Therapeutic Efficacy of Engineered T Cells Targeting CD19 in a B-Cell Lymphoma Model.

The success of monoclonal antibodies in the treatment of certain cancers demonstrates that immune based therapies can work and are particularly effective in B cell malignancies. However, tumours can still avoid antibody mediate mechanisms of attack and there is currently no estalbished method of effectively recruiting T cells to harness their potential anti-tumour effects. We are exploring gene therapy approaches to endow T cells with antibody type specificity in order to more efficiently target and lyse tumours and thereby improve the overall immune therapy of cancer

T cells grafted with a CD19 specific receptor consisting of a CD19 scFv linked to human CD3zeta (CD19z) were tested for their potency against B cell lymphoma lines in vivo. T cells were engineered using retroviral vestors to possess a CD19 specific receptor which endows the T cells with specificity for B cell lymphoma. The vector incorporates a truncated hCD34 gene as a marker to facilitate assessment of transduced cells using as clinically applicable, non-immunogenic marker gene. Mice bearing B cell lymphoma were treated with a systemic infusion of targeted T cells with or without non-myeloablative chemotherapy. Human T cells targeting CD19 cured 40% of SCID/beige mice with 6 day established metastatic tumour but only in conjunction with a single dose of cyclophosphamide. Murine T cells expressing the CD19z receptor were also effective with cure of 24hr established s.c human CD19+ tumour in SCID/beige and immunocompetent mice. Pretreatment with cyclophosphamide did not affect T cell engraftment or efficacy in immuno-compromised animals but was necessary for T cell engraftment in immuno-competent animals.

These results which parallel the approach successfully used with tumour infiltrating lymhocytes in melanoma patients conclusively demonstrate that the combination of engineered T cells with “pre-conditioning” chemotherapy significantly impacts upon tumour growth in vivo and this evidence supports the development of phase I clinical trials targeting B cell lymphoma.