A large multicentre, randomized, double-blind, cross-over study in healthy volunteers to compare pharmacokinetics, pharmacodynamics and safety of a pegfilgrastim biosimilar with its US- and EU-reference biologics.

AIMS: Recombinant PEGylated human granulocyte colony-stimulating factor (pegfilgrastim) is indicated for the reduction of chemotherapy-induced neutropenia and prevention of febrile neutropenia. Biosimilar pegfilgrastim is expected to reduce the financial burden of this complication of chemotherapy. The aim of this study was to demonstrate biosimilarity between Sandoz biosimilar pegfilgrastim and its US- and EU-approved reference biologics. METHODS: Phase I, randomized, double-blind, single-dose, 3-period, 6-sequence cross-over, multicentre study to evaluate the pharmacokinetics, pharmacodynamics, safety and immunogenicity of Sandoz biosimilar pegfilgrastim with US- and EU-references in healthy adults. RESULTS: Pharmacokinetic and pharmacodynamic similarity was demonstrated between the 3 biologics, as the 90% confidence interval for all primary pharmacokinetic and pharmacodynamic endpoint comparisons were contained within the predefined similarity margins of 0.80-1.25. Safety, immunogenicity and tolerability were also similar. CONCLUSIONS: Sandoz biosimilar pegfilgrastim demonstrated pharmacokinetic and pharmacodynamic similarity to both US- and EU-reference biologics. No meaningful differences in safety, local tolerability and immunogenicity were identified.

Differences in immunogenicity associated with non-product related variability: insights from two pharmacokinetic studies using GP2017, an adalimumab biosimilar.

Introduction: Antidrug antibody (ADA) development is known to occur with adalimumab treatment and impacts adalimumab exposure. Here, we compare the impact of immunogenicity on pharmacokinetics (PK) across two randomized PK studies of GP2017, an approved biosimilar adalimumab, in healthy subjects. Methods: Healthy male subjects (N= 107 in study GP17-104; N= 90 in study GP17-103) received a single 40 mg subcutaneous injection of the same GP2017 drug product batch. Cross-study PK comparison was performed for log-transformed Cmax, AUC0-360h, AUC0-last, and AUC0-inf, using an ANCOVA model. Results: The proportion of ADA-positive subjects was higher in GP17-103 (in total 71.1%) vs. GP17-104 (57.9%). Comparison of GP2017 PK between studies showed that the exposure was lower in GP17-103 vs GP17-104, with 90% confidence intervals (CIs) for geometric mean ratios of AUC0-last and AUC0-inf being outside the range of 0.80-1.25. A subgroup analysis showed that in ADA-negative subjects 90% CIs for all PK parameters were within range, with geometric mean ratios close to 1.00. Conclusion: The differences in GP2017 PK between the two groups are not considered to be product-related, but may be due to currently unknown factors related to differences between the two study populations.

GP2017, an adalimumab biosimilar: pharmacokinetic similarity to its reference medicine and pharmacokinetics comparison of different administration methods.

Background: To compare the pharmacokinetics of Sandoz biosimilar adalimumab (GP2017) with reference adalimumab (Humira) in healthy volunteers (PK similarity study) and to compare the pharmacokinetics of GP2017 administered by autoinjector (AI) or prefilled syringe (PFS; delivery study). Methods: Healthy male subjects were randomized to receive a single 40 mg subcutaneous injection of GP2017, US-licensed or EU-authorized reference adalimumab (US/EU-Humira; PK similarity study) or a single 40 mg subcutaneous injection of GP2017 via AI or PFS (delivery study). Pharmacokinetics, safety, and immunogenicity were assessed over 72 days post-injection. Results: The geometric mean ratios (90% confidence intervals) for Cmax and AUC0-inf were 1.05 (0.99-1.11) and 1.04 (0.96-1.13) for GP2017/EU-Humira and 1.00 (0.94-1.06) and 1.08 (1.00-1.18) for GP2017/US-Humira, all within the prespecified margin of 0.80-1.25 (PK similarity study). Pharmacokinetic parameters of GP2017 matched between AI and PFS (delivery study). Safety and immunogenicity were similar across groups in both studies. Conclusion: PK similarity between GP2017, EU- and US-Humira was demonstrated. The safety profile of GP2017 was consistent with previous reports for Humira. These results contribute to the 'totality-of-the-evidence' supporting biosimilarity of GP2017 to Humira. PK and tolerability were equivalent for GP2017 dosed by AI or PFS. Trial registration: PK similarity study EudraCT no. 2015-000579-28; Delivery study: EudraCT no. 2014-002879-29.

Proposed biosimilar pegfilgrastim shows similarity in pharmacokinetics and pharmacodynamics to reference pegfilgrastim in healthy subjects.

AIMS: This study aimed to demonstrate that the pharmacokinetic (PK) and pharmacodynamic (PD) profile of Sandoz proposed biosimilar pegfilgrastim (LA-EP2006) matches reference pegfilgrastim (Neulasta® ) in healthy subjects. Safety and immunogenicity were also assessed. METHODS: The phase I, randomized, double-blind, two-period crossover study consisted of two treatment periods separated by an 8-week washout period. Healthy subjects aged 18-45 were randomized to either proposed biosimilar/reference pegfilgrastim or reference pegfilgrastim/proposed biosimilar. Proposed biosimilar and reference pegfilgrastim were administered on Day 1 of each treatment period (single 6 mg subcutaneous injection). Blood samples for PK/PD analysis were taken predose and ≤336 h postdose. PK/PD similarity was claimed if 90% (PK) and 95% (PD) confidence intervals (CI) for geometric mean ratios of the area under the serum concentration-time curve (AUC) from time of dosing and extrapolated to infinity (AUC0-inf ), or to the last measurable concentration (AUC0-last ), maximum observed serum concentration (Cmax ), absolute neutrophil count (ANC) area under the effect curve from the time of dosing to the last measurable concentration (AUEC0-last ) and ANC maximum effect attributable to the therapy under investigation (Emax ) were completely contained within the predefined margin (0.8 to 1.25). RESULTS: Overall, 169 subjects completed the study. PK/PD similarity was demonstrated; 90% CIs of geometric mean ratio of proposed biosimilar/reference for PK: AUC0-inf (1.0559-1.2244), AUC0-last (1.0607-1.2328), Cmax (1.0312-1.1909) and 95% CIs for PD (ANC): AUEC0-last (0.9948-1.0366), Emax (0.9737-1.0169) were completely contained within predefined margin of 0.8 to 1.25. Both biologics had similar safety profiles, were well tolerated and had low incidence of anti-drug antibodies. No neutralizing or clinically relevant antibodies were detected. CONCLUSIONS: PK/PD similarity of Sandoz proposed biosimilar pegfilgrastim and reference pegfilgrastim was confirmed. No clinically meaningful differences in safety, tolerability and immunogenicity were observed in healthy subjects.

Application of Pharmacometric Analysis in the Design of Clinical Pharmacology Studies for Biosimilar Development.

This article provides an overview of four case studies to demonstrate the utility of pharmacometric analysis in biosimilar development to help design sensitive clinical pharmacology studies for the demonstration of biosimilarity. The two major factors that determine the sensitivity of a clinical pharmacokinetic/pharmacodynamic (PK/PD) study to demonstrate biosimilarity are the size of the potential difference to be detected (signal) and the inter-subject variability (noise), both of which can be characterized and predicted using pharmacometric approaches. To maximize the chance to detect any potential difference between the proposed biosimilar and the reference drug, the dose selected for the clinical pharmacology study should fall on the steep part of the dose-response curve. Pharmacometric analysis can be used to characterize the dose-response relationship using PD- or PK/PD-linked models. The understanding of the PD endpoints in terms of dynamic range of the response and the location of the studied dose on the dose-response curve can provide strategic advantage in the trial design. To reduce the inter-subject variability (noise), pharmacometric analysis can help avoid high variability associated with low doses, and decrease variability by controlling certain covariates in the inclusion/exclusion criteria. Pharmacometric analysis also can help select or justify margins for the equivalence test of PD endpoints. Pharmacometric analysis will assume an ever-increasing role in the clinical development of biosimilar drugs, as it helps to ensure that sufficient sensitivity is built into the study design to detect potential PK and PD differences.

GP2015, a proposed etanercept biosimilar: Pharmacokinetic similarity to its reference product and comparison of its autoinjector device with prefilled syringes.

AIMS: To assess pharmacokinetics (PK) and safety of GP2015, a proposed etanercept biosimilar, in two studies: comparison with etanercept originator (ETN, bioequivalence study) and comparison of GP2015 administered via an autoinjector (AI) or prefilled syringes (PFS, delivery study). METHODS: Both studies were randomized, two-sequence, two-period, crossover studies conducted in healthy male subjects. In the bioequivalence study, subjects were randomized to receive a single 50 mg subcutaneous (s.c.) injection of GP2015 or ETN. In the delivery study, subjects were randomized to receive a single 50 mg s.c. injection of GP2015 via AI or PFS. Following a wash-out period of 35 days, subjects in the bioequivalence study received single 50 mg s.c. injection of GP2015 or ETN, and subjects in the delivery study received single 50 mg s.c. injection of GP2015 via AI or PFS. RESULTS: The geometric mean ratios (90% confidence interval) of GP2015/ETN for Cmax (1.11 [1.05-1.17]), AUC0-tlast (0.98 [0.94-1.02]) and AUC0-inf (0.96 [0.93-1.00]) were within the predefined bioequivalence range of 0.80-1.25. The geometric mean ratios (90% confidence interval) of AI/PFS for Cmax (1.01 [0.94-1.08]), AUC0-tlast (1.01 [0.95-1.07]) and AUC0-inf (1.01 [0.96-1.07]) were also within the range 0.80-1.25. No new safety issues were reported. Three subjects had low titres of non-neutralising anti-drug antibodies during a follow-up visit in the bioequivalence study. CONCLUSIONS: The PK of GP2015 was similar to ETN, demonstrating bioequivalence. The safety profile of GP2015 was consistent with previous reports for ETN. The GP2015 AI provided equivalent dosing and tolerability to the GP2015 PFS.

Efficacy and safety of multiple doses of QGE031 (ligelizumab) versus omalizumab and placebo in inhibiting allergen-induced early asthmatic responses.

BACKGROUND: Omalizumab is an established anti-IgE therapy for the treatment of allergic diseases that prevents IgE from binding to its receptor. QGE031 is an investigational anti-IgE antibody that binds IgE with higher affinity than omalizumab. OBJECTIVE: This study compared the effects of QGE031 with those of omalizumab on clinical efficacy, IgE levels, and FcεRI expression in a clinical model of allergic asthma. METHODS: Thirty-seven patients with mild allergic asthma were randomized to subcutaneous omalizumab, placebo, or QGE031 at 24, 72, or 240 mg every 2 weeks for 10 weeks in a double-blind, parallel-group multicenter study. Inhaled allergen challenges and skin tests were conducted before dosing and at weeks 6, 12, and 18, and blood was collected until 24 weeks after the first dose. RESULTS: QGE031 elicited a concentration- and time-dependent change in the provocative concentration of allergen causing a 15% decrease in FEV1 (allergen PC15) that was maximal and approximately 3-fold greater than that of omalizumab (P = .10) and 16-fold greater than that of placebo (P = .0001) at week 12 in the 240-mg cohort. Skin responses reached 85% suppression at week 12 in the 240-mg cohort and were maximal at week 18. The top doses of QGE031 consistently suppressed skin test responses among subjects but had a variable effect on allergen PC15 (2-fold to 500-fold change). QGE031 was well tolerated. CONCLUSION: QGE031 has greater efficacy than omalizumab on inhaled and skin allergen responses in patients with mild allergic asthma. These data support the clinical development of QGE031 as a treatment of asthma.

Pharmacokinetic and pharmacodynamic characteristics of single-dose Canakinumab in patients with type 2 diabetes mellitus.

PURPOSE: Interleukin (IL)-1ß, an inflammatory molecule, contributes to the development of atherothrombosis and worsening of islet ß-cell function. Canakinumab, a human monoclonal antibody, targets IL-1ß-dependent inflammation and reduces the vascular inflammatory biomarker, high-sensitivity C-reactive protein (hsCRP), and other inflammatory cardiovascular biomarkers. Here, we aimed to assess the pharmacokinetic (PK) and pharmacodynamic characteristics, including the effect on hsCRP, of canakinumab in patients with type 2 diabetes mellitus (T2DM) after a 2-hour single-dose intravenous infusion. METHODS: This multicenter, randomized, double-blind, placebo-controlled, dose-escalation study was conducted in patients with T2DM (diagnosed ≥6 months before screening) on a stable daily dose of metformin. Patients were randomly assigned to receive a single intravenous dose of canakinumab 0.03, 0.1, 0.3, 1.5, or 10 mg/kg or placebo. The study was initially designed with 1 small cohort (15 patients, 0.3 mg/kg) on a stable dose of metformin ≥500 mg/d for an initial tolerability evaluation; all other patients were on a stable dose of ≥850 mg/d of metformin. The PK profile was assessed at 0 and 2 hours and at days 2, 14, 28, 56, 84, and 168. Changes in hsCRP and hemoglobin (Hb) A1c levels were assessed at weeks 4, 8, 12, and 24. FINDINGS: Of the 231 enrolled patients, 222 completed the study. Median hsCRP values at screening ranged from 1.8 to 3.2 mg/L, and the median daily dose of metformin ranged from 1000 to 2000 mg. Exposure to canakinumab was dose proportional. The mean half-life ranged from 17 to 26 days, and mean systemic clearance ranged from 0.094 to 0.128 mL/h/kg. Dose-related reductions in hsCRP were significantly greater with canakinumab compared with those with placebo at week 4 (-0.2 mg/L, -0.5 mg/L, -1.5 mg/L, and -1.7 mg/L with the 0.1-, 0.3-, 1.5-, and 10-mg/kg doses, respectively; all, P < 0.05). Significant reductions in hsCRP were maintained up to week 12 with the 2 highest doses of canakinumab (-0.8 mg/L with 1.5 mg/kg and -1.3 mg/L with 10 mg/kg; both, P < 0.05). A placebo-adjusted decrease in HbA1c of 0.31% at week 12 was reported with canakinumab 10 mg/kg (P = 0.038), and a reduction of 0.23% at week 4 was found with canakinumab 1.5 mg/kg (P = 0.011). IMPLICATIONS: The findings from this study suggest that IL-1ß blockade after single-dose administration of canakinumab at 1.5 and 10 mg/kg provided sustained suppression of hsCRP levels for 12 weeks in patients with T2DM. ClinicalTrials.gov identifier: NCT00900146.

Safety and tolerability of canakinumab, an IL-1ß inhibitor, in type 2 diabetes mellitus patients: a pooled analysis of three randomised double-blind studies.

BACKGROUND: We aimed to assess the safety and tolerability of different doses of canakinumab versus placebo in patients with type 2 diabetes mellitus (T2DM). METHODS: Data were pooled from three studies in 1026 T2DM patients with different routes of administration, treatment regimens and follow-up duration. Canakinumab groups were categorised as low (0.03 mg/kg i.v. once; N = 20), intermediate (0.1 and 0.3 mg/kg i.v. once, 5 and 15 mg s.c. monthly; N = 247), medium (1.5 mg/kg i.v. once, 50 mg s.c. monthly and 150 mg s.c. once; N = 268), and high doses (10 mg/kg i.v. once and 150 mg s.c. monthly; N = 137) and compared with placebo (N = 354). Incidences of adverse events (AEs), serious AEs (SAEs), discontinuations due to AEs, deaths, AEs of special interest related to interleukin-1ß inhibition and T2DM disease, and laboratory abnormalities related to haematology and biochemistry parameters were reported. Safety was also analysed by age (<65, ≥65) and gender. RESULTS: Average exposure across all groups was ≈ 6 months (maximum ~17 months). No dose response in AEs was observed but a trend towards more patients having at least one AE across canakinumab groups relative to placebo (P = 0.0152) was observed. SAEs were few and the incidence rate for most canakinumab groups was lower than that of placebo group except for the high-dose group (0.94% versus 0.58% per month in placebo). A total of five patients discontinued treatment due to AEs across treatment groups. No death was reported in any of the three studies. A small, non-significant increase in the incidence rate of infection AEs was observed on canakinumab groups relative to placebo. Canakinumab was associated with mostly mild decreases in WBC, neutrophils and platelet counts. Additionally, mild increases in SGPT, SGOT and bilirubin were reported. Overall, despite small differences, no clinically relevant findings were observed with respect to laboratory values and vital signs. CONCLUSIONS: This pooled analysis demonstrated that canakinumab was safe and well tolerated over a treatment period up to 1.4 years at the four pooled doses evaluated, in agreement with safety findings reported in the individual studies.

Pharmacokinetic and pharmacodynamic properties of canakinumab in patients with gouty arthritis.

Pharmacokinetics and pharmacodynamics of the anti-interleukin (IL)-1ß monoclonal antibody, canakinumab, in gouty arthritis patients from three studies are reported. Canakinumab has low serum clearance (0.214 L/day), low steady-state volume of distribution (7.44 L), a 25.8-day half-life, and approximately 60% subcutaneous absolute bioavailability in a typical 93-kg patient. Creatinine clearance had a small positive impact on serum canakinumab clearance that is not likely to be clinically relevant. Binding to circulating IL-1ß was demonstrated by increases in total serum IL-1ß following canakinumab dosing. Total IL-1ß kinetics and canakinumab pharmacokinetics were characterized by a population-based pharmacokinetic-binding model, where the estimated apparent in vivo dissociation constant (signifying binding affinity of canakinumab to circulating IL-1ß) was 0.99 nmol/L in gouty arthritis patients. Canakinumab treatment provided rapid, sustained decreases in C-reactive protein and serum amyloid A, provided superior pain relief to triamcinolone acetonide, and increased time to first recurrent attack (P ≤ 0.01 favoring all canakinumab doses vs. triamcinolone acetonide).

Bioequivalence of canakinumab liquid pre-filled syringe and reconstituted lyophilized formulations following 150 mg subcutaneous administration: a randomized study in healthy subjects.

BACKGROUND: Canakinumab is a human anti-interleukin-1beta antibody approved for the treatment of cryopyrin associated periodic syndrome currently formulated as a lyophilized powder requiring reconstitution. A new formulation (solution for injection as pre-filled syringe) has been developed to avoid reconstitution. OBJECTIVE: The objective of this study was to evaluate the bioequivalence of pre-filled syringe and reconstituted formulations following 150 mg administration in healthy subjects. METHODS: This was an open-labeled, randomized, single dose, parallel-group study in 130 healthy subjects, followed for 120 days. Subjects received a single subcutaneous injection of 150 mg canakinumab after either reconstitution or in pre-filled syringe formulation, followed by pharmacokinetics/pharmacodynamics evaluations and safety assessments. The main outcome measure for the study was the pharmacokinetic bioequivalence of the two formulations, which was concluded if the 90% confidence intervals for the ratios of AUC(last) (area under the serum concentration-time curve from time zero to time of last measurable concentration) and C(max) (maximum serum concentration) were entirely contained within the interval, 0.80-1.25. RESULTS: The arithmetic mean values for the exposure parameters C(max) and AUC(last) were similar for the two formulations. The geometric mean ratio (pre-filled syringe vs. lyophilized form) of C(max) and AUC(last) were 0.99 and 1.01. The associated 90% confidence intervals were 0.90 to 1.08 and 0.94 to 1.09, respectively. Most common adverse events were headache and nasopharyngitis. Neutropenia occurred in 2 cases (reported as serious adverse events). No deaths occurred. CONCLUSION: The 150 mg liquid pre-filled syringe and lyophilized formulations of canakinumab are bioequivalent.

A phase I study of zoledronic acid and low-dose cyclophosphamide in recurrent/refractory neuroblastoma: a new approaches to neuroblastoma therapy (NANT) study.

BACKGROUND: Zoledronic acid, a bisphosphonate, delays progression of bone metastases in adult malignancies. Bone is a common metastatic site of advanced neuroblastoma. We previously reported efficacy of zoledronic acid in a murine model of neuroblastoma bone invasion prompting this Phase I trial of zoledronic acid with cyclophosphamide in children with neuroblastoma and bone metastases. The primary objective was to determine recommended dosing of zoledronic acid for future trials. PROCEDURE: Escalating doses of intravenous zoledronic acid were given every 28 days with oral metronomic cyclophosphamide (25 mg/m(2)/day). Toxicity, response, zoledronic acid pharmacokinetics, bone turnover markers, serum IL-6, and sIL-6R were evaluated. RESULTS: Twenty-one patients, median age 7.5 (range 0.8-25.6) years were treated with 2 mg/m(2) (n = 4), 3 mg/m(2) (n = 3), or 4 mg/m(2) (n = 14) zoledronic acid. Fourteen patients were evaluable for dose escalation. A median of one (range 1-18) courses was given. Two dose limiting toxicities (grade 3 hypophosphatemia) occurred at 4 mg/m(2) zoledronic acid. Other grades 3-4 toxicities included hypocalcemia (n = 2), elevated transaminases (n = 1), neutropenia (n = 2), anemia (n = 1), lymphopenia (n = 1), and hypokalemia (n = 1). Osteosclerosis contributed to fractures in one patient after 18 courses. Responses in evaluable patients included 1 partial response, 9 stable disease (median 4.5 courses, range 3-18), and 10 progressions. Zoledronic acid pharmacokinetics were similar to adults. Markers of osteoclast activity and serum IL-6 levels decreased with therapy. CONCLUSIONS: Zoledronic acid with metronomic cyclophosphamide is well tolerated with clinical and biologic responses in recurrent/refractory neuroblastoma. The recommended dose of zoledronic acid is 4 mg/m(2) every 28 days.

Investigation of the pharmacokinetic interactions of deferasirox, a once-daily oral iron chelator, with midazolam, rifampin, and repaglinide in healthy volunteers.

Deferasirox, a newly developed iron chelator, was coadministered orally with either a known inducer of drug metabolism or with cosubstrates for cytochrome P450 (CYP) to characterize the potential for drug-drug interactions. In the induction assessment, single-dose deferasirox pharmacokinetics were obtained in the presence and absence of a repeated-dose regimen of rifampin. In the CYP3A interaction evaluation, midazolam and its active hydroxylated metabolite were assessed after single doses of midazolam in the presence and absence of steady-state concentrations of deferasirox. To test for interaction at the level of CPY2C8, single-dose repaglinide pharmacokinetics/pharmacodynamics were determined with and without repeated-dose administration of deferasirox. After rifampin, a significant reduction (44%) in plasma exposure (AUC) to deferasirox was observed. Upon coadministration of midazolam, there was a modest reduction of up to 22% in midazolam exposure (AUC, C(max)), suggesting a modest induction of CYP3A4/5 by deferasirox. Def erasirox caused increases in repaglinide plasma C(max) and AUC of 1.5-fold to over 2-fold, respectively, with little change in blood glucose measures. Specific patient prescribing recommendations were established when coadministering deferasirox with midazolam, repaglinide, and rifampin. These recommendations may also apply to other substrates of CYP3A4/5 and CYP2C8 or potent inducers of glucuronidation.

In vitro and in vivo induction of cytochrome p450: a survey of the current practices and recommendations: a pharmaceutical research and manufacturers of america perspective.

Cytochrome P450 (P450) induction is one of the factors that can affect the pharmacokinetics of a drug molecule upon multiple dosing, and it can result in pharmacokinetic drug-drug interactions with coadministered drugs causing potential therapeutic failures. In recent years, various in vitro assays have been developed and used routinely to assess the potential for drug-drug interactions due to P450 induction. There is a desire from the pharmaceutical industry and regulatory agencies to harmonize assay methodologies, data interpretation, and the design of clinical drug-drug interaction studies. In this article, a team of 10 scientists from nine Pharmaceutical Research and Manufacturers of America (PhRMA) member companies conducted an anonymous survey among PhRMA companies to query current practices with regards to the conduct of in vitro induction assays, data interpretation, and clinical induction study practices. The results of the survey are presented in this article, along with reviews of current methodologies of in vitro assays and in vivo studies, including modeling efforts in this area. A consensus recommendation regarding common practices for the conduct of P450 induction studies is included.

Biodistribution and plasma protein binding of zoledronic acid.

The bisphosphonate zoledronic acid is a potent inhibitor of osteoclast-mediated bone resorption. To investigate drug biodistribution and elimination, (14)C-zoledronic acid was administered intravenously to rats and dogs in single or multiple doses and assessed for its in vitro blood distribution and plasma protein binding in rat, dog, and human. Drug exposure in plasma, bones, and noncalcified tissues was investigated up to 240 days in rats and 96 h in dogs using radiometry after dissection. Drug biodistribution in the rat and within selected bones from dog was assessed by autoradiography. Concentrations of radioactivity showed a rapid decline in plasma and noncalcified tissue but only a slow decline in bone, to approximately 50% of peak at 240 days post dose, whereas the terminal half-lives (50-200 days) were similar in bone and noncalcified tissues, suggesting redistribution of drug from the former rather than prolonged retention in the latter. Uptake was highest in cancellous bone and axial skeleton. At 96 h after dose, the fraction of dose excreted was 36% in rat and 60% in dog; 94 to 96% of the excreted radioactivity was found in urine. Blood/plasma concentration ratios were 0.52 to 0.59, and plasma protein binding of zoledronic acid was moderate to low in all species. The results suggest that a fraction of zoledronic acid is reversibly taken up by the skeleton, the elimination of drug is mainly by renal excretion, and the disposition in blood and noncalcified tissue is governed by extensive uptake into and slow release from bone.

The clinical pharmacokinetics of darifenacin.

Darifenacin hydrobromide is a selective muscarinic M(3) receptor antagonist that is indicated for use in treatment of overactive bladder disorder. Darifenacin was found to have a short terminal elimination half-life after intravenous and immediate-release oral dosage forms (3-4 hours) but this increased with a prolonged-release (PR) formulation (14-16 hours). The absolute bioavailability of darifenacin from 7.5 and 15 mg PR tablets was estimated to be 15.4% and 18.6%, respectively. With repeated once-daily oral administration of the PR formulation, peak plasma concentrations of darifenacin are achieved approximately 7 hours post-dose. After oral administration, darifenacin is well absorbed from the gastrointestinal tract and very little unchanged drug (<2%) is recovered in the faeces. Steady state is achieved after 6 days of once-daily administration of the PR formulation. As expected, values of peak plasma concentration (C(max)) and area under the plasma concentration-time curve are dose dependent, although the increase in plasma concentrations is proportionally greater than the increase in dose owing to saturation of presystemic metabolism. From intravenous administration, it has been established that darifenacin possesses a moderate-to-high hepatic extraction ratio, with high plasma clearance (36-52 L/h) and a volume of distribution (165-276L) that exceeds total body water. It is highly protein bound (98%), primarily to alpha(1)-acid glycoprotein. Darifenacin is subject to extensive hepatic metabolism, with 3% of unchanged drug excreted in urine and faeces. Metabolism is mediated by hepatic cytochrome P450 2D6 and 3A4, the main metabolic routes being monohydroxylation in the dihydrobenzfuran ring, dihydrobenzfuran ring opening, and N-dealkylation of the pyrrolidine nitrogen. Several possibly important drug-drug interactions have been identified with darifenacin, including ketoconazole, erythromycin and fluconazole, each of which increases darifenacin mean C(max) by 9.52-, 2.28- and 1.88-fold, respectively. When given with imipramine, darifenacin causes 1.6-fold higher plasma concentrations of the antidepressant and its major metabolite. Moderate hepatic impairment, but not renal insufficiency, has been shown to increase plasma concentrations of the drug. The pharmacokinetic profile of darifenacin is not affected by food.

FTY720, a novel immunomodulator in de novo kidney transplant patients: pharmacokinetics and exposure-response relationship.

The pharmacokinetics, safety, and preliminary efficacy of FTY720, a novel immunomodulator, were examined in de novo renal transplant patients. Both noncompartmental and population methods were used to estimate pharmacokinetic estimates in the patients. The steady-state plasma concentrations of FTY720 increased in accordance with maintenance dose level, indicating linearity in clearance and volume of distribution over the 0.25- to 2.5-mg dose range. The pharmacokinetics of FTY720 in de novo renal transplant patients were characterized by the long terminal phase half-life of approximately 200 hours across doses, high volume of distribution (>3000 L), and low clearance (10.8 L/h). The intersubject variation of clearance was 55%, and the intrasubject variation of FTY720 concentrations was 28%. The population analysis revealed significant positive relationships between baseline alkaline phosphatase and clearance, as well as between baseline body weight on apparent volume of distribution. There was no relationship between FTY720 concentrations within a given FTY720 dose cohort and the rate of allograft rejection.

QT and QTc interval with standard and supratherapeutic doses of darifenacin, a muscarinic M3 selective receptor antagonist for the treatment of overactive bladder.

Prolongation of QT interval on an electrocardiogram is a valuable predictor of a drug's ability to cause potentially fatal ventricular tachyarrhythmia (torsades de pointes). Darifenacin is a muscarinic M3 selective receptor antagonist developed for the treatment of overactive bladder, a debilitating condition that is particularly prevalent in the older population. This 7-day, randomized, parallel-group study (n=188) measured QT/QTc interval in healthy volunteers receiving once-daily darifenacin at steady-state therapeutic (15 mg) and supratherapeutic (75 mg) doses, alongside controls receiving placebo or moxifloxacin (positive control, 400 mg) once daily. There was no significant increase in QTcF interval with darifenacin treatment compared with placebo. Mean changes from baseline at pharmacokinetic Tmax versus placebo were -0.4 and -2.2 milliseconds in the darifenacin 15 mg and 75 mg groups, respectively, compared with +11.6 milliseconds in the moxifloxacin group (P<.01). This study demonstrates that darifenacin does not prolong QT/QTc interval.

Effect of age on the pharmacokinetics of duloxetine in women.

AIMS: The effect of age on duloxetine pharmacokinetics was evaluated in healthy volunteers and in patients with urinary incontinence. METHODS: Twenty-four healthy subjects (12 women 65-77 years, and 12 women 32-50 years) were given a single 40-mg oral dose of duloxetine in Study 1. Plasma concentration-time data were analysed by noncompartmental pharmacokinetic methods. Sparse plasma samples were obtained from patients with urinary incontinence treated in two phase II studies: 70 women (24-77 years) who received duloxetine 20 mg day(-1), 30 mg day(-1), or 40 mg day(-1) in Study 2A and 128 women (28-64 years) who received duloxetine 20 mg day(-1), 40 mg day(-1), or 80 mg day(-1) in Study 2B. Based upon the combined data, a model was developed to characterize population pharmacokinetics of duloxetine using the nonlinear mixed-effects modelling program (NONMEM). RESULTS: In Study 1, the elderly (> or = 65 years) exhibited a statistically significant slower elimination rate constant lambdaz compared with younger subjects [elderly-younger difference = -0.022 h(-1)[95% confidence interval (CI) -0.036, -0.008]]. However, no statistically significant differences in either CL/F [elderly-younger difference = -17.4 l h(-1) (95% CI -41.1, 6.23)] or V/F [elderly-younger difference = 115.9 l (95% CI -168.6, 400.4)] were observed. The population pharmacokinetic analysis of Studies 2A and 2B revealed that the CL/F of duloxetine decreased with increasing age. Despite statistical significance, the age effect only accounted for 3% of the interindividual variability in CL/F and unexplained sources of the variation in clearance were still substantial (> 50%). Adverse events were generally mild to moderate, and the incidence of adverse events was generally similar in elderly and non-elderly participants in these studies. CONCLUSIONS: Whereas the results suggest that age has an effect on duloxetine pharmacokinetics, primarily reflected as a slower lambdaz in the elderly, the magnitude of mean changes in CL/F, or V/F was small relative to the large interindividual variation in pharmacokinetics. Elderly participants had a safety profile of duloxetine comparable to their younger counterparts. Specific dose recommendations for duloxetine in the elderly are not warranted.

Bioavailability and bioequivalence trials: statistics & pharmacokinetic principles.

This document has been prepared as a set of workshop material, which will be presented in the International Congress on Medical and Care Compunetics in June 2004 in Den Hague, The Netherlands. The workshop is divided into two parts and deals with the fundamentals of the bioavailability and bioequivalence studies. First part of the workshop deals with the pharmacokinetic principles, and the second part discusses the statistical approaches and the data analysis using the Statistical Analysis Software (SAS).