Sitagliptin on its own as Januvia/Xelevia/Tesavel can be used with metformin, and with both metformin and a sulphonylurea, in type 2 diabetes patients. The company presented the results of three studies of Januvia/Xelevia to support the use of Janumet in patients who were not satisfactorily controlled on their existing metformin treatment. Two of the studies looked at sitagliptin as an add-on to metformin: the first compared it with placebo (a dummy treatment) in 701 patients, and the second compared it with glipizide (a sulphonylurea) in 1,172 patients. The third study compared sitagliptin with placebo, when used as an add-on to glimepiride (another sulphonylurea), with or without metformin, in 441 patients.
The results of three further studies were used to support the use of Janumet. The first included 1,091 patients who were not satisfactorily controlled on diet and exercise alone and compared the effect of Janumet with that of metformin or sitagliptin alone. The second included 278 patients who were not satisfactorily controlled on the combination of metformin and rosiglitazone (a PPAR-gamma agonist) and compared the effects of adding sitagliptin or placebo. The third included 641 patients who were not satisfactorily controlled on a stable dose of insulin, three-quarters of whom were also taking metformin. This study also compared the effects of adding sitagliptin or placebo.
In all of the studies, the main measure of effectiveness was the change in the levels of a substance in the blood called glycosylated haemoglobin (HbA1c), which gives an indication of how well the blood glucose is controlled.
The company carried out additional studies to show that the active substances in Janumet are absorbed by the body in the same way as the two medicines given separately.