Sanofi criticizes study flagging Lantus cancer risk

Another study has drawn links between Sanofi's ($SNY) insulin drug Lantus and cancer. But the French drugmaker is pointing out potential flaws in that research, including the "small" number of patients whose records were examined. In fact, it's promising that its own Lantus research, due to be presented later this week, shows no increased risk of cancer.

The new study, conducted by Swedish researchers, looked at medical records of 23,000 patients, including 2,724 women who developed cancer and 20,542 who didn't. The analysis determined that having diabetes and being overweight increased cancer risk, Reuters says, but it also found that patients taking Lantus had twice as many cancers as those using the diabetes drug metformin.

Sanofi questions the utility of comparing patients on insulin for their diabetes with those using metformin, because insulin patients tend to be older and have a longer history of diabetes. Deutsche Bank's Mark Clark, who recommends Sanofi shares, questioned the Swedish study's results, saying that, as an "uncontrolled retrospective" analysis, it's "very unreliable."

The Swedish research follows a 2009 analysis that suggested Lantus might pose an increased risk of cancer. But as Bloomberg points out, two other studies found no links between the long-acting insulin and cancer risk. The FDA and its European counterpart reviewed the data, eventually deciding the cancer risk was inconclusive. Soon after, Sanofi announced it would conduct its own study of Lantus' potential links with cancer.

Sanofi's Riccardo Perfetti said the company's study of patients in Sweden, Norway, Finland, Denmark and Scotland has been wrapped up, and it will be submitted to regulators before year's end. A U.S. study will finish early next year, with European research following that. Altogether, those studies include 1 million patients and should help resolve outstanding questions about the drug's risks. The company's own records have found no cancer signals, Perfetti told Bloomberg.

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