Garousi Javad, Ding Haozhong, von Witting Emma, Xu Tianqi, Vorobyeva Anzhelika, Oroujeni Maryam, Orlova Anna, Hober Sophia, Gräslund Torbjörn, Tolmachev Vladimir
Department of Protein Science, KTH-Royal Institute of Technology, SE-106 91 Stockholm, Sweden.
Department of Immunology, Genetics and Pathology, Uppsala University, SE-751 85 Uppsala, Sweden.
Pharmaceutics. 2021 Nov 3;13(11):1847. doi: 10.3390/pharmaceutics13111847.
Albumin binding domain derived affinity proteins (ADAPTs) are a class of small and folded engineered scaffold proteins that holds great promise for targeting cancer tumors. Here, we have extended the in vivo half-life of an ADAPT, targeting the human epidermal growth factor receptor 2 (HER2) by fusion with an albumin binding domain (ABD), and armed it with the highly cytotoxic payload mertansine (DM1) for an investigation of its properties in vitro and in vivo. The resulting drug conjugate, ADAPT6-ABD-mcDM1, retained binding to its intended targets, namely HER2 and serum albumins. Further, it was able to specifically bind to cells with high HER2 expression, get internalized, and showed potent toxicity, with IC values ranging from 5 to 80 nM. Conversely, no toxic effect was found for cells with low HER2 expression. In vivo, ADAPT6-ABD-mcDM1, radiolabeled with Tc, was characterized by low uptake in most normal organs, and the main excretion route was shown to be through the kidneys. The tumor uptake was 5.5% ID/g after 24 h, which was higher than the uptake in all normal organs at this time point except for the kidneys. The uptake in the tumors was blockable by pre-injection of an excess of the monoclonal antibody trastuzumab (having an overlapping epitope on the HER2 receptor). In conclusion, half-life extended drug conjugates based on the ADAPT platform of affinity proteins holds promise for further development towards targeted cancer therapy.
白蛋白结合域衍生的亲和蛋白（ADAPTs）是一类小型折叠工程支架蛋白，在靶向癌症肿瘤方面具有巨大潜力。在此，我们通过与白蛋白结合域（ABD）融合，延长了一种靶向人表皮生长因子受体2（HER2）的ADAPT的体内半衰期，并为其配备了高细胞毒性载荷美登素（DM1），以研究其体外和体内特性。所得药物偶联物ADAPT6-ABD-mcDM1保留了与预期靶点（即HER2和血清白蛋白）的结合能力。此外，它能够特异性结合高表达HER2的细胞，被内化，并显示出强大的毒性，IC值范围为5至80 nM。相反，对于低表达HER2的细胞未发现毒性作用。在体内，用Tc放射性标记的ADAPT6-ABD-mcDM1在大多数正常器官中的摄取量较低，主要排泄途径为通过肾脏。24小时后肿瘤摄取量为5.5% ID/g，高于此时除肾脏外所有正常器官的摄取量。肿瘤摄取可通过预先注射过量的单克隆抗体曲妥珠单抗（在HER2受体上具有重叠表位）来阻断。总之，基于亲和蛋白ADAPT平台的半衰期延长药物偶联物在靶向癌症治疗的进一步开发方面具有前景。
