Pancreatic ductal adenocarcinoma (PDAC) is largely refractory to immune checkpoint blockade (ICB). This resistance is driven by malignant cells adopting transcriptional and epigenetic programs that suppress antigen presentation and T cell engagement. We sought to identify pharmacological strategies capable of remodeling these tumor-intrinsic evasion programs to restore tumor immune visibility.

We performed a target-agnostic, high-throughput pharmacological co-culture screen pairing PDAC cells with antigen-specific CD8+ T cells under PD-1 blockade. Leading candidates were validated across human and murine PDAC models, including primary tumor-derived systems, engineered to permit T cell recognition via T cell engagers (human) or OVA antigen expression (murine). To uncover mechanistic insights in vitro, RNA- and ATAC-seq profiling was performed, supported by protein analysis and loss-/gain-of-function strategies. In vivo efficacy of the leading candidate was evaluated in combination with anti-PD1 using syngeneic subcutaneous and orthotopic models. Permission was obtained from the relevant regulatory authority and properly informed consent given in those studies involving human (Prot. n 61413, Prog 1911) or animal subjects (R-065-23GN).

The co-culture screen identified CM-444, a dual histone deacetylase (HDAC) and DNA methyltransferase (DNMT) inhibitor, as a potent enhancer of T cell-mediated cytotoxicity. Transcriptomic and epigenomic analyses revealed that CM-444 induces coordinated tumor-intrinsic reprogramming toward an immune-permissive state. This was characterized by the restoration of MHC Class I and II expression, activation of IFN and TNF signaling, and upregulation of gene programs supporting immunological synapse formation and T cell effector function. In vivo, CM-444 restricted tumor growth, increased functional CD8+ T cell infiltration, and markedly potentiated anti-PD1 therapy. Integrative analyses further showed that CM-444 reverses malignant-cell signatures associated with clinical anti-PD-1 resistance in melanoma patients. These results suggest that the efficacy of this combination is primarily driven by the reversal of tumor-intrinsic immune evasion.

Our findings demonstrate that dual epigenetic modulation via CM-444 pharmacologically remodels immune-evasive tumor states. This approach provides a robust strategy to bypass intrinsic resistance and sensitize checkpoint-refractory PDAC to immunotherapy.

I would also like to acknowledge the contributions of - Iker Feliu, Gabriela Novoa, Uxua Mancheño, Elisabeth Guruceaga, Beatriz Tavira, Imanol Arozarena, Vincenzo Corbo, Antonio Pineda.