An autologous anti-mesothelin CAR T-cell therapy. Patient T cells are engineered ex vivo using circular mRNA to transiently express a mesothelin-targeting chimeric antigen receptor (no genomic integration) and administered by IV infusion weekly ×4 (dose escalation 1×10^8 to 2×10^9 cells). The CAR engages mesothelin on tumor cells to drive HLA-independent T-cell activation, cytotoxicity, cytokine release, and proliferation.