Merck KGaA (MRK.XE) may appeal a negative opinion on its multiple sclerosis pill Cladribine made by an advisory panel of the European Medicines Agency, Merck KGaA said Friday.

The EMA's Committee for Medicinal Products for Human Use, or CHMP, said that the benefits don't outweigh the risks, the company said in a statement.

Merck KGaA said it is committed to making the drug available in Europe and is "evaluating all options to gain approval in the European Union, including a potential appeal to request re-examination of the submission by the CHMP."

Cladribine, which has the potential to become a blockbuster drug with peak sales of more than EUR1 billion, has recently been approved in Australia and Russia, but lost the race for approval in the U.S. to Novartis AG's (NVS) rival product Gilenia, which received FDA approval Wednesday.

Merck previously said it expects an FDA decision in the fourth quarter.

Merck Serono initiated global submissions for Cladribine pills in mid-2009 and to date has submitted regulatory applications for Cladribine covering about 40 countries.

Like Novartis's Gilenia, cladribine aims to reduce relapses in people with relapsing forms of MS. The two treatments raise the possibility for the first time that oral treatments might become available alongside the more cumbersome injections and infusions currently used to treat MS.

-By Natascha Divac and April van Ert, Dow Jones Newswires; +49 69 29725 500; djnews.frankfurt@dowjones.com