After a potential carcinogen, Nitroso-STG-19 (NTTP), was found in samples of Merck’s sitagliptin-containing diabetes drugs, the New Jersey drugmaker says it has identified the root cause of the nitrosamine impurity and hopes to fix the issue this year.

In August, the FDA said it had become aware of higher than acceptable levels of NTTP in certain samples of sitagliptin, which is used to manufacture Merck’s type 2 diabetes mellitus drugs Januvia and Janumet. But the agency allowed the company to temporarily continue distributing sitagliptin with above-acceptable NTTP limits in order to avoid a shortage and ensure access to the medicine, noting it could be dangerous for diabetes patients to stop taking their medication abruptly.

“The company has already instituted additional quality controls and expects to be able to consistently reduce NTTP levels to meet the long-term acceptable daily intake level this year,” Merck said.