According to the European Association for the Study of Diabetes, Sanofi-Aventis SA's Lantus diabetes drug was linked to an increased risk of cancer in studies in Germany and Sweden.

As a result an "urgent" call for further research into the connection was issued. The diabetes research group said it had given its findings to the European Medicines Agency, the European Union's drug regulator, and to Sanofi.

However on Friday, Sanofi-Aventis said new data on the safety of Lantus had not reached any definitive conclusions about whether the drug was linked to an increased cancer risk.

The French drug maker added that they had been made aware of the study results associated with a follow up of four patients but added just as the study authors had said, no definitive conclusions could be drawn on possible link to the occurrence of the malignancies. That clinical studies, which represent the gold standard of evidence, did not indicate an association between Lantus and cancer, it added.

Sanofi said it would work in close collaboration with regulatory agencies and scientific experts to continue to vigorously monitor the safety of Lantus. In a statement Jean- Pierre Lehner, the company's chief medical officer said, "We consider that the results of these patient registries are not conclusive."

"Given the extensive clinical evidence covering over 70,000 patients and the results of post-marketing surveillance arising from 24 million patient-years of experience, Sanofi-Aventis stands behind the safety of Lantus," Lehner added.

According to the statement a German study of about 127,000 insulin-treated patients in an insurance database showed a "statistically significant link between patients who had used Lantus insulin and those who had been diagnosed with cancer." The group added that the study didn't take into consideration Levemir, insulin produced by Novo Nordisk.

The group said research was subsequently conducted using patient databases in Sweden, Scotland and the U. K. The Swedish study found that patients on Lantus alone had twice the risk of breast cancer than patients on insulin's other than Lantus, the Scottish study showed a non- significant increased risk of breast cancer, while the U. K. study found no link between Lantus and cancer.

The studies are published in the group's journal, Diabetologia.

Lantus, a long-acting, injectable form of insulin that is used to control the blood sugar level in diabetics, who have difficulty producing insulin naturally, was approved for sale in the U. S. in 2000. It was the first once-a-day form of insulin, wherein there is a steady release of insulin into the blood over 24 hours.

Sanofi, who is banking on Lantus saw its stock fall 12 % over the last two days which reduced its market value by 7.7 billion Euros ($10.8 billion).

In the statement Edwin Gale, a professor of diabetic medicine at the University of Bristol and editor of Diabetologia, and Ulf Smith, president of the diabetes group, said that the studies had limitations, so further research is needed. "We believe people are entitled to know that use of Lantus insulin might be associated with greater risk, but this must also be balanced against the possibility that we might be causing unnecessary alarm by raising these concerns," they said.

In a statement the researchers said, "A large combined analysis of the best available databases worldwide is the best way forward, and EASD and Sanofi-Aventis are pledged to carry this investigation forward until we have either confirmed these preliminary observations or, more hopefully, finally put them to rest."