LOS ANGELES (Reuters) - The Food and Drug Administration said on Friday it was reviewing if Takeda Pharmaceutical Co Ltd's blockbuster diabetes drug Actos may be linked to bladder cancer.
Actos is the Japanese drugmaker's top-selling product with sales of about $4 billion a year, but the pill is due to face generic competition after it loses U.S. patent protection in January 2011.
The FDA said early data from an ongoing Takeda study showed no overall association with Actos and bladder cancer. But an increased risk of bladder cancer was seen among patients with the longest Actos exposure and the highest cumulative doses.
The preliminary results are based on 5-year data from an ongoing 10-year trial by Takeda.
"At this time, FDA has not concluded that Actos increases the risk of bladder cancer," the agency said in a statement.
Patients should not stop taking Actos unless told to do so by their doctor, the agency said.
Takeda said the results were early, and the company was committed to completing the 10-year study to get a better picture of bladder cancer rates.
"Looking at the completion of the study will give us the most accurate look at that," Dr. Robert Spanheimer, Takeda medical director for Actos, said in an interview.
Actos is in the same class of drugs as GlaxoSmithKline PLC's Avandia, which has not been associated with bladder cancer but has been linked to heart risks in some studies. Glaxo has said overall scientific evidence does not show that the drug increases heart attack risk.
The FDA is weighing whether Avandia should stay on the market with new restrictions or be removed. In July, an advisory panel voted 20-12 in favor of keeping the drug on the market, although many urged tight restrictions.
Avandia's opponents have argued that the drug is too dangerous to be sold and they have pointed to Actos as a safer alternative. Actos sales have grown while use of Avandia, or rosiglitazone, fell amid a debate about risks.
Concerns about bladder cancer arose with Actos, or pioglitazone, from cases seen in male rats. The drug's prescribing instructions mention those findings.
A guide for patients also notes that bladder cancer occurred in "a few more people who were taking pioglitazone than in people who were taking other diabetes medicines," but adds, "There were too few cases to know if the bladder cancer was related to pioglitazone."
Bladder cancer occurs in an estimated 20 per 100,000 people per year in the United States and is thought to be higher in diabetics, the FDA said.
(Reporting by Deena Beasley and Lisa Richwine)
