Merck & Co was celebrating yesterday after the US Food and Drug Administration approved Januvia, its new drug for diabetes that is considered one of the brightest prospects in the company’s pipeline.

Januvia (sitagliptin phosphate), the first dipeptidyl peptidase-4 inhibitor to be registered in the USA, should now get a few weeks in which to build a position in the market while the FDA considers an application for rival drug Galvus (vildagliptin) from Novartis.

Analysts at Morgan Stanley recently suggested that the market for DPP-4 inhibitors could be in the region of $3 billion in the USA alone, assuming they win a half share of the market for an older class of diabetes medication, the sulfonylureas.

The key point of difference for the DPP-4 inhibitors is that they seem less likely to cause weight gain, which can compound diabetics’ already elevated risk of developing heart disease, than other medicines for the disease.

Januvia has been approved as monotherapy and as add-on therapy to either of two other types of oral diabetes medications, metformin or thiazolidinediones such as GlaxoSmithKline’s Avandia (rosiglitazone) and Takeda/Lilly’s Actos (pioglitazone). It is used to improve blood glucose control in patients with type 2 diabetes when diet and exercise is not enough. The recommended dose of Merck’s drug is 100mg once daily.

Januvia is already approved in Mexico and has been filed in the European Union, with a global roll-out expected to take place in the coming months.

Meanwhile, GlaxoSmithKline and Bristol-Myers Squibb also have compounds in this class in Phase III clinical development, called Redona (denagliptin) and saxagliptin respectively.

According to Merck, almost 21 million people in the USA, or 7% its population, have diabetes, with type 2 accounting for 90%-95% of the cases.

Worryingly, less than 50% of adult diabetics achieve the American Diabetes Association target level of glucose control, so the need for new effective treatments is urgent. Estimates already put the number of diabetics worldwide at 194 million, and this figure could cap 333 million by 2025.

"For the millions of Americans with type 2 diabetes, who continue to have inadequate blood sugar control, the approval of Januvia marks an important advance in the fight against diabetes," said Dr Steven Galson, Director of the FDA's Center for Drug Evaluation and Research.

"We now have another new option that treats the disease in an entirely new way that can be added to existing treatment regimens to help patients gain more control over their blood sugar levels."