IL-15 superagonists for reprogramming the immunosuppressive microenvironment in gastrointestinal adenocarcinomas

Gastrointestinal (GI) adenocarcinomas pose a significant therapeutic challenge due to highly immunosuppressive tumor microenvironments that limit effective antitumor immune responses. Dense stromal fibrosis, immune exclusion and poor responses to immune checkpoint inhibitors are hallmarks of treatment-resistant malignancies, most notably pancreatic ductal adenocarcinoma (PDAC) and subsets of gastric cancer. In this regard, IL-15 superagonists such as N-803, NIZ985, RLI, and NKTR-255 have emerged as promising immunotherapeutic candidates, as they selectively expand natural killer (NK) cells and CD8⁺ T-cells without the systemic toxicity and regulatory T-cell activation observed with IL-2 therapy. IL-15 superagonists have emerged as more effective therapeutic agents when used in conjunction with local inhibitors of TGF-β and IL-10, stromal remodeling, and vascular normalization. They are supported by increasingly conclusive mechanistic, preclinical and early clinical data. A combination of these interventions circumvents extracellular matrix-provoked immune barriers, reverses VEGF-induced endothelial dysfunction, and enhances the trafficking of lymphocytes into tumor cores. Moreover, several localized therapeutic delivery strategies, such as endoscopic delivery, implantable depots, biomaterial scaffolds, and nanocarriers, can improve intratumoral cytokine retention and reduce systemic inflammatory toxicity. Together, these advances define a new paradigm for cytokine-immunotherapy: IL-15 superagonists serving as key mediators of reprogramming of the tumor microenvironment. Therapeutic strategies targeting IL-15 have the potential to restore cytotoxic immunity, improve access to immune cells, and promote responsiveness to the checkpoint blockade, making them a promising yet investigational approach to converting immune-cold GI malignancies into more treatment-responsive disease states, though further clinical validation is required.