Nanogel-controlled delivery of caerin peptides enables sustained intratumoural retention and immunometabolic reprogramming

Host-defence peptides possess both direct cytotoxic and immunomodulatory activities but their therapeutic application is limited by rapid degradation and insufficient intratumoural retention. Here, we report a self-assembling nanogel delivery system that enables sustained intratumoural release of the amphibian peptides caerin 1.1 and 1.9 (F1/F3) and enhances their antitumour efficacy. F1/F3 suppressed tumour growth in immune-competent and PBMC-humanised mouse models but showed minimal activity in immunodeficient mice, confirming a predominantly immune-dependent mechanism. To overcome delivery limitations, F1/F3 was encapsulated within the self-assembled nanofibrous network of the short D-configuration peptide Nap-G D F D F D Y (NAP-GFFY) to form an injectable nanogel (F1/F3–NAP-GFFY). Physicochemical characterisation demonstrated that the nanogel formed a stable supramolecular nanofibrous structure with sustained-release properties and structural stability under acidic, enzymatic, and thermal stress conditions. Nanogel-mediated delivery significantly prolonged intratumoural peptide retention following local administration and resulted in enhanced tumour suppression and prolonged survival compared with free peptide treatment. Mechanistically, nanogel-mediated delivery induced coordinated reprogramming of the tumour microenvironment. Integrated transcriptomic, proteomic and metabolomic analyses revealed activation of antigen processing and presentation pathways, interferon-responsive signalling, cytotoxic immune programs and inflammasome-associated responses. Concurrent metabolic alterations, including lipid remodelling, mitochondrial β-oxidation and redox regulation, indicated adaptive immunometabolic restructuring. These changes were accompanied by increased infiltration of CD4 + and CD8 + effector T cells, expansion of dendritic cell populations and reduction of immunosuppressive monocytic MDSCs in tumours and draining lymph nodes. This study demonstrates that nanogel-controlled delivery transforms F1/F3 into a sustained local immunotherapeutic system that integrates controlled release, prolonged tumour retention and immune activation. This work highlights the potential of self-assembling peptide nanogels as a versatile platform for enhancing peptide-based cancer immunotherapy.