BASEL, Switzerland – Clinical trials have failed to show that a cancer drug made by Novartis is more effective in higher doses, the pharmaceutical company said Friday.

Patients with chronic myeloid leukemia showed no statistically significant improvement when treated with an 800 milligram dose of Glivec than those who received the standard 400 milligram dose, which is prescribed currently by doctors.

Glivec – known as Gleevec in the United States – is the second best-selling drug for Novartis after blood pressure medication Diovan.

Novartis' American depository reciepts fell 41 cents to $49.94.