Swiss biotech firm Serono SA, which earlier Thursday agreed to sell a majority stake in the company to German drugmaker Merck KGaA for $13.31 billion, said its oral cladribine treatment for multiple sclerosis has received "fast-track" status from the U.S. Food and Drug Administration.

This designation covers patients with relapsing forms of multiple sclerosis.

Serono's oral form of cladribine is currently being evaluated in a multi-center, multi-national Phase III study called CLARITY. It is a two-year, double-blind, placebo-controlled study involving more than 1,200 patients. Patient enrollment is planned to be completed by the end of 2006.

"Thanks to decades of research, there are injectible drugs available to treat some forms of MS, but there is certainly a need for more and even better therapies to treat all forms of the disease. Having an effective oral therapy for MS would be a major step forward in improving quality of life for people with MS," said John Richert, VP of research and clinical programs, at the National Multiple Sclerosis Society.

Fast-track programs are designed to facilitate the development and expedite the review of new drugs that could treat serious or life-threatening conditions, and that demonstrate the potential to address unmet medical needs. Oral cladribine is now eligible for priority review, and the FDA can review data as it is received, instead of waiting until Serono's new drug application is completed.

Cladribine interferes with the behavior and the proliferation of certain white blood cells, particularly lymphocytes, which are involved in the process of multiple sclerosis.

Multiple sclerosis is a chronic, inflammatory condition of the nervous system and is the most common, non-traumatic, neurological disease in young adults. Multiple sclerosis affects about two million people worldwide. The relapsing forms of multiple sclerosis are the most common.