Vildagliptin, an investigational diabetes drug made by Novartis AG, significantly reduced blood sugar levels in patients with type 2 diabetes when given in combination with pioglitazone, researchers said on Tuesday.

Vildagliptin (Galvus), one of a new class of diabetes drugs called DPP-4 inhibitors, helps control of blood sugar primarily by improving pancreatic islet function. This results in the production of more beta cells, which in turn stimulate the production of more insulin, which lowers blood sugar.

The effects of the combination of 100 milligrams of vildagliptin and 30 mg of pioglitazone (Actos) were even more dramatic in a subgroup of patients who had the highest blood sugar levels, according to data presented at the American Diabetes Association scientific meeting in Washington.

The six-month, late-stage clinical trial involved 592 patients who had not been treated for type 2 diabetes, the most common form of the disease, which is prevalent in the obese population.

Patients who received the combination treatment had reductions in levels of hemoglobin A1C - a common measure of blood sugar - of 1.9 percent compared with a 1.4-percent reduction with pioglitazone treatment alone, a statistically significant difference.

In a subgroup of patients with A1C levels of 9 percent or greater before study entry, the combination produced a 2.8-percent reduction, researchers said. According to ADA guidelines, the desired level of A1C is 7 percent or less.

Sixty-five percent of patients treated with the two drugs reached optional blood sugar levels, compared with 42.5 percent with Galvus alone and 42.9 percent with pioglitazone alone.

In obese patients, vildagliptin plus pioglitazone reduced A1C levels by 2.2 percent from an average starting level of 8.6 percent, researchers said.

“We were pleased to see the especially steep reductions of glucose in the subanalysis of patients with the highest blood sugar levels,” Dr. Julio Rosenstock, one of the study’s lead investigators, said in a statement. “These patients usually require a multidrug strategy to reach glycemic goal,” he added.

Patients treated with the combination had no significant weight gain and less fluid retention than those taking pioglitazone alone, researchers said.

Weight gain is a problem with some older diabetes drugs, especially since obesity is the leading cause of type 2 diabetes, and many patients stop taking their medicine when they begin to gain weight.