Novartis said tests have shown liver-safety problems with high doses of diabetes drug Galvus (vildagliptin), its DPP-4 inhibitor that has been approved for sale in Europe, which will likely delay the drug's introduction in Europe by several months.

Data showed patients taking a 100 milligram dose of Galvus once daily had more frequent liver-enzyme elevation when compared with those taking 50 milligrams a day or 50 milligrams twice daily, Novartis said.

The company has proposed to regulators that prescribing recommendations be revised to call for once- or twice-daily 50 milligram doses of Galvus, rather than the single higher dose.

The announcement comes as a new blow to Novartis, which for the past year has watched Galvus fall further and further behind rival diabetes drug Januvia (sitagliptin).

While Januvia was approved by the FDA as a once-daily treatment for type 2 diabetics a year ago and is off to a strong start in the U.S. market, Galvus remains stalled at the FDA where worries about skin toxicity have led regulators to seek additional testing.

As a result, Galvus is not expected to make it to the U.S. market until 2009 at the earliest.

Both Galvus and Januvia are DPP-4 inhibitors, which are designed to enhance the body's own ability to lower elevated blood sugar. A major attraction of this class of drugs is that unlike many existing diabetes medications, DPP-4 inhibitors do not appear to result in weight gain.