Mitochondrial DNA A3243G variant-associated MELAS: Recent advances in clinical trials, therapeutic interventions, and...

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome, most often caused by the m.3243A>G mitochondrial DNA variant, represents one of the most clinically significant inherited mitochondrial disorders. This variant disrupts mitochondrial tRNALeu(UUR) function, leading to impaired mitochondrial protein synthesis and progressive multisystem dysfunction. This narrative review synthesizes recent clinical trials, therapeutic advances, and emerging disease-modifying strategies for m.3243A>G-associated MELAS, with emphasis on evidence published between 2024 and 2026, drawing on PubMed/MEDLINE, Embase, the Cochrane Library, ClinicalTrials.gov, and the EU Clinical Trials Register. Key advances include: i) regulatory approval of high-dose taurine supplementation (9-12 g/day), which achieved complete prevention of stroke-like episodes in 60% of participants in a phase III trial; ii) phase IIb data (company-reported) indicating that sonlicromanol (KH176) showed signals of improvement in cognition, mood, and fatigue, supporting progression to a phase III registrational trial (KHENERFIN, NCT06451757); iii) ongoing trials of zagociguat and TTI-0102 targeting vascular dysfunction and oxidative stress; iv) KL1333, a novel NAD+ modulator, in phase II evaluation (FALCON trial); and v) promising preclinical gene-based approaches-including mitochondria-targeted TALENs, DdCBE base editors, and mitoARCUS nucleases-demonstrating heteroplasmy shifting in patient-derived cells and animal models, though direct clinical applicability to m.3243A>G MELAS requires further investigation. The therapeutic landscape for MELAS is evolving from symptomatic care toward mechanism-based disease modification, led by taurine as the first regulatory-approved disease-modifying therapy and complemented by late-stage small molecules and mitochondrial genome-editing technologies.