* Study suggests possible cancer link with high-dose Lantus
* New research echoes worries last year over Lantus safety
* Sanofi says available data to date largely inconclusive
* Shares down 4 percent
(Adds further analyst reaction, more details on study)
By Noelle Mennella and Ben Hirschler
PARIS/LONDON, June 18 (Reuters) - Shares in French drugmaker Sanofi-Aventis SASY.PA fell 4 percent on Friday after a small Italian study rekindled fears about a possible link between its Lantus diabetes drug and cancer.
Writing in the journal Diabetes Care, Florence-based researchers said they had found the possibility of an association between cancer and higher doses of Lantus, or glargine, in their observational study.
The findings were made available online at link.reuters.com/vaq72m.
Sanofi played down the importance of the study, saying: “The risk of cancer among diabetics has fuelled intense scientific debates for several decades, but the available data on this subject remain largely inconclusive”.
Industry analyst Philippe Lanone of Natixis also questioned the significance of the latest research, saying such observational studies carried little scientific weight, while Morgan Stanley analysts said the sell-off was unwarranted.
Shares in Sanofi plunged in June last year when another study suggested a possible link between the long-acting insulin and cancer. U.S. and European regulators, however, both went on to back the product, and prescriptions for Lantus, which had sales of 3.1 billion euros ($3.8 billion) last year, held up despite the controversy.
Lantus is a key driver for Sanofi as older medicines face patent expiry, making investors highly sensitive to perceived problems with the product.
The drug also faces looming competition from Novo Nordisk's NOVOb.CO next-generation degludec insulins, clinical trial results for which will be aired at a major medical meeting later this month. [ID:nLDE65E0DH]
Sanofi shares were down 4 percent at 49.08 euros by 1130 GMT, after a low at 47.45 euros, to be the biggest losers on France's benchmark CAC-40 index .FCHI which was down 0.1 percent.
Edoardo Mannucci of the diabetes agency at the Careggi Teaching Hospital in Florence and colleagues said the possibility of a link between higher doses of Lantus and cancer “should be considered”.
But analysts said the group’s analysis, which followed 1,340 patients, was very small-scale compared to ongoing research involving nearly 1 million subjects which is due to report at the end of 2011.
“This makes a ripple in the stock markets because we have had a sniff of this story before and it opens an old wound,” said Jefferies analyst Jeffrey Holford. “But I don’t think it is going to influence prescribing behaviour.”
Morgan Stanley said the latest fears about Lantus came just two days after the American Diabetes Association and the American Cancer Society published a joint statement supporting the safety of insulin treatments. (Additional reporting by Kirsti Knolle, Christoph Steitz, Raoul Sachs and James Regan; Editing by Will Waterman and Dan Lalor) ($1 = 0.8076 euro)