Takeda Pharmaceutical Co., Asia’s biggest drugmaker, may face as many as 10,000 lawsuits in U.S. courts over allegations that its Actos diabetes drug causes bladder cancer, and a group of judges is preparing to decide where those suits should be consolidated.

The drug was marketed for Takeda in the United States by Indianapolis-based Eli Lilly and Co. from July 1999 to March 2006 and in several other countries until this year.

U.S. regulators found in June that an analysis of a company-sponsored study showed some users of Actos, the world’s best-selling diabetes medication, faced an increased risk of developing the potentially fatal disease.

The evidence linking Actos to bladder cancer “is unusually strong and clear,” Paul J. Pennock, a New York-based lawyer representing former users of the drug, said in a telephone interview. He said his firm, Weitz & Luxemberg, represents 1,200 former Actos users and that total cases may reach 10,000.

“We are getting calls every day about Actos,” he said.

Pennock was set to appear Thursday before a judicial panel in Savannah, Ga., to argue that federal court suits over the drug, whose chemical name is pioglitazone, should be gathered for pretrial proceedings in Louisiana or Ohio.

Takeda officials this year pulled Actos, its top-selling drug, off the market in Germany and France after it was linked to an increased cancer risk. The medication had sales of $4.8 billion in the last fiscal year, 27 percent of the Osaka, Japan-based company’s revenue.

The drugmaker declined to comment on the impact of the lawsuits to its earnings or whether it plans to set aside money for the litigation.

“Takeda already revised the information on risks regarding bladder cancer on leaflets in the U.S. and Japan and is in the process of updating in Europe,” Mitsuo Oguri, a Takeda spokesman in Tokyo, said. “Takeda remains confident on the efficacy of pioglitazone for treating type 2 diabetes, while it continues to monitor the safety profile of the medicine.”

The company’s lawyers said in a September court filing that so far it had been sued 54 times over Actos in federal courts around the U.S.

Terrence Allen, a warehouse worker, filed one of them, against Takeda and Lilly. He took the drug over a five- year-period starting in 2006 and was diagnosed with bladder cancer in January.

Stefanie Prodouz, a spokeswoman for Lilly, didn’t return calls for comment on the Actos suits naming the drugmaker as a defendant.

Allen, of Attica, N.Y., said he’s had two surgeries to remove cancerous tissue from his bladder and may be facing another after the Christmas holiday.

“If somebody had told me I could get cancer from Actos, I never would have taken it,” he said. “There were other products out there that could have helped treat my diabetes without putting me through all of this.”

Allen, 57, said he sued the drugmaker to help alert other diabetics that Actos poses serious health risks. He’s also hoping the litigation will force Takeda to take responsibility for his injuries, he said.

“To some degree, I would like my pound of flesh from the company,” he said.

Plaintiffs’ lawyers say they expect thousands more former Actos users to join Allen in suing Takeda over the drug given its rise in popularity after GlaxoSmithKline Plc’s Avandia diabetes drug was found to pose an increased heart-attack risk.

Glaxo officials pulled the drug from European markets and curtailed sales in the U.S. in 2007 after studies found Avandia posed greater risk of heart attacks and strokes than Actos.

The London-based drugmaker has paid more than $6 billion for legal costs tied to Avandia and other medicines. In the wake of Avandia’s problems, Actos’s sales rose from about $3 billion in 2006 to almost $5 billion last year.

Will Kemp, a Las Vegas-based attorney representing former Actos users, said the suits will differ from Avandia cases because the alleged injuries are more distinctive.

“Bladder cancer is considered to be a signature injury because there aren’t a lot of other things that cause that particular illness,” he said. “With a heart attack or stroke, you’d have a slew of other potential causes to deal with.”

Turner Branch, a New Mexico-based plaintiffs’ lawyer, said Takeda also will face claims that Actos caused heart attacks and strokes like Avandia. “I think this is going to be very large litigation with a large number of cases,” he added.

Before corralling the litigation in one court, judges on the so-called Multi-District Litigation panel will hear arguments Thursday on which federal court should be selected.

Similar cases in courts across the U.S. can be consolidated before one judge for pretrial exchange of information. The consolidation is intended to save money by streamlining document exchanges and avoiding duplication.

Lawyers for Takeda and some of the plaintiffs are arguing in court papers that the Actos suits should be consolidated in federal court before U.S. District Judge James Zagel in Chicago or before U.S. District Judge Rebecca Doherty in Lafayette, La.

Other plaintiffs’ attorneys are suggesting the cases be collected before U.S. District Judge Daniel Polster in Cleveland, according to court filings. Another group of lawyers seek to have the suits consolidated in federal court in Birmingham, Ala.