Intolerance to quinidine in a n-of-1 trial for KCNT1 associated epilepsy of infancy with migrating focal seizures.

Quinidine has been proposed as a repurposed licensed drug for the treatment of seizures in KCNT1 gain-of-function associated Epilepsy of Infancy with Migrating Focal Seizures (EIMFS). Sparse evidence from case reports suggests limited effectiveness and tolerability. Here we report the adaptation of a n-of-1 trial protocol and results of adjunctive quinidine intervention. We adapted a n-of-1 trial protocol from two unpublished protocols and with expert advice including input from pediatric neurology, cardiology and pharmacy colleagues. We tailored this protocol to a severely disabled patient with EIMFS and a de novo c.1420C>T p.Arg474Lys missense variant. We discussed outcome measures with the family of the patient and initiated adjunctive inpatient quinidine treatment with appropriate safety measures. The trial was terminated as a result of intolerable gastrointestinal adverse effects following the initiation dose. Subsequent reports suggest that quinidine may not be effective for this genotype. Quinidine is poorly tolerated across cardiological and neurological indications. Current pooled evidence suggests limited effectiveness for KCNT1 associated epilepsies at doses ≤40mg/kg/d. It is important to report all clinical evidence in precision medicine trials, whether positive or negative, to counter publication bias. This study highlights universal issues around outcome measurement and the evaluation of evidence in rare disease interventions.