An odyssey of monoclonal gammopathies: focusing on precursors and the progression from MGUS and SMM to multiple Myeloma, with a brief overview of novel therapeutic strategies

Monoclonal gammopathies span a continuum from monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM) to overt multiple myeloma (MM). This gradual clonal evolution is driven by primary cytogenetic lesions, secondary genomic events, and epigenetic remodeling within a permissive bone-marrow microenvironment. Traditional biomarkers (serum M-protein and free-light-chain ratios) provide useful but incomplete prognostic information because they do not capture spatial heterogeneity or temporal clonal dynamics. Recent advances highlight circulating tumor cells (CTCs), minimal residual disease (MRD) assessment via next-generation flow (NGF) and sequencing (NGS), and liquid biopsy approaches as minimally invasive tools that refine risk stratification and anticipate malignant progression. Therapeutic paradigms have shifted from melphalan-based chemotherapy and autologous stem cell transplantation to triplet and quadruplet combinations incorporating immunomodulatory drugs, proteasome inhibitors, and monoclonal antibodies, while next-generation immunotherapies, BCMA-directed CAR-T cells, bispecific antibodies, and cereblon E3 ligase modulators, offer unprecedented depth of response. Yet major challenges persist, including predicting individual progression in precursor states, overcoming drug resistance and relapse, managing therapy-associated toxicities, and ensuring access to advanced therapies across heterogeneous patient populations. Integrating multi-omics profiling, artificial intelligence (AI)-based analytics, and dynamic biomarkers promises to transform the natural history of these disorders, shifting the trajectory of monoclonal gammopathies from inevitable progression toward durable remission and potential cure. This review delineates the biological continuum underpinning disease progression from MGUS and SMM to MM, and provides a concise overview of recent advances in molecular diagnostics and novel therapeutic strategies within this context.