PARIS/LONDON - Sanofi-Aventis said on Wednesday a group of independent experts had concluded that studies highlighting a possible link between its Lantus diabetes drug and an increased risk of cancer were flawed.
A multidisciplinary board of experts from the United States, France, Germany, Italy and Canada reached the conclusion after being asked by the French drugmaker to assess four studies published last month in the medical journal Diabetologia.
They found significant methodological limitations and shortcomings and said the results were inconsistent and inconclusive.
But they added the important scientific questions raised called for further analysis of existing data on Lantus, as well as more basic and clinical investigations.
Sanofi shares were up 1.2 percent at 42.70 euros by 0910 GMT, outperforming a 0.4 percent advance in the DJ Stoxx European drugs sector index .SXDP.
Sanofi is relying on its long-acting insulin Lantus to offset a fall in sales of other products, such as Plavix and Lovenox, which could soon face generic competition.
Its stock dived last month when worries about a possible but uncertain link with cancer first surfaced.
The drugmaker said at the time that the data was of poor quality and no firm conclusions could be drawn -- though that did not stop analysts slashing sales forecast for the drug.
Wednesday's statement, signed by 14 medical experts, may go some way to restore confidence, but analyst Jeffrey Holford at stockbroker Jefferies said it did not shed any significant new light on the controversy.
What the market is really waiting for is not statements from experts on data we've already seen but new information, new studies and new data, he said.
Matthew Riddle, professor of medicine at Oregon Health Sciences University in the United States and one of the 14 experts, said the problems with the studies in Diabetologia meant there was no reason to change clinical practice.
The nature of these limitations and their potential magnitude are such that, individually or in aggregate, these studies provide inconsistent and inconclusive results which do not justify new clinical recommendations to patients, he said.
Jean-Pierre Lehner, Sanofi's chief medical officer, said: We are moving forward confidently with the external scientific and medical experts and health authorities toward next steps to resolve this controversy.
Lantus had sales of 2.45 billion euros ($3.43 billion) in 2008 and had been expected to continue to grow strongly, reflecting the growing incidence of diabetes worldwide.
The last big safety scare over a diabetes drug involved GlaxoSmithKline's pill Avandia, which was linked to heart attack risk in a U.S. study in 2007. Glaxo contested those findings, but sales of the drug still halved.
That precedent has spooked many investors, although it may not offer a direct parallel to the case of Lantus.
In the case of Avandia, safety concerns were championed by a high-profile medical expert -- U.S. cardiologist Steve Nissen -- and received massive U.S. media coverage. But with Lantus there is no big name campaigner involved and media coverage has been much more low key.
We're seeing daily and weekly prescription data pointing to a slight deterioration in Lantus, said Holford. It looks nothing like Avandia in terms of the rundown in prescriptions but you just don't know if it is going to be a slow death.
Investors are watching closely to see how the affair plays out for Sanofi's rivals.
Beneficiaries could include Denmark's Novo Nordisk, provided its rival long-acting insulin Levemir remains free of similar safety scares -- as well as makers of other types of diabetes medicines. ($1=.7149 euros) (Editing by Greg Mahlich)