A study of 858 patients with type-2 diabetes found that adding the DPP-4 inhibitor saxagliptin to metformin achieved similar reductions in HbA1c levels to the treatment with the sulphonylurea glipizide and metformin.

However, fewer patients given saxagliptin experienced side effects such as weight gain during the one-year study period.

A separate study of 1,172 patients with type-2 diabetes compared the DPP-4 inhibitor sitagliptin with the sulphonylurea glipizide.

The researchers found that patients given sitagliptin were five times more likely to achieve a composite outcome encompassing HbA1c reduction of 0.5 percentage points, lack of hypoglycaemia and absence of weight gain.

Patients treated with sitagliptin experienced a weight reduction compared with those given glipizide.

The study presented last week was a post hoc analysis of data from a trial in patients with inadequate glycaemic control on metformin monotherapy.

Results of a study of the as-yet-unlicensed drug linagliptin, also a DPP-4 inhibitor, showed that it was also not associated with weight gain or an increased risk of hypoglycaemia.

The research also showed that linagliptin has a primarily non-renal route of excretion, which is a novel pharmaceutical feature for a DPP-4 inhibitor. The drug acted similarly in patients with mild and moderate renal impairment and patients with normal renal function.

DPP-4 inhibitors have been shown to increase levels of the incretin hormones glucagon-like peptide 1 and gastric inhibitory peptide, leading to improvements in a body's ability to lower blood glucose levels.

• American Diabetes Association meeting 2010