Post-CAR T-Cell Early Reconstitution of Peripheral T-Cell Subsets Is Heterogeneous and Independent of the Cell Therapy Outcome in High Grade B-Cell Lymphoma

The development of chimeric antigen receptor T-cells (CAR T-cells) targeting tumor antigens has been an important breakthrough in the management of patients with B-cell lymphoma. As usage of this therapy spread worldwide, rapid progress has been made in the clinical management of CAR T-cell recipients. Several studies have also been devoted to analyses of the infused material and to the follow-up of CAR T-cells after infusion, using labelled recombinant proteins of the target, usually CD19. Prior to CAR T-cell infusion, patients are pre-treated in order to perform lymphodepletion allowing for better engraftment of the engineered cells. Little is known however of the rate and type of peripheral immunity reconstitution.

In order to evaluate whether the speed and type of basic T-cell subsets recovery could provide insights on the outcome of CAR T-cell recipients, this study was designed to assay the percentages of peripheral CD3+, CD4+ and CD8+ lymphocytes over the first 10 days post CAR T-cell infusion (Kymriah® or Yescarta®) for patients with high grade B-cell lymphoma. Blood samples collected for daily monitoring of complete blood counts were used. Briefly, 100 µL of peripheral blood were incubated with antibodies to CD45, CD3, CD4, CD8, CD19, red blood cells were lysed and the samples analyzed in flow cytometry (Canto II, BD Biosciences, San Jose, CA). All analyzes were performed with the Kaluza software (Beckman Coulter, Miami, FL) and cell percentages retrieved. In most instances, CBC were too low to evaluate differentials and calculate absolute counts, although lymphocytes were clearly seen in flow cytometry.

A cohort of 50 patients was collected prospectively between November 2018 and February 2022. It included 33 males and 17 females with a mean age of 61 years. The median follow-up after CAR T-cells infusion, available for 49 patients, was 10.1 months.

Apart from one patient who relapsed early after infusion, CD19+ B-cells were constantly absent. Sequential analyses of T-cell subsets yielded extremely variable and patient-dependent patterns of reconstitution. The parameters evaluated and ultimately compared to patient outcome were as follows : i)inversion of the CD4/CD8 ratio, i.e. predominance of CD8+ cells over the analysis period, ii) patients with predominant CD8 cells at onset, iii)kinetics of CD8 predominance in patients with CD4/CD8 inversion and iv)kinetics of CD4 cells.

The CD4/CD8 ratio was or became inverted in 60% of the patients, while 26% had higher percentages of CD8+ than CD4+ cells at onset. In patients where CD8 predominance was observed, this occurred later than day 3 for 53% of them. Finally CD4 T-cell decreased over time in 50% of the patients, while they remained stable (independently of CD8+ cells increase) in 36%. CD4 percentage increase was only seen in 3 cases and the pattern was fluctuating for the last 3 patients.

These different patterns were analyzed according to patient outcomes at the time of last follow-up. These data are summarized in table 1. All in all, progression post CAR T-cell infusion was observed in 38% of the patients while 62% remained in CR. None of the four patterns examined showed any correlation with these outcomes.

This study indicates that the assessment of peripheral T-lymphocytes subsets after CAR T-cells infusion is not significantly associated to the ultimate outcome of patients who received this therapy for high grade lymphoma. Patient-dependent variations are thus potentially dictated by individual characteristics, environmental stimuli or even by the biological characteristics of the CAR T-cells product itself. This is currently explored in our department.

Gastinne:Gilead/Kite, Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Support for attending meetings/travel, participation in a data safety monitoring board or advisory board. Touzeau:BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees. Le Gouill:Novartis, Kite/Gilead, Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support. Moreau:AbbVie, Janssen, Celgene, Amgen, and Sanofi: Honoraria. Chevallier:Takeda: Honoraria; Abbvie: Honoraria; Pfizer: Research Funding; Incyte: Research Funding; Jazz Pharmaceuticals: Honoraria.