The European Commission has approved doxecitine and doxribtimine (sold as Kygevvi) as the first and only treatment for people in the European Union with thymidine kinase 2 deficiency (TK2d), according to a press release published recently by the maker of doxecitine and doxribtimine, UCB.
“For the first time, people across Europe living with this ultra-rare, life-threatening mitochondrial disease have access to an approved treatment beyond supportive care,” said Donatello Crocetta, chief medical officer at UCB.
This approval marks a major shift from supportive care alone to a disease-targeting therapy. The decision applies to children and adults with genetically confirmed TK2d whose symptoms began at or before age 12.
Read more about therapies for TK2d
Doxecitine and doxribtimine works by helping restore mitochondrial DNA in muscle cells, targeting an underlying cause of the disease rather than just managing symptoms. The treatment was previously approved by the Food and Drug Administration (FDA) for patients in the U.S. in November 2025.
The European Commission’s approval was based on pooled data from two studies involving 39 patients with symptom onset at or before age 12. Across these studies, patients experienced meaningful improvements in function and daily living.
Motor function improved in many participants. After starting treatment, 26 of 31 patients (84%) regained at least one developmental motor milestone, such as sitting upright or holding their head up without assistance. This suggests the therapy may help restore abilities that were previously lost.
Feeding support needs also improved, with fewer patients requiring feeding tubes after treatment initiation and some able to discontinue use.
For patients and families, this approval introduces a long-awaited option that may improve strength, reduce dependence on medical devices and potentially extend survival. While the approval was granted under exceptional circumstances due to the rarity of the disease, it represents a meaningful step forward and offers new hope to a community with significant unmet need.
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