Background Chimeric antigen receptor (CAR) T cell therapy has achieved successful remissions in relapsed/refractory B-cell leukemia and B-cell lymphomas in recent years.¹ However, the observed heterogeneity in therapeutic responses underscoring immune monitoring in peripheral blood to provide insight into mechanisms, and potentially identify predictive markers.² Notably, Asian populations have been largely underrepresented in CAR-T cell therapy trials.³ This study, conducting with longitudinal immunomonitoring of the aims to discover predictive biomarkers for the response to CAR-T cell therapy.

Methods Blood samples were collected from patients with B-ALL or lymphoma that received anti-CD19 CAR-T therapy in Singapore General Hospital. A comprehensive immunophenotyping was employed for both responders (R=5) and non-responders (NR=3) using a 33-plex flow cytometry panel. Dimension reduction was performed to obtain clusters of interest, which were then manually gated for statistical analysis.

Results Our analyses uncovered distinct immune cell clusters with significant differences between the responder (R) and non-responder (NR) groups within the first three months following CAR-T cell infusion. At 1-month timepoint, a reduced frequency of CD16⁺ dendritic cells and increased proportion of γδ T cells, especially CD38⁺γδ T cells were associated with response. At 2-month timepoint, CD38⁺ NK and CD38⁺γδ T cells were found significantly enriched in R group. At 3-month timepoint, a successful response was correlated with a high presence of CD4⁺ central memory T cells and a reduced frequency of CD39⁺ Tregs. Further meta-clustering analysis revealed a trend towards elevated CD38 expression in CD3⁺, CD4⁺, CD8⁺, γδ T and CD45⁺ clusters in R group during the first 2 months as well as decreased CD39 expression in Tregs in R group over 3 months.

Conclusions Collectively, these results revealed the distinctly dynamic reconstruction of immune cells during the first 3 months following CAR-T infusion and identified the predictive values of CD38⁺ immune clusters in Asian patients. Ongoing works include analysing all time points and expanding to other modalities such as cytokines, proteomics and AI.

References

1. Sterner RC, Sterner RM. CAR-T cell therapy: current limitations and potential strategies. Blood Cancer J. Apr 6 2021;11(4):69.

2. Qi T, McGrath K, Ranganathan R, Dotti G, Cao Y. Cellular kinetics: A clinical and computational review of CAR-T cell pharmacology. Adv Drug Deliv Rev. Sep 2022;188:114421.

3. Gajra A, Zalenski A, Sannareddy A, Jeune-Smith Y, Kapinos K, Kansagra A. Barriers to Chimeric Antigen Receptor T-Cell (CAR-T) Therapies in Clinical Practice. Pharmaceut Med. Jun 2022;36(3):163–171.

Ethics Approval The Centralized Institutional Review Board of SingHealth provided ethical approval for the use of patient materials in this study (CIRB ref.: 2022/2322; iSHaRe Ref. No. 202203–00014). Written informed consent is not required for deidentified subjects in Singapore.