US FDA says possible carcinogen found in some Merck diabetes drugs

WASHINGTON – The US Food and Drug Administration said on Tuesday (Aug 9) certain samples of sitagliptin, a compound in Merck’s diabetes drugs Januvia and Janumet, were contaminated with a possible carcinogen.

The agency said it would temporarily allow Merck to distribute drugs with sitagliptin containing a higher than normally acceptable amount of the impurity Nitroso-STG-19, also known as NTTP, in to avoid a shortage.

Merck said it notified authorities it had detected that some batches of the drugs contained the impurities and implemented additional quality to make sure its drugs will meet the interim acceptable limits.

“We remain confident in the safety, efficacy and quality of our sitagliptin-containing medicines,” Merck said, noting that no significant impact on supply is expected.

Shares of Merck, which was not immediately available for comment.

Sales of Januvia and a related combination medicine called Janumet totalled US$1.23 billion (S$1.7 billion) in the second quarter.

NTTP belongs to the nitrosamine class of compounds, some of which are classified as probable or possible human carcinogens, based on laboratory tests, the agency said. Agency scientists evaluated the risk of exposure to NTTP at interim acceptable intake levels up to 246.7 nanogram per day and determined that it presents minimal additional cancer risk when compared to a lifetime of exposure to NTTP at the 37 nanogram per day level.

In recent years, some drugmakers have had to recall some batches of drugs like Pfizer’s anti-smoking treatment, Chantix, and stopped selling others like the heartburn treatment ranitidine, often sold under the brand name Zantac, due to the presence of nitrosamines.

Nitrosamines are common in water and foods, including cured and grilled meats, dairy products and vegetables. Exposure to the impurities above acceptable levels over long periods of time could increase the risk of cancer.

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