ABSTRACT
AIMS: The aims of this study were to develop a population pharmacokinetic (PK) model for risperidone ISM® and to investigate the relationships between active moiety exposure, as described by apparent clearance (CL40), and several covariates using all data from five clinical studies. METHODS: A population PK model was developed using active moiety concentrations from a study in healthy volunteers and two studies in patients with schizophrenia. Data from a comparative bioavailability study in medically stable patients and a Phase III study in patients with acute exacerbation of schizophrenia were then incorporated, using empirical Bayesian feedback and model refinement in NONMEM. Finally, covariate analysis was performed on CL40. RESULTS: The final model adequately described the pharmacokinetics of 6288 active moiety concentrations in 17 healthy volunteers and 430 patients with schizophrenia. This one-compartment disposition model had a complex absorption process, combining a small amount immediately entering the central active moiety compartment, two first-order absorption processes and a combined zero-order and first order process, with first-order elimination from the central compartment. Significant covariates on CL40 were BMI and sex. Goodness-of-fit (GOF) plots and visual predictive checks (VPC) confirmed acceptable description of the data. CONCLUSIONS: The population PK model adequately described active moiety concentrations from five clinical studies after risperidone ISM® administration. Relationships between active moiety exposure and covariates were defined in order to facilitate simulations for future studies. The model showed that risperidone ISM® rapidly achieves therapeutic plasma levels within the first hours after the first injection that are maintained sustainedly throughout the whole dosing interval following once-monthly gluteal injections of 100 mg and 75 mg.
ABSTRACT
PURPOSE: To demonstrate the pharmacokinetic/pharmacodynamic (PK/PD) equivalence of a biosimilar enoxaparin to the reference drug, and to assess its safety and tolerability in healthy volunteers. PATIENTS AND METHODS: A randomized, double-blind, crossover, 2-sequence, single-dose study was conducted in healthy volunteers of both sexes. Participants were sequentially and randomly administered single subcutaneous injections of enoxaparin 100 mg manufactured by Rovi (test; Madrid, Spain) and Clexane® (enoxaparin 100 mg manufactured by Sanofi, reference) separated by a 1-week washout period. The primary PK/PD variables were maximum activity (Amax) and area under the effect curve from time 0 to the last measured activity (T) (AUEC0-T) and AUEC from time 0 to infinity (AUEC0-inf) of anti-FXa activity, and Amax and AUEC0-T of anti-FIIa activity. Secondary variables were Amax and AUEC0-T, AUEC0-inf of tissue factor pathway inhibitor, and the ratio of AUEC0-T anti-FXa to anti-FIIa activity. Biosimilarity would be shown when the 95% CI of the ratio of geometric least squares means (95% CI RGLSMs) of primary PK/PD parameters fell within the standard range of bioequivalence, ie, 80%-125%. RESULTS: The study sample consisted of 46 volunteers (33 males) aged 18-44 years and with body mass index ranging from 19.0 to 31.1 kg/m2. Three subjects did not complete the study. The curves of anti-FXa, anti-FIIa and tissue factor pathway inhibitor activities corresponding to administration of the test and reference products were comparable. The 95% CI RGLSMs of Amax, AUEC0-T and AUEC0-inf for anti-FXa activity were 94.6%-105.9%, 99.8%-108.0% and 100.0%-108.6% respectively; Amax and AUEC0-T for anti-FIIa activity were 94.7%-112.6% and 90.9%-117.9% respectively. In addition, the 95% CI RGLSMs of all secondary variables fell within the range 80%-125%. The incidence and types of adverse events after administration of the test and reference drugs were similar. CONCLUSION: The results conclusively showed that the enoxaparin manufactured by Rovi is equivalent to the reference enoxaparin in all primary and secondary PK/PD parameters, as required by the European Medicines Agency to grant marketing authorization to a biosimilar low molecular-weight heparin.
