Antibody-derived therapeutics represent a major and rapidly expanding segment of modern biopharmaceuticals, with established clinical utility across oncology, inflammatory diseases, and immune-mediated disorders. The therapeutic performance of monoclonal antibodies (mAbs) arises from multiple functional mechanisms, including antigen neutralization, antibody-dependent cell-mediated cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), and modulation of immune signaling pathways. As a result, successful mAb development requires detailed functional and biophysical characterization to fully understand their mechanism of action. Central to both pharmacodynamic behavior and in vivo efficacy is the specific interaction between the antibody and its target antigen, necessitating robust analytical strategies capable of accurately interrogating binding properties. Surface Plasmon Resonance (SPR) is extensively utilized during mAb development as a label-free technique for evaluating binding kinetics, affinity, and functional activity in vitro. SPR-based methods enable quantitative assessment of receptor–antibody interactions and determination of active antibody concentrations required for target engagement. In particular, competition assays performed using SPR provide valuable insight into epitope overlap and neutralizing potential. Nevertheless, traditional SPR formats that depend on purified recombinant proteins frequently fail to recapitulate the complexity of antigen presentation and molecular context encountered on living cell membranes. To overcome these limitations, this study presents an advanced SPR methodology incorporating intact, live cells as the binding substrate, thereby offering a more biologically relevant platform for potency evaluation. The approach enables interrogation of two key competitive interaction modes: functional neutralization, measured through inhibition of ligand–receptor engagement on cell surfaces, and competitive epitope binding between antibodies directed against the same membrane-associated antigen. By integrating cellular systems into SPR analysis, this strategy enhances the physiological relevance and interpretability of potency measurements, supporting improved monoclonal antibody characterization during early-stage therapeutic development.