Supporting the recommended paediatric dosing regimen for rufinamide in Lennox-Gastaut syndrome using clinical trial simulation

Rufinamide was approved for the treatment of seizures associated with Lennox-Gastaut syndrome (LGS) as adjunctive therapy in patients aged 4 years and older. Rufinamide pharmacokinetics (PK) has been established on pooled data from several clinical studies in epilepsy, including one in LGS patients. Demographic covariates and drug-drug interactions with several antiepileptic drugs have been explored using population PK modelling. Two types of drug-drug interactions models were developed and compared. The PK analysis demonstrated that the co-administration of valproate decreases rufinamide clearance, requiring potential dose adjustment. To explore rufinamide exposure under different dosing regimens in LGS patients, clinical trial simulations were performed. The objective of the simulations was to select the doses giving an exposure shown to be safe and efficacious in larger populations. The concentrations simulated in a subgroup of patients with body weight less than 30 kg presented a larger inter-individual variability than in other patients. Additional simulations demonstrated that this increased variability was due partly to greater valproate concentrations in some of the children treated with rufinamide. Simulations of the rufinamide exposure under different maximum daily dose in presence and in absence of valproate co-administration were used to establish the dosing recommendation. The simulations support the proposal of a lower maximum daily rufinamide dose for patients under 30 kg receiving both drugs: the dose of 600 mg/day was proposed as a maximum daily dose in children also receiving valproate concomitantly, whereas in absence of valproate, the maximum daily dose is 1000 mg/day.