ZURICH (Reuters) - Santhera Pharmaceuticals said on Monday a study of its medicine Raxone in primary progressive multiple sclerosis showed no difference between the treatment and placebo groups in disease progression, another setback for the Swiss drug company.

Raxone, also known as idebenone, is Santhera’s lead product and is authorized in the European Union, Norway, Iceland, Liechtenstein and Israel for treatment of Leber’s hereditary optic neuropathy (LHON).

But efforts to expand its use have faltered, including in January when a key European Medicines Agency’s panel baulked at recommending it in Europe for Duchenne muscular dystrophy (DMD), despite an appeal by the company.

That rejection prompted a share drop of more than a third.

This latest MS study, sponsored by the U.S. National Institutes of Health, was completed by just 66 patients, something Santhera called out as a potential limiting factor in making a determination about its efficacy.

“Clearly, the small sample size is a limitation when studying a therapeutic intervention in such a complex, relentlessly progressing neurological disease,” said

Chief Executive Thomas Meier in a statement.