Differentiation of BCMA-specific induced pluripotent stem cells into CD8ab⁺ T cells targeting myeloma

• A pre-clinical framework to epigenetically reprogram BCMA-specific CD8ab⁺ memory T cells using iPSC technology to target multiple myeloma

• BCMA-specific iPSC-derived hematopoietic progenitor cells having specific regulatory elements that control CD8⁺ T cell lineage commitment.

A major hurdle in adoptive T cell therapy is cell exhaustion and failure to maintain anti-tumor responses. Here, we introduce an induced pluripotent stem cell (iPSC) strategy for reprogramming and revitalization of precursor exhausted BCMA-specific T cells to effectively target multiple myeloma (MM). Heteroclitic BCMA_72-80 LMFLLRKI)-specific CD8⁺ memory cytotoxic T lymphocytes (CTL) were epigenetically reprogrammed to a pluripotent state, developed into hematopoietic progenitor cells (HPC: CD34⁺ CD43⁺/CD14^- CD235a^-), differentiated into the T cell lineage and evaluated for their poly-functional activities against MM. The final T cell products demonstrated; 1) mature CD8αβ⁺ memory phenotype, 2) high expression of activation/costimulatory molecules (CD38, CD28, 41BB), 3) no expression of immune checkpoint and senescence markers (CTLA4, PD1, LAG3, TIM3; CD57), and 4) robust proliferation and poly-functional immune responses to MM. The BCMC-specific iPSC-T cells possessed a single T cell receptor clonotype with cognate BCMA peptide recognition and specificity for targeting MM. RNAseq analyses revealed distinct genome-wide shifts and a distinctive transcriptional profile in selected iPSC clones, which can develop CD8αβ⁺ memory T cells. This includes a repertoire of gene regulators promoting T cell lineage-development, memory CTL activation, and immune response regulation [LCK, IL7R; 4-1BB, TRAIL, GZMB, FOXF1, ITGA1]. This study highlights the potential application of iPSC technology to an adaptive T cell therapy protocol and identifies specific transcriptional patterns that could serve as a biomarker for selection of suitable iPSC clones for successful development of antigen-specific CD8αβ⁺ memory T cells to improve MM patient outcome.