BackgroundDLBS3233, a combined bioactive fraction of Cinnamomum burmanii and Lagerstroemia speciosa, has preclinically demonstrated its beneficial effects on glucose and lipid metabolism through the upregulation of insulin-signal transduction. This study evaluated the clinical efficacy of an add-on therapy with DLBS3233 in type-2 diabetes mellitus subjects inadequately controlled by metformin and other oral antidiabetes. MethodsThis was an open and prospective clinical study for 12 weeks of therapy, involving type-2 diabetes mellitus patients who had been treated with two oral antidiabetic agents for at least 3 months prior to screening, yet, with HbA1c level was still beyond 7.0 %. DLBS3233 was given orally at the dose of 100 mg once daily in addition to their baseline oral antidiabetes medication. The primary end point was the reduction of HbA1c level; and the secondary end points were changes of fasting and 1-h postprandial glucose, homeostatic model assessment-insulin resistance, adiponectin, and lipid profile, from their respective baseline. Results After 12 weeks of treatment, the HbA1c level was reduced by 0.65±1.58 % (p=0.001) from baseline (9.67±2.11 %); while the 1-h-PG level was reduced by -1.45±3.89 mmol/L (p=0.021) from baseline (15.29±4.49 mmol/L). Insulin sensitivity, lipid profile and adiponectin level were improved to a considerable extent. DLBS3233 did not adversely affect body weight, liver, and renal function. Most adverse events observed were tolerably mild and they all had been resolved by the end of the study. ConclusionsThe add-on oral antidiabetes therapy with DLBS3233 at the dose of 100 mg once daily helped type-2 diabetes mellitus patients to improve their glycemic control, enhance insulin sensitivity, lipid profile, and adiponectin level. In addition, DLBS3233 treatment concomitantly with other oral antidiabetic agents was proven safe and tolerable in type-2 diabetes subjects.