Fingolimod is an immunomodulating medication developed by Novartis and approved for the treatment of multiple sclerosis (MS) under the brand name Gilenya. Fingolimod may also be useful for treating Rett syndrome.

How fingolimod works

Rett syndrome is a serious neurodevelopmental disease that primarily affects girls. Most cases of Rett syndrome are caused by mutations in the MECP2 gene, which provides instructions for making a protein that is involved in controlling when other genes are active. Mutations in MECP2 cause this protein to be made incorrectly or in low amounts. This causes a number of neurological problems, which all contribute to Rett syndrome.

One of these problems is an increase in inflammation in the brain. MECP2 normally suppresses inflammatory signaling molecules called cytokines, keeping the immune system under control.

Fingolimod is a compound that is metabolized into an active form that binds to and blocks specific receptors called the sphingosine 1-phosphate receptors 1, 3, 4, and 5. These receptors are found on cells that make up the vasculature and control how they interact with each other. Tight barriers between the cells mean that the movement of immune cells out of the lymph nodes is prevented while open barriers mean that the free movement of immune cells from the lymph nodes to the bloodstream is permitted.

By blocking these receptors, fingolimod keeps the interactions between the cells tight, blocking the ability of immune cells to leave lymph nodes and reach the circulation, and possibly the brain.

Some studies have shown that fingolimod may also be able to improve the functional output of the nervous system. The mechanism is unknown, but the results indicate that fingolimod may have a direct therapeutic effect on the nervous system as well as the immune system.

Fingolimod in clinical trials for Rett syndrome

Preclinical studies with fingolimod in cells grown in the laboratory and in mouse models of Rett syndrome indicated that the treatment reduced inflammation and improved movement and cognition in the animals.

A Phase 1/2 clinical trial (NCT02061137) assessed the safety and efficacy of oral fingolimod in children older than 6 with Rett syndrome. The trial was completed in 2018, but the results have not yet been published. If the trial shows positive results in terms of safety and efficacy, the treatment could advance to a Phase 2 trial with more patients to further test the hypothesis that it may slow the loss of motor and language skills caused by the disease.


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