German drug maker Merck KGaA's Merck Serono unit won European Commission approval to market a new formulation of its Rebif drug to treat relapsing multiple sclerosis, the company said on Thursday.

The new Rebif has been designed to be better tolerated when injected, Merck said in a statement.

The marketing authorisation covers all 27 European Union countries, as well as Norway, Iceland and Liechtenstein, Merck said, adding that the drug would be launched in various EU countries starting next month.

This new formulation will represent an improvement in the therapy of MS patients being treated with Rebif, said Per Soelberg Soerensen, of the Danish Multiple Sclerosis Research Centre at Copenhagen University Hospital, in the statement.

Shares in Merck were 0.3 percent higher at 90.88 euros by 0731 GMT, compared with a 0.5 percent gain on the German blue-chip DAX index. The DJ healthcare index was 0.1 percent higher.