Monoclonal antibodies as effective therapeutic agents for solid tumors.

Monoclonal antibodies (mAbs) against growth factors or their receptors have been revealed to be effective therapeutic agents for solid tumors. Trastuzumab (humanized anti-HER2 mAb) is the first mAb approved for the treatment of a solid tumor, metastatic breast cancer. Large-scale phase III clinical trials are now ongoing to further evaluate the additive effects on chemotherapy and the efficacy as a maintenance monotherapy. Another anti-HER2 mAb CH401 that we developed also seems to have good potential. This chimeric mAb completely suppressed the growth of established human tumor xenografts in SCID mice after a single injection. Furthermore, CH401 characteristically showed much stronger induction of apoptosis in HER2-overexpressing gastric cancer cells compared to trastuzumab. Additional targets now being intensively evaluated are epidermal growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF). Both cetuximab (chimeric anti-EGFR mAb) and bevacizumab (humanized anti-VEGF mAb) have recently been shown to be of clinical value for metastatic colorectal cancer. Anti-idiotype mAbs are unique as active immunotherapeutic agents, and survival benefits have been observed in clinical trials for solid tumors.