Association of enrichment of CD7⁺CXCR3⁺ CAR T cells in infusion products with remission in relapsed or refractory diffuse large B-cell lymphoma.

7020 Background: Chimeric antigen receptor (CAR) T-cell therapy is the standard of care for relapsed or refractory diffuse large B-cell lymphoma (R/R DLBCL), yet more than half of patients do not achieve durable remission. Identifying predictive biomarkers in CAR T-cell infusion products (IPs) could guide strategies to improve outcomes. Methods: This was a single-centre observational study conducted at Lausanne University Hospital (CHUV), Switzerland. IPs from 13 patients with R/R DLBCL who underwent CAR T-cell therapy were analyzed using a 39-marker mass cytometry panel. We compared phenotypic and functional markers between long-term responders (R) and non-responders (NR). Both unsupervised and supervised analyses were performed. Additionally, longitudinal blood samples collected over 30 days after infusion were examined to track CAR T-cell subpopulation dynamics. Results: At a median follow-up of 13.5 months, median progression-free survival (PFS) was 13.3 months (95% CI 9.7–24.3) in R (n=8) versus 3.5 months (95% CI 0.5–5.4) in NR (n=5) (hazard ratio 56.67 [95% CI 7.3–439.3]; p=0.0001). A subset of CD3⁺CXCR3⁺CD7⁺ CAR T-cells—present within both CD4⁺ and CD8⁺ subsets—was significantly enriched in R. These cells showed increased expression of perforin, granzyme B, and NKG2D (restricted to CD8⁺ cells). In contrast, NR had a higher frequency of CXCR3⁺CD7⁺LAG3⁺ CAR T-cells. Surface expression levels of CD3, CD7, CXCR3, and NKG2D were higher in R, whereas LAG3, Ki67, and CD71 were elevated in NR. A predictive cut-off ratio of CD3⁺CXCR3⁺CD7⁺LAG3⁺CAR⁺ T-cells <0.83 and CD3⁺CXCR3⁺CD7⁺NKG2D⁺CAR⁺ T-cells >1.034 yielded a predictive accuracy of 0·92. Serum CXCL9 and CXCL10 concentrations did not differ between groups. Conclusions: The enrichment of CD7⁺CXCR3⁺ CAR T-cells and expression of NKG2D in R, as opposed to elevated LAG3 and CD71 in NR, emerged as robust correlates of therapeutic outcome. These findings could inform the development of biomarker-driven strategies to optimize CAR T-cell products and enhance the likelihood of sustained remission.