Pharmacokinetics of cenobamate as monotherapy compared with adjunctive therapy

Cenobamate was approved by the US Food and Drug Administration (FDA) based on studies of adjunctive therapy in patients with focal epilepsy. To support the use of cenobamate monotherapy, this pharmacokinetic (PK)-based simulation analysis evaluated the predicted PK exposure of cenobamate when used as monotherapy versus adjunctive therapy.

A population pharmacokinetic (PopPK) model of cenobamate was developed using pooled human data from eight phase 1 studies in healthy subjects or special populations, and three phase 2 and 3 studies in patients with focal seizures (N = 960). Concomitant antiseizure medications (ASMs) with a statistically significant effect on the apparent systemic clearance (CL/F) of cenobamate in the PopPK model were used to compare simulated patient plasma exposures (area under the plasma concentration vs time curve [AUC]) following monotherapy versus adjunctive therapy. Treatment equivalence between monotherapy and adjunctive therapy was concluded if the 90% confidence interval (CI) of the geometric mean AUC ratio was within 0.8-1.25.

In the PopPK model, statistically significant effects on cenobamate CL/F were shown for clobazam (decreased cenobamate CL/F by 19%) and carbamazepine (increased cenobamate CL/F by 15%); these differences were not considered clinically meaningful. Other ASMs (lacosamide, lamotrigine, levetiracetam, oxcarbazepine, topiramate, and valproate) when coadministered with cenobamate did not have significant effects on the disposition (ie, PK or efficacy) of cenobamate. The geometric mean ratio (90% CIs) of cenobamate AUC for adjunctive therapy/monotherapy was 0.87 (0.816-0.925) for adjunctive carbamazepine and 1.24 (1.147-1.339) for adjunctive clobazam. The 90% CI was within the no-effect limits (90% CIs 0.8-1.25) for adjunctive carbamazepine and partially exceeding no-effect limits for adjunctive clobazam.

Based on the results from this PopPK analysis, cenobamate monotherapy can be expected to result in comparable exposures to those that have been demonstrated to be safe and effective when used as adjunctive therapy for the treatment of focal seizures, supporting the use of cenobamate as monotherapy in these patients.