Abstract. Background/Aim: EPH receptor A2 (EPHA2) is highly expressed in aggressive types of human cancer, and is expected to be an excellent target molecule for antibody treatments. In this study, we investigated the therapeutic potential of antibody to EPHA2 against melanoma in vitro. Materials and Methods: We generated three monoclonal antibodies (mAbs) to EPHA2 and examined cell-surface expression by flow cytometry. To investigate the ability to inhibit tumor cell migration therapy with mAbs to EPHA2, we performed a wound scratch assay and invasion assay. We investigated the therapeutic effects of immunotoxins consisting of toxin-conjugated EPHA2 mAbs. Results: All human melanoma cell lines studied expressed EPHA2. Like natural ligand ephrin-A1, one of EPHA2 mAbs, SHM16, inhibited metastatic behavior of cells, such as migration and invasion. In addition, drastic growth inhibition and cytotoxicity were found using immunotoxin-conjugated SHM16. Conclusion: These observations indicate a promising role for EPHA2 as a target in antibody treatments for melanoma, and demonstrate the potential therapeutic effects of an agonistic antibody to EPHA2.Melanoma is the most aggressive type of skin cancer. While melanoma accounts for fewer than 5% of all skin cancer cases, it is responsible for the large majority of deaths due to skin cancer. The type of treatment will depend not only on stage and location of the melanoma, but also on the patient's overall health. When melanoma has not grown deeper than the epidermis, it is usually treated by surgery (wide excision). When this is not possible, therapeutic options including injections of Bacille Calmette-Guerin (BCG) vaccine, interferon, or interleukin-2 (IL2) directly into the melanoma, radiation therapy, and chemotherapy (1, 2). The treatment of widespread melanoma has changed in recent years as newer forms of immunotherapy and molecularly-targeted drugs have been shown to be more effective than chemotherapy (3-6).Receptor tyrosine kinases (RTKs) transmit signals that regulate cell proliferation and differentiation, promote cell migration and survival, and modulate cell metabolism. They play critical roles in a wide range of biological processes, including embryonic development, growth of an organism, angiogenesis, synaptic plasticity, and oncogenesis (7-9). EPH receptors, the largest subfamily of RTKs, are involved in many biological processes including angiogenesis, tissue-border formation, cell migration, and axon guidance (10, 11). EPH receptors and their ephrin ligands are important mediators of cell-to-cell communication that regulate cell attachment to the extracellular matrix, cell shape and cell motility. They have been studied extensively for their roles in the developmental process. In recent years, EPH receptors and ephrins have been found to be integral players in cancer formation and progression. EPH receptor A2 (EPHA2) and ephrin-A1 are especially known to be involved in the development and maintenance of many types of solid tumors (12)(13)(14).EPHA2 was ori...