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BERLIN — In a breakthrough that underscores the power of medical repurposing, researchers have identified sildenafil—the active ingredient in the well-known medication Viagra—as a potentially life-changing treatment for Leigh syndrome. This rare and devastating mitochondrial disorder, which primarily affects infants and young children, currently has no approved cure or disease-modifying therapy.
The study, published in the journal Cell in March 2026, was led by a collaborative team from Charité – Universitätsmedizin Berlin, Heinrich Heine University Düsseldorf, and the Fraunhofer Institute for Translational Medicine and Pharmacology. By screening over 5,500 existing drugs, the researchers discovered that sildenafil could restore cellular energy and significantly improve clinical symptoms in patients, ranging from increased mobility to the cessation of life-threatening seizures.
Understanding the “Powerhouse” Failure: What is Leigh Syndrome?
To understand why this discovery is significant, one must first look at the biology of Leigh syndrome. Often described as a neurometabolic disorder, it is caused by genetic mutations that disrupt the mitochondria—the “powerhouses” of the cell responsible for generating energy.
When mitochondria fail, tissues that require the most energy, such as the brain and muscles, suffer first. The disease typically emerges within the first year of life, manifesting as:
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Progressive neurological decline: Loss of previously acquired motor skills.
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Metabolic crises: Sudden episodes of rapid worsening triggered by common infections or stress.
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Physical symptoms: Muscle weakness (hypotonia), seizures, difficulty swallowing, and respiratory failure.
Leigh syndrome affects approximately 1 in 36,000 to 40,000 live births globally. However, in certain genetically isolated regions, such as the Saguenay–Lac-Saint-Jean region of Quebec, the incidence can be as high as 1 in 2,000. Historically, the prognosis has been grim, with many children not surviving past early childhood.
From 5,500 Drugs to One Breakthrough
The journey to this discovery began in the lab using cutting-edge “organoid” technology. Researchers generated patient-derived neurons from stem cells and created miniature brain models to test how different compounds affected diseased cells.
Of the thousands of drugs screened, sildenafil emerged as a top candidate. While the public knows it for treating erectile dysfunction, sildenafil is a phosphodiesterase-5 (PDE5) inhibitor. In the context of Leigh syndrome, the researchers found it did more than just affect blood flow; it normalized the electrical activity of nerve cells and enhanced mitochondrial function.
“This is the largest drug screening for the treatment of Leigh syndrome to date,” noted Dr. Ole Pless of the Fraunhofer ITMP. “It showed that sildenafil… improved the electrical functionality of the nerve cells.”
Real-World Results: The Pilot Study
Following the lab success, the team conducted an open-label pilot study involving six patients aged 9 months to 38 years. The results, though preliminary, were described as remarkable:
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Mobility Gains: One child’s walking distance increased tenfold, from 500 meters to 5,000 meters.
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Crisis Prevention: One patient, who previously suffered monthly metabolic crises, saw these episodes stop entirely.
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Seizure Control: Several patients reported a total cessation of epileptic seizures.
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Muscle Strength: Overall improvements in strength and faster recovery times after illness were noted across the cohort.
“Such effects significantly improve the quality of life of Leigh syndrome patients,” said Prof. Markus Schuelke, a lead author from Charité’s Department of Pediatric Neurology. “We are very pleased to have found a promising drug candidate.”
The Mechanism: Jump-Starting the Engine
How does a drug for blood flow help a genetic energy disorder? The researchers compare sildenafil’s effect to “jump-starting a faltering engine.”
By inhibiting the PDE5 enzyme, sildenafil helps normalize the “membrane potential” of the mitochondria. This allows the cells to produce energy more efficiently and fosters the maturation of neurons. Crucially, because this mechanism targets a common pathway of energy failure, it appears effective across different types of genetic mutations—a major hurdle in treating Leigh syndrome, which is linked to over 75 different genes.
Expert Perspectives: Cautious Optimism
The medical community has reacted with a mix of excitement and professional caution. Vivian Gama, a cell biologist at Vanderbilt University who was not involved in the study, called the paper “really exciting,” highlighting how the data converged across cell models, animal studies, and human patients.
However, some experts urge families to wait for larger trials. Michael Johnson, a mitochondrial specialist, noted the difficulty in studying Leigh syndrome due to its unpredictable nature. “It’s challenging to disentangle the effects of the drug from normal progression,” Johnson cautioned, suggesting that the “episodic” nature of the disease means symptoms can sometimes fluctuate naturally.
Prof. Alessandro Prigione of University Hospital Düsseldorf pointed out a significant advantage: sildenafil already has an established safety profile in children, as it is currently used to treat pediatric pulmonary hypertension. This “head start” on safety data could fast-track its availability if future trials succeed.
The Path Forward: Public Health and Future Trials
The European Medicines Agency (EMA) has already granted sildenafil “orphan drug” status for Leigh syndrome, a designation intended to encourage the development of drugs for rare diseases.
The next step is the SIMPATHIC EU project, a Europe-wide, placebo-controlled clinical trial. This trial will be the gold standard needed to prove that the improvements seen in the pilot study were truly caused by the medication and not by chance.
For the thousands of families living under the shadow of Leigh syndrome, this research represents a shift from “supportive care” to the possibility of “active treatment.” While sildenafil is not a cure—it does not fix the underlying genetic mutation—it may provide a way to manage the most debilitating symptoms and extend life.
A Note of Caution: Researchers and physicians emphasize that parents should not attempt to administer sildenafil to children with Leigh syndrome outside of a clinical trial or direct medical supervision. The dosages used in the study were precisely controlled, and improper use could lead to serious side effects.
Medical Disclaimer
This article is for informational purposes only and should not be considered medical advice. Always consult with qualified healthcare professionals before making any health-related decisions or changes to your treatment plan. The information presented here is based on current research and expert opinions, which may evolve as new evidence emerges.
References
- https://www.ndtv.com/health/viagra-ingredient-sildenafil-may-help-treat-a-rare-and-fatal-childhood-disease-leigh-syndrome-11305668
