CD19 CAR T Cells Expressing IL-12 Eradicate Lymphoma in Fully Lymphoreplete Mice through Induction of Host Immunity

Chimeric antigen receptor (CAR) T cell therapy represents a significant advancement in cancer therapy. Larger studies have shown ∼90% complete remission rates against chemoresistant and/or refractory CD19⁺ leukemia or lymphoma. Effective CAR T cell therapy is highly dependent on lymphodepleting preconditioning, which is achieved through chemotherapy or radiotherapy that carries with it significant toxicities. These can exclude patients of low performance status. In order to overcome the need for preconditioning, we constructed fully mouse first and second generation anti-murine CD19 CARs with or without interleukin-12 (IL-12) secretion. To test these CARs, we established a mouse model to reflect the human situation without preconditioning. Murine second generation CAR T cells expressing IL-12 were capable of eradicating established B cell lymphoma with a long-term survival rate of ∼25%. We believe this to be the first study in a truly lymphoreplete model. We provide evidence that IL-12-expressing CAR T cells not only directly kill target CD19⁺ cells, but also recruit host immune cells to an anti-cancer immune response. This finding is critical because lymphodepletion regimens required for the success of current CAR T cell technology eliminate host immune cells whose anti-cancer activity could otherwise be harnessed by strategies such as IL-12-secreting CAR T cells.

Donor origin CAR T cells: graft versus malignancy effect without GVHD, a systematic review

CD19, CD20 chimeric antigen receptor T (CAR T) cell therapy has shown promising results for the treatment of relapsed or refractory hematological malignancies. Best results have been reported in acute lymphoblastic leukemia patients with a complete response rate above 80%. Patients who received donor-derived CAR T cells for the relapsed malignancy after stem cell transplantation (allogenic hematopoietic stem cell transplant) were identified from the published trials. A total of 72 patients from seven studies were treated with donor-derived CAR T cells. Only five out of 72 patients (6.9%) developed graft versus host disease. Use of donor-derived CAR T cell for relapse prophylaxis, minimal residual disease clearance or salvage from relapse is therefore highly effective, and risk of graft versus host disease flare is very low. Side effects include cytokine release syndrome, tumor lysis syndrome, B-cell aplasia along with CNS toxicity.

Immunotherapy for metastatic melanoma

Melanoma has traditionally been considered an immunogenic tumor. A number of approaches have been studied for enhancement of antitumor immunity. The first cytokine approved for the treatment of metastatic melanoma, interleukin-2, has resulted in prolonged responses in a small subset of patients, providing hope that immunotherapy might be useful for this disease. Ipilimumab, a monoclonal antibody to CTLA-4, was recently approved and a number of other promising investigational approaches are currently being pursued. This manuscript discusses more recent advances in the treatment of melanoma employing a variety of immune-enhancing approaches.