A recombinant protein drug includes a parent protein drug coupled with a modified kininogen-1 peptide. The modified kininogen-1 peptide has the sequence of SEQ ID NO:2 or a homolog having a sequence identity of 80% or higher. The parent protein drug is a bispecific antibody having a first targeting domain linked by a bridging domain with a second targeting domain. The modified kininogen-1 peptide is fused between the first targeting domain and the bridging domain, or between the bridging domain and the second targeting domain. A method for increasing the serum half-life of a protein drug includes constructing a fusion protein comprising the protein drug coupled with a modified kininogen-1 peptide.本發明公開一種重組蛋白質藥物，包括親代蛋白質藥物連結經修飾的激肽原-1(kininogen-1)胜肽。該經修飾的激肽原-1胜肽具有SEQ ID NO：2的序列或與其有80%以上序列相似度的同源物。該親代蛋白質藥物是雙特異性抗體，其透過橋接域連接第一靶向域及第二靶向域。該經修飾的激肽原-1胜肽可融合至第一靶向域及橋接域之間、或橋接域及第二靶向域之間。本發明另公開一種用於增加蛋白質藥物的血清半衰期的方法，包括建構融合蛋白，當中該蛋白質藥物連結經修飾的激肽原-1胜肽。本發明的重組蛋白質藥物通過包含經修飾的激肽原-1胜肽，藉以延長蛋白質藥物的體內半衰期。
