EMA grants positive CHMP opinion for Kygevvi® for Treatment of TK2d
International Mito Patients (IMP) and the global mitochondrial disease community are celebrating an important regulatory milestone in Europe: the European Medicines Agency’s (EMA) Committee for Medicinal Products for Human Use (CHMP) has adopted a positive opinion recommending the granting of marketing authorisation under exceptional circumstances for KYGEVVI® (doxecitine and doxribtimine) for the treatment of Thymidine Kinase 2 Deficiency (TK2d) in paediatric and adult patients whose symptoms began on or before age 12.
This positive CHMP opinion represents a critical step toward European Union approval of the first potential treatment for TK2d — an ultra-rare, life-threatening genetic mitochondrial disease that has historically had no authorised disease-modifying therapies in Europe. The recommendation now moves to the European Commission, which will make the final decision on EU-wide marketing authorisation.
Transformative Progress for the TK2d Community
“Today’s positive CHMP opinion represents a momentous advance for people and families affected by TK2d across Europe,” said Paula Morandi, Chair of International Mito Patients. “For a community that has long faced a devastating disease with only supportive care options, this milestone brings renewed hope. We honour the patients, caregivers, clinicians, researchers, and advocates whose voices and experiences helped make this progress possible.”
TK2d is an ultra-rare mitochondrial DNA depletion syndrome that causes progressive muscle weakness, loss of motor function, respiratory complications, and shortened life expectancy, often beginning in early childhood. Until now, treatment options in Europe have been limited to supportive and palliative care.
About the Treatment
KYGEVVI® (doxecitine and doxribtimine), developed and manufactured by UCB, is a fixed-dose combination of pyrimidine nucleosides designed to address the underlying biochemical defect in TK2d by supporting mitochondrial DNA maintenance and function. The CHMP’s recommendation is based on clinical evidence indicating that the therapy may improve motor function and help slow disease progression in eligible patients.
Authorisation under exceptional circumstances reflects the reality of ultra-rare diseases like TK2d, where generating comprehensive datasets can be challenging. This pathway includes specific post-authorisation obligations to continue monitoring safety and effectiveness.
“We now look forward to the European Commission’s final decision,” Paula added. “As we move closer to potential approval, collaboration between regulators, healthcare systems, and patient communities will be essential to ensure timely and equitable access once authorised.”
A Global Perspective on Treatment Innovation
This European regulatory milestone follows the U.S. Food and Drug Administration (FDA) approval of KYGEVVI® in 2025 — the first authorised treatment for TK2d in the United States. Together, these decisions reflect growing global momentum in developing therapies for rare mitochondrial diseases and demonstrate the power of scientific innovation combined with strong patient advocacy.
IMP remains committed to supporting regulatory engagement, community education, and improved care pathways for people living with mitochondrial diseases worldwide.
Acknowledgements
IMP extends sincere gratitude to:
- Patients and families who participated in clinical research and shared their lived experiences
- Clinicians and researchers dedicated to advancing understanding of TK2d
- UCB, the company responsible for the development of KYGEVVI®, and its partners for their long-term scientific commitment to rare disease innovation
- Patient advocacy organisations and clinical networks working to improve awareness, diagnosis, and access
About Thymidine Kinase 2 Deficiency (TK2d)
Thymidine Kinase 2 Deficiency is a rare, inherited mitochondrial DNA depletion syndrome characterised by severe and progressive muscle weakness and associated complications. It is estimated to affect fewer than one in a million people worldwide and has historically lacked disease-modifying treatment options.
