A phase I clinical study conducted by Haas et al. [41] investigated the safety and activity of anti-MSLN CAR-T cells in patients with malignant pleural mesothelioma, ovarian cancer and pancreatic ductal adenocarcinoma, (NCT02159716) and found that in only 3 of 15 patients the expression of MSLN on tumor cells was >75%. The gene discussed is MSLN; the disease is malignant pleural mesothelioma.