A surprising medical breakthrough has brought new hope to families affected by Leigh syndrome, a rare and often fatal genetic disorder that primarily strikes young children. Researchers at Charité – Universitätsmedizin Berlin have discovered that sildenafil, the active ingredient in the erectile dysfunction drug Viagra, significantly improves symptoms and quality of life in patients with this devastating condition.
Leigh syndrome is a severe mitochondrial disease caused by genetic mutations that impair the body’s ability to produce energy in cells, particularly affecting the brain and muscles. Most children diagnosed with the condition experience rapid neurological decline, seizures, muscle weakness, and breathing difficulties, with many not surviving past age three. Until now, no approved treatments existed that could alter the disease’s tragic course, leaving families with limited options beyond supportive care.
The discovery emerged from an extensive drug screening process. Scientists tested more than 5,500 already-approved medications using patient-derived nerve cells and brain organoids that replicate key features of Leigh syndrome, including energy production deficits and disrupted cell growth. Sildenafil stood out as the most promising candidate. In laboratory tests, it restored cellular metabolism, supported nerve cell growth, and helped cells better cope with energy shortages.
Building on these encouraging lab results, the team moved to animal models. Experiments in mice and pigs carrying disease-linked mutations showed that sildenafil modestly extended lifespan and improved mitochondrial function. The drug appeared to strengthen neurons and protect against the severe energy crises that characterize the disorder.
The most compelling evidence came from a small pilot study involving six patients with Leigh syndrome caused by MT-ATP6 mutations. The participants, ranging in age from nine months to 38 years, received sildenafil as an individual therapeutic trial. Within months, remarkable improvements appeared. Motor skills strengthened noticeably, with one child’s walking distance increasing tenfold from roughly 500 meters to 5,000 meters. Patients showed greater resistance to metabolic crises, fewer seizures in some cases, and overall better daily functioning. One teenager who had been considered for palliative care experienced stabilized symptoms and continued taking the medication for over seven years.
Lead researcher Markus Schuelke described the findings as a genuine surprise, noting the drug’s unexpected ability to address core mitochondrial dysfunction. While the results remain preliminary and require confirmation in larger clinical trials, the team expressed excitement about identifying a readily available drug candidate for this serious hereditary disease. Plans for a comprehensive clinical study are already underway later this year.
Sildenafil works as a PDE-5 inhibitor, a mechanism long known for its effects on blood flow. In the context of Leigh syndrome, researchers believe it improves mitochondrial performance and helps neurons handle energy deficits more effectively. Its established safety profile from decades of use in other conditions could accelerate development as a treatment option.
For families facing Leigh syndrome, this development offers a rare glimmer of optimism. The disorder’s progressive nature has left parents feeling powerless, but early signs of improved muscle strength, mobility, and resilience to energy crashes suggest sildenafil could meaningfully extend quality time and slow decline.
Experts caution that larger, controlled trials are essential to confirm efficacy, determine optimal dosing for children, and monitor long-term effects. Nevertheless, repurposing an existing medication like sildenafil could bring a treatment to patients far faster than developing a new drug from scratch.
This unexpected application of a well-known compound highlights the value of drug repurposing in rare diseases. As research advances, scientists hope sildenafil—or refined versions—will provide the first disease-modifying therapy for Leigh syndrome, transforming outcomes for affected children worldwide.
The study, published in the journal Cell, marks an important step forward in mitochondrial medicine and underscores how scientific creativity can uncover new uses for familiar medications. Families and clinicians now await results from upcoming trials with cautious hope that a simple pill could change the trajectory of this heartbreaking childhood disease.
