Population pharmacokinetics of remlifanserin (ACP-204), a serotonin 2A receptor inverse agonist

Remlifanserin, or ACP-204, is a potent serotonin 2A receptor inverse agonist under investigation for treatment of Alzheimer's disease psychosis and Lewy body dementia psychosis. A population pharmacokinetics (popPK) model for remlifanserin was developed to evaluate the impact of covariates affecting pharmacokinetic variability and assess the clinical relevance of these factors in a virtual population.

A popPK model was developed using remlifanserin plasma concentrations (n = 3935) from 209 participants across seven Phase 1 trials (10 to 180 mg, oral). Data were pooled and analyzed using non-linear mixed-effects modeling. Intrinsic (demographics, hepatic/renal function) and extrinsic (food effect) factors were assessed. Model evaluation included goodness-of-fit plots and prediction-corrected visual predictive checks (pcVPCs). Interindividual variability was estimated for key parameters; residual variability was modeled using proportional error. Simulated steady-state exposures (maximum plasma concentration at steady state [C_max,ss] and area under the plasma concentration-time curve over the 24-h dosing interval at steady state [AUC_0-24,ss]) in a virtual population (n = 1000; 60 mg/day) were derived using PK parameters sampled from the final model. The clinical relevance of significant covariates was evaluated using geometric mean ratios and 90% confidence intervals (CIs) of exposures using a 0.8 to 1.25 boundary presented in a forest plot.

The final popPK model was a one-compartment model with first-order absorption with lag time and linear elimination. Typical parameter estimates included apparent oral clearance (35.4 L/h), apparentoral volume of distribution (V/F) (male, 930 L; female, 799 L), absorption lag time (ALAG1) (fasted, 0.720 h; fed, 0.929 h)and absorption rate constant (K_a) (0.692/h). Goodness-of-fit plots and pcVPCs demonstrated that the model adequately captured the central tendency and magnitude of variability in remlifanserin concentrations. Statistically significant relationships were found between food and ALAG1 and between sex and V/F (P < 0.001); however, neither factor had a clinically relevant impact on C_max,ss or AUC_0-24,ss.

The pharmacokinetics of oral remlifanserin (10 to 180 mg) are well described by dose-proportional linear kinetics. No intrinsic or extrinsic factors exhibited a clinically relevant effect on steady-state remlifanserin exposures.