Longitudinal Analysis of Multiple Myeloma: Therapeutic Response and Immune Microenvironment Dynamics in the Context of Tumor Heterogeneity [CITE-Seq]

Multiple myeloma (MM) is a hematological malignancy characterized by an expansion of malignant plasma cells in the bone marrow. For newly diagnosed MM (NDMM), standard three-drug treatment regimens—such as the combination of bortezomib, lenalidomide, and dexamethasone (VRd)—and the more recent inclusion of a fourth drug, anti-CD38 antibody immunotherapy, have significantly improved patient outcomes by targeting multiple mechanisms of tumorigenesis. This treatment approach typically involves several cycles of VRd induction therapy, followed by high dose melphalan (HDM) and autologous stem cell transplant (ASCT), and maintenance therapy. Treatment responses vary widely, with some patients requiring longer and more intense therapy and others exhibiting more rapid responses and longer relapse-free remission.This cycle of remission, maintenance, and eventual relapse persists despite advancements in treatment modalities, including immunotherapy, leaving MM incurable. This study characterizes the tumor state and immune microenvironment in MM patients across variable graded patient responses. Using a multimodal, longitudinal approach, we investigate immune and microenvironmental cellular changes during treatment in NDMM patients and in a second cohort of RRMM patients. For the NDMM cohort, longitudinal blood and bone marrow aspirate samples were collected at diagnosis, throughout induction therapy, following autologous stem cell transplant (ASCT), and at post-transplant intervals of 60 days, 90 days, and 1 and 2 years. Multi-omic profiling of these samples magnifies the individual heterogeneity between tumor and therapeutic response. The longitudinal aspect of the study allowed us to focus on individual-level longitudinal responses instead of cross-patient effects, enabling detailed insights into tumor and microenvironment dynamics. Using Olink proteomic analysis of plasma and bone marrow interstitial fluid (BMIF), and single-cell analyses (3’ CITE-seq, scRNA-seq, flow cytometry) of peripheral blood mononuclear cells (PBMC) and bone marrow mononuclear cells (BMMC) we longitudinally characterized tumor, the immune microenvironment, and therapeutic responses. This revealed distinct immune states and pathways associated with therapeutic response, and tumor survival, highlighting potential targets and therapeutic strategies to improve patient outcomes.