To obtain an optimized T-type calcium channel blocker with reduced off-target hERG toxicity, we modified the structure of the original compound by introducing a zwitterion and reducing the basicity of the nitrogen. Among the structurally modified compounds we designed, compounds 5 and 6, which incorporate amides in place of the original compound's amines, most appreciably alleviated hERG toxicity while maintaining T-type calcium channel blocking activity. Notably, the benzimidazole amide 5 selectively blocked T-type calcium channels without inhibiting hERG (hERG/T-type⩾220) and L-type channels (L-type/T-type=96), and exhibited an excellent pharmacokinetic profile in rats.
Keywords: L-type calcium channel; Pharmacokinetics; T-type calcium channel blocker; hERG.
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