52P - Tumor-targeted cytokine release by genetically-engineered myeloid cells rescues CAR-T activity and engages endogenous T cells against high-grade glioma in mouse models

Background

Chimeric antigen receptor T cells (CAR Ts) have shown limited efficacy in solid tumors due to poor penetration, constrained activity, and early exhaustion into the immunosuppressive tumor microenvironment (TME). While stimulatory cytokines can counteract immune suppression, their systemic administration entails risk of toxicities and counter-regulatory responses.

Methods

Here, we leveraged a population of tumor-associated TIE2 expressing macrophages (TEMs) to specifically release interferon-a (IFN) and/or orthogonal interleukin-2 (oIL2) in the TME through a hematopoietic stem cell-based gene therapy to broadly reprogram it toward immune activation. To investigate whether TME reprogramming could favor CAR-T function in hostile conditions, we took advantage of immunocompetent mice orthotopically challenged with a novel high-grade glioma (HGG) model (mGB2), faithfully recapitulating the human disease. We generated CAR Ts, either bearing an orthogonal IL-2 receptor or not, by optimizing a high-efficiency lentiviral-based transduction protocol of murine T cells.

Results

Targeted cytokine delivery rescued CAR Ts functionality against the clinically relevant antigen B7H3 in the mGB2 model which was refractory to CAR Ts alone. Immunophenotypic and transcriptomic analyses at single-cell resolution showed inhibition of CAR-T premature terminal exhaustion and induction of effector/memory states featuring activation of signaling pathways and transcriptional networks putatively boosting anti-tumor activity, resulting in tumor growth inhibition and survival prolongation. Importantly, IFN, especially when combined with private oIL2 signaling to CAR Ts, also engaged an endogenous T cell response spreading to tumor-associated antigens beyond B7H3. This accounted for rejection of B7H3^KO mGB2 rechallenge in mice that cleared the primary tumor.

Conclusions

Overall, the rescued CAR and endogenous T cell function delayed HGG growth and prolonged mice survival, suggesting that the combination of the above two gene and cell therapies, which are already under clinical testing as monotherapies, could achieve synergistic effects also in HGG patients.

Legal entity responsible for the study

The authors.

Funding

Fondazione AIRC per la Ricerca sul Cancro; Louis-Jeantet Foundation through the 2019 Jeantet-Collen Prize for Translational Medicine.

Disclosure

B. Gentner, L. Naldini: Financial Interests, Personal, Ownership Interest: Genenta science. All other authors have declared no conflicts of interest.