Santhera Pharmaceuticals Holding AG said the Bertarelli Group combined its ownership in the company with that of the Iglu Group to form a new shareholder group.

The collective now owns 1,179,977 shares of the company, representing 18.84% of Santhera. The Bertarelli Group previously owned 8.71% of the company with the remaining 10.13% under Iglu's control.

The Bertarelli Group represents billionaires Ernesto Bertarelli, Donata Guichard-Bertarelli and Maria-Iris Bertarelli who inherited Serono, a Swiss biotech which was sold to Merck KGaA in 2006 for €10.6 billion.

Santhera itself is a Swiss pharmaceutical company whose lead product, Raxone, is authorized in the EU, Norway, Iceland and Liechtenstein for the treatment of Leber's hereditary optic neuropathy, an eye disease.

Raxone is also being developed for the treatment of Duchenne muscular dystrophy and primary progressive multiple sclerosis.

In an emailed response to S&P Global Market Intelligence, Santhera CEO Thomas Meier said that both groups had been shareholders of the company for several years.

"We will certainly speak with representatives of this new shareholder group over the coming days but, given the regular and positive interactions we had over the past years with both groups, I am confident that this new group will continue to support the management and the company in its ambitions for the future," Meier said.