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

发现针对疾病靶标的选择性配体仍然是一项艰巨的挑战。筛选运动的成功，例如在大周期筛选中，取决于建立大量和结构多样化的化合物集合的能力。在目前的策略中，基于噬菌体的基于共价连接到有机核心上的环肽的配体选择显示出巨大的前景。然而，使用有机核心进行环化可以显著降低感染性，限制环的大小和多样性，最终增加对最终分子的限制。在这里，我们将探索一种不使用有机核心来形成环状结构的替代策略。相反，我们将设计通过编码赖氨酸和脱氢丙氨酸残基之间的稳定仲胺键循环的多肽谱系，脱氢丙氨酸残基通过双烷基化/消除过程从半胱氨酸残基转化而来。然后，将针对不同的疾病目标和选择进行迭代亲和力选择，以验证该方法。然后将制备从选择中获得的HIT，并在各种结合和物理化学分析以及相关的基于细胞的效力分析中对其进行表征。我们相信，拟议策略的进一步发展，从而绕过了使用有机支架进行多肽环化的限制，将提供进入理论上巨大的分子空间的化学途径，这在很大程度上是其他当前方法无法达到的，从而使合成化学的精确度能够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.