Chemo-Selective Cys-Pen Disulfide for Proximity-Induced Cysteine Cross-Linking

A GSH-resistant FK228 analogue containing a stable disulfide bond

FK228 is a potent natural pan HDAC inhibitor approved by the FDA for the treatment of cutaneous T-cell lymphoma as well as peripheral T-cell lymphoma. It is generally believed that the mechanism of FK228 acting on HDACs is by reducing its disulfide bond after entering the cell, and the dithiol group may chelate with Zn2+ and form a weak reversible covalent bond with cysteine in the catalytic pocket of HDACs, therefore inhibiting the activity of HDACs. However, due to the weak stability of the disulfide bond in FK228, it has been difficult to obtain direct evidence for the above conjecture. Thus, improving the stability of the FK228 disulfide bond will help to explore the exact mechanism of FK228. In this study, based on the stability and target-induced covalent properties of the Cysteine-Penicillamine (Cys-Pen) disulfide bond reported previously, the Pen was introduced into the modification of FK228. Specifically, the d-Cys in FK228 was replaced by d-Pen, the total synthetic pathway was optimized, and the novel synthetic FK228 analogue (FK-P) stability was verified. FK-P can also be used as a new drug molecule in the future to participate in the research of related biological mechanisms or the treatment of diseases.

The expanding repertoire of covalent warheads for drug discovery

The reactive functionalities of drugs that engage in covalent interactions with the enzyme/receptor residue in either a reversible or an irreversible manner are called 'warheads'. Covalent warheads that were previously neglected because of safety concerns have recently gained center stage as a result of their various advantages over noncovalent drugs, including increased selectivity, increased residence time, and higher potency. With the approval of several covalent inhibitors over the past decade, research in this area has accelerated. Various strategies are being continuously developed to tune the characteristics of warheads to improve their potency and mitigate toxicity. Here, we review research progress in warhead discovery over the past 5 years to provide valuable insights for future drug discovery.