Genetic Engineering of T-cells for Adoptive Immunotherapy of Chronic Lymphocytic Leukemia

The immune system is highly effective at removing large-numbers of virally infected cells without damaging normal non-infected tissues, however it often remains unresponsive to cancer cells. In this project, we plan to modify T-cells, a key component of the immune system, so that they kill established cancers. We propose taking normal T-cells from patients with a form of cancer known as chronic lymphocytic leukaemia (CLL), and genetically engineer them in the laboratory so that they kill the leukaemia cells, with a view to ultimately giving them back to the patient as a treatment. This engineering exploits our detailed understanding of how the immune system works. In a sense we will use nature‘s toolkit to create a cancer killing immune response. We will test these T-cells in mice with human leukaemias, to establish safety and effectiveness of this new form of treatment. We plan to use the data amassed from this project to prepare the ground-work for a clinical study in patients with CLL that have failed standard treatment. This work represents the beginning of a new field of therapy, where T-cells can be engineered to specifically remove harmful cell populations without damaging healthy normal tissue

Administration of tumor-specific T-cells (adoptive immunotherapy) has proven to be an effective cancer treatment but is limited by the difficulty in selecting and expanding tumour-specific T-cells to all but a few malignancies. Genetic modification of T-cells with chimeric T-cell receptors (cTCRs), allows us to graft T-cells with any desired specificity, overcoming this limitation. In fact, cTCRs allow radical avenues of immunotherapy such as the generation of large numbers of T-cells recognizing tissue-specific self antigens. CD19 is a B-cell surface antigen expressed by nearly all B-cells and B-cell malignancies. We have developed a CD19 specific cTCR - we plan to build on this receptor to engineer autologous T-cells into an effectively therapy for Chronic Lymphocytic Leukemia (CLL), a common malignancy which remains predominantly incurable.

To accomplish this, we aim to (1) improve the cTCR itself, (2) to engineer T-cell to release a cytokine payload, (3) to incorporate a suicide gene into the retroviral vector, (4) to test the contribution of these components in an animal model and finally (5) to perform preparatory work for a phase I clinical study. (1) Co-stimulatory signals are essential to induce an effective and lasting immune response but are frequently not supplied by tumour cells. By introducing portions of co-stimulatory molecules into the intracellular portion of cTCRs it is possible to generate cTCRs which transmit co-stimulatory signals. We will generate CD19 specific cTCRs which transmit synergistic CD28 and OX40 co-stimulatory signals in cis. (2) By driving expression of a cytokine from Nuclear Factor of Activated T-cell (NF-AT) response elements in our retroviral vector, we can engineer T-cells to release cytokines upon activation (i.e. at the site of tumour). We plan to use our engineered T-cells to deliver IL-12, a potent activator of both innate and adaptive immunity increasing efficacy without systemic toxicity. (3) To improve safety in clinical studies, a means of removing adoptively transferred T-cells in case of adverse events is desirable. In the same vector, we will co-express a form of capase 9 which can be activated by exposure to an otherwise inert small-molecule chemical inducer of dimerization (CID).

(4) The safety and efficacy of these modifications will be tested sequentially in a suitable animal model, using bioluminescence to track adoptively transferred T-cells in vivo. (5) Finally, we will establish the processes required for large-scale production of clinical grade vector and transduced T-cells under Good Manufacturing Practise conditions.

Scientifically, with this fellowship, we hope test what is required immunologically to target tissue-specific self-antigens in this manner. Medically, this fellowship should form the pre-clinical data for an innovative phase I clinical study.