• Posted April 9, 2025

Experimental Drug Can Slow MS Disability

An experimental drug can help patients with advanced multiple sclerosis (MS) delay the progressive disability that comes with their disorder, a new clinical trial suggests.

The drug, tolebrutinib, delayed disability progression by 31% in people with a type of MS called non-relapsing secondary progressive multiple sclerosis (SPMS), researchers reported in the New England Journal of Medicine.

“This is the first clinical trial showing a positive effect in delaying disability progression in non-relapsing SPMS, a later form of the disease where neurological function gradually worsens over time and disability increases relentlessly,” lead researcher Dr. Robert Fox said in a news release. He's a neurologist at the Cleveland Clinic's Mellen Center for MS Research and Treatment.

Tolebrutinib is under review by the U.S. Food and Drug Administration (FDA). There currently are no FDA-approved treatments for SPMS, researchers said in background notes. 

For the clinical trial, researchers recruited more than 1,100 MS patients between 18 and 60 years of age at 264 sites across 31 countries. Patients were randomly assigned to either take a daily oral dose of tolebrutinib or a matching placebo tablet.

Tolebrutinib is a tyrosine kinease inhibitor, a type of drug originally developed to treat lymphomas and blood diseases. These drugs work by blocking enzymes that promote cell growth and division.

After six months, just under 23% of patients given tolebrutinib had progression in their MS-related disability, compared with nearly 31% of those taking placebo. That amounted to a 31% reduction of disability with the experimental drug.

Tolebrutinib also demonstrated other positive benefits, results show:

• Nearly twice as many patients taking the drug experienced improvements in their disability, 8.6% versus 4.5% with placebo.

• Tolebrutinib also caused a sustained 20% increase in a timed 25-foot walk test after three months.

• Patients on the drug also had fewer new or growing brain and spinal cord lesions associated with MS, compared to placebo.

But researchers warned that tolebrutinib appears to increase patients’ risk of liver injury. Levels of an enzyme reflecting injury were elevated in 4% of tolebrutinib patients versus 1.6% of placebo patients.

“If approved, the drug will likely require intensive monitoring of liver function enzymes during the first three months of therapy, with less frequent monitoring thereafter,” Fox said. 

“It appears that about 1 in 200 patients will have severe elevation of liver enzymes during the first three months of use, so careful monitoring is important, and the drug should be stopped immediately in those with liver enzyme elevations,” he added.

Tolebrutinib appears to work by reducing inflammation in the brain and spinal cord, Fox said.

“The drug offers the potential for a new class of medications for the treatment of MS, the leading cause of non-traumatic disability in young adults,” Fox said.

The clinical trial was sponsored by Sanofi, the developer of tolebrutinib.

More information

The Cleveland Clinic has more on tyrosine kinase inhibitors.

SOURCE: Cleveland Clinic, news release, April 8, 2025