MK-0941 is selective, allosteric glucokinase activator (GKA) that activates glucokinase (hexokinase subtype IV) with greater selectivity than over different hexokinase isoforms. In chronic oral toxicity studies in animals with MK-0941, cataracts were observed in rats and dogs at drug exposures of 3 and 1.5 times, respectively, the maximum predicted human exposure based on doses planned for further clinical development. No cataracts were observed in either species at drug exposures equal to the maximum predicted human exposure. In patients receiving stable-dose insulin glargine, the glucokinase activator MK-0941 led to improvements in glycemic control that were not sustained. MK-0941 was associated with an increased incidence of hypoglycemia and elevations in triglycerides and blood pressure.