US EditionUltra-Rare Mitochondrial Disease Gets First FDA-Approved Drug
Kygevvi is the first FDA-approved therapy for TK2 deficiency, improving survival with a 4% mortality rate versus 36% in untreated patients, based on clinical data.
- On Nov. 3, 2025, the U.S. Food and Drug Administration approved KYGEVVI for thymidine kinase 2 deficiency in patients with symptom onset on or before 12 years, and UCB said it is the first and only FDA-approved treatment for TK2d.
- TK2d is an ultra‑rare, life‑threatening mitochondrial disease affecting about 120 patients, with prevalence estimated at less than two per million, typically beginning in childhood.
- A survival analysis of 78 matched pairs showed three deaths in treated patients versus 28 in controls, supporting approval with data from one Phase 2 study, two retrospective reviews, and an expanded access program.
- UCB expects KYGEVVI to be commercially available in the U.S. in Q1, 2026, and the label warns of elevated liver transaminases and gastrointestinal adverse reactions.
- FDA designations granted to KYGEVVI also earned UCB a Rare Pediatric Disease Priority Review Voucher, and after 10 years treated patients' survival was 9.6 years versus 5.7 years for controls.
43 Articles
43 Articles
Globe Newswire
FDA Approves KYGEVVI® (doxecitine and doxribtimine), the First and Only Treatment for Adults and Children Living with Thymidine Kinase 2 deficiency (TK2d), a Rare and Devastating Mitochondrial Disease
This novel therapy offers the first FDA-approved option to address the root cause of this ultra-rare condition, which causes progressive muscle weakness...
LoudounTimes.com
U.S. FDA approves KYGEVVI® (doxecitine and doxribtimine), the first and only treatment for adults and children living with thymidine kinase 2 deficiency (TK2d)
Approved indication: KYGEVVI® (doxecitine and doxribtimine) powder for oral solution (2g/2g) is approved for the treatment of thymidine kinase 2 deficiency (TK2d) in adults and pediatric patients with an age of symptom onset on or before 12 years.1Survival benefit: Treatment…
Ultra-Rare Mitochondrial Disease Gets First FDA-Approved Drug
(MedPage Today) -- The FDA approved doxecitine and doxribtimine powder (Kygevvi) for thymidine kinase 2 deficiency (TK2d), an ultra-rare mitochondrial depletion syndrome, the agency announced on Monday. A pair of pyrimidine nucleosides, the doxecitine...
FDA Approves Doxecitine and Doxribtimine Combination Therapy as First Treatment for Thymidine Kinase 2 Deficiency | NeurologyLive - Clinical Neurology News and Neurology Expert Insights
UCB's Kygevvi becomes the first FDA-approved treatment for thymidine kinase 2 deficiency, offering hope to patients with this rare neuromuscular disorder.
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