(Adds label details, clarifies patent expiration; updates shares)
By Bill Berkrot
Feb 26 (Reuters) - French drugmaker Sanofi SA's new Toujeo diabetes drug won U.S. regulatory approval, but with wording on its prescribing label that analysts say could make marketing difficult.
Toujeo is a more potent follow-up to the drugmaker's top-selling Lantus insulin product, which accounts for a fifth of Sanofi sales. Sanofi is hoping to convert patients to Toujeo as Lantus is due to lose its U.S. patent protection this month.
The U.S. Food and Drug Administration late Wednesday approved the once daily, long-acting basal insulin to treat type 1 and the far more prevalent type 2 diabetes.
Analysts noted, however, that lower rates of hypoglycemia, a potentially dangerous drop in blood sugar, seen in clinical trials comparing Toujeo to Lantus, was not mentioned on the FDA-approved label. It also highlighted the need for higher doses to achieve the same level of blood glucose control as Lantus.
"The Toujeo label is probably going to be viewed as more undifferentiated than investors have been expecting," Bernstein analysts said in a research note. Citi analysts called the label "not great."
Shares in Sanofi closed down 1.75 percent at 87.54 euros in Paris on Thursday.
Sanofi bought some patient conversion time with a patent infringement lawsuit filed last year against Eli Lilly and Co that keeps a cheaper Lantus generic off the market for 30 months.
In addition to gaining patients through conversions, "there's about a million new patients for basal insulin each and every year," said Joe Balzer, head of U.S. commercial operations for Toujeo, which is still awaiting European approval.
Toujeo has the same active ingredient as Lantus, called insulin glargine, but at three times the concentration and with a design to release the insulin more gradually.
Lantus is the world's most prescribed insulin with sales of $7.2 billion in 2014. Warnings of faltering U.S. sales of Lantus contributed to the sudden sacking of Sanofi Chief Executive Officer Chris Viehbacher last year.
His successor, Olivier Brandicourt, is set to assume the top post at the beginning of April as Toujeo goes on sale.
The company has not revealed pricing for Toujeo and declined to discuss any potential discounting strategy in a market analysts see as becoming increasingly price sensitive.
More than 370 million people worldwide have diabetes, according to the International Diabetes Federation. As many as 95 percent have type 2, often associated with obesity which raises the risk of numerous serious health problems.
(Reporting by Bill Berkrot in New York, additional reporting by Andrew Callus in Paris; editing by Lisa Shumaker, Keith Weir and G Crosse)