Novartis has found safety problems in higher doses of its key Galvus diabetes drug and will revise prescribing recommendations before launching in Europe, further complicating the product's path to market.
Switzerland's Novartis said on Tuesday it would also discuss the data and recommendations on the potential blockbuster -- which has been approved in the European Union but not yet launched -- with other regulators.
"It's new information that this drug causes liver toxicity, but it seems to be doing so only at the 100 milligram dose, that's the encouraging thing," said Vontobel analyst Karl Heinz Koch.
"But certainly it raises more question marks as to the U.S. approval," Koch said.
Data showed patients taking 100mg doses of Galvus once daily had more frequent liver enzyme elevation when compared to those taking 50mg per day or 50mg twice daily, Novartis said.
The company has proposed changing recommendation to use of once- or twice-daily 50mg doses, rather than the single higher dose.
Galvus has been approved for use in the European Union, but faces a lengthy delay in getting to market in the United States following a request for more safety data. It now faces a further delay of a few months in the EU as the label is finalised, Vontobel's Koch said.
Novartis has said it aims to resubmit the drug in the United States in 2009.
Galvus works in a similar way to Merck's recently launched Januvia but its path to U.S. approval has been delayed by worries over skin toxicity.
Merck's big lead means Novartis may be at a disadvantage when its drug is finally approved in the United States, the world's biggest drugs market, some analysts say.
Both Galvus and Januvia are so-called DPP-4 inhibitors, which are designed to enhance the body's own ability to lower elevated blood sugar and could become an important new way to control type 2 diabetes, the most common form of the disease.
The manufacturers and many analysts believe DPP-4 drugs could become blockbusters because they are not associated with weight gain, a major side effect of some established diabetes drugs.