PROBLEM TO BE SOLVED: To provide bispecific binding molecules specifically binding to CD3 and a surface target antigen on cancer cells.SOLUTION: The present invention provides a bispecific binding molecule characterized by containing (a) an antibody specifically binding to CD3, and(b) a Fyn-SH3-derived polypeptide binding to a surface target antigen on cancer cells, the Fyn-SH3-derived polypeptide consisting of a specific 63 amino acid sequence, which has at least one substituted, deleted, or added amino acid within amino acid positions 10 to 19, and has at least one substituted, deleted, or added amino acid within positions 29 to 36, and further having at least 85% sequence identity to a sequence consisting of a specific 63 amino acid sequence, the amino acid positions 12 to 17 and 31 to 34 being excluded in identity determination.SELECTED DRAWING: NoneCOPYRIGHT: (C)2019,JPO&INPIT【課題】ＣＤ３と、癌細胞上の表面標的抗原と、に特異的に結合する二重特異的結合分子の提供。【解決手段】（ａ）ＣＤ３に特異的に結合する抗体と（ｂ）癌細胞上の表面標的抗原に結合するＦｙｎ－ＳＨ３由来ポリペプチドとを含み、Ｆｙｎ－ＳＨ３由来ポリペプチドは特定の６３アミノ酸配列からなり、アミノ酸位置１０～１９内の少なくとも１つのアミノ酸は置換、欠失、又は付加されていること、かつ２９～３６内の少なくとも１つのアミノ酸は、置換、欠失、又は付加されており、さらに特定の６３アミノ酸配列からなる配列に対して少なくとも８５％の配列同一性を有し、同一性の決定では、アミノ酸位置１２～１７および３１～３４が除外されること、を特徴とする二重特異的結合分子の提供。【選択図】なし
