In a groundbreaking advancement for the treatment of rare mitochondrial disorders, researchers have discovered that sildenafil, commonly known for its use in erectile dysfunction and pulmonary hypertension, significantly alleviates symptoms in patients suffering from Leigh syndrome. This rare, debilitating metabolic disorder affecting predominantly infants and children has long been considered untreatable, leaving patients with severe neurological deterioration and often shortened lifespans. Published recently in the prestigious journal Cell, the study, led by a collaborative team from Charité – Universitätsmedizin Berlin along with Heinrich Heine University Düsseldorf, University Hospital Düsseldorf, and the Fraunhofer Institute for Translational Medicine in Hamburg, marks a promising turning point in Leigh syndrome therapy.
Leigh syndrome stems from genetic mutations that cause mitochondrial dysfunction, the mitochondria being the essential cellular organelles responsible for energy production. This energetic deficit impairs crucial brain regions, leading to symptoms such as muscle weakness, seizures, paralysis, and delayed cognitive development. Manifesting typically in infancy or early childhood, the syndrome progresses relentlessly, and until now, no effective pharmacological treatments have existed. The high severity coupled with the rarity of Leigh syndrome—affecting approximately one in 36,000 live births—posed immense challenges for both research and clinical trials.
Unexpectedly, sildenafil emerged as a potential therapeutic candidate during an extensive drug screening endeavor. Known pharmacologically as a phosphodiesterase type 5 (PDE-5) inhibitor, sildenafil’s primary mechanism involves vasodilation—expanding blood vessels to improve circulation. While its reputation largely revolves around treating erectile dysfunction in adults, its established application in pediatric pulmonary hypertension and availability of long-term safety data in children made it a particularly attractive candidate for repurposing in rare metabolic disorders like Leigh syndrome.
The pilot clinical study involved six patients, ranging from nine months to 38 years of age, all diagnosed with Leigh syndrome. Remarkably, after just a few months of continuous sildenafil administration, patients exhibited improvements particularly in muscular strength, while some experienced remission of neurological symptoms. Notably, recovery from metabolic crises—episodes of acute energy metabolism failure which exacerbate disease severity—was substantially accelerated. Such outcomes are especially important as metabolic crises often lead to rapid deterioration in Leigh syndrome patients.
One compelling example presented by Prof. Markus Schuelke from Charité’s Department of Pediatric Neurology highlighted a child whose ambulatory capacity increased tenfold, extending walking distances from 500 meters to an impressive 5,000 meters. Another patient saw a dramatic reduction in almost monthly metabolic crises, while yet another reported complete cessation of epileptic seizures. These clinical improvements underline sildenafil’s capacity to not only manage but potentially modify the disease trajectory, thus significantly enhancing patient quality of life.
The journey to this revelation involved intricate and innovative methodologies, essential given the intricacies of studying brain-based rare diseases. Due to the rarity and severity of Leigh syndrome, direct access to brain or nerve tissues in living patients is ethically and practically impossible. To circumvent this, the research team utilized patient-derived skin cells, inducing them into pluripotent stem cells—a state where they can differentiate into multiple cell types, including neurons. These neuronal cells mimicked the defective energy metabolism characteristic of Leigh syndrome, providing an invaluable laboratory model for testing thousands of compounds.
The screening process examined over 5,500 active substances, mostly drugs already approved for other conditions or with extensive safety profiles. Among these, sildenafil distinguished itself by improving the electrical functionality of patient-derived nerve cells. Beyond cellular assays, further validation ensued using brain organoids—three-dimensional miniature brain replicas grown from stem cells—which demonstrated enhanced nerve cell growth upon sildenafil exposure. Animal models supplemented these findings, with treated subjects showing improved energy metabolism and extended life expectancy, fortifying the robustness of the initial data.
These comprehensive preclinical results paved the way for clinical application. As Prof. Alessandro Prigione from University Hospital Düsseldorf noted, the wealth of existing safety data for sildenafil, especially in pediatric uses, was crucial in justifying compassionate use in individuals with Leigh syndrome. The first patient was treated at Charité, followed by additional cases across Germany and Italy. Encouragingly, all patients tolerated the drug well, adding a layer of feasibility to broader clinical application.
Recognizing sildenafil’s potential and the urgent medical need for effective Leigh syndrome treatments, the European Medicines Agency (EMA) has granted the drug orphan drug designation (ODD). This status simplifies regulatory pathways, expediting development and approval processes for treatments targeting rare diseases. Building on this momentum, the research consortium is now preparing a comprehensive, Europe-wide placebo-controlled clinical trial under the SIMPATHIC EU project to validate these preliminary findings rigorously and establish sildenafil as an approved therapy for Leigh syndrome.
This discovery not only offers hope for a disease long deemed untreatable but also exemplifies the paradigm shift towards precision medicine leveraging patient-specific cellular models. It highlights the immense value of drug repurposing, particularly in the realm of rare diseases where traditional drug development faces significant hurdles due to limited patient numbers and complex pathologies.
While challenges remain in translating these promising results into widespread clinical practice, the multi-center, international collaboration underlining this study serves as a model for tackling ultra-rare diseases. As further research unfolds, sildenafil could emerge as the first effective medical intervention for Leigh syndrome, dramatically improving life expectancy and quality for affected children and adults worldwide.
In conclusion, this innovative study demonstrates how a well-known drug can be redirected using cutting-edge stem cell technologies and organoid models to address unmet medical needs in mitochondrial disease. The prospect of a safe, efficacious therapy for Leigh syndrome heralds a new era of hope and underscores the power of translational medicine.
Subject of Research:
Leigh syndrome, a rare mitochondrial disease, and the therapeutic effects of sildenafil on its neurological and muscular symptoms.
Article Title:
Pluripotent Stem Cell-Based Drug Discovery Uncovers Sildenafil as a Treatment for Mitochondrial Disease
News Publication Date:
March 11, 2026
Web References:
http://dx.doi.org/10.1016/j.cell.2026.02.008
References:
Zink A et al. Pluripotent stem cell-based drug discovery uncovers sildenafil as a treatment for mitochondrial disease. Cell. 2026 Mar 11. doi: 10.1016/j.cell.2026.02.008
Image Credits:
© HHU | Stephanie Le, AG Prigione
Keywords:
Leigh syndrome, sildenafil, mitochondrial disease, rare disease, phosphodiesterase inhibitor, pluripotent stem cells, organoids, drug repurposing, pediatric neurology, mitochondriopathy, metabolic disorders, translational medicine
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