CMTM6-Silencing Microbial Immunotherapy Reprograms PDAC Tumors and Restores T-cell Function

Despite recent advances in immunotherapy for advanced malignancies, Pancreatic ductal adenocarcinoma (PDAC) remains largely refractory to current immunotherapy due to dense fibrosis, limited antigen presentation, and myeloid-driven immune suppression. Here we report the tumor-targeting, immune remodeling, and safety profiles of the attenuated Salmonella enterica serovar Typhimurium strain CRC2631, and of iSTORM, a next-generation derivative engineered for tumor-localized CMTM6 silencing. CRC2631 preferentially colonizes orthotopic and genetically engineered PDAC tumors, with enrichment in primary lesions and metastases. Tumor-localized CRC2631 induces chemokine and adhesion programs consistent with leukocyte recruitment, increases intratumoral activated T-cell fractions, and triggers transcriptional signatures aligned with innate sensing, interferon signaling, antigen-processing and presentation, and apoptosis programs. iSTORM extends this platform by delivering CMTM6-targeting shRNA to modulate a PD-L1-stabilizing, myeloid-associated immune-evasion programs within tumor-colonized tissue. Compared with CRC2631, iSTORM increases intratumoral CD8+ T cells, shifts T-cell state toward activation with reduced exhaustion-prone features, strengthens antigen-presentation programs, and achieves deeper tumor control. A lyophilized formulation preserves immune remodeling while improving deployability. Mechanistically, glycan arrays and functional studies support mannose-rich glycan-guided tumor engagement. iSTORM toxicity studies, including systemic cytokine, hematologic, blood chemistry, and lethality demonstrate a favorable safety profile. Collectively, these findings establish iSTORM as a safe, programmable, CMTM6-silencing microbial immunotherapy platform that selectively targets and penetrate PDAC tumors to unleash anti-tumor immune activities.