New Potent α-Glucohydrolase Inhibitor MDL 73945 With Long Duration of Action in Rats

Inhibition of intestinal α-glucohydrolase activity is one approach for reducing the glycemic response from dietary carbohydrate and may prove useful for the treatment of diabetes mellitus. In this article, we describe the pharmacological properties of a time-dependent intestinal α-glucohydrolase inhibitor, MDL 73945. When preincubated 2 h with a rat intestinal mucosa preparation before substrate addition, MDL 73945 was a potent inhibitor of sucrase, maltase, glucoamylase, and isomaltase activities (MDL 73945 concentrations required to cause a 50% decrease in enzyme activity, 2 × 10⁻⁷, 1 × 10⁻⁶, 5 × 10⁻⁶, and 8 × 10⁻⁶ M, respectively); without preincubation, it was 10- to 500-fold less potent. In rats, a single oral dose of MDL 73945 administered simultaneously with 2 g/kg body wt sucrose resulted in a dose-dependent reduction in the area under the 0- to 3-h glycemic response curve, which was significant at 1 (45% reduction) and 3 (65% reduction) mg/kg. When administered 1 h before sucrose, the compound was more potent, with 0.3 mg/kg MDL 73945 significantly reducing the glycemic response to sucrose by 62%. A reduction in the glycemic response to sucrose was accompanied by reduced insulin secretion. MDL 73945 was slightly less effective against a starch load, with 3 and 10 mg/kg MDL 73945 administered 0.5 h before starch reducing the glycemic response by 39 and 52%, respectively. MDL 73945 was more effective against a sucrose load in streptozocin-administered rats than in control rats and was as effective after 16 daily doses as after a single dose. Doses that reduced the glycemic response to carbohydrate did not inhibit liver lysosomal α-glucosidase activity or cause lysosomal glycogen accumulation. In cynomolgus monkeys, an oral dose of 1 mg/kg MDL 73945 reduced the glycemic and insulin responses to sucrose. Based on these findings, MDL 73945 may be useful for reducing postprandial hyperglycemia in subjects with diabetes mellitus.