Selective targeting of multiple myeloma by B cell maturation antigen (BCMA)-specific central memory CD8+ cytotoxic T lymphocytes: immunotherapeutic application in vaccination and adoptive immunotherapy

To expand the breadth and extent of current multiple myeloma (MM)-specific immunotherapy, we have identified various antigens on CD138(+) tumor cells from newly diagnosed MM patients (n = 616) and confirmed B-cell maturation antigen (BCMA) as a key myeloma-associated antigen. The aim of this study is to target the BCMA, which promotes MM cell growth and survival, by generating BCMA-specific memory CD8(+) CTL that mediate effective and long-lasting immunity against MM. Here we report the identification of novel engineered peptides specific to BCMA, BCMA(72-80) (YLMFLLRKI), and BCMA(54-62) (YILWTCLGL), which display improved affinity/stability to HLA-A2 compared to their native peptides and induce highly functional BCMA-specific CTL with increased activation (CD38, CD69) and co-stimulatory (CD40L, OX40, GITR) molecule expression. Importantly, the heteroclitic BCMA(72-80) specific CTL demonstrated poly-functional Th1-specific immune activities [IFN-gamma/IL-2/TNF-alpha production, proliferation, cytotoxicity] against MM, which were correlated with expansion of Tetramer(+) and memory CD8(+) CTL. Additionally, heteroclitic BCMA(72-80 )specific CTL treated with anti-OX40 (immune agonist) or anti-LAG-3 (checkpoint inhibitor) display increased immune function, mainly by central memory CTL. These results provide the framework for clinical application of heteroclitic BCMA(72-80) peptide, alone and in combination with anti-LAG3 and/or anti-OX40 therapy, in vaccination and/or adoptive immunotherapeutic strategies to generate long-lasting anti-tumor immunity in patients with MM or other BCMA expressing tumors.