The EMA has recommended that Kygevvi (doxecitin and doxribtimine) be given marketing authorization in the European Union for patients with genetically confirmed thymidine kinase 2 deficiency (TK2d).[1][2] The drug is intended for adults and pediatric patients with onset of symptoms up to 12 years of age.[1][2] It is the first and only approved treatment for this condition.[1][2] US approval is supported by data from one phase 2 study (NCT03845712), two retrospective record review studies (NCT03701568 and NCT05017818), and an expanded access program (NCT06590493).[1][2] These studies included a total of 82 unique patients with TK2d and symptom onset within 12 years.[2] The treatment reduced the overall risk of death from baseline by approximately 86 percent.[2] The most common side effects (incidence ≥5%) are diarrhea, abdominal pain, vomiting, elevated alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels.[2] The drug will be available in the US in the first quarter of 2026.[1]