Several drugmakers say their new class of diabetes fighters called DPP-4 inhibitors improve blood-sugar control when added to a popular standard treatment.

A standard, first-line treatment is the generic pill metformin, and studies by

Merck

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and by the team of

Bristol-Myers Squibb

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and

AstraZeneca

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say their DPP-4 inhibitors plus metformin do a better job of blood-sugar control than metformin alone.

The research was presented in Chicago during the annual scientific convention of the American Diabetes Association.

Merck's research should help its marketing efforts because it has the only commercial DPP-4 inhibitors. Once-a-day Januvia has been available since October. In April, the Food and Drug Administration approved Janumet, a combination of Januvia and metformin, which is taken twice a day. The research on Januvia and metformin tested quantities of the drugs that are in the same proportion as found in Janumet.

For Bristol-Myers Squibb and AstraZeneca, the stakes are even higher because their drug, saxagliptin, is still in late-stage clinical testing. They need as much favorable research data as possible not only to convince the FDA to approve their drug but also to get doctors to try their once-a-day product instead of the Merck drugs or other types of diabetes medications.

The Merck and Bristol-AstraZeneca drugs are designed to control blood-sugar in two ways -- telling the liver to produce less glucose and signaling the pancreas to make more glucose-burning insulin. The drugs are aimed at Type 2 diabetics. With Type 2 diabetes, people don't produce enough insulin or their bodies don't adequately process insulin.

Test of 'Patients'

Bristol and AstraZeneca say a test of 743 patients over 24 weeks showed a combination of their drug plus metformin produced a statistically significant improvement in blood-sugar control compared with metformin by itself. The study examined the drop in HbA1c, a measurement of how much sugar is in the blood during a period of two to three months.

Their presentation late Monday afternoon was the first report in a scientific setting on late-stage clinical trial data for saxagliptin. The companies said saxagliptin plus metformin also produced statistically significant improvements vs. metformin in another key indicator, fasting plasma glucose, or the amount of blood-sugar in someone who hasn't eaten for eight to 12 hours.

Merck's research on Januvia plus metformin, presented at the ADA Saturday, found that the drug combination produced a statistically significant improvement in blood-sugar, as measured by HbA1c, than metformin alone as an initial treatment for diabetes. The study looked at 762 patients over 54 weeks.

"Initial therapy with one agent is often unsuccessful at getting patients to blood-sugar goals," Dr. John Amatruda, Merck's vice president for clinical research, said. "Many patients may require initial combination therapy."

At the moment, Januvia is approved by the FDA as a single therapy for Type 2 diabetes. The FDA also says Januvia plus metformin may be used when a single drug doesn't control blood-sugar. The FDA says Janumet is approved for patients for whom Januvia or metformin doesn't control blood-sugar or for patients already being treated by both drugs.

Merck submitted clinical trial data to the FDA in February seeking approval for Januvia plus metformin as an initial therapy for Type 2 diabetics. The company expects to hear from the FDA in October.