Everolimus dosing recommendations for tuberous sclerosis complex–associated refractory seizures

Objective: The present analysis examined the exposure-response relationship by means of the predose everolimus concentration (C_min) and the seizure response in patients with tuberous sclerosis complex–associated seizures in the EXIST-3 study. Recommendations have been made for the target C_min range of everolimus for therapeutic drug monitoring (TDM) and the doses necessary to achieve this target C_min. Methods: A model-based approach was used to predict patients' daily C_min. Time-normalized C_min (TN-C_min) was calculated as the average predicted C_min in a time interval. TN-C_min was used to link exposure to efficacy and safety end points via model-based approaches. A conditional logistic regression stratified by age subgroup was used to estimate the probability of response in relation to exposure. A multiplicative linear regression model was used to estimate the exposure-response relationship for seizure frequency (SF). An extended Cox regression model was used to link exposure to the time to first adverse event. Results: There was a strong, consistent, and highly significant relationship between everolimus exposure and efficacy, measured by TN-C_min and SF, regardless of patient's age and concomitant use of cytochrome P450 3A4 (CYP3A4) inhibitors/inducers. Results of an extended Cox regression analyses indicated that twofold increases in TN-C_min were not associated with statistically significant increases in the risk of stomatitis or infections. Significance: The recommended TDM is to target everolimus C_min within a range of 5-7 ng/mL initially and 5-15 ng/mL in the event of an inadequate clinical response, and safety is consistent with previous reports. Starting doses depend on age and the concomitant use of CYP3A4/P-glycoprotein inducers/inhibitors.