Kygevvi®, the treatment developed by UCB for thymidine kinase 2 deficiency (TK2d), has just received a positive opinion from the European Medicines Agency (EMA) toward obtaining marketing authorization.
On January 30, 2026, the European Medicines Agency (EMA) issued a favorable opinion for the marketing authorization (MA) of Kygevvi® for patients suffering from thymidine kinase 2 deficiency (TK2d) whose first symptoms appeared at or before the age of twelve. As a reminder, this combination of doxecitine and doxribtimine, developed by UCB, was approved by the FDA last November.
A MA under exceptional circumstances
The EMA’s positive opinion is based on preclinical studies and results from a Phase 2 clinical trial involving 39 patients, which suggest an improvement in motor function following treatment with Kygevvi®. However, given the rarity of TK2d, the laboratory cannot provide exhaustive data on the safety and efficacy of the treatment under normal conditions of use. Consequently, the EMA recommends that the MA be granted under “exceptional circumstances,” involving “specific obligations that will be reviewed annually.” In this spirit, the agency is also requiring UCB to conduct a new study to further confirm the efficacy and safety of Kygevvi®.
An excellent news for the European patients!
It now remains for the European Commission to vote on the MA; subsequently, it will be up to each individual state to establish pricing and reimbursement levels. The journey to ensure European patients have access to the treatment is therefore not yet over. However, a major milestone has been reached, and “this is excellent news!” says Vincent Proccacio, professor of genetics and head of the NeuroMitOmics (NeMO) research axis at Angers University Hospital. Finally, while awaiting this MA, the expanded access program for Kygevvi® continues, notably in France.
Thymidine kinase 2, a key enzyme
The TK2 gene, located in the nuclear DNA, codes an enzyme called thymidine kinase 2, which is essential for mitochondrial function. It is involved in the “repair” and synthesis of mitochondrial DNA. When the enzymatic activity of thymidine kinase 2 is insufficient, mitochondria accumulate mitochondrial DNA damages, leading to dysfunction in high-energy-demand tissues, particularly muscles, resulting in muscle impairment affecting motor and respiratory functions, characteristic of TK2 deficiency.