UCB Secures FDA Approval for First Ever TK2 Deficiency (TK2d) Therapy
UCB has gained approval from the U.S. Food and Drug Administration for KYGEVVI™ (doxecitine and doxribtimine) to treat thymidine kinase 2 deficiency (TK2d) in adults and children whose symptoms began at age 12 or younger.
It is the first authorised therapy for this rare mitochondrial disease, which causes progressive muscle weakness and has previously only been managed with supportive care.
TK2d is life-threatening, especially when symptoms appear early in childhood. Many patients face a high risk of death within a few years of onset.
The condition is extremely rare, with a global prevalence estimated at fewer than two cases per million people.
The decision is supported by data from a Phase 2 study, two retrospective chart reviews, and an expanded access programme including 82 treated patients.
When compared with matched untreated patients, KYGEVVI showed a substantial improvement in survival, reducing the risk of death by about 86%. Treatment durations ranged up to 12 years.
Common side effects include diarrhoea, abdominal pain, vomiting, and increased liver enzymes. Patients will require monitoring, and dose adjustments may be needed.
Regulatory review is ongoing in Europe. UCB expects KYGEVVI to be available in the U.S. in early 2026, along with patient support services.
