Correlation of Peripheral Chimeric Antigen Receptor T-cell (CAR-T Cell) mRNA Expression Levels with Toxicities and Outcomes in Patients with Diffuse Large B-cell Lymphoma

Cytokine-release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) are significant complications in patients with relapsed/refractory diffuse large B-cell lymphoma undergoing chimeric antigen receptor T-cell (CAR-T cell) therapy. However, it remains unclear whether CAR-T cell expression itself is clinically relevant. We assessed CAR-T cell mRNA expression and DNA concentration by digital droplet PCR in peripheral blood from 14 sequential CAR-T cell recipients. Patients were grouped according to CAR-T cell peak expression. Patients with high CAR-T cell peak expression (8 patients; 57%) had higher rates of ICANS (p=0.0308) and intensive care unit admission (p=0.0404), longer durations of hospitalization (p=0.0077), and, although not statistically significant, a higher rate of CRS (p=0.0778). There was a correlation of CAR-T cell mRNA expression with DNA concentration, but CAR-T cell expression levels failed to correlate to response or survival. Our data suggest that higher CAR-T cell peak mRNA expression is associated with increased risk for ICANS and possibly CRS, requiring further investigation in larger studies.