Daijiworld Media Network - Washington

Washington, Nov 4: In a historic medical breakthrough, the US Food and Drug Administration (FDA) has approved KYGEVVI—a combination of doxecitine and doxribtimine—as the first-ever treatment for Thymidine Kinase 2 Deficiency (TK2d), a devastating ultra-rare mitochondrial disorder. The approval, announced on November 3, marks a transformative milestone for both children and adults with symptom onset up to age 12.

Until now, no approved medication existed for TK2d, leaving patients and families reliant solely on supportive care. KYGEVVI is expected to alter the disease trajectory, offering longer survival and improved muscle function to those once faced with grim prognoses.

What is TK2 Deficiency?

Thymidine Kinase 2 Deficiency (TK2d) is a genetic mitochondrial disorder caused by mutations in the TK2 gene, impairing the body’s ability to repair and replicate mitochondrial DNA (mtDNA)—the energy-producing component of cells. The condition leads to severe muscle weakness, respiratory difficulties, and often fatal respiratory failure, typically in infancy or early childhood.

With only around 120 cases reported worldwide, TK2d is classified as ultra-rare, occurring in roughly 1.64 per million people. Due to its rarity and overlapping symptoms with other neuromuscular diseases, diagnosis often takes years and requires genetic testing or muscle biopsy.

A Milestone Approval

The FDA’s approval of KYGEVVI represents a first-in-class therapy that targets the root cause of mitochondrial dysfunction. The treatment works by supplying nucleosides deoxycytidine and deoxythymidine, bypassing the enzyme deficiency to restore mtDNA levels and improve mitochondrial energy production.

In clinical trials involving 82 patients, KYGEVVI demonstrated remarkable outcomes:

• 86% reduction in overall mortality risk compared to untreated patients.

• 75% of children regained at least one lost motor skill.

• Several patients were able to reduce or stop ventilatory support.

Common side effects included gastrointestinal discomfort and elevated liver enzymes, prompting recommendations for liver monitoring before and during treatment.

Hope for Patients and Families

For families battling TK2 deficiency, the approval is nothing short of life-changing. Many children with early-onset disease had a life expectancy of just one to three years, but now, treatment offers a chance for meaningful recovery and prolonged life.

Experts say this success could pave the way for further advancements in mitochondrial medicine, emphasizing a shift from managing symptoms to treating the biochemical cause.

Moreover, the approval highlights the urgent need for early diagnosis—as studies show patients who start treatment earlier tend to have better outcomes.

What’s Next

KYGEVVI is expected to become commercially available in the United States by early 2026, with regulatory reviews ongoing in Europe and other regions.

The approval not only brings new hope to TK2d patients but also symbolizes a major step forward in the global fight against mitochondrial diseases, setting a new precedent for precision therapies targeting genetic and metabolic disorders.