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Millions of people worldwide live with mitochondrial diseases. These are inherited conditions that make it hard for the body's cells to produce energy. For a long time, patients had few options besides treatments that helped with symptoms. Now, a new drug has been approved that treats the root cause of some mitochondrial diseases. This breakthrough gives hope to many families and sets a new direction for future treatments.
Mitochondrial diseases occur when a person's genes cause problems in the mitochondria, our cells' power plants. When they can't do their job, the body doesn't get enough energy. This can cause people to feel tired, weak or dizzy, or lead to problems with their muscles, brain, heart, hearing or vision. There are many types of mitochondrial disease, and symptoms can show up at any age. Some people can still live fairly normal lives. For others, especially young children, the disease can get worse quickly and become life-threatening.
One of the rarest and most severe forms of mitochondrial disease is thymidine kinase 2 deficiency. Children with this condition sometimes learn to walk or eat like other kids, but then lose these abilities over time. Many need help from machines or wheelchairs. Frequent hospital visits are common. Without treatment, some children may not survive for more than a few years.
In the past, doctors could only offer supportive care for mitochondrial diseases. This involves providing supplements, vitamins and physical therapy to help individuals maintain their strength and stay as healthy as possible. As the disease gets worse, some people need feeding tubes or breathing machines. These treatments may help alleviate symptoms, but they don't address the underlying issue within the cells. For many families, this has meant watching their loved one's health slowly get worse, even with the best care.
In November 2025, the FDA approved a therapy for one of these rare mitochondrial diseases. The drug, which goes by the unusual name KYGEVVI, differs from earlier treatments in that it addresses the underlying genetic problem rather than just easing symptoms. This new medicine combines two compounds, both of which are building blocks for DNA and other nucleic acids. By providing these essential ingredients, the drug helps compensate for the cell's defect, allowing the mitochondria to function properly again.
Studies of this therapy in children and adults have shown that many patients experienced improvements, including increased strength and better breathing and swallowing capabilities. People taking the medicine had fewer infections and spent less time in the hospital. Some patients were even able to walk or breathe independently again after losing these abilities. These changes made life easier for families and allowed patients to be more independent. Most people who received this treatment experienced only mild side effects, such as an upset stomach. These problems were usually easy to manage. Importantly, the benefits of the medicine lasted for several years, with many patients keeping their improved strength and abilities.
This is the first medicine to actually repair the damaged DNA in patients' mitochondria, showing real results in people, not just in lab animals. Furthermore, this approval represents a significant step forward for individuals with rare diseases. It demonstrates that new medicines for these conditions are feasible and offers hope that additional treatments will follow. Excitement around this success could help bring more money and attention to research, making it easier for scientists and doctors to find better options for people with other types of mitochondrial disease.
Momentum is already building in the field. Several promising experimental drugs, including elamipretide, sonlicromanol and KL1333, are advancing through human clinical trials for related mitochondrial disorders such as Barth syndrome and DNA depletion syndromes. The success of KYGEVVI is fueling optimism and investment, marking what many see as the beginning of a new era for mitochondrial medicine.
The road ahead for mitochondrial disease and other rare conditions holds considerable promise. To continue making progress, new treatments must be designed with real patients' needs in mind, focusing on what truly improves their quality of life. This recent drug approval shows that positive change is happening. With more support and teamwork, the future could be much brighter for everyone living with mitochondrial disease.