Swiss pharmaceutical producer group Roche said it would discontinue a late-stage study of investigational anti-amyloid medicine gantenerumab in pre-dementia Alzheimer's disease, following a pre-planned futility analysis and recommendation by the independent Data Monitoring Committee.

The drugmaker said it was ending a late-stage study of the experimental drug after it failed to prove effective, underlining the difficulty of treating the disease and seriously pressuring the company's shares.

Germany's MorphoSys is Roche's partner on the Alzheimer's project. US firm ImmunoGen also contributes technology.

In the breast cancer application, Roche said that in a late-stage study in people with the previously untreated advanced HER2-positive form of the disease three of its treatments, Herceptin, Perjeta and Kadcyla, helped people live without their disease worsening. However, the two treatment arms containing Kadcyla did not significantly improve progression-free survival.

Roche suffered a setback with another experimental Alzheimer's drug earlier this year, but the company said it had no plans to abandon research on this disease.

"This is the first Phase III trial to evaluate a potential disease-modifying medicine in this early prodromal stage of Alzheimer's disease. We remain committed to investigating new medicines for this devastating illness," said Chief Medical Officer Sandra Horning.

Gantenerumab continues to be studied in another Phase III trial involving patients with later stage disease, and Roche has two other experimental Alzheimer's drugs in Phase II tests, crenezumab and RG1577.