Chimeric Antigen Receptor-Immune Cell-Based Therapies for Clear Cell Renal Cell Carcinoma: Latest Advancements and...

Clear cell renal cell carcinoma (ccRCC) accounts for approximately 75% of renal cell carcinomas and is defined by near-universal VHL inactivation, leading to constitutive HIF stabilisation, metabolic reprogramming, and an immunologically distinct tumour microenvironment (TME). Although ccRCC is characterised by abundant immune infiltration, this paradoxically correlates with poor prognosis, reflecting a TME that imposes interconnected physical, immunological, and metabolic barriers to effective immunotherapy. Chimeric antigen receptor (CAR)-based therapies have revolutionised the treatment of haematological malignancies, but their translation to ccRCC has encountered substantial hurdles. The first-in-human trial targeting carbonic anhydrase IX (CAIX) was limited by on-target off-tumour toxicity and CAR immunogenicity-lessons that fundamentally reshaped the field. CD70 has since emerged as the dominant clinical target, expressed in over 80% of ccRCCs with a highly restricted normal tissue distribution. The phase I COBALT-RCC trial of CTX130, an allogeneic CRISPR-Cas9-edited CD70-directed CAR-T cell product, provided formal proof of concept, achieving disease control in 81.3% of heavily pretreated patients and a durable complete response now exceeding three years-the first such sustained remission reported for any CAR-T cell product in a solid malignancy. Nevertheless, the low frequency of durable responses and universal loss of CAR-T cell persistence by day 28 underscore that major barriers remain. Beyond CD70, the field has diversified across multiple platforms, including CAR-natural killer (NK) cells, CAR-natural killer T (NKT) cells, and CAR-macrophages, each offering distinct biological advantages. This review synthesises current knowledge of the ccRCC TME, the preclinical landscape of CAR-based therapies, and emerging clinical evidence from more than 30 registered trials. We discuss target antigens; engineering strategies to overcome TME barriers, including cytokine armouring, chemokine receptor co-expression, switch receptors, and metabolic reprogramming; and rational combination approaches. We argue that the convergence of optimised target selection, cellular engineering, combination strategies, and biomarker-driven trial design may ultimately improve outcomes for patients with ccRCC. However, achieving a cure remains an aspirational goal, and significant barriers must first be overcome.