Transplantation of unrelated umbilical cord blood (CB) derived stem cells is often used to treat adult patients with B-cell acute lymphoblastic leukemia (B-ALL). However, patients can relapse post transplant and prognosis of those with advanced or refractory disease is poor. We hypothesize that additional therapy involving adoptive transfer of CB derived T cells modified to express a CD19-specific chimeric antigen receptor (CAR) could improve patient outcome following CB transplantation in this population. We have previously demonstrated that human T cells which express the anti-CD19 1928z CAR, containing the signaling domains of the co-stimulatory CD28 receptor and CD3z chain, effectively eradicate CD19+ tumors in SCID-Beige mice, and have shown promise in early clinical trials.
In this study, we demonstrate the ability to effectively isolate and expand T cells from CB, necessary for application of adoptive CB T cell therapy. We compared T cell expansion in in vitro cultures with the addition of exogenous stimulatory cytokines, including IL-2, IL-7, IL-12, IL-15 or combinations thereof. We demonstrate that in vitro culture in the context of exogenous IL-12 combined with IL-15 resulted in optimal expansion of CB T cells (over 150-fold). In addition, expansion of T cells in the context of exogenous IL-12 and IL-15 resulted in a favorable phenotype, with maximal expression of memory T cell markers, CD62L and CCR7. Furthermore, these cells were shown to produce high levels of IFNγ and express high levels of CD107a following stimulation with PHA. CB T cells expanded in IL-12 and IL-15 were therefore shown to have a unique memory cell phenotype combined with effector T cell function.
Previous studies in our laboratory have demonstrated that expression of IL-12 in tumor targeted T cells resulted in increased anti-tumor function. Given these studies and the favorable effect of IL-12 on CB T cell expansion we used retroviral modification to express both 1928z CAR and IL-12 in CB T cells. CB T cells modified with both IL-12 and 1928z were shown to have increased cytokine secretion when cultured with CD19+ tumor cells, compared to UCB T cells modified with a CAR alone. Additionally, these cells were demonstrated to have increased lytic function, resulting in increased specific lysis of CD19+ tumor cells in a 51Cr release assay.
Our data suggest that CB T cells modified to express both CAR and IL-12 will have improved anti-tumor function, and could therefore decrease relapse and improve overall survival following CB transplant for the treatment of B-ALL.
Giralt:Millenium: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Onyx: Membership on an entity's Board of Directors or advisory committees, Research Funding.