Epcoritamab in Chronic Lymphocytic Leukemia and Richter Syndrome

Study Description: Subjects enrolled in GCT3013-03, a phase 1b/2 study of epcoritamab in R/R CLL and RS, at the National Institutes of Health (NIH) Clinical Center (CC) will be invited to simultaneously participate in this companion correlative study. Subjects will undergo percutaneous lymph node coreneedle biopsies, bone marrow biopsies, lymphapheresis, and blood draws for pharmacodynamic evaluation of tumor and immune cells in affected tissue sites and blood before and during treatment with epcoritamab. Objectives: Primary Objective: -Assess the pharmacodynamic effects of epcoritamab in the tumor microenvironment. Secondary Objectives: * Assess the pharmacodynamic effects of epcoritamab in blood * Investigate clonal dynamics during treatment with epcoritamab Exploratory Objective: -Evaluate pharmacodynamic and predictive biomarkers Endpoints: Primary Endpoint: -Immunophenotype and transcriptome of T cells and tumor cells in lymph node and bone marrow Secondary Endpoints: * Immunophenotype and transcriptome of T cells and tumor cells in peripheral blood * DNA sequencing of tumor cells Exploratory Endpoints: -Tests include, but are not limited to single cell multiomics, bulk lymph node transcriptome cytokine analysis