Long-Term Effects of Belantamab Mafodotin Plus Bortezomib, Lenalidomide and Dexamethasone (VRd) on T Cell Exhaustion Phenotype
Authors: Lorenzo Mauro , Garcés Juan-José , Burgos Leire , Manrique Irene , Lasa Marta , Puig Noemi , Sotolongo-Ravelo Janet , González-Rodríguez Marta , Castellanos Bárbara , Cedena Romero Maria Teresa , Paiva Bruno , Gonzalez-Calle Veronica , Mateos Maria-Victoria , Garayoa Mercedes , Paíno Teresa 
Published: December 2024

Introduction: GEM Bela-VRd (NCT04802356) is a multicenter, open label clinical trial evaluating the addition of belantamab mafodotin (belamaf), a BCMA-targeting monoclonal antibody-drug conjugate, to the standard VRd regimen (bortezomib, lenalidomide, dexamethasone) for newly diagnosed transplant-eligible multiple myeloma (NDTE MM) patients. Initial results indicate that this combination is safe and might improve outcomes. This study focuses on evaluating therapy effects on immune cell populations across treatment evolution, specifically examining T cell activation and exhaustion markers through flow cytometry.

Material and methods: We utilized FlowCT (v1.0), a semi-automated bioinformatic pipeline, to analyze the peripheral blood (PB) and bone marrow (BM) aspirates of MM patients at screening (SCR, n = 50), cycle 2 (C2, n = 60) and C6 (n = 67) of Bela-VRd. All samples were stained with an 8-color tube containing common T cell markers for the identification of the main T cell subpopulations, in addition to TIM3, PD-1 and ICOS as exhaustion markers; and granzyme B (GzmB), CD25 and CD127 as activation markers. Phenotyping by Accelerated Refined Community (PARC) was used as main clustering algorithm, Infinicyt (v2.0) was used to aid cluster annotation. Statistical differences among timepoints were assessed by ANOVA, with HSD Tukey post-hoc.

Results: Treatment evolution was characterized by a significant reduction in CD8+/CD127+ T cells (mean, 6.33% SCR, 2.58% C2, 3.09% C6, p&lt;0.05 in PB; 5.61% SCR, 2.43% C2, 2.52% C6, p&lt;0.05 in BM), and increase in CD4+/PD-1+ T cells (1.85% SCR, 2.6% C2, 3.61% C6, p&lt;0.05 in PB; 2.05% SCR, 3.42% C2, 4.26% C6, p&lt;0.05 in BM) in both compartments. Regulatory T cells (Treg, CD4+/CD127-/CD25+) were upregulated in PB in C2 compared to SCR (4.36% SCR, 6.36% C2, p&lt;0.05), but regressed in C6 (5.54%, p=0.16). There was a population of CD8+ T cells which did not express any other marker that got upregulated in both PB and BM in C6 compared to SCR; and in C6 when compared to C2 in PB (mean, 9.41% SCR, 9.02% C2, 14.38% C6, p&lt;0.05 in PB; 9.37% SCR, 12.14% C2, 15.21% C6, p&lt;0.05 in BM). Importantly, none of the cell clusters associated with effector T cell exhaustion got altered over time: CD8+/PD-1+ (8.81% SCR, 12.23% C2, 11.08% C6 in PB; 13.14% SCR, 17.4% C2, 16.15% C6 in BM), CD8+/TIM3+ (5.64% SCR, 6.78% C2, 6.34% C6 in PB; 5.09% SCR, 5.00% C2, 4.26% C6 in BM), or CD8+/PD-1+/ICOS+/GzmB+ T cells (3.27% SCR, 3.57% C2, 3.67% C6 in PB; 1.14% SCR, 3.09% C2, 4.21% C6 in BM).

Our data indicate that, despite an increase in Tregs over time, the fact that there is no increase of markers of T cell exhaustion such as ICOS or TIM3 suggests that the combination of belamaf with VRd as frontline therapy could be a viable option, as it does not generate a phenotype incompatible with other therapies after future relapses, such as CAR-T or bispecific antibodies.

Ongoing analysis will be extended to natural killer (NK), plasma cells, and dendritic cells to gain a more comprehensive understanding of the immune response dynamics throughout the treatment regimen.

“Funding and product for this study was provided by GSK [NCT04802356, Investigator Sponsored Study 12380]. GSK was provided the opportunity to review a preliminary version of this manuscript for factual accuracy, but the authors are solely responsible for final content and interpretation”.