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1.  Population pharmacokinetic/ pharmacodynamic modelling of eltrombopag in healthy volunteers and subjects with chronic liver disease 
Aims
To characterize the pharmacokinetics (PK)/pharmacodynamics (PD) of eltrombopag in chronic liver disease (CLD).
Methods
The PK/PD model was developed using data from 79 CLD patients using nonlinear mixed-effects modelling.
Results
The PK of eltrombopag were described by a two-compartment model with dual sequential first-order absorption. Gender, race and severity of CLD were predictors of the apparent clearance of eltrombopag. The PD of eltrombopag in CLD were adequately described by a four-compartment lifespan model, in which eltrombopag stimulated platelet precursor production rate. East Asian CLD patients were less sensitive to the stimulatory effect of eltrombopag. Following a daily dose regimen of 50 mg eltrombopag, the time to achieve peak platelet counts was longer for the CLD population compared with patients who had immune thrombocytopenic purpura, but was comparable to patients with hepatitis C. Likewise, it took a longer time for platelet counts to rebound back to baseline once eltrombopag treatment was discontinued.
Conclusions
The time course of the platelet response in CLD was different from that in immune thrombocytopenic purpura but comparable to that in hepatitis C.
doi:10.1111/bcp.12244
PMCID: PMC4371540  PMID: 24117976
chronic liver disease; eltrombopag; platelet count; population pharmacokinetics/pharmacodynamics
2.  Population pharmacokinetics of recombinant human C1 inhibitor in patients with hereditary angioedema 
Aims
To characterize the pharmacokinetics (PK) of recombinant human C1 inhibitor (rhC1INH) in healthy volunteers and hereditary angioedema (HAE) patients.
Methods
Plasma levels of C1INH following 294 administrations of rhC1INH in 133 subjects were fitted using nonlinear mixed-effects modelling. The model was used to simulate maximal C1INH levels for the proposed dosing scheme.
Results
A one-compartment model with Michaelis–Menten elimination kinetics described the data. Baseline C1INH levels were 0.901 [95% confidence interval (CI): 0.839–0.968] and 0.176 U ml−1 (95% CI: 0.154–0.200) in healthy volunteers and HAE patients, respectively. The volume of distribution of rhC1INH was 2.86 l (95% CI: 2.68–3.03). The maximal rate of elimination and the concentration corresponding to half this maximal rate were 1.63 U ml−1 h−1 (95% CI: 1.41–1.88) and 1.60 U ml−1 (95% CI: 1.14–2.24), respectively, for healthy volunteers and symptomatic HAE patients. The maximal elimination rate was 36% lower in asymptomatic HAE patients. Peak C1INH levels did not change upon repeated administration of rhC1INH. Bodyweight was found to be an important predictor of the volume of distribution. Simulations of the proposed dosing scheme predicted peak C1INH concentrations above the lower level of the normal range (0.7 U ml−1) for at least 94% of all patients.
Conclusions
The population PK model for C1INH supports a dosing scheme on a 50 U kg−1 basis up to 84 kg, with a fixed dose of 4200 U above 84 kg. The PK of rhC1INH following repeat administration are consistent with the PK following the first administration.
doi:10.1111/bcp.12132
PMCID: PMC3845313  PMID: 23594263
hereditary angioedema; NONMEM; pharmacokinetics; recombinant human C1 inhibitor
3.  Population pharmacokinetics of farletuzumab, a humanized monoclonal antibody against folate receptor alpha, in epithelial ovarian cancer 
Purpose
The purpose of this analysis was to develop a population pharmacokinetic model for farletuzumab, a humanized immunoglobulin (Ig)G1 monoclonal antibody (mAb) to the folate receptor alpha, which is a receptor over-expressed in ovarian cancer, but largely absent from normal tissue.
Methods
In total, 2,472 samples were included in the building of the pharmacokinetic model. Farletuzumab 12.5–400 mg/m2 had been administered via intravenous infusion to 79 patients with advanced ovarian cancer enrolled in one of the two clinical studies. Data were analyzed by a nonlinear mixed-effects modeling approach.
Results
Farletuzumab pharmacokinetics was best described by a two-compartment model with first-order (linear) elimination. In the final model, estimated values of clearance and volume of distribution of the central compartment were 0.00784 l/h and 3.00 l, respectively. Body weight was the only covariate investigated that explained inter-patient variability in clearance and the central volume of distribution. There was no effect of age, human anti-human antibodies, or concomitant chemotherapy on the pharmacokinetics of farletuzumab. Simulations showed that, when the mg/kg/week dose was maintained, steady-state exposure to farletuzumab was similar with dosing every week or every 3 weeks.
Conclusions
The pharmacokinetic parameters of farletuzumab are similar to those of other IgG mAbs. The results support weight-based dosing of farletuzumab on a weekly or 3-weekly schedule.
doi:10.1007/s00280-012-1959-y
PMCID: PMC3485533  PMID: 22955257
Farletuzumab; Population pharmacokinetics; Monoclonal antibody; Ovarian neoplasms; Folate receptor alpha
4.  Challenges and Opportunities in Establishing Scientific and Regulatory Standards for Assuring Therapeutic Equivalence of Modified Release Products: Workshop Summary Report 
The AAPS Journal  2010;12(3):371-377.
Modified release products are complex dosage forms designed to release drug in a controlled manner to achieve desired efficacy and safety. Inappropriate control of drug release from such products may result in reduced efficacy or increased toxicity. This workshop provided an opportunity for pharmaceutical scientists from academia, industry, and regulatory agencies to discuss current industry practices and regulatory expectations for demonstrating pharmaceutical equivalence and bioequivalence of MR products, further facilitating the establishment of regulatory standards for ensuring therapeutic equivalence of these products.
doi:10.1208/s12248-010-9201-5
PMCID: PMC2895434  PMID: 20440588
bioequivalence; interchangeability; modified release; pharmaceutical equivalence; therapeutic equivalence

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