Anti-tumor effect of ATA3271 was assessed using a MSTO-211H-derived tumor cell line overexpressing MSLN and PDL1.... Upon MSLN engagement, ATA3271 showed proliferation, efficient tumor cell lysis in the presence of high-level cell-surface PD-L1 expression and secretion of effector cytokines....In an orthotopic mouse model of pleural mesothelioma, ATA3271 demonstrated anti-tumor efficacy without toxicities.