FDA Grants Rare Pediatric Disease Designation to Sarizotan for Treating Rett Syndrome

The U.S. Food and Drug Administration (FDA) has granted rare pediatric disease designation to sarizotan for the treatment of breathing difficulties in people with Rett syndrome.

This designation provides priority review to investigational treatments that have the potential to provide clinically meaningful benefits for people with serious diseases — like Rett — which mainly affect people younger than 18, and with a prevalence of less than 200,000 individuals in the United States.

If sarizotan is ultimately approved, its developer — Newron Pharmaceuticals — may be eligible for a voucher redeemable for priority review of a subsequent application for a different product. This program is an incentive to develop treatments that might otherwise not be profitable.

“The decision of the FDA to designate sarizotan for the treatment of a rare pediatric population, following an earlier decision to grant it an Orphan Drug designation (ODD), highlights the critical need within the Rett community for treatments,” Ravi Anand, Newron’s chief medical officer, said in a press release.

Sarizotan is an experimental oral treatment for breathing problems in Rett syndrome. Apnea — when a person temporarily stops breathing — is present in about 70% of people with Rett, contributing to other comorbidities, or the simultaneous presence of two chronic diseases or conditions in the same patient, and to reduced quality of life.

The potential therapy works by binding to specific receptors of the neurotransmitters serotonin and dopamine. Studies in mouse models of Rett syndrome suggest that sarizotan may normalize serotonin levels in the brain — which are typically lower in Rett patients — and normalize breathing.

Newron is conducting a Phase 2/3 clinical study (NCT02790034), known as STARS, to evaluate the efficacy, safety, and tolerability of sarizotan. The study is testing the investigational medication in more than 130 Rett syndrome patients with respiratory symptoms.

Participants are receiving daily doses of either sarizotan — 10 to 20 mg, based on age and weight — or a placebo, for 24 weeks. After this double-blind period, all participants will have the opportunity to join an open-label extension study in which all will receive sarizotan.

The study is being conducted at 14 centers throughout the U.S., Europe, Asia, and Australia.

“We are looking forward to the results of our Sarizotan Treatment of Apneas in Rett Syndrome (STARS) study … which we expect within the next few weeks,” Anand said.

Sarizotan was originally developed as a treatment for levodopa-induced dyskinesia, or involuntary muscle movements, which is commonly seen in people with Parkinson’s disease.

Levodopa, the mainstay treatment for motor problems in Parkinson’s, helps counter the shortage of dopamine in the brain. However, most patients who use levodopa experience dyskinesia within the first five years of treatment.

Earlier this month, Newron launched the International Rett Syndrome Burden of Illness Survey, under the banner “The Voices of Rett.” This study is designed to examine the physical, emotional, and financial impact of Rett syndrome on patients, their families, and their caregivers. It aims to raise awareness and help identify treatments and other resources for the disorder.