Combination Immunotherapy with NY-ESO-1-Specific CAR⁺ T Cells with T-Cell Vaccine Improves Anti-Myeloma Effect

Adoptive transfer of T cells expressing chimeric antigen receptor (CAR) has demonstrated clinical effectiveness in early phase clinical trials, with persistence of effector cells typically leading to improved outcomes. Most CARs directly dock with cell-surface antigens, but this limits the number of tumor-derived targets. Thus, we have adapted two technologies to target intracellular antigens and improve survival of infused T cells. This was accomplished by expressing a CAR on T effector cells that functions as a mimetic of T-cell receptor (TCR) to recognize NY-ESO-1 in the context of HLA A2 and adapting HLA-A2⁺ T cells to serve as antigen presenting cells (T-APC) by expressing NY-ESO-1 antigen. NY-ESO-1 is a desirable target for T-cell therapy of high risk multiple myeloma (MM) with efficacy in trials infusing T cells expressing TCR recognizing this antigen. We hypothesized combined immunotherapy with NY-ESO-1-specific CAR⁺ T cells and an NY-ESO-1⁺ T-APC vaccine will lead to enhanced anti-myeloma efficacy due to improved persistence of the CAR⁺ T effector cells. An NY-ESO-1-specific CAR and control TCR were expressed on primary T cells using the Sleeping Beauty (SB) transposon/transposase system. T-APC was generated by electro-transfer of DNA plasmids from SB system coding for NY-ESO-1 and membrane-bound IL-15 (mbIL15). The tethered cytokine functions as co-stimulatory molecule to improve the potency of the vaccine. In vitro studies confirmed the NY-ESO-1-specific CAR⁺ (and TCR⁺) T cells could be numerically expanded upon co-culture with T-APC. A mouse model of NY-ESO-1⁺HLA-A2⁺(CD19^neg) multiple myeloma was used to compare tumor growth for CAR⁺ T effector cells with and without T-APC. The NY-ESO-1-specific CAR⁺ T effector cells displayed anti-tumor effect that was superior to control mice without T cells and mice receiving CD19-specific control CAR⁺ T cells. Mice receiving both NY-ESO-1-specific CAR⁺T effector cells and T-APC exhibited further improvement in anti-myeloma activity. This group demonstrated superior persistence of T effector cells with recovered cells exhibiting a memory phenotype. In summary, T cells can target intracellular NY-ESO-1 using a TCR mimetic CAR. Improved anti-tumor effect attributed to better persistence can be achieved by co-infusion of T-APC vaccine. These data provide the foundation to assess T cells targeting NY-ESO-1 in a clinical trial.