PD-L1/LpxC-IN-1 (Compound 12b) is an inhibitor of PD-L1 and LpxC, with IC50 values of 5.2 μM and 0.081 μM, respectively. This compound disrupts bacterial lipopolysaccharide biosynthesis, leading to bacterial cell lysis and death. It effectively inhibits Gram-negative bacteria, exhibiting a minimum inhibitory concentration (MIC) of 0.25-0.5 μg/mL against K. pneumoniae ATCC 13883, E. coli ATCC 8739, S. typhimurium ATCC 14028, and P. aeruginosa ATCC 9027. Additionally, PD-L1/LpxC-IN-1 modulates the immune response by downregulating the expression of inflammatory cytokines IL-2 and IFN-γ, and upregulating CD4+ and CD8+ cells, thus activating the immune system and mitigating excessive inflammatory responses. In a mouse model of K. pneumoniae ATCC 13883 infection, PD-L1/LpxC-IN-1 demonstrated antibacterial activity.