Photo Credit: Design Cells
The following is a summary of “Affinity fine-tuning anti-CAIX CAR-T cells mitigate on-target off-tumor side effects,” published in the March 2024 issue of Oncology by Wang et al.
One of the primary challenges impeding the efficacy of chimeric antigen receptor (CAR) T cell therapies in combating solid tumors lies in the occurrence of on-target off-tumor (OTOT) toxicity, attributable to the shared epitopes between malignant and normal tissues. To enhance the safety profile of CAR-T cells, a meticulously designed affinity/avidity fine-tuned CAR was engineered, facilitating CAR-T cell activation exclusively in the presence of highly expressed tumor-associated antigens (TAAs) while minimizing recognition of the same antigen at physiological levels on healthy cells.
Leveraging direct stochastic optical reconstruction microscopy (dSTORM) for single-molecule resolution alongside flow cytometry, the researchers meticulously delineated the distinct expression profiles of carbonic anhydrase IX (CAIX) in clear cell renal cell carcinoma (ccRCC) patient samples versus healthy bile duct tissues. Establishing a Tet-On doxycycline-inducible CAIX-expressing cell line allowed us to mimic a spectrum of CAIX densities, spanning from CAIX-high skrc-59 tumor cells to CAIX-low MMNK-1 cholangiocytes. The evaluation of CAR-T cell-mediated killing revealed that the low-affinity/high-avidity fine-tuned G9 CAR exhibited a broader therapeutic window compared to the high-affinity/high-avidity G250 variant employed in the initial anti-CAIX CAR-T clinical trial, which unfortunately manifested significant OTOT effects.
Furthermore, their investigation extended to the assessment of G9’s therapeutic efficacy on patient-derived clear cell renal cell carcinoma organotypic tumor spheroid (PDOTS) ex vivo cultures, wherein G9 CAR-T cells demonstrated superior efficacy, migration, and cytokine release within these representative tumor models. Additionally, in an orthotopic mouse model of renal cell carcinoma (RCC), G9 CAR-T cells exhibited enhanced tumor control relative to their G250 counterparts. Their findings underscore the successful mitigation of OTOT side effects by G9, thereby rendering CAIX an actionable immunotherapeutic target with significant implications for advancing CAR-T cell-based cancer therapies.
Source: molecular-cancer.biomedcentral.com/articles/10.1186/s12943-024-01952-w