P-083: Rejuvenated BCMA-specific CD8+ Cytotoxic T lymphocytes derived from induced pluripotent stem cells for treatment of Multiple Myeloma

Background This study reports on the reprogramming of B-Cell Maturation Antigen (BCMA)-specific CD8+ cytotoxic T lymphocytes (CTL) to induced pluripotent stem cells (iPSC) and their differentiation into rejuvenated antigen-specific CD8+ CTL as a potential therapeutic option to effectively treat cancer patients. Along with characterization of BCMA-specific iPSC by key stem cell markers, pluripotency potential and normal karyotypes, we further detected their polarization into mesoderm development associated with activation of transcriptional regulators SNAI2, TBX3, PLVAP, HAND1 and CDX2 during embryoid body formation. BCMA-specific iPSC clones utilized distinctive commitment pathways during T cells re-differentiation. RNAseq analyses of the “iPSC committed to rejuvenated memory CD8+ T cells” showed unique transcriptional profiles as evidenced by upregulation of transcriptional regulators determining CD4/CD8 T cell differentiation ratio, memory CTL formation, NF-kappa-B / JNK pathway activation, and cytokine transporter/cytotoxic mediator development. In parallel, regulators controlling B and T cell interactions or CD4+ Th cells and inhibitory receptor development were downregulated. The rejuvenated CD8+ BCMA-specific CTL re-differentiated from the iPSC demonstrated (1) mature T cell phenotype and highly enriched central and effector memory T cells without induction of checkpoint molecules; (2) high proliferation and poly-functional anti-myeloma activities in an antigen-specific and HLA-A2-restricted manner; (3) specific immune recognition of cognate HLA-A2 heteroclitic BCMA72-80 (YLMFLLRKI) peptide; and (4) distinct sole clonotype for T cell receptor. Furthermore, the specific iPSC clones maintained their differentiation potential into CD8+ T cells upon sub-cloning or long-term culture under feeder-free culture conditions. Conclusion In conclusion, these results establish a framework for iPSC-based regenerative medicine to provide rejuvenated and highly functional memory CD8+ BCMA-specific CTL as an adoptive immunotherapy to improve patient outcome in multiple myeloma.