Constitutive Expression of CD40L by CAR-Modified Tumor Targeted T Cells Enhances Anti-Tumor Efficacy Both in Vitro and in Vivo

Abstract 4120

T cells can be genetically modified to target tumor antigens through the expression of a chimeric antigen receptor (CAR). Recent reports have demonstrated the effectiveness of CAR modified T cells in patients with relapsed or refractory malignancies. However, CAR modified T cells have yet to demonstrate the ability to recruit an endogenous anti-tumor response which would greatly enhance their therapeutic benefit. To overcome these limitations we have developed a bi-cistronic gamma-retroviral vector allowing for constitutive co-expression of a CD19-specific CAR (19–28z) and human CD40 ligand (CD40L; CD154). The CD40 ligand/CD40 system has been demonstrated to activate dendritic cells (DCs) and alter the phenotype of B cells (upregulation of co-stimulatory and adhesion molecules and secretion of pro-inflammatory cytokines) with subsequent stimulation of CD8⁺ T cell activation and proliferation. We now demonstrate T cells genetically modified to constitutively express CD40L undergo enhanced proliferation and up-regulated secretion of pro-inflammatory cytokines including GM-CSF and INF-g. Furthermore, T cells modified to constitutively express CD40L, upon co-culture, will alter the phenotype of CD40⁺ B cell tumor cell lines by enhancing the expression co-stimulatory molecules (CD80/CD86), adhesion molecules (CD54/CD58/CD70) and death receptors (CD95; Fas). These findings were similarly evident in primary patient tumor samples (e.g. CLL cells) when co-cultured with autologous T cells modified to constitutively express CD40L. We further demonstrate maturation of monocyte derived DCs with subsequent secretion of IL-12 following co-culture with autologous T cells modified to constitutively express CD40L. T cells transduced with the bi-cistronic 19–28z/CD40L vector showed enhanced in vitro cytotoxicity against a panel of CD19⁺ tumor cell lines. Furthermore, infusion of 19–28z/CD40L modified T cells enhances the survival of CD19⁺ tumor bearing immunodeficient mice (SCID/Beige) when compared to mice treated with T cells modified to express the anti-CD19 19–28z CAR alone. We conclude that further genetic modification of CAR targeted T cells to constitutively express the co-stimulatory CD40L may enhance the anti-tumor efficacy of this adoptive T cell therapy. Our data suggests this enhanced T cell efficacy may be due to both autocrine and paracrine mediated mechanisms.