Chapter 32 • Because of their tumor selectivity, monoclonal antibodies offer exceptional opportunities for targeted therapy. • When naked, monoclonal antibodies can kill tumors by receptor blockade and by actively inducing apoptosis. • Tumor cytotoxicity is mediated through white cells by activating antibody-dependent cell-mediated cytotoxicity, and in the presence of serum, by complement-mediated cytotoxicity. • Bispecific or multifunctional constructs can greatly enhance the antitumor effect of antibodies. • Antibodies can deliver effector molecules in the form of drug conjugates, radioimmunoconjugates, immunocytokines, immunotoxins, immunoenzymes, immunoliposomes, and retargeted killer cells. • Naked antibodies generally do not have overlapping toxicity profiles with chemotherapy and radiation therapies, and dose-limiting toxicities of immunoconjugates vary depending on the cytotoxic moiety (e.g., myelosuppression in radioimmunoconjugates) being used. • Antibodies are likely to be most beneficial at the time of minimal residual disease, especially when used in conjunction with standard therapy. • The following antibodies are licensed by the Food and Drug Administration and are in use for the cancers listed (target molecule in bold): Alemtuzumab (Campath): B-chronic lymphocytic leukemia (CD52) Bevacizumab (Avastin): colorectal cancer (VEGF) Cetuximab (Erbitux): colorectal cancer, head and neck cancer (EGFR) Ibritumomab (Zevalin): non-Hodgkin lymphoma (Yttrium-90, CD20) Rituximab (Rituxan): non-Hodgkin lymphoma (CD20) Trastuzumab (Herceptin): breast cancer (HER2) Ipilimumab (Yervoy): melanoma (CTLA4) Ofatumumab (Arzerra): CLL (CD20) Brentuximab vedotin (Adcetris): refractory/relapsed Hodgkin disease and anaplastic large-cell lymphoma (CD30)
Therapeutic Antibodies and Immunologic Conjugates
Summary of Key Points
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