Biomarker analysis to unravel mechanisms of resistance to glofitamab monotherapy in large B cell lymphoma

Abstract Background: Glofitamab, a CD20-CD3 T-cell bispecific, has demonstrated high and durable complete responses (CR) in patients (pts) with aggressive Non-Hodgkin Lymphoma (NHL). Glofitamab monotherapy is approved for relapsed or refractory diffuse large B cell lymphoma (R/R DLBCL) after ≥2 lines of therapy. This study aimed to comprehensively investigate the correlation between baseline molecular tumor characteristics, including intrinsic and extrinsic factors, and treatment outcomes in pts with R/R large B-cell lymphoma (LBCL) receiving glofitamab monotherapy. Methods: The analysis includes pts with R/R LBCL (DLBCL, HGBCL or trFL) with at least 2 prior lines of therapy enrolled in the Phase I/II study NP30179 (NCT03075696). Pts received obinutuzumab pretreatment to mitigate cytokine release syndrome, followed by glofitamab step-up dosing in cycle 1 as part of a fixed-duration treatment of 12 cycles. We present data for pts treated with approved target dose of 30 mg or with ≥10 mg of glofitamab, considered efficacious, with available baseline RNA-seq data (n=151/246, 63%). T cell phenotyping in peripheral blood was performed with a validated flow cytometry panel at IQVIA. Tumor responses were assessed by an Independent Review Committee (IRC) using Lugano 2014 criteria. Associations of individual genes, biological processes (using Hallmark gene sets), and Tumor Microenvironment (TME) related signatures (using xCell) with outcomes were performed using differential gene expression (DGE) with limma-voom, linear regression, Cox regression, and gene set enrichment analysis (GSEA). P-values were adjusted for multiple testing using the Benjamini-Hochberg method; results with adjusted p-values <0.05 were considered significant. Results: In baseline tumor biopsies Hallmark gene sets indicative of high tumor proliferation, protein synthesis and DNA repair – specifically MYC targets, G2M checkpoints, and E2F targets, oxidative phosphorylation, unfolded protein response as well as DNA repair – were significantly enriched in pts who did not achieve a CR. These signatures were also associated with shorter progression-free survival (PFS) and duration of CR (DoCR; all mentioned GSEA p<0.0001) B-cell and memory B-cell signatures from xCell were significantly up-regulated in CR pts compared to non-CR pts (p=0.0012 for both). High expression of these signatures was associated with longer PFS (HR [95%CI] = 0.58 [0.4-0.85], 0.63 [0.43-0.91]) but showed no association with DoCR (HR [95%CI] = 0.84 [0.4-1.79], 0.99 [0.45-2.17]). Analysis of CD4 and CD8 T-cell signatures from xCell demonstrated a trend for increased expression of CD4+ memory T-cells, CD4+ T central memory (cm) and CD8+ Tcm in CR as compared to non-CR pts. High expression of CD4+ memory T-cells, CD4+ Tcm and CD8+ Tcm signatures was associated with longer DoCR (HR [95%CI] = 0.3 [0.14-0.64], 0.3 [0.12-0.74], 0.5 [0.24-1.04]) and PFS (HR [95%CI] = 0.6 [0.41-0.88], 0.57 [0.36-0.88], 0.6 [0.41-0.88]). Additional results from multivariate analysis will be presented. To gain more insights in the biological features of pts not responding to glofitamab we further characterized pts exhibiting a high proliferation gene signature, defined by high MYC targets, G2M checkpoints and E2F targets. Those pts showed a significant enrichment in the Dark Zone (DZ) signature (p<0.0001), indicating a highly active germinal center B-cell like (GCB) phenotype. A negative correlation was observed between the proliferation phenotype and CD4+ and CD8+ T-cell related signatures from xCell. A similar trend for negative correlation was noted with T cell immune phenotyping in the periphery. Additional analysis on the correlation with mutation profile and lymphoma related signatures will be presented. Conclusions: This comprehensive biomarker analysis reveals distinct roles for tumor-intrinsic and TME features in determining glofitamab outcomes in pts with R/R LBCL. While tumor intrinsic characteristics related to B-cell phenotype and high proliferation strongly influence the likelihood of achieving an initial response, features of T cells in the TME appear to be more critical for achieving a durable response. Molecular features of high proliferation, characterized by a highly active GCB phenotype and T-cell exclusion, might be a main driver of resistance to glofitamab monotherapy. Acknowledgments: The NCT03075696 study is sponsored by F. Hoffmann-La Roche Ltd.