PROBLEM TO BE SOLVED: To provide: single-domain antibodies (sdAbs) for treating or preventing a disease that do not rely on exogenous targeting sequences or chemical compositions to enter a cell and that are effective in targeting only affected cells in a body; proteins comprising the same; nucleic acids encoding polypeptides; compositions comprising the sdAbs; and methods of use for prophylactic, therapeutic or diagnostic purposes.SOLUTION: The invention provides anti-KRAS (G12D) single-domain antibodies comprising specific amino acid sequences.SELECTED DRAWING: NoneCOPYRIGHT: (C)2020,JPO&INPIT【課題】細胞に進入するための外因性標的配列または化学組成物に依存せず、かつ体内の罹患した細胞のみを標的とするのに有効な疾患を治療または予防する単一ドメイン抗体(sdAb)、これを含むタンパク質、及びポリペプチドをコードする核酸、ならびにsdAbを含む組成物、及び予防、治療、または診断目的での使用方法の提供。【解決手段】特定のアミノ酸配列を含む、抗KRAS(G12D)単一ドメイン抗体。【選択図】なし