French drug maker Sanofi-Aventis confirmed on Friday it was in talks with the U.S. Food and Drug Administration about its antibiotic Ketek following a report the U.S. regulator wanted a warning label on the drug.

The Wall Street Journal, citing an internal FDA memo, reported Ketek had been linked to 12 cases of liver failure, including four deaths, and the FDA was recommending the company put a warning label on the drug.

“Sanofi continues to believe that Ketek is safe and effective,” said a company spokesman in Paris.

“We are in talks with the FDA to evaluate secondary effects on the liver and as we are in discussions we are not going to start commenting on these figures,” the spokesman added, when asked about the alleged cases.

He said all secondary effects were reported to the FDA and talks on labeling had been going on for several months. He said the company did not have a copy of the memo cited by the newspaper.

The Wall Street Journal said U.S. lawmakers have questioned the FDA’s 2004 approval of the drug amid charges of faulty data from one of the trials.

Ketek, which was approved to treat respiratory infections, drew renewed scrutiny in January when researchers reported that three patients using the drug developed severe liver damage and one died.

The FDA rejected the drug in 2001 and 2003, asking for more safety information.

Sanofi shares eased in early trade on Friday, losing 1.22 percent to 72.80 euros by 0922 GMT.