This is a fully human IgG1 monoclonal antibody using the same sequences as the therapeutic antibody ofatumumab. It works by recognizing CD20 antigens expressed on tumor cells in certain cancers. However, it should be noted that CD20 is not exclusive to tumors and can also be found on normal B-cells. Ofatumumab is indicated for the treatment of recurrent, progressive, or recurrent chronic lymphocytic leukemia (CLL) or CLL in treatment-naive patients for whom fludarabine-based therapy is deemed unsuitable. Its administration may involve monotherapy or combination with other medications, based on the patient profile and previous treatment history. Despite sharing a similar molecular mechanism of action with rituximab, another CD20 monoclonal antibody used in the treatment of rheumatoid arthritis and B-cell non-Hodgkin’s lymphoma, ofatumumab has a higher affinity towards CD20. It binds to both small and large extracellular loops of the CD20 molecule, inducing immune effector functions including complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC), which promote the lysis of malignant B-cells.