The Food and Drug Administration is studying unconfirmed reports that a widely used class of diabetes drugs, which includes Merck & Co's Januvia, may cause inflammation of the pancreas and pre-cancerous changes to the pancreas.
The agency, in a notice on its website on Thursday, said this is the first time it has communicated potential pre-cancerous links to the medicines, known as incretin mimetics.
The drugs for type 2 diabetes also include Victoza from Danish drugmaker Novo Nordisk and Onglyza from Bristol-Myers Squibb Co and AstraZeneca Plc.
Patients should continue taking their medicines as directed until speaking with healthcare professionals, the agency said. The FDA said it is investigating findings from academic researchers that highlighted the potential risk.
"These findings were based on examination of a small number of pancreatic tissue specimens taken from patients after they died from unspecified causes," the agency said.
The FDA has asked the researchers to explain how they collected and studied the specimens and to provide tissue samples so the agency can further assess any possible risks.
In the meantime, the FDA said it has not reached any new conclusions about safety risks of the class of drugs.
The agency noted it has previously warned the public about acute pancreatitis, including fatal and nonfatal cases, seen with the medicines. Package insert labels for the class of drugs already warn about risk of the potentially dangerous inflammation.
"It's too early to tell, but we'll keep an eye on it," Edward Jones analyst Judson Clark said, when asked about the significance of the potential safety issues in Thursday's FDA advisory.
But Clark said he did not expect any immediate changes in prescribing habits for the drugs because the pancreatitis risk is already noted on the drug labels.
The class of medicines, which mimic a natural hormone called incretin, prompt the pancreas to release insulin when blood sugar is rising. They are approved to treat type 2 diabetes, the most common form of diabetes which usually develops in adulthood and is closely linked to obesity.
Merck's Januvia and its related drug, Janumet, had combined sales last year of almost $6 billion, making them by far the company's biggest product franchise. Onglyza and a related drug called Kombiglyze had sales last year of $709 million.
Shares of Merck were down 1.1 percent at $44.08, while Bristol-Myers shares were down 0.8 percent at $38.18 on Thursday afternoon on the New York Stock Exchange. Shares of AstraZeneca were up 1 percent at $46.31, also on the NYSE. Novo Nordisk shares closed down 1 percent in Copenhagen.