Response to azacitidine and the TIM-3 inhibitor, sabatolimab, in MDS and CMML is associated with distinct immune and antigen-presentation states
Targeting the immune checkpoint TIM-3 is of interest in myeloid neoplasms, yet the hematopoietic and immune changes associated with anti-TIM-3 therapy remain poorly characterized. We used single-cell RNA sequencing to profile bone marrow (BM) and peripheral blood from patients with myelodysplastic syndrome (MDS) and chronic myelomonocytic leukemia (CMML) treated with the hypomethylating agent azacitidine combined with sabatolimab, a monoclonal antibody targeting TIM-3, and integrated Human Cell Atlas reference datasets for comparison. CITE-seq profiling showed that TIM-3 was predominantly expressed on dendritic cells and NK cells, with variable expression across other populations, including CD34 cells and CD8 T cells. At baseline, we identified a population of CD34 myeloid-biased progenitors specific to MDS/CMML samples ("HSPC-like") characterized by inflammatory gene expression programs and features of impaired differentiation. In MDS, elevated baseline HLA class II expression across hematopoietic stem and progenitor cells (HSPCs), HSPC-like cells, and multiple myeloid populations was associated with response. Consistent with this finding, trajectory analysis suggested that nonresponders bypassed HLA class II-high states during myeloid differentiation. In MDS, the presence of distinct CD8 T-cell populations and increased interferon-response programs in CD8 T and NK cells at baseline was also associated with response. In both MDS and CMML, treatment among responders was associated with contraction of BM CD8 and CD4 T-cell populations characterized by type I interferon-responsive and inflammatory programs, including IFIT1, IFIT2, and TNF, along with expansion of a distinct GZMH/IFITM1-expressing cytotoxic CD8 T-cell population. Together, these findings identify baseline antigen-presentation and immune-response programs associated with therapeutic response and reveal coordinated remodeling of myeloid and lymphoid compartments during azacitidine/sabatolimab treatment in MDS and CMML.