Model-based simulation to support the extended dosing regimens of atezolizumab.

PURPOSE: The currently recommended dosages of atezolizumab for patients with non-small cell lung cancer (NSCLC) and urothelial carcinoma (UC) is 840 mg every 2 weeks, 1200 mg every 3 weeks (q3w), and 1680 mg every 4 weeks (q4w). However, it has been argued that these dosages may not be optimal. This study aimed to explore the feasibility of extended dosing regimens by population pharmacokinetics (PK) simulations and exposure-response (E-R) relationships. METHODS: All simulations were conducted based on the established population PK and E-R model for safety (i.e., adverse events of special interest, AESI) and efficacy (i.e., objective response rate, ORR) for patients with NSCLC or UC. The PK, AESI, and ORR profiles of the following dosing regimens were simulated: (i) 840 mg q4w, (ii) 1200 mg every 6 weeks (q6w), and (iii) 1680 mg q8w. These regimens were compared with those of the 1200 mg q3w standard regimen. RESULTS: The simulation revealed that the ranking of efficacy for different extended dosing regimens were 1680 mg q8w ≅ 1200 mg q3w ≅ 1200 mg q6w > 840 mg q4w based on the predicted probability of ORR in patients with NSCLC and UC, and this ranking order was similar to that of the safety outcome of the AESI. The minimum serum concentration at steady-state (Cmin,ss) values for all dosing regimens was all higher than the target effective concentration of 6 µg/mL. CONCLUSION: The findings from this simulation suggest that extended dosing regimens are unlikely to significantly impair clinical outcomes and may provide more therapeutic benefits to patients in terms of safety.

Investigation of the Discriminatory Ability of Pharmacokinetic Metrics for the Bioequivalence Assessment of PEGylated Liposomal Doxorubicin.

PURPOSE: The purpose of the study was to construct a population pharmacokinetic model for pegylated liposomal doxorubicin and use the final model to investigate the discrimination performance of pharmacokinetic metrics (e.g., Cmax, AUC and partial AUC) of various analytes (e.g., liposome encapsulated doxorubicin, free doxorubicin and total doxorubicin) for the identification of formulation differences by means of Monte Carlo simulations. METHODS: A model was simultaneously built to characterize the concentration time profiles of liposome-encapsulated doxorubicin and free doxorubicin using NONMEM. The different scenarios associated with changes in release rate (Rel) were simulated based on the final parameters. 500 simulated virtual bioequivalence (BE) studies were performed for each scenario, and power curves for the probability of declaring BE were also computed. RESULTS: The concentration time profiles of liposome-encapsulated doxorubicin and free doxorubicin were well described by a one- and two-compartment model, respectively. pAUC0-24 h and pAUC0-48 h of free doxorubicin was most responsive to changes in the Rel when the Rel (test)/Rel (reference) ratios decreased. In contrast, when the Rel (test) increased, AUC0-t of liposome-encapsulated doxorubicin was the most responsive metric. CONCLUSIONS: In addition to the traditional metrics, partial AUC should be included for the BE assessment of pegylated liposomal doxorubicin.

Pharmacokinetics of vancomycin in adults receiving extracorporeal membrane oxygenation.

BACKGROUND/PURPOSE: Extracorporeal membrane oxygenation (ECMO) alters the pharmacokinetics (PK) of vancomycin in neonates; but data on adults is limited. METHODS: This is a prospective, matched cohort, single center, pharmacokinetic study. For each adult patient who received vancomycin therapy in the ECMO group (with either centrifugal pump or roller pump), a control patient was matched by age (≥ 60 years or < 60 years), gender, and creatinine clearance (CLCr) in intensive care units. After vancomycin was administered for at least four doses, serial blood samples were drawn at 0.5 hours, 1 hour, 2 hours, 3 hours, 5 hours, 7 hours, 11 hours, 23 hours, 35 hours, and 47 hours post vancomycin infusion according to the dosing intervals. The serum concentration-time profile was fitted to a noncompartment model and a nonlinear mixed effect model to determine the PK parameters. RESULTS: Twenty-two critically ill adults without renal replacement therapy were enrolled. There were no significant differences between the ECMO group and the matched group in demographics, renal function, and PK parameters. However, vancomycin clearance in the roller pump group was significantly lower than that in the matched control (0.83 ± 0.43 mL/min/kg vs. 0.97 ± 0.43 mL/min/kg, p = 0.002). CONCLUSION: Vancomycin clearance in patients receiving ECMO with a roller pump was significantly lower than that in the matched cohort. Vancomycin PK parameters in patients on ECMO with a centrifugal pump were comparable to those in the matched control group.

Evaluation of etanercept dose reduction in patients with rheumatoid arthritis using pharmacokinetic/pharmacodynamic modeling and simulation.

OBJECTIVES: In this study, we attempt to explore the feasibility of alternative dosing regimens of etanercept in patients with rheumatoid arthritis (RA) using pharmacokinetic/pharmacodynamic (PK/PD) modeling and simulation. METHODS: All data used for estimation of PK/PD model parameters were collected from previously published literatures. American College of Rheumatology (ACR) 20/50/70 response rate and a disease activity score in 28 joints (DAS28) was selected as the principal clinical endpoint for further PK/PD modeling. The cumulative AUC (area under the concentration-time curve) of etanercept for different dosing regimens was calculated based on the final PK model and was then linked to the time course of clinical endpoints. Ten different dosing regimens were simulated in this study. RESULTS: The PK model that best fit the serum concentration-time data for etanercept was a one-compartment model with first order absorption and elimination. Based on the PK/PD analysis, the relationship between the predicted cumulative AUC of etanercept to the ACR 20/50/70 response rate and DAS28 score was well characterized by Emax logistic and inhibitory Emax model, respectively. In our simulations, the following dosing regimens that are equally effective to current recommended dosage of 25 mg twice weekly (b.i.w.): (1) 25 mg once weekly (q.w.); (2) 50 mg every 2 weeks (q2w); (3) 25 mg b.i.w. for 3 months and 25 mg q2w thereafter; and (4) 50 mg q.w. for 3 months and 50 mg q2w thereafter. CONCLUSION: In this study, the clinical data was well described by the models developed, and several alternative dosing regimens were proposed. Further clinical studies in patients are still needed to confirm our findings.