltration of CD8 + T cells into the tumor leading to a sustained T cell dependent tumor regression. Here, we aim to generate an optimized arenavirus based on LCMV for the application of this new anti-tumoral mechanism in cancer patients. Methods: We aimed to adapt LCMV strain WE to tumor tissues. We performed multiple passaging of the wild-type strain LCMV-WE in several murine and human cancer cells. The occurring mutations were identified, their role in tumor cell tropism confirmed in vitro and in vivo , and the most effective ones were combined in an attenuated reassortant LCMV. Results: We identified several mutations, which showed accelerated propagation in cancer cells. By combining the identified mutations in attenuated reassortant LCM viruses, we generated arenavirus strains with accelerated entry and replication in a broad spectrum of human cancer cells. One of these strains exhibited strong anti-tumoral efficacy in a variety of tumor models with minimal replication in healthy tissues and no severe disease symptoms in immune compromised murine model systems. Dissecting the anti-tumoral mechanism revealed that tumor-specific T cells were expanded, T cells recruited to tumors and differentiated into potent effector cells. Due to this specific mode of action, this virus strain amplified the anti-tumoral activity of a BiTE (Trp1/CD3) and CAR-T cells to result in a strong synergistically acting tumor therapy. In non-human primates, treatment with this strain led to substantially increased virus-mediated cytokine and chemokine levels as well as T cells in the blood by maintaining a safe application. Conclusions: In conclusion, by using the biological principle of mutation and selection, we developed an arenavirus-based immune therapy safely applied in preclinical model systems and GLP studies as well as harbouring a unique mode of action and proprietary anti-tumoral efficacy. Combination with T cell-directed therapies including BITEs results in strong synergistic anti-tumoral responses.