PROBLEM TO BE SOLVED: To provide an antibody, a humanized antibody, a surface reconstruction antibody, an antibody fragment, a derivative antibody, and a conjugate with a cytotoxic agent which specifically bind to and inhibit class A Eph receptors, antagonize a growth factor for proliferation and survival of tumor cells, and have merely a minimum working activity or preferentially lack for the working activity.SOLUTION: There is provided an antibody or an epitope binding fragment thereof which specifically binds to an antagonist of EphA2 receptors and acts as an antagonist of the receptors. The antibody or the epitope binding fragment of the antibody is a monoclonal antibody. The monoclonal antibody has an ability to inhibit proliferation of cancer cells, an ability to inhibit migration of the cancer cells, and an ability to inhibit angiogenesis upon its administration. The EphA2 monoclonal antibody is useable in treating tumor expressing class A Eph receptors, such as breast cancer, colon cancer, lung cancer, ovary cancer, synovial sarcoma, and pancreatic cancer. In addition, the derivatized antibody is usable in diagnosis and imaging of the tumor expressing class A Eph receptors at a high level.【課題】Ｅｐｈ受容体のＡクラスに特異的に結合し、阻害し、腫瘍細胞の増殖及び生存に対する増殖因子に拮抗し、最小限の作動活性しか持たない、又は作動活性を優先的に欠く、抗体、ヒト化抗体、表面再構成抗体、抗体断片、誘導体化抗体、及び細胞毒性薬との抱合体の提供。【解決手段】ＥｐｈＡ２受容体に特異的に結合し、該受容体の拮抗物質である、抗体又はそのエピトープ結合性断片。前記抗体又は該抗体のエピトープ結合性断片がモノクローナル抗体であり、癌細胞の増殖を阻害する能力があり、癌細胞の遊走を阻害する能力があり、血管新生を阻害する能力がある前記モノクローナル抗体の投与。【効果】ＥｐｈＡ２モノクローナル抗体は、乳癌、結腸癌、肺癌、卵巣癌、滑膜肉腫、膵癌等、Ｅｐｈ受容体のＡクラスを高レベルで発現する腫瘍の治療並びに、前記誘導体化抗体は、Ｅｐｈ受容体のＡクラスを高レベルで発現する腫瘍の診断及び画像化に使用できる。【選択図】なし
