Takeda Pharmaceutical Co.'s diabetes drug Actos may raise bladder cancer risks in patients who take the medicine for more than a year, U.S. regulators said.

A five-year interim analysis of data from a decade-long company-sponsored study showed a greater likelihood of bladder cancer in patients who took the drug for the longest periods of time, and at the highest cumulative doses, the Food and Drug Administration said in a safety announcement Wednesday.

The medicine from Osaka-based Takeda, Asia's biggest drugmaker, wasn't linked to an overall increased cancer risk in all patients who took it.

Actos, the world's biggest-selling diabetes drug, had shown a potential risk of bladder cancer in earlier studies on rats and humans. Takeda won FDA approval of the treatment in 1999 and agreed to conduct the 10-year study to assess that risk. Actos became the market leader after a 2007 study showed a 43 percent higher chance of heart attacks from London-based GlaxoSmithKline PLC's Avandia.

Takeda said it is working with the FDA to make "appropriate updates" to the drug's prescribing information. The company is "confident in the therapeutic benefits of Actos and its importance as a treatment for Type 2 diabetes," Takeda said.

The FDA announcement updated preliminary findings released nine months ago. The agency had said Sept. 17 that while it hadn't found a statistically significant link between Actos and bladder cancer, the risk appeared to be higher in patients who took the drug for the longest duration, and at the highest cumulative doses.

The median duration of therapy was two years for patients treated with Actos, according to the FDA announcement. Treatment times ranged from 2.4 months to 8.5 years.