The Evolution of Immunotherapy; Looking at Anti-CD20 Monoclonal Antibodies

Megan C. Lewicki1 1 Second Year Undergraduate Student, Biochemistry and Immunology Major Programs, University of Toronto, Toronto, Ontario Over the past 10 years, immunotherapy has emerged as one of the most promising fields in neoplastic research. Immunotherapy involves introducing an antibody into the blood that recognizes and flags a particular cell marker expressed by malignant cells, allowing the immune system to destroy them. In 1997 the first immunotherapeutic drug, Rituximab, a CD20 monoclonal antibody, was approved by the FDA for treating Non-Hodgkin’s Lymphoma. Since then, Rituximab has become the most commercially successful cancer therapy with sales of over $ 10 billion worldwide. More CD20 therapeutics are now appearing on the market along with many immunotherapies targeting other cancer and autoimmune cell markers. Their popularity and potential for future use comes from their specificity when binding to target cells, leaving most healthy cells untouched. Immunotherapies can also have significantly reduced side effects compared to traditional chemotherapies. Rituximab in particular has enjoyed great success in treating B cell lymphomas, since CD20 is only expressed on early B cells and more differentiated B cells, but not on healthy precursor B cells. More recent CD20 therapies are designed to improve the efficiency of targeted cell death and further decrease side effects. Such an approach is used by the drugs Zevalin and Bexxar, which target CD20 cells with conjugated radioactive isotopes, delivering radiation to specific cells. Another effective strategy is conjugating chemotherapeutic agents to CD20 antibodies to deliver chemotherapy only to target cells. This has already been accomplished for a CD33 antibody, Mylotarg, in treating acute myeloid leukemia. The future prospects for antibody oncology are bright.