Characterization of the Population Pharmacokinetics of Moxidectin in Adults Infected with Strongyloides Stercoralis: Support for a Fixed-Dose Treatment Regimen

Background Moxidectin has recently attracted attention as a novel candidate for the treatment of helminth infections, including Strongyloides stercoralis. This study aims to characterize the population pharmacokinetics (PPK) of moxidectin in S. stercoralis-infected adults using a pharmacometric approach, and to perform model-based simulations to explore different drug dosing strategies. Methods A PPK study embedded in a dose-escalation phase IIa trial was conducted in NamBak, Laos. Eight micro blood samples were collected from each of 96 S. stercoralis-infected adults following a moxidectin dose-ranging study, from 2 to 12 mg. A PPK model was developed using nonlinear mixed-effects modeling, and dosing strategies were explored using simulations in S. stercoralis-infected subjects with varying age and body weight (n = 5000 per dosing strategy). Results A two-compartment model including delayed absorption with lag-time best described the available PK data. Allometric scaling was applied to account for the influence of body weight. High clearance was found in the infected adults (4.47 L/h [95% confidence interval 3.63-5.39] for a 70 kg individual) compared with that previously reported for healthy adults. Model-based simulations indicated similar variability in mean +/- standard deviation area under the curve from time zero to infinity of 1907 +/- 1552 and 2175 +/- 1670 ng x h/mL in the 60-70 kg weight group, after 8 mg fixed- or weight-based dosing, respectively. Conclusion We describe the first PPK model for moxidectin in adults with S. stercoralis infection. Equivalent exposures after fixed-dose and weight-dependent dosing strategies support the use of a simple fixed-dose approach, particularly in large-scale treatment programs.

Automated summary

Moxidectin population pharmacokinetics in S. stercoralis-infected adults was characterized using a pharmacometric approach, with simulations indicating similar exposure levels after fixed-dose and weight-based dosing strategies.