Intravenous iRGD‐Guided, RBC‐Membrane Camouflaged Lactococcus Lactis Remodels Cold NSCLC and Enhances PD‐1 Blockade

Abstract Resistance to programmed‐death‐1/programmed‐death‐ligand‐1 (PD‐1/PD‐L1) blockade in non‐small‐cell lung cancer (NSCLC) arises mainly from weak tumor immunogenicity and limited effector T‐cell infiltration. Here, this work presents an intravenously deliverable “living medicine” that addresses these barriers through biomimetic cloaking, tumor‐penetrating guidance, and synthetic‐biology‐driven cytokine release. Lactococcus lactis is engineered to co‐secrete Flt3L and OX40L (FOLactis) and then camouflage with red‐blood‐cell membranes, producing long‐circulating mRBC@FOLactis. Conjugation of the iRGD peptide (iRGD‐mRBC@FOLactis) enables trans‐endothelial migration and deep (≥200 µm) interstitial penetration, yielding a fourfold increase in intratumorally bacterial accumulation versus unmodified FOLactis. In the orthotopic Lewis lung carcinoma (LLC) model, a single intravenous dose of iRGD‐mRBC@FOLactis combined with anti‐PD‐1 antibody achieves complete tumor regression in 60% of mice, doubles median survival ( p < 0.001), and generates systemic tumor‐specific immune memory. Mechanistically, local Flt3L and OX40L secretion expands cross‐presenting dendritic cells (DCs), boosts CD8⁺ T‐cell priming, and converts immunologically “cold” tumors into inflamed, T‐cell‐rich lesions, thereby overcoming primary resistance to checkpoint blockade. This multifunctional probiotic platform establishes a generalizable strategy for systemic delivery of living therapeutics and offers a powerful adjunct to PD‐1/PD‐L1 blockade for NSCLC and other treatment‐resistant solid tumors.