The US Food and Drug Administration has dealt Merck & Co a blow in turning down its request to have cardiovascular outcomes data added to the labels of its diabetes drugs Januvia and Janumet.

Merck (which is known as MSD outside of the US and North America) is seeking to include data from TECOS (Trial Evaluating Cardiovascular Outcomes with Sitagliptin) in the prescribing information of sitagliptin-containing medicines.

In April 2015, Merck reported that Januvia, a DPP-4 inhibitor first approved in the US in 2006, met the main goal of the 14,724-patient TECOS trial of showing non-inferiority for the composite cardiovascular endpoint - the time to the first of any of the following confirmed events: CV-related death, non-fatal myocardial infarction, non-fatal stroke or unstable angina requiring hospitalisation.

The trial, which was directed by an independent academic research alliance between the University of Oxford Diabetes Trials Unit and the Duke University Clinical Research Institute, also showed there was no increase in hospitalisation for heart failure in the sitagliptin group versus placebo.

More detailed results unveiled later in the year revealed that the primary endpoint occurred in 11.4 percent of Januvia patients versus 11.6 percent in the placebo group, underpinning the firm’s attempt to expand the drug’s label.

However, the regulator has issued a complete response letter rejecting the application. Merck hasn’t revealed the nature of the rejection, but said it would review the letter and then discuss next steps with the FDA.

The addition of the cardiovascular outcomes data to the label would give Januvia a competitive edge within the DPP-4 field, which also includes AstraZeneca’s Onglyza (saxagliptin) and Takeda’s Nesina (alogliptin), as well as equal footing with those from other classes of diabetes drugs shown to reduce risk of cardiovascular related death, such as Boehringer Ingelheim’s SGLT2 inhibitor Jardiance (empagliflozin) and Novo Nordisk’s GLP-1 receptor agonist Victoza (liraglutide).