• Spatiotemporal control of lung-site exposure improves the in vivo performance and therapeutic index of a cationic antimicrobial peptide. • Infection-associated lung enrichment is achieved via macrophage-membrane functionalization after systemic administration. • Protease-responsive activation (elevated MMP-3) promotes on-site peptide release and antibacterial action at infected lesions. • Systemic treatment reduces pulmonary bacterial burden and inflammation and improves survival in an antibiotic-resistant E. coli pneumonia model. A key biopharmaceutic barrier in systemic treatment of pulmonary infections is achieving sufficient drug exposure at infected lung sites with cationic antimicrobial peptides (AMPs), which are prone to proteolytic degradation, rapid clearance, and off-target interactions in circulation. S-thanatin (Ts) is a cationic AMP with potent in vitro antibacterial activity and low resistance liability, yet its unfavorable in vivo fate limits therapeutic efficacy. To address this limitation, we implemented a spatiotemporally controlled systemic delivery strategy that couples pathogen-associated localization with enzyme-activated, on-site release. As a practical formulation to realize this concept, Ts@CPN@PM was electrostatically assembled with bacteria-pre-stimulated macrophage membranes for pathogen-associated targeting and equipped with a matrix metalloproteinase-3 (MMP-3)-cleavable NFF-3 switch for infection-microenvironment-triggered release. Ts@CPN@PM achieved ∼95 % in vitro Ts release under elevated MMP-3 conditions and preferentially accumulated in infected lungs (>70 % by fluorescence quantification). In an antibiotic-resistant E. coli pneumonia model, Ts@CPN@PM improved survival (10 % to 60 %), reduced pulmonary bacterial burden (∼2 log CFU/g), and attenuated inflammatory responses. Ts@CPN@PM showed favorable cytocompatibility and hemocompatibility in vitro , and systemic biosafety was confirmed in healthy mice. Overall, these findings support spatiotemporal control of lung-site exposure as a feasible route to improve the in vivo fate and therapeutic index of cationic AMPs for pulmonary bacterial infections.
Tao et al. (Wed,) studied this question.