PEG-PLGA-based GSH-responsive nanoparticles deliver a PI3Kγ inhibitor to remodel the immuno-metabolic microenvironment in PD-1-resistant triple-negative breast cancer

Triple-negative breast cancer (TNBC) has a low response rate to immune checkpoint inhibitors (ICIs), and programmed cell death protein-1 (PD-1) resistance remains a key obstacle to durable immunotherapeutic benefit. The lactate-phosphoinositide 3-kinase gamma (lactate-PI3Kγ) axis contributes to tumor immunometabolic reprogramming and immunosuppression. This study aimed to develop glutathione (GSH)-responsive polyethylene glycol-poly(lactic-co-glycolic acid) (PEG-PLGA) nanoparticles for delivery of the PI3Kγ inhibitor IPI-549 and to evaluate their effects on the TNBC immunometabolic microenvironment. sNP@IPI-549 was prepared by nanoprecipitation and characterized for particle size, zeta potential, morphology, GSH responsiveness, drug release, biosafety, and pharmacokinetics. Cell and animal models, together with flow cytometry, immunofluorescence, enzyme-linked immunosorbent assay, western blotting, single-cell transcriptomics, and targeted metabolomics, were used to evaluate macrophage, T-cell, and PD-1-resistant tumor responses. Triplicate characterization showed a hydrodynamic diameter of approximately 135 nm, a PDI of 0.12, an encapsulation efficiency of 72.3 ± 4.1%, and a drug loading of 5.2 ± 0.3%. sNP@IPI-549 showed GSH-triggered release, inhibited TNBC cell proliferation, migration, and invasion, induced G0/G1 arrest (58% to 71%), and promoted apoptosis (28–30%). It also shifted macrophages toward an immune-activated phenotype, enhanced CD8+ T-cell proliferation and cytotoxicity, reduced PD-L1 protein expression in tumor tissues, and suppressed tumor progression in a PD-1-resistant 4T1-R model. Short-term biosafety assessment showed stable body weight, comparable food intake, no significant hematological or biochemical abnormalities, and no obvious major-organ injury. Single-cell multi-omics and targeted metabolomics further indicated increased arginine/NOx signaling and reduced lactate and ornithine/polyamine metabolism. Overall, sNP@IPI-549 provides experimental evidence that GSH-responsive IPI-549 delivery can modulate the lactate-PI3Kγ axis and partially improve immune responses in PD-1-resistant TNBC models, supporting further preclinical validation.