Fc-Mediated Antibody Effector Function, Inflammation Resolution and Oligoclonality on TCR Rearrangements Predict Sustained MRD Negativity in Newly Diagnosed Multiple Myeloma Treated with Immunotherapy Regimens

Background: Targeted immunotherapy combinations including anti-CD38 monoclonal antibody daratumumab have significantly increased the depth of response and clinical outcome in newly diagnosed multiple myeloma (NDMM). Despite this improvement, 30-40% of patients still progress early and fail to achieve sustained minimal residual disease (MRD) negativity through largely unknown resistance mechanisms. Here we integrate whole genome sequencing (WGS) and single cell RNA (scRNA), surface protein (CITE), and TCR sequencing from patients with NDMM to characterize genomic and immune microenvironment features related to the failure to achieve sustained remission. Methods: 5'single-cell RNA-sequencing with an additional capture of the TCR and surface protein markers (CITEseq) was performed at both induction (T1) and at the end of induction (T2) with DKRd (Daratumumab-Carfilzomib, Lenalidomide and dexamethasone). A total of 148,280 cells were analyzed for RNA and CITE from 17 patients at T1 and 18 at T2. Twenty-seven cell types were identified and changes in their gene expression were examined. Data were integrated with 40,000 healthy bone marrow cells from the Human Cell Atlas. For TCR-seq, a total of 22,882 ⍺β clonotypes were analyzed. Fc-mediated antibody effector function is associated with sustained MRD negativity The microenvironment changed drastically between diagnosis and end of induction. The achievement of sustained MRD negativity were associated with an expansion of activated CD56-bright NK cells at T1 (chi-squared=4, p=0.044). Furthermore, significant changes in the monocyte profile were seen between timepoints and response groups. We identified a subset of resident-like macrophages expressing markers such as IL1B and CXCL2 suggesting that there are some immune hot tumors that are associated with suboptimal responses. Although there weren't absolute differences in T-cell subsets, PCA analysis showed that the combination of CD8 effector 1, CD16+monocytes and CD56+NK profiles could be used to identify a subset of good responders achieving sustained MRD negativity. Inflammation resolution is associated with sustained MRD negativity when complete response is achieved, significant changes in the microenvironment were observed and expansion of CD16+ monocytes associated with sustained MRD negativity. These data were validated prospectively using flow cytometry (n=31). These data suggest that the presence of cells mediating Fc-dependent immune effector mechanisms at diagnosis could predict good response and the resolution of tumor induced inflammation after treatment is associated with anti-inflammatory CD16+ monocytes. Oligoclonality in T-cell is associated with treatment and response TCR analysis was available for 22,882 cells and showed that there were significantly fewer clonotypes between T1 and T2 (Kruskal-Wallis chi-squared = 4.0, df = 1, p-value = 0.044) reflecting both the impact of treatment, possible antigen selection, and/or the disappearance of the chronic antigen in the form of the malignant plasma cells. Patients that failed to achieve MRD negativity at T2 had significantly more clonotypes suggesting an ineffective T-cell response to residual tumor. Diversity analysis is currently ongoing. Conclusion: In this multilayered analysis we show changes that the composition of the microenvironment is related to the level of response in the context of DKRd treatment. Fc-mediated antibody effector function and inflammation resolution are associated with sustained MRD negativity phenotypes response suggesting a significant contribution of the microenvironment to response, opening the way for therapeutic manipulation to enhance response. TCR analysis reveals for the first time that oligoclonal profiles seen on treatment may influence the fitness of the immune response.