Site-specific Bioorthogonal Chemistry on Phage for the Display of Secondary Amine Cyclised Peptides

针对疾病靶点的选择性配体的发现仍然是一个巨大的挑战。筛选活动的成功，例如在大环化合物筛选中，取决于建立大规模和结构多样化的化合物集合的能力。在目前的策略中，基于共价连接到有机核心的环肽的配体的基于噬菌体的选择显示出很大的希望。然而，使用有机核进行环化可以显著降低感染性，限制环的大小和多样性，并最终增加对最终分子的限制。在这里，我们将探索一种替代策略，不使用有机核心来形成环状结构。相反，我们将设计通过编码的赖氨酸和脱氢丙氨酸残基之间的稳定仲胺键环化的肽库，使用双烷基化/消除程序从半胱氨酸残基转化。然后将进行针对不同疾病靶标和选择的迭代亲和力选择以验证该方法。然后将制备从选择中获得的命中物，并在各种结合和物理化学测定以及基于相关细胞的效价测定中进行表征。我们相信，所提出的策略的进一步发展，从而规避了使用有机支架的肽环化的限制，将提供化学进入理论上巨大的分子空间，这在很大程度上是目前其他方法无法达到的，允许合成化学的精确性被带到扩大噬菌体上的化学多样性。

The discovery of selective ligands against disease targets remains a formidable challenge. The success of screening campaigns, for example in macrocycle screening, depends on the ability to build large and structurally diverse collections of compounds. Among current strategies, phage-based selection of ligands based on cyclic peptides attached covalently to an organic core shows great promise. However, the use of organic cores for cyclisation can reduce significantly the infectivity, limits loop size and diversity and finally adds constraint into the final molecule. Here we will explore an alternative strategy that does not use an organic core to form the cyclic structure. Instead, we will design peptide repertoires cyclised through a stable secondary amine bond between an encoded lysine and a dehydroalanine residue, converted from a cysteine residue using a bis-alkylation/elimination procedure. Iterative affinity selections against different disease targets and selections will be then performed to validate the approach. Hits obtained from the selection, will then be prepared and characterised in various binding and physicochemical assays as well as relevant cell based potency assays. We believe that further development of the proposed strategy, which thus circumvents the constraints of peptide cyclisation using an organic scaffold, will provide chemical access to a theoretically vast molecular space largely inaccessible by other current approaches, allowing the precision of synthetic chemistry to be brought to expand chemical diversity on phage.