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Background With a median survival of 15-30 months and a lack of effective treatment, novel therapies for chronic myelomonocytic leukemia (CMML) are urgently needed. Current options are rarely curative, as hypomethylating agents offer low response rates and allogeneic stem cell transplantation is not available to most. Adoptive T-cell therapy (ACT) is a potent strategy against other refractory cancers. However, it has not been investigated for CMML. Therefore, for the first time, we investigated the landscape of common TAAs and personalized neoantigens and subsequently established the feasibility of generating novel multi-epitope specific cytotoxic CD4 + T cells directed against identified CMML targets.Methods We performed nCounter gene expression profiling on bone marrow cells from CMML/MDS MPN patient cohort ( NCT02775383) obtained from the National MDS Natural History Study biobank and healthy controls to identify overexpressed TAAs. Peptide libraries for these targets and common neoantigens identified from genetic study were synthesized.Multi-epitope CD4+ T-cells were generated from healthy and CMML/MDS subjects by co-culturing them with autologous dendritic cells (MoDCs) pulsed with peptide pools in standard (Th1) or proinflammatory (Th1.17) conditions and then restimulated. Finally, using flow cytometry, we assessed T-cell reactivity against both peptides and full-length proteins. We also examined their polyfunctionality, proliferative capacity, and metabolic fitness upon repetitive stimulation.Results Gene expression profiling identified 14 Cancer-Testis Antigens (CTAs) overexpressed in at least 40% of patients, with PRAME, SPACA3, and MAGEA4 being most frequent. Importantly, the top 7 antigens were co-expressed in 50% of subjects, and common immunogenic mutations (e.g., KRAS, NRAS, ASXL1, TET2) were also present, suggesting the possibility of generating multi-TAA products concurrently targeting multiple antigens.Robust and highly polyfunctional T cell responses against CTAs (including PRAME, MAGE-A1, A3, A4, CT45A1 & WT1) and selected neoantigens were induced under Th1.17 conditions demonstrating superior reactivity, while retaining bioenergetic stability and marked proliferative capacity despite repetitive stimulation vs. Th1 counterparts. Moreover novel Th1.17 T cells also recognized naturally processed tumor targets, and were reliably generated even from pancytopenic MDS patient samples.Conclusions This study provides a critical preclinical proof-of-concept for T-cell therapy in CMML. We not only identified landscape of targetable tumor antigens but also developed a superior method for generating potent, multi-specific cytotoxic CD4 + T-cells. The enhanced functionality and durability of our Th1.17 cells, along with the demonstration that they can be generated from even the most vulnerable patients, lays the essential groundwork for translating this multi-epitope specific T-cell strategy into clinical trials.