Single Cell Analysis Reveals Immune Dysfunction in Large B-Cell Lymphoma (LBCL) Patients With Hypomagnesemia Receiving Axi-Cel: Results from ZUMA-1 Trial and Mayo Clinic Cohort

Introduction: Magnesium (Mg) plays a critical role in modulating immune surveillance. While the prognostic impact of hypomagnesemia in patients (pts) with LBCL undergoing stem cell transplant is established, little is known of its role in CART-cell therapy. Methods: We investigated the effects of Mg levels before lymphodepletion (LD) in 108 relapsed/refractory LBCL pts enrolled in the ZUMA-1 trial and in an independent cohort of 57 LBCL pts receiving axicabtagene ciloleucel (Axi-cel) at Mayo Clinic. Results: The two groups had similar characteristics. In ZUMA-1, 21% pts had Mg levels lower than 1.7 mg/dL (Mglow), 45% within normal range (Mgnl) and 34% had a high level (Mghigh). The Mayo Clinic cohort showed a similar distribution, with 21% Mglow, 53% Mgnl and 26% Mghigh. In ZUMA-1, the ORR was 65%, 83% and 92% in the Mglow, Mgnl and Mghigh groups (p = 0.03). Lower Mg associated with inferior PFS (p = 0.022) and OS (p = 0.001). Similar results were observed in the Mayo Clinic cohort. Of note, the Mglow group had a higher level of inflammatory cytokines (e.g., IL-6, IL1a, IL-8 and MIP1a), suggesting an immune modulatory effect. To explore the impact of different Mg levels on immune response, we performed single-cell RNA-seq of peripheral blood cells collected before LD (Pre-CART) and at CART peak. Using CellChat analysis, we found that at Pre-CART pts with Mghigh had a higher number of interactions between CD16 and CD14 monocytes and between these cells with CD4 and CD8 T cells compared to those with Mglow. Similarly, CD8 T effector memory (TEM) cells had an increased number of interactions with CD4 cells and CD16 monocytes (Figure 1A). Remarkably, at CART peak the same interactions decreased dramatically in pts with Mghigh. There was a profound decrease in the interaction strength of all CD8 T cell subsets and TEM cells in the Mghigh group (Figure 1B). In contrast, pts with Mglow had significantly increased interactions between CD8 T cells and CD14 monocytes. A transcription factors analysis identified a significant enrichment for SPI1, which plays an essential role for monocyte differentiation, in Mglow compared to those Mghigh pts. There was also an enrichment of the histone methyltransferase KMT2A, which may alter the chromatin accessibility to allow transcription factors binding and gene activation. Moreover, Mglow pts showed an upregulation of the proto-oncogene MYC, which favors cell growth and orchestrates changes in the tumor microenvironment (Figure 1C). Finally, we performed ligand-receptor analyses which identified a significant downregulation of the interaction of multiple HLA subtypes of CD8 T cells with CD14 and CD16 monocytes, CD4 and CD8 TEM cells in Mghigh compared to Mglow pts (Figure 1D) The research was funded by: the University of Iowa/Mayo Clinic Lymphoma SPORE CA97274; Mayo Clinic Center for Individualized Medicine, Bernard E. and Edith B. Waterman, Henry J. Predolin Foundation Keywords: aggressive B-cell non-Hodgkin lymphoma, cellular therapies, diagnostic and prognostic biomarkers No conflicts of interests pertinent to the abstract.