Population pharmacokinetics of atacicept in systemic lupus erythematosus: An analysis of three clinical trials.

B cell stimulating factor (BLyS) and a proliferation-inducing ligand (APRIL) are targets for novel treatments in patients with systemic lupus erythematosus (SLE). Atacicept is a recombinant, soluble fusion protein that blocks BLyS and APRIL activity. This study characterized the pharmacokinetic (PK) profile of atacicept using a population PK model and identified covariates explaining the PK variability. Total atacicept concentrations from a phase I study in healthy volunteers and two phase II studies in patients with SLE, using subcutaneous administration, were modeled using a quasi-steady-state approximation of the target-mediated drug disposition model with first-order absorption. The model included 3640 serum atacicept concentration records from 37 healthy volunteers and 503 patients with SLE and described total atacicept concentrations of the three trials, providing precise estimates of all parameters. Body weight and baseline BLyS concentration were the only statistically significant covariates, whereas no differences were found between patients and healthy volunteers. Apparent clearance and volume of the central compartment increased with body weight and initial target concentration increased with baseline BLyS. The change on atacicept exposure was moderate, with a difference in area under the curve compared with the median of 20%-32% for body weight, and 7%-18% for BLyS. Therefore, the effects of these covariates on atacicept exposure are not expected to be clinically relevant. The model described the complete total atacicept concentration-time profiles without finding any differences between healthy subjects and patients with SLE and supports the 150 mg once weekly dose for further trials.

Safety, pharmacokinetics, and pharmacodynamics of intravenous ferric carboxymaltose in children with iron deficiency anemia.

BACKGROUND: Iron deficiency is the primary cause of anemia in children. Intravenous (IV) iron formulations circumvent malabsorption and rapidly restore hemoglobin. METHODS: This Phase 2, non-randomized, multicenter study characterized the safety profile and determined appropriate dosing of ferric carboxymaltose (FCM) in children with iron deficiency anemia. Patients aged 1-17 years with hemoglobin <11 g/dL and transferrin saturation <20% received single IV doses of undiluted FCM 7.5 mg/kg (n = 16) or 15 mg/kg (n = 19). RESULTS: The most common drug-related treatment-emergent adverse event was urticaria (in three recipients of FCM 15 mg/kg). Systemic exposure to iron increased in a dose-proportional manner with approximate doubling of mean baseline-corrected maximum serum iron concentration (157 µg/mL with FCM 7.5 mg/kg; and 310 µg/mL with FCM 15 mg/kg) and area under the serum concentration-time curve (1901 and 4851 h·µg/mL, respectively). Baseline hemoglobin was 9.2 and 9.5 g/dL in the FCM 7.5 and 15 mg/kg groups, respectively, with mean maximum changes in hemoglobin of 2.2 and 3.0 g/dL, respectively. CONCLUSIONS: In conclusion, FCM was well tolerated by pediatric patients. Improvements in hemoglobin were greater with the higher dose, supporting use of the FCM 15 mg/kg dose in pediatric patients (Clinicaltrials.gov NCT02410213). IMPACT: This study provided information on the pharmacokinetics and safety of intravenous ferric carboxymaltose for treatment of iron deficiency anemia in children and adolescents. In children aged 1-17 years with iron deficiency anemia, single intravenous doses of ferric carboxymaltose 7.5 or 15 mg/kg increased systemic exposure to iron in a dose-proportional manner, with clinically meaningful increases in hemoglobin. The most common drug-related treatment-emergent adverse event was urticaria. The findings suggest that iron deficiency anemia in children can be corrected with a single intravenous dose of ferric carboxymaltose and support use of a 15 mg/kg dose.

Population pharmacokinetic modeling and simulation of maribavir to support dose selection and regulatory approval in adolescents with posttransplant refractory cytomegalovirus.

Maribavir was approved by the US Food and Drug Administration for the treatment of patients aged ≥12 years and weighing ≥35 kg with posttransplant cytomegalovirus infection/disease refractory (with/without resistance) to valganciclovir, ganciclovir, cidofovir, or foscarnet, with an oral dose of 400 mg twice daily. With no pediatric clinical data available and difficulty in trial recruitment, population pharmacokinetic modeling and simulations were conducted to predict the pharmacokinetics and inform maribavir dosing in adolescents.

Pediatric Population Pharmacokinetic Modeling and Exposure-Response Analysis of Ambrisentan in Pulmonary Arterial Hypertension and Comparison With Adult Data.

This study aimed to develop a population pharmacokinetic (PK) model of ambrisentan in pediatric patients (8 to <18 years) with pulmonary arterial hypertension (PAH) and compare pediatric ambrisentan systemic exposure with previously reported adult data. Association of ambrisentan exposure with efficacy (6-minute walking distance) and safety (adverse events) were exploratory analyses. A population PK model was developed using pediatric PK data. Steady-state systemic exposure metrics were estimated for the pediatric population and compared with previously reported data in adult patients with PAH and healthy subjects. No covariates had a significant effect on PK parameters; therefore, the final covariate model was the same as the base model. The pediatric population PK model was a 2-compartment model including the effect of body weight (allometric scaling), first-order absorption and elimination, and absorption lag time. Steady-state ambrisentan exposure was similar between the pediatric and adult population when accounting for body weight differences. Geometric mean area under the concentration-time curve at steady state in pediatric patients receiving ambrisentan low dose was 3% lower than in the adult population (and similar in both populations receiving high dose). Geometric mean maximum plasma concentration at steady state in pediatric patients receiving low and high doses was 11% and 18% higher, respectively, than in the adult population. There was no apparent association in the pediatric or adult population between ambrisentan exposure and change in 6-minute walking distance or incidence of ambrisentan-related adverse events in pediatric patients. The similar ambrisentan exposure and exposure-response profiles observed in pediatric and adult populations with PAH suggests appropriateness of body-weight-based dosing in the pediatric population with PAH.

Population pharmacokinetics of recombinant human C1 esterase inhibitor in children with hereditary angioedema.

BACKGROUND: Recombinant human C1 esterase inhibitor (rhC1-INH) is indicated in the United States for the treatment of acute hereditary angioedema (HAE) attacks in adolescents and adults; it is also indicated in Europe for children aged 2 years and older. A need exists for further insight into potential pharmacokinetic (PK) differences in functional C1-INH levels by age (ie, children, adolescents, and adults). OBJECTIVE: To perform population PK modeling to predict C1-INH levels by age after by age rhC1-INH administration. METHODS: Data from a phase 2 pediatric trial (children aged 4-13 years at screening) were added to a database of 6 trials in adults and adolescents. An unpublished population PK model was refined and used to simulate C1-INH exposure. RESULTS: Analysis included 153 individuals (14 healthy volunteers; 139 patients with HAE) and 1788 functional C1-INH measurements (59 from 20 patients in the pediatric trial). Bodyweight (population weight, 16-128 kg) was a key predictor of C1-INH volume of distribution. Age was not a predictor of C1-INH PK after the inclusion of bodyweight in the model. Simulations of the recommended rhC1-INH dosing regimen (bodyweight <84 kg, 50 U/kg; ≥84 kg, 4200 U) revealed that overall C1-INH exposure was comparable among age groups. Predicted peak functional C1-INH concentrations were at or above the lower level of normal (≥0.7 U/mL) for 99.8% of adults (≥18 years), 99.8% of adolescents (14-17 years), and 96.0% of children (2-13 years). CONCLUSION: The analyses support the same weight-based rhC1-INH dosing for HAE attacks in children as currently recommended for adolescents and adults. These results support clinical trial data, which revealed similar safety and efficacy profiles across these age groups.

A Physiologically Based Pharmacokinetic Model to Predict Potential Drug-Drug Interactions and Inform Dosing of Acumapimod, an Oral p38 MAPK Inhibitor.

Acumapimod, an investigational oral p38 mitogen-activated protein kinase inhibitor for treatment during severe acute exacerbations of chronic obstructive pulmonary disease, is metabolized primarily by cytochrome P450 3A4 (CYP3A4) and is a P-glycoprotein (P-gp) substrate. Concerns about drug-drug interactions (DDIs) have meant patients receiving drugs that inhibit CYP3A4 were ineligible for acumapimod trials. We report on how 2 acumapimod clinical DDI studies and a physiologically-based pharmacokinetic (PBPK) model assessing how co-administration of a weak (azithromycin) and strong (itraconazole) CYP3A4 inhibitor affected acumapimod systemic exposure, informed decision making and supported concomitant use of CYP3A4 and P-gp inhibitors. Studies MBCT102 and MBCT103, respectively, demonstrated that co-administration of azithromycin or itraconazole had no clinically meaningful impact on acumapimod pharmacokinetics. Findings were consistent with PBPK model results. Safety profiles were similar when acumapimod was co-administered with azithromycin or itraconazole. These studies highlight the value of PBPK modeling in drug development, and its potential to inform DDI investigations.

Population Pharmacokinetic Analysis of Fluticasone Furoate/Umeclidinium Bromide/Vilanterol in Patients with Chronic Obstructive Pulmonary Disease.

BACKGROUND: Population pharmacokinetic methods were used to characterize the pharmacokinetics of fluticasone furoate (FF), umeclidinium (UMEC), and vilanterol (VI) in patients with chronic obstructive pulmonary disease (COPD) when administered as a fixed-dose combination via a single closed inhaler. METHODS: Plasma concentration data from three studies were analyzed using non-linear mixed-effects modeling in NONMEM®. RESULTS: The pooled dataset consisted of 2948, 2589, and 3331 FF, UMEC, and VI observations from 714, 622, and 817 patients with COPD, respectively. There were 41%, 13%, and 21% of observations below the quantification limit for FF, UMEC, and VI, respectively. The pharmacokinetics of FF, UMEC, and VI were all adequately described by a two-compartment model with first-order absorption. The following covariates were statistically significant, but none were considered to be clinically relevant. For FF, Japanese heritage and FF/VI treatment on apparent inhaled clearance (CL/F) with FF CL/F 35% lower in patients of Japanese heritage across all treatments and FF CL/F 42% higher in patients with COPD following FF/VI administration. This is in line with the product label. For UMEC, weight, age, and smoking status on CL/F and weight on apparent volume of distribution (V2/F) with every 10% increase in age from 60 years of age leading to approximately a 6% decrease in UMEC CL/F and every 10% increase in weight from 70 kg leading to approximately a 6% increase in UMEC CL/F and approximately an 8% increase in UMEC V2/F. For a subject with COPD who smoked, UMEC CL/F was 28% higher. For VI, weight on CL/F and smoking status on V2/F with an approximately 4% increase in VI CL/F for every 10% increase in weight from 70 kg, and for a subject with COPD who smoked, VI V2/F was 46% higher. The majority of these covariates have been previously identified in historical analyses. None of these effects were clinically relevant in terms of systemic exposures and do not warrant dose adjustment. CONCLUSIONS: All FF, UMEC, and VI plasma concentrations were well interspersed with historical data and were all adequately described by a two-compartment model with first-order absorption. There were no clinically relevant differences in FF, UMEC, or VI systemic exposures when administered as FF/UMEC/VI, FF/VI + UMEC, or the dual combinations FF/VI and/or UMEC/VI.

Oliceridine, a Novel G Protein-Biased Ligand at the µ-Opioid Receptor, Demonstrates a Predictable Relationship Between Plasma Concentrations and Pain Relief. II: Simulation of Potential Phase 3 Study Designs Using a Pharmacokinetic/Pharmacodynamic Model.

Oliceridine is a novel G protein-biased ligand at the µ-opioid receptor that differentially activates G protein coupling while mitigating ß-arrestin recruitment. Unlike morphine, oliceridine has no known active metabolites; therefore, analgesic efficacy is predictably linked to its concentration in the plasma. Oliceridine is primarily hepatically metabolized by CYP3A4 and CYP2D6. Using a pharmacokinetic/pharmacodynamic model relating oliceridine plasma concentrations to its effect on pain intensity as measured by numeric pain-rating scale (NPRS) scores, we have simulated potential dosing regimens using both fixed-dose regimens and as-needed (prn) dosing regimens in which various doses of oliceridine were administered if NPRS scores indicated moderate to severe pain (≥4 on a 0-10 scale). In addition, regimens in which oliceridine was self-administered via a patient-controlled analgesia device were also simulated. The simulated population included 10% CYP2D6 poor metabolizers (PM). The simulation results suggest that oliceridine doses of 1-3 mg prn should be effective in reducing NPRS scores relative to placebo. The simulations also revealed that a 1-mg "supplemental dose" given 0.25 hour after the loading dose would decrease NPRS scores further in almost one-third of patients. In addition, if oliceridine is administered prn, a longer interval between doses is observed in simulated PM patients, consistent with their reduced oliceridine clearance. Because this longer average dosing interval is predicted to decrease oliceridine exposure in PM patients, the need to know the patient's CYP2D6 genotype for dosing is effectively obviated.

Oliceridine (TRV130), a Novel G Protein-Biased Ligand at the µ-Opioid Receptor, Demonstrates a Predictable Relationship Between Plasma Concentrations and Pain Relief. I: Development of a Pharmacokinetic/Pharmacodynamic Model.

Conventional opioids bind to µ-opioid receptors and activate 2 downstream signaling pathways: G-protein coupling, linked to analgesia, and ß-arrestin recruitment, linked to opioid-related adverse effects and limiting efficacy. Oliceridine (TRV130) is a novel G protein-biased ligand at the µ-opioid receptor that differentially activates G-protein coupling while mitigating ß-arrestin recruitment. Using data derived from both phase 1 studies in healthy volunteers as well as data from a phase 2 study examining the efficacy of oliceridine for the treatment of postbunionectomy pain, we have developed a population pharmacokinetic/pharmacodynamic model linking the pharmacokinetics of oliceridine to its effect on pain, as measured by the Numeric Pain Rating Scale score. Phase 1 data consisted of 145 subjects (88% male, 12% female), who received single doses of oliceridine ranging between 0.15 and 7 mg, as well as multiple doses ranging from 0.4 to 4.5 mg every 4-6 hours. Sixteen of these subjects were CYP2D6 poor metabolizers, who have lower oliceridine clearance than extensive metabolizers. Approximately 265 subjects (10% male, 90% female) came from the phase 2 study, in which they received active doses ranging from 0.5 to 4 mg every 3-4 hours. The final model was a 3-compartment model that included covariates of body weight, sex, and CYP2D6 status. The PD model was an indirect response model linked to plasma oliceridine concentrations and included the placebo pain response over the 48-hour treatment period. The EC50 for oliceridine on pain relief was estimated as 10.1 ng/mL (95%CI, 8.4-12.1 ng/mL). Model qualification showed that the model robustly reproduced the original data.

A population pharmacokinetic meta-analysis of custirsen, an antisense oligonucleotide, in oncology patients and healthy subjects.

AIMS: Custirsen (OGX-011/TV-1011), a second-generation antisense oligonucleotide that reduces clusterin production, is under investigation with chemotherapy in prostate and lung cancer. This meta-analysis evaluated the population pharmacokinetics (PK) of custirsen in cancer patients and healthy subjects. METHODS: The population PK analysis used custirsen plasma concentrations from five Phase 1 studies, one Phase 1/2 study, and one Phase 3 study in two stages. Cancer patients received multiple doses of custirsen (40-640 mg intravenously over 120 min) with chemotherapy; healthy subjects received single or multiple doses (320-640 mg). An interim population PK model was developed using a nonlinear mixed-effect approach incorporating data from four Phase 1 or 1/2 studies, followed by model refinement and inclusion of two Phase 1 and one Phase 3 studies. RESULTS: The final model was developed with 5588 concentrations from 631 subjects with doses of 160-640 mg. Custirsen PK was adequately described by a three-compartment model with first-order elimination. For a representative 66-year-old individual with body weight 82 kg and serum creatinine level 0.933 mg dl-1 , the estimated typical (95% CI) parameter values were clearance (CL) = 2.36 (2.30-2.42) l h-1 , central volume of distribution (V1 ) = 6.08 (5.93-6.23) l, peripheral volume of distribution (V2 ) = 1.13 (1.01-1.25) l, volume of the second peripheral compartment (V3 ) = 15.8 (14.6-17.0) l, inter-compartmental clearance Q2 = 0.0755 (0.0689-0.0821) l h-1 , and Q3 = 0.0573 (0.0532-0.0614) l h-1 . Age, weight and serum creatinine were predictors of CL; age was a predictor of Q3 . CONCLUSION: A population PK model for custirsen was successfully developed in cancer patients and healthy subjects, including covariates contributing to variability in custirsen PK.

Population pharmacokinetic and pharmacodynamic analyses of safinamide in subjects with Parkinson's disease.

Safinamide is an orally administered α-aminoamide derivative with both dopaminergic and non-dopaminergic properties. Nonlinear mixed effects models for population pharmacokinetic (PK) and pharmacokinetic-pharmacodynamic (PKPD) analyses were developed using records from, respectively, 623 and 668 patients belonging to two Phase 3, randomized, placebo-controlled, double-blind efficacy studies. The aim was to estimate safinamide population PK parameters in patients with Parkinson's disease (PD) on stable levodopa therapy, and to develop a model of safinamide effect on the PD phase of normal functioning (ON-time). The final models were internally evaluated using visual predictive checks (VPCs), prediction corrected-VPC, and nonparametric bootstrap analysis. Safinamide profiles were adequately described by a linear one-compartmental model with first-order absorption and elimination. CL/F, Vd/F, and KA (95% confidence interval [CI]) were 4.96 (4.73-5.21) L/h, 166 (158-174) L, and 0.582 (0.335-0.829) h-1, respectively. CL/F and Vd/F increased with body weight, while age, gender, renal function, and exposure to levodopa did not influence safinamide PK. The observed ON-time values were adequately described by a linear model, with time in the study period as dependent variable, and rate of ON-time change and baseline plus offset effect as slope and intercept parameters. Safinamide treatment resulted in an increase in ON-time of 0.73 h (week 4), with further ON-time increase with the same slope as placebo. The increase was not influenced by age, levodopa, or safinamide exposure. The population models adequately describe the population PK of safinamide and safinamide effect on ON-time. No dose adjustments in elderly and mild to moderate renally impaired patients are requested.

Population Pharmacokinetic and Pharmacodynamic Modeling and Effects on Platelet Counts of Different Dosages of Eltrombopag in Chinese Patients With Chronic Primary Immune Thrombocytopenia.

PURPOSE: This study characterized the population pharmacokinetic (pop-PK) and PK/pharmacodynamic (pop-PK/PD) properties of eltrombopag and evaluated platelet count (PLTC) response to different eltrombopag dosages through simulations in Chinese adult patients with chronic primary immune thrombocytopenia (cITP). METHODS: Pop-PK and pop-PK/PD models were developed from Chinese patients with cITP. Model-based simulations were then performed to predict PLTC response. FINDINGS: The pop-PK properties of eltrombopag were described by a 2-compartment model with first-order absorption and elimination and absorption lag time. Steady-state exposure in these Chinese patients was ~55% greater than that in non-East Asian patients. The pop-PK/PD properties of eltrombopag were described by a model with 4 transit compartments where the increase in platelet production rate was linearly related to the plasma eltrombopag concentration. Eleven percent of the patients were identified as nonresponders to eltrombopag. Simulations showed that ~70% to 80% of steady-state PLTC response was achieved at week 2, and the percentages of patients who achieved a PLTC of 50 to 150 × 10(9) cells/L were comparable between weeks 2 and 6 with 12.5-, 25-, 50-, and 75-mg once-daily dosing. The 25-mg once-daily dosage was associated with a more balanced response than were the 12.5-, 50-, and 75-mg once-daily dosages with regard to efficacy (percentages of patients with PLTC 50-150 × 10(9) cells/L, 27% vs 20%, 30%, and 30%, respectively) and the risk for thrombocytosis (percentages of patients with PLTC >250 × 10(9) cells/L, 4% vs 1%, 10%, and 16%). Simulations of PLTCs with the dose-titration regimen showed that ≥42% of patients achieved a PLTC 50 to 150 × 10(9) cells/L at week 6 or later, compared with ≤30% when the 12.5-, 25-, 50-, and 75-mg once-daily fixed doses were given. No more than 5% of patients who underwent dose titration had a PLTC >250 × 10(9) cells/L throughout 24 weeks of treatment, compared with 3%, 7%, 16%, and 24% when the once-daily fixed doses of eltrombopag were given. IMPLICATIONS: The pop-PK and pop-PK/PD properties of eltrombopag in these Chinese adult patients with cITP were adequately characterized in the present analyses. The modeling and simulation results support the eltrombopag dose-titration regimen, with 25 mg once daily as a starting dosage and a 2-week titration interval, in Chinese patients with cITP.

Modeling and simulation support eltrombopag dosing in thrombocytopenic patients with chronic HCV infection.

PURPOSE: The pharmacokinetics of eltrombopag and its stimulation of platelet production were characterized in patients with chronic hepatitis C virus (HCV) infection to optimize an eltrombopag dosing regimen for treatment of HCV-related thrombocytopenia before and throughout peginterferon (pegIFN)-based antiviral therapy. METHODS: Population pharmacokinetic analysis for eltrombopag included 663 individuals (healthy subjects, n = 28; patients with HCV, n = 635). Population pharmacokinetic/pharmacodynamic analysis for platelet response involved patients with HCV only. Simulations were conducted using various dosing scenarios in the same patient population. RESULTS: Eltrombopag pharmacokinetics were described by a two-compartment model with dual sequential first-order absorption and elimination. Age, race, sex, and severity of hepatic impairment were predictors of eltrombopag clearance. The effect of eltrombopag on platelet counts was adequately described by a model with four transit compartments in which eltrombopag concentrations stimulated the production rate of platelet precursors in an Emax manner. CONCLUSIONS: Modeling and simulation results support once-daily eltrombopag 25 mg as an appropriate starting dosing regimen followed by biweekly dose escalation (in 25-mg increments) up to once-daily eltrombopag 100 mg to raise platelet counts sufficiently for initiation of pegIFN-based antiviral therapy in patients with HCV. Biweekly dose adjustment allows patients to stay on the lowest possible eltrombopag dose during antiviral therapy.

Development of in vitro-in vivo correlation for extended-release niacin after administration of hypromellose-based matrix formulations to healthy volunteers.

Development of in vitro-in vivo correlations (IVIVCs) for extended-release (ER) products is commonly pursued during pharmaceutical development to increase product understanding, set release specifications, and support biowaivers. This manuscript details the development of Level C and Level A IVIVCs for ER formulations of niacin, a highly variable and extensively metabolized compound. Three ER formulations were screened in a cross-over study against immediate-release niacin. A Multiple Level C IVIVC was established for both niacin and its primary metabolite nicotinuric acid (NUA) as well as total niacin metabolites urinary excretion. For NUA, but not for niacin, Level A IVIVC models with acceptable prediction errors were achievable via a modified IVIVC rather than a traditional deconvolution/convolution approach. Hence, this is in contradiction with current regulatory guidelines that suggest that when a Multiple Level C IVIVC is established, Level A models should also be readily achievable. We demonstrate that for a highly variable, highly metabolized compound such as niacin, development of a Level A IVIVC model fully validated according to agency guidelines may be challenging. However, Multiple Level C models are achievable and could be used to guide release specifications and formulation/manufacturing changes.

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.

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.

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)G(1) 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/m(2) 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.

Challenges and opportunities in establishing scientific and regulatory standards for assuring therapeutic equivalence of modified release products: workshop summary report.

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.

Challenges and opportunities in establishing scientific and regulatory standards for assuring therapeutic equivalence of modified-release products: workshop summary report.

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 regulatory expectations and industry practices for demonstrating pharmaceutical equivalence and bioequivalence of MR products, further facilitating the establishment of regulatory standards for ensuring therapeutic equivalence of these products.