Discovery of novel heterocyclic derivatives as potential glycogen phosphorylase inhibitors with a cardioprotective effect.

The purpose of this study was to evaluate the effect of GP inhibitor as a potential pharmaceutical target on MI/R injury. Four different structural types of novel compounds (I, II, III, and IV) were designed and synthesized, obtaining 31 novel GP inhibitors. SAR studies revealed that the conjugates of 5-chloroindole with benzo six-membered heterocyclic were found to elevate the activity. In particular, compound IIIh (IC = 0.21 ± 0.03 µM) emerged as a potent derivative against RMGPa, being approximately 2-fold less potent than that of PSN-357. In order to screen out a compound for in vivo activity test, we further conducted an experiment of inhibition against three different subtypes of GPa (HLGPa, HMGPa and HBGPa) and the corresponding affinity experiment. As a result, compound IIIh showed strong inhibitory activity against the above three subtypes of GP, especially on HBGPa (IC = 0.09 ± 0.002 µM), which was relatively close to that of positive control ingliforib (IC = 0.16 ± 0.02 µM). The affinity of compound IIIh to HBGPa was 4.3 times higher than that of HLGPa, and 1.1 times higher than that of HMGPa. This fact further proved that compound IIIh has a higher inhibitory effect on HMGPa than the other two subtypes. Besides, in vivo activity evaluation demonstrated that compound IIIh exhibited obviously cardioprotective effect on MI/R injury mice. The discovery of compound IIIh provides a new strategy for developing novel GP inhibitors with myocardial ischemia protection.