53P - Integrin-_v_6 targeted CAR T-cells in an immunocompetent orthotopic model of pancreatic cancer

Background

Pancreatic cancer confers a dismal prognosis and better therapies are needed. Integrin αvβ6 is expressed in >90% of human pancreatic cancers with minimal expression in healthy tissues. αvβ6-targeted CAR T-cells are efficacious in heterotopic immunodeficient pancreatic models. However, these models do not recapitulate the profoundly immunosuppressive tumour microenvironment (TME) that is a hallmark of pancreatic cancer, and a barrier to effective therapy. This study aimed to create and evaluated αvβ6-targeted CAR T-cell therapies in an orthotopic, immunocompetent, metastatic model of PDAC.

Methods

We created a 2^nd generation murine CAR with the αvβ6-targeting A20FMDV2 peptide in a γ-retroviral backbone, and transduced splenocytes from C57BL/6 mice. Non-targeting (NT) CAR T-cells lacking the A20FMDV2 peptide were used as controls. In vitro cytotoxicity was evaluated with murine pancreatic cancer cells with minimal (TB32043) and ectopic expression of αvβ6 (TB32043mb6s2) using WST-1 viability assays, with T-cell activation measured by IFNγ assays. In vivo activity of the CAR T-cells were assessed in both immunocompetent C57BL/6 and immunodeficient NSG mice who had received orthotopic injections of TB32043mb6s2 cells, with cyclophosphamide preconditioning in C57BL/6 mice. The immune tumour microenvironment of TB32043mb6s2 tumours was evaluated using CyTOF.

Results

αvβ6-targeted murine CAR T-cells demonstrated dose-depending αvβ6-specific in vitro cytotoxicity and T-cell activation. αvβ6 CAR T-cells were tolerated in vivo in mice with metastatic pancreatic cancer, and led to improved survival in both immunocompetent mice (31 vs 21 days, p<0.05 vs NT CAR T-cells) and immunodeficient mice (39 vs 27 days, p<0.05). CyTOF evaluation of αvβ6-expressing TB32043mb6s2 tumours found the TME comprised ∼90% of the tumour, with immune cells comprising ∼ half of the TME.

Conclusions

Integrin-αvβ6 targeted CAR T-cell therapy was tolerated and improved survival in mice with an orthotopic immunocompetent model of pancreatic cancer. Further pre-clinical development is warranted.

Legal entity responsible for the study

Queen Mary University of London.

Funding

Pancreatic Cancer UK, Cancer Research UK, Medical Research Council.

Disclosure

All authors have declared no conflicts of interest.