The U.S. Food and Drug Administration granted priority review to Cladribine, a multiple sclerosis drug manufactured by Merck KGaA, expediting the time it takes to get an approval from 10 to six months.

The priority review process is granted to drugs "that offer major advances in treatment, or provide a treatment where no adequate therapy exists," according to the agency.

Cladribine is intended to treat patients with relapsing forms of multiple sclerosis, a chronic disease that affects the central nervous system by inhibiting communication between the brain and spinal cord with the rest of the body.

The new drug 2-chlorodeoxyadenosine works by suppressing the immune cells called lymphocytes to treat multiple sclerosis.

Cladribine was first approved in Russia in 2010 after a large clinical trial with more than 1,000 showed that patients treated with the oral medication had a significant reduction in relapse rates of multiple sclerosis.

Although multiple sclerosis is a commonly diagnosed neurological disorder among young adults with 2.5 million people affected worldwide, relatively few treatment options exist for patients with the condition.

The German-based company Merck expects to change the reality with the approval of Cladribine.

The agency's decision, which the company expects to get in the fourth quarter,“is a critical milestone on the path to potential approval for short-course therapy with cladribine” said Fereydoun Firouz, head of Merck’s EMD Serono unit in the USA.