Kygevvi (doxecitine + doxribtimine) authorised for thymidine kinase 2 deficiency

Sponsor: UCB Pharma Limited $UCB
Drug: Kygevvi · doxecitine and doxribtimine
Indication: Thymidine kinase 2 deficiency (TK2d) with age of symptom onset on or before 12 years — paediatric and adult

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MHRA authorised UCB's Kygevvi (doxecitine + doxribtimine) as the first treatment for paediatric and adult patients with thymidine kinase 2 deficiency (TK2d) with age of symptom onset on or before 12 years. TK2d is an ultra-rare mitochondrial disease that impairs the maintenance of mitochondrial DNA in muscle and produces progressive skeletal muscle weakness — historically with no approved disease-modifying therapy.

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From the source

Doxecitine and Doxribtimine in the treatment of paediatric and adult patients with thymidine kinase 2 deficiency (TK2d) with an age of symptom onset on or before 12 years.

From: Medicines and Healthcare products Regulatory Agency Published: 7 July 2026

The Medicines and Healthcare products Regulatory Agency (MHRA) has today granted a marketing authorisation for Kygevvi (doxecitine and doxribtimine) for the treatment of paediatric and adult patients with thymidine kinase 2 deficiency (TK2d) with an age of symptom onset on or before 12 years.

Reproduced from MHRA News · view original · public domain or open-licensed government work

Background Drug-class context · Wikipedia

Thymidine kinase 2 deficiency (TK2d) is a rare, autosomal-recessive mitochondrial DNA depletion / multiple deletion syndrome caused by pathogenic variants in the TK2 gene. TK2 is a mitochondrial-matrix kinase essential for the salvage synthesis of deoxyribonucleoside triphosphates required to replicate mitochondrial DNA (mtDNA) in post-mitotic tissues, particularly skeletal muscle. Loss of TK2 activity depletes mtDNA in muscle, producing progressive myopathy, respiratory failure, and — in early-onset forms — death in early childhood. TK2d has historically had no approved disease-modifying therapy; treatment was limited to supportive care. Kygevvi is a fixed-combination nucleoside substrate replacement therapy: doxecitine (dC, deoxycytidine) and doxribtimine (dT, deoxythymidine) bypass the deficient TK2 enzyme by providing the downstream nucleoside pools directly, restoring mtDNA replication capacity. The active substances were originally developed by Modis Therapeutics as MT1621, subsequently acquired by Zogenix, and now under UCB following UCB's acquisition of Zogenix in 2022. The European Commission granted marketing authorisation for Kygevvi following a positive CHMP opinion at the January 2026 plenary; the MHRA's July 7, 2026 authorisation extends approval into the UK market.

Source: Wikipedia · CC BY-SA

Topic mitochondrial disease

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