Sarizotan was an oral therapy that Newron Pharmaceuticals was developing to treat breathing problems in patients with Rett syndrome.

Newron terminated sarizotan’s development after a lack of effectiveness seen in the Phase 2/3 STARS clinical trial (NCT02790034).

How does sarizotan work?

Breathing problems are common in Rett syndrome. Patients may experience shallow breathing, hyperventilation (rapid and deep breathing), breath-holding (taking a breath and failing to let it out), swallowing air, or apnea (failing to take breaths after exhalation). These episodes are involuntary and can cause dizziness, and they can affect mental focus and coordination. They may also interfere with such basic tasks as eating and drinking.

Studies in Rett syndrome patients have shown deficits in the amount of serotonin and other critical chemical messengers of the brain that transmit neuronal messages.

Sarizotan is a chemical compound that binds to serotonin and dopamine receptors in brain cells. Working with mouse models, researchers found that sarizotan can make up for the deficits in serotonin levels in the brain and restore normal breathing. They used three different mouse models of Rett syndrome, and showed that sarizotan reduced apnea by about 75% to 80%. It also corrected irregular breathing patterns.

Sarizotan in clinical trials

Newron Pharmaceuticals sponsored the STARS study based on the positive results in these preclinical animal studies. This trial, a Phase 2 randomized, double-blind study at multiple centers in the U.S., the U.K., Italy, India, and Australia, aimed to evaluate the efficacy, safety, and tolerability of sarizotan in Rett patients with respiratory symptoms.

Final results showed that treatment with sarizotan did not reduce apnea episodes while awake compared to a placebo, thereby failing to achieve the trial’s primary goal. The therapy also failed to achieve secondary objectives. These included evaluations of effectiveness by caregivers, assessments of respiratory distress, and tests of motor function.

Other details

Sarizotan was designated orphan drug as a potential treatment of Rett syndrome in the U.S. and the European Union in 2015.

Newron announced its decision to end its sarizotan development program for Rett on May 4, 2020, noting the “difficulties inherent in translating effects in animal models to human clinical studies.”


Last updated: May 14, 2020


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