Merck & Co is celebrating more good news for its diabetes franchise following approval from US regulators for Janumet, a combination of its dipeptidyl peptidase-4 inhibitor Januvia with metformin.

The US Food and Drug Administration has backed Janumet just months after Januvia (sitagliptin) was given the green light as a 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). Janumet combines sitagliptin with metformin in one pill and is the first to be approved to treat type-2 diabetes by targeting all causes of the disease.

The drug will help Merck compete for a bigger share of the $17 billion market for diabetes treatments, with Januvia and Janumet expected to have more than $2 billion in combined annual sales by 2010. Deutsche Bank analyst Barbara Ryan told Bloomberg that the approval is important "mostly as a convenience and from a co-pay perspective,'' adding that "the data would suggest that Januvia is being used above and beyond anything else on the market as an add-on therapy, and it is being added on to metformin.''

Januvia has made a massive impact on the diabetes market since it was launched in October last year and has forged ahead of Novartis' potential competitor Galvus (vildagliptin) which is having major problems getting past the FDA