Drug regulators in Germany and France have ordered doctors to stop prescribing the type 2 diabetes drug pioglitazone (Actos) following a French study suggesting a heightened risk of bladder cancer.
But the European Medicines Agency (EMA), the FDA, and their Japanese counterpart have withheld action pending additional review of the data.
The French study, conducted by the nation's health insurance agency, examined cancer rates in some 155,000 people taking pioglitazone in France from 2006 to 2009 and 1.3 million other diabetics who were not receiving the agent.
The researchers found an adjusted hazard ratio of 1.22 (95% CI 1.05 to 1.43) for bladder cancer among those on pioglitazone.
There also appeared to be a dose effect, with a higher risk (HR 1.75, 95% CI 1.22 to 2.50) among patients receiving a cumulative dosage of 28,000 mg or more during the study period.
The study was completed on Tuesday. France's regulatory agency officially suspended sales of pioglitazone on Thursday, and Germany followed suit early Friday.
Both agencies recommended that patients currently taking the drug continue to do so until they talk to their doctors about alternative medications.
In addition to Actos, a product called Competact that combines pioglitazone with metformin was included in the suspensions.
The EMA released a statement noting that it started its own review of pioglitazone in March but was not ready to pull the drug yet.
The agency's Committee for Medicinal Products for Human Use "is currently reviewing all relevant data, including data from pharmacoepidemiological studies, non-clinical and clinical data, post-marketing reports of bladder cancer, and published data to assess their impact on the balance of benefits and risks of these medicines.
The Committee will now also assess the results of the French study and its potential impact on the use of these medicines across the whole EU," the statement indicated.
The EMA committee will meet later this month to discuss the data and make recommendations for possible EMA actions.
The drug's manufacturer, Takeda, said it has received no indication that U.S. or Japanese regulators are planning immediate actions. The FDA began a review of pioglitazone and cancer risk last September.
A U.S. study published earlier this year using data from the Kaiser Permanente health plan and involving some 30,000 pioglitazone users and 160,000 other diabetics indicated that the risk of bladder cancer was not significantly higher.
But when the analysis was restricted to patients taking the drug for at least two years, there was a significantly increased risk (HR 1.4, 95% CI 1.03 to 2.0), according to a report in .