CA9 and nonpapillary renal cell carcinoma: Despite the tremendous success of CAR-T therapy in hematologic malignancies, its role in solid malignancies is in early development.62,63 The first CAR-T study in RCC targeted the carbonic anhydrase IX (CAIX), a transmembrane protein, that has been found to be upregulated in ccRCC.64 The study enrolled 12 patients, with grades II-IV liver toxicities observed in 4 of the 8 patients across the initial 2 cohorts.