EMD Serono Research Institute, Inc, One Technology Place, Rockland, MA 02370, USA.
Protein Eng Des Sel. 2011 May;24(5):447-54. doi: 10.1093/protein/gzq123.
The strand-exchange engineered domain (SEED) platform was designed to generate asymmetric and bispecific antibody-like molecules, a capability that expands therapeutic applications of natural antibodies. This new protein engineered platform is based on exchanging structurally related sequences of immunoglobulin within the conserved CH3 domains. Alternating sequences from human IgA and IgG in the SEED CH3 domains generate two asymmetric but complementary domains, designated AG and GA. The SEED design allows efficient generation of AG/GA heterodimers, while disfavoring homodimerization of AG and GA SEED CH3 domains. Using a clinically validated antibody (C225), we tested whether Fab derivatives constructed on the SEED platform retain desirable therapeutic antibody features such as in vitro and in vivo stability, favorable pharmacokinetics, ligand binding and effector functions including antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity. In addition, we tested SEED with combinations of binder domains (scFv, VHH, Fab). Mono- and bivalent Fab-SEED fusions retain full binding affinity, have excellent biochemical and biophysical stability, and retain desirable antibody-like characteristics conferred by Fc domains. Furthermore, SEED is compatible with different combinations of Fab, scFv and VHH domains. Our assessment shows that the new SEED platform expands therapeutic applications of natural antibodies by generating heterodimeric Fc-analog proteins.
链交换工程结构域（SEED）平台旨在生成不对称和双特异性抗体样分子，这一能力扩展了天然抗体的治疗应用。这个新的蛋白质工程平台是基于在保守的 CH3 结构域中交换免疫球蛋白的结构相关序列。在 SEED CH3 结构域中交替来自人 IgA 和 IgG 的序列会产生两个不对称但互补的结构域，分别命名为 AG 和 GA。SEED 设计允许高效生成 AG/GA 杂二聚体，同时不利于 AG 和 GA SEED CH3 结构域的同源二聚化。我们使用经过临床验证的抗体（C225）来测试基于 SEED 平台构建的 Fab 衍生物是否保留了理想的治疗性抗体特征，例如体外和体内稳定性、良好的药代动力学、配体结合和效应功能，包括抗体依赖性细胞介导的细胞毒性和补体依赖性细胞毒性。此外，我们还测试了 SEED 与结合结构域（scFv、VHH、Fab）的组合。单价和二价 Fab-SEED 融合体保留了完整的结合亲和力，具有出色的生化和物理稳定性，并保留了 Fc 结构域赋予的理想抗体样特征。此外，SEED 与不同的 Fab、scFv 和 VHH 结构域组合兼容。我们的评估表明，新的 SEED 平台通过生成异源二聚体 Fc 类似蛋白来扩展天然抗体的治疗应用。
