Microantibody: Directed evolution ofMolecular-targeting Peptides in Phage-displayed Libraries

由于抗体药物的生物物理性质、免疫原性、非细胞渗透性、制造成本高等原因，抗体药物的使用受到限制。为了使抗体具有局限性的新应用成为可能，我们开发了一种具有非免疫球蛋白结构域的替代结合分子。该分子是螺旋-环-螺旋肽。在之前的工作中，我们构建了一个螺旋-环-螺旋肽的噬菌体展示文库，然后筛选G-CSF受体的文库，以获得分子靶向肽。在这里，我们研究了结合肽作为抗体药物替代品的能力。该肽与受体具有较强的结合亲和力（K_d: 4 nM），具有酶抗性（小鼠血清半衰期：15天），且无免疫原性。由于具有与抗体相同的性质，这种肽被命名为“微抗体”。此外，我们检查筛选抗VEGF的螺旋-环-螺旋肽库，以成功获得紧密结合肽。半理性策略结合了定向进化和新设计，提供了一种产生抗体后治疗的新方法。

Use of antibody medicines has been limited due to the biophysical properties, immunogenicity, non-cell permeability, high cost to manufacture, and so on. To enable new applications where antibodies showsome limitations, we have developed an alternative-binding molecule with non-immunoglobulin domain. The molecule is a helix- loop- helix peptide. In previous work, we constructed a phage-displayed library of the helix-loop-helix peptides and then screened the library for G-CSF receptor to obtain a molecular-targeting peptide. Here, we examined the ability of the binding peptide as an alternative to antibody medicines. The peptide showed strong binding affinity (K_d: 4 nM) to the receptor, an enzyme-resistant property(half-life: 15 days in mouse sera), and non-immunogenicity. This peptide is named “microAntibodes” due to having the same properties as those of antibodies. Furthermore, we examined to screen the library of helix-loop-helix peptides against VEGF to successfully gain a tight-binding peptide. The semi-rational strategy, which combines directed evolution with de novodesign, provides a new way to generate a post-antibody therapy.