Selective Covalent Targeting of Pyruvate Kinase M2 Using Arsenous Warheads

There is growing interest in covalent targeted inhibitors
in drug
discovery against previously “undruggable” sites and
targets. These molecules typically feature an electrophilic warhead
that reacts with nucleophilic groups of protein residues, most notably
the thiol group of cysteines. One main challenge in the field is to
develop versatile utilizable warheads. Here, we characterize the unique
features of novel arsenous warheads for reaction with thiol species
in a reversible manner and further demonstrate that organoarsenic
probes can be chemically tuned toward specific molecular targets by
developing selective and potent inhibitors of pyruvate kinase M2 (PKM2).
We show that compound 24 is a covalent and allosteric
inhibitor of PKM2 and its orally bioavailable prodrug 25 exerts efficacious inhibition of PKM2-dependent tumor growth in vitro and in vivo. Our results introduce 25 and its derivatives as useful pharmacological tools and
provide a general road map for targeting the protein cysteinome using
arsenous warheads.

当前，针对既往被定义为“不可成药”（undruggable）的位点与靶点开发共价靶向抑制剂，已成为药物发现领域备受关注的研究方向。此类分子通常带有亲电弹头（electrophilic warhead），可与蛋白质残基的亲核基团发生反应，其中最具代表性的是半胱氨酸的巯基（thiol group）。该领域的核心挑战之一，在于开发具备通用实用性的弹头。本研究针对新型亚砷弹头（arsenous warheads）的独特性质展开系统表征，这类弹头可与巯基类物质发生可逆结合反应；同时进一步证实，有机砷探针可通过化学修饰实现对特定分子靶点的靶向调控——我们通过开发丙酮酸激酶M2（pyruvate kinase M2, PKM2）的选择性强效抑制剂验证了这一点。研究表明，化合物24是一种共价变构PKM2抑制剂，其口服生物可利用的前药25在体外与体内均能有效抑制PKM2依赖的肿瘤生长。本研究将化合物25及其衍生物作为极具应用价值的药理学工具推出，并为利用亚砷弹头靶向蛋白质半胱氨酸组（protein cysteinome）提供了通用的研究路线图。