Fcy Receptor-Mediated Pharmacogenomics of Antibody Therapies in Type 1 Diabetes

PROJECT SUMMARY. Antibody and antibody fusion protein therapies targeting adaptive immune cells have shown variable inter-subject levels of success at halting autoimmune destruction of the insulin-producing pancreatic β-cells in individuals recently diagnosed with Type 1 Diabetes (T1D). Responsiveness to many

antibody therapies vary in other autoimmune diseases and cancer according to Fc gamma receptor (FcγR) variants impacting a patient’s capacity for Fc-mediated mechanisms of action (Fc-MoA) such as antibody dependent cellular cytotoxicity (ADCC) and antibody dependent cellular phagocytosis (ADCP). Indeed,

pharmacodynamics of low-dose α-thymocyte globulin (LD-ATG) and clinical efficacy of rituximab (α-CD20) have been demonstrated to be affected by FcγR variants in the context of transplantation or rheumatoid arthritis and lymphoma, respectively. However, whether responsiveness to these therapies in individuals with T1D are

similarly affected by FcγR-associated variants remains unknown. Therefore, I hypothesize that FcγR-associated variants may influence efficacy of therapeutic antibodies with FcγR-binding capabilities in recent-onset T1D via regulation of ADCC and ADCP. Indeed, I have identified a significant association between an FCGR2B

expression QTL (eQTL) and quantitative metabolic response (QR) in the LD-ATG trial (TN19). The objectives of my proposed studies are to build on this finding by identifying genetic variants in FcγR loci that associate with therapeutic efficacy in additional completed T1D immunotherapy trials and to evaluate the consequences of

modified FcγR expression and/or function on Fc-MoA. In Aim 1, I will perform quantitative trait locus (QTL) analysis of FcγR-associated single nucleotide polymorphisms (SNPs) and copy number variants (CNVs) versus treatment efficacy and target cell depletion in TrialNet (TN) and Immune Tolerance Network (ITN) studies of

native Fc-containing antibody therapeutics in recent-onset T1D. I will analyze associations between genotype microarray, clinical endpoints, and flow cytometry data from the rituximab (TN05) and alefacept (Inducing Remission in T1D With Alefacept [T1DAL], ITN) trials. In Aim 2, I will determine impacts of FcγR-associated

variants on cell type-specific FcγR protein expression and regulation of Fc-MoA of therapeutic antibodies for T1D. Here, I will characterize human whole blood samples by flow cytometry to evaluate associations between cell type-specific FcγR protein expression and previously defined whole blood eQTLs, with a focus on the LD-

ATG response-associated FCGR2B variant. I will also employ rapid and fluorometric ADCC (RFADCC) assays to measure LD-ATG- and rituximab-mediated ADCC and ADCP induction by genotype-selected natural killer (NK) cell and monocyte effectors and T cell or B cell targets, respectively. I expect my findings will support a

precision medicine approach to identify individuals with or at-risk for T1D who are likely to respond positively to native Fc-containing immunotherapies, as well as to guide dose optimization strategies for non-responders.