A functional and mechanistic explanation for the unique clinical success of the glucokinase activator dorzagliatin for treatment of type 2 diabetes

Abstract

Glucokinase activators (GKA) are a long-sought therapeutic modality for the treatment of Type 2 Diabetes (T2D). However, all GKAs failed clinical trials, with the recent exception of dorzagliatin (Hua Medicine). A comprehensive approach using human islet perfusions, enzyme kinetics, x-ray crystallography, and modeling studies was applied to compare the effects of dorzagliatin with the failed GKA MK-0941 (Merck Pharmaceuticals), which is well-characterized both clinically and mechanistically. Dorzagliatin improves glucose stimulation of insulin secretion (GSIS) in a dose- and glucose-dependent manner, in contrast to MK-0941 which induces maximal insulin secretion at low doses and glucose concentrations. To understand these functional differences, the atomic resolution structure of the dorzagliatin-glucokinase (GK) complex was determined and compared with the GK/MK-0941 structure. MK-0941 binds to a pocket accessible in both open and closed conformations, has a strong interaction with Y214, mutation of which produces the most clinically severe activating mutation, and produces a high energy barrier for the open-to-close transition. In contrast, dorzagliatin only binds favorably to the closed form of glucokinase, interacting primarily with R63, and causing a low energy barrier for the open-to-close transition. This provides the molecular rationale for the clinical success of dorzagliatin which can guide the future development of next-generation allosteric activators of GK.