ABSTRACT Curative therapy for multiple myeloma remains elusive despite remarkable advances in drug therapy, biologics and autologous hematopoietic stem cell transplant. Adoptive cell therapy using T cells modified by gene transfer to express synthetic chimeric antigen receptors (CAR-T) that retarget specificity to a surface molecule expressed on myeloma cells is an exciting advance and has been highly effective for reducing tumor burden and inducing complete responses in a fraction of patients with refractory disease. Although the initial responses to CAR-T are impressive, relapses are frequent and heterogeneity in the expression of target antigens on the tumor and lack of CAR-T persistence have been identified as underlying causes for disease recurrence. The premise of this proposal is that these barriers can be overcome by advanced approaches to T cell engineering. We will design novel synthetic hybrid T cell receptors that have markedly greater Ag sensitivity compared to CAR-T and simultaneously target more than one MM antigen to prevent escape of tumor cells expressing low levels of or lacking a single antigen. A new approach that instructs memory and stemness transcriptional and epigenetic states in engineered T cells that have been associated with superior T cell persistence after adoptive transfer will be developed to improve therapeutic efficacy. Further advances in adoptive T cell therapy will be necessary and should be informed by a comprehensive understanding of other mechanisms that enable rare myeloma cells to persist in the bone marrow tumor microenvironment and regrow. We have assembled a rich resource of blood and bone marrow samples obtained from patients prior to and at multiple time points after treatment with BCMA targeted CAR-T cell and will use high dimensional analytic techniques to identify tumor intrinsic and extrinsic mechanisms associated with response and relapse. By employing cutting edge synthetic biology and immunologic techniques we will accelerate development of more effective immunotherapies for MM. The specific aims are: Aim 1: Design and evaluate highly sensitive chimeric TCRs that recognize two myeloma Ag. Aim 2: Determine if inducing a memory stem cell phenotype in MM-specific T cells through CD27 costimulation improves antitumor efficacy. Aim 3: Determine mechanisms of resistance in MM patients receiving BCMA CAR-T alone or combined with a gamma secretase inhibitor.