Which of the following is a common monoclonal antibody used in cancer therapy?

Rituximab is a common monoclonal antibody used in cancer therapy, specifically targeting CD20, a protein found on the surface of B cells. This targeted therapy is particularly effective in treating certain types of non-Hodgkin lymphoma and chronic lymphocytic leukemia. Monoclonal antibodies like Rituximab work by binding to specific antigens on cancer cells, marking them for destruction by the immune system or directly inhibiting their growth.

In contrast, Metformin is primarily used for managing type 2 diabetes and does not have a role in cancer therapy. Prednisone is a corticosteroid used for its anti-inflammatory and immunosuppressive properties, but it is not a monoclonal antibody or primarily targeted at cancer. Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) used for pain relief and inflammation, rather than a cancer treatment. Thus, Rituximab stands out as the appropriate choice among the options provided, due to its specific mechanism of action and established role in oncology.