Merck & Co said the U.S. Food and Drug Administration declined an application to include information on the labels of its diabetes drugs - Januvia and Janumet - that the treatments do not raise the risk of major heart problems.
Merck is reviewing the agency's response to its application, the company said on Friday.
The application was submitted on the basis of a keenly watched study in 14,724 patients with type 2 diabetes and a history of heart disease. (reut.rs/2nkYtt2)
The study's results, announced in 2015, showed that adding Januvia to usual care did not increase major heart problems any more than the addition of a placebo did.
The results also showed no increase in hospitalization rates for heart failure, which had been a particular concern with DPP-4 inhibitors, the class of drugs to which Januvia belongs.
Januvia is an oral medication, known chemically as sitagliptin, that helps lower blood sugar levels. Janumet is a related combination product.
The two treatments generated sales of more than $6 billion last year.
Merck's shares were down 1.1 percent at $62.50 before the bell on Friday.
(Reporting by Natalie Grover in Bengaluru; Editing by Sai Sachin Ravikumar)