Pharmacokinetic and Pharmacodynamic Characteristics of Tripegfilgrastim, a Pegylated G-CSF, in Pediatric Patients with Solid Tumors.

A long-acting granulocyte colony-stimulating factor, tripegfilgrastim, was approved in Korea for the prevention of chemotherapy-induced neutropenia in adult patients. In this study, we evaluated the pharmacokinetics, pharmacodynamics, and safety of tripegfilgrastim in pediatric patients. A phase I, open-label, single ascending-dose study was performed in pediatric patients with solid tumors or lymphoma (ClinicalTrials.gov, NCT02963389). The patients were stratified according to age groups (aged 6 to 12 or 12 to 19 years) and received a single subcutaneous dose of tripegfilgrastim 60 µg/kg or 100 µg/kg. Tripegfilgrastim was administered 24 hours after the end of the chemotherapy, and serial blood sampling and safety monitoring were conducted. Twenty-seven patients with solid tumors were enrolled in this study. Tripegfilgrastim was detectable in plasma for an extended period (terminal half-life > 40 hours), and plasma concentrations increased slightly less than dose proportionally. The mean duration of grade 4 neutropenia was reduced as the average tripegfilgrastim concentration during the initial neutrophil recovery process increased. No substantial differences in the pharmacokinetic and pharmacodynamic responses were observed between the two age groups. When stratified by body weight, weighing more than 45 kg has a higher risk of a prolonged neutropenia period when receiving the lower dose (60 µg/kg) of tripegfilgrastim. Tripegfilgrastim was generally safe and well-tolerated in the pediatric patients. These results justify further clinical investigations of tripegfilgrastim at 100 µg/kg dose in pediatric patients.

Biosimilarity Assessment of 2 Filgrastim Therapeutics in Healthy Volunteers.

This study aimed to compare the pharmacokinetic, pharmacodynamic, and safety profiles of a proposed biosimilar and innovator filgrastim therapeutics in healthy volunteers. In a crossover design, 23 subjects received a single subcutaneous injection of 300-µg filgrastim, followed by a 7-day washout period. Assessed pharmacokinetic parameters were the maximum observed filgrastim serum concentration (Cmax ), time to reach Cmax (tmax ), the area under the concentration-time curve (AUC), and elimination half-life. Pharmacodynamics were assessed by the maximum observed absolute neutrophil count effect (Emax ), tmax,E (time to reach Emax ), and the area under the effect of the absolute neutrophil count -time curve. The test/reference ratio (90% confidence intervals) of Cmax of 0.992 (0.860-1.143), AUC0-inf of 0.995 (0.891-1.111), Emax of 0.952 (0.841, 1.078), and area under the effect of the absolute neutrophil count -time curve from time zero to 96 hours of 0.939 (0.854-1.032), were all well within the predefined equivalence boundaries of 80% and 125%. Obtained values for tmax (∼4 hours), tmax,E (∼15 hours), and elimination half-life (∼3.5 hours) were comparable between 2 treatment groups. The local tolerability and incidence of adverse events were comparable, with no clinically meaningful difference between biosimilar and innovator products. Altogether, the results suggested a high similarity of the proposed biosimilar to the innovator filgrastim in healthy volunteers.

Pharmacokinetics of Voxelotor in Patients With Renal and Hepatic Impairment.

Two open-label studies assessed the safety, tolerability, and pharmacokinetics of Oxbryta (voxelotor) in subjects with hepatic or renal impairment. Eight subjects with severe renal impairment (estimated glomerular filtration rate <30 mL/min/1.73 m2 ) and 8 healthy age-, sex-, and body mass index-matched controls were administered a single oral dose of voxelotor 900 mg. Seven patients with mild (Child-Pugh A), moderate (Child-Pugh B), and severe (Child-Pugh C) hepatic impairment and healthy age-, sex-, and body mass index-matched controls (7:7:7:7) were administered a single oral dose of voxelotor 1500 mg, except those with severe hepatic impairment (600 mg). There was no apparent effect of renal function on the excretion of voxelotor based on comparable half-life values between subjects with severe renal impairment and healthy matched controls. Mean area under the concentration-time curve from time 0 to infinity (AUC0-inf ) values were lower by approximately 50% (plasma) and 25% (whole blood) in subjects with severe renal impairment compared with controls. Accordingly, dose adjustment is not required in patients with severe renal impairment. Voxelotor plasma and whole-blood exposures were slightly increased in subjects with mild and moderate hepatic impairment. Mean AUC0-inf values were approximately 9% to 18% higher compared with those of healthy matched controls. Dose adjustment is therefore not required in patients with mild or moderate hepatic impairment. Voxelotor mean AUC0-inf values were approximately 90% higher in subjects with severe hepatic impairment. A lower voxelotor dose (1000 mg) is recommended for patients with severe hepatic impairment. Voxelotor was well tolerated in all treatment groups.

A phase 1/2 ascending dose study and open-label extension study of voxelotor in patients with sickle cell disease.

New treatments directly targeting polymerization of sickle hemoglobin (HbS), the proximate event in the pathophysiology of sickle cell disease (SCD), are needed to address the severe morbidity and early mortality associated with the disease. Voxelotor (GBT440) is a first-in-class oral therapy specifically developed to treat SCD by modulating the affinity of hemoglobin (Hb) for oxygen, thus inhibiting HbS polymerization and downstream adverse effects of hemolytic anemia and vaso-occlusion. GBT440-001 was a phase 1/2 randomized, double-blind, placebo-controlled, single and multiple ascending dose study of voxelotor in adult healthy volunteers and patients with SCD, followed by a single-arm, open-label extension study. This report describes results of voxelotor (500-1000 mg per day) in patients with sickle cell anemia. The study evaluated the safety, tolerability, pharmacokinetic, and pharmacodynamic properties of voxelotor and established proof of concept by improving clinical measures of anemia, hemolysis, and sickling. Thirty-eight patients with SCD received 28 days of voxelotor 500, 700, or 1000 mg per day or placebo; 16 patients received 90 days of voxelotor 700 or 900 mg per day or placebo. Four patients from the 90-day cohort were subsequently enrolled in an extension study and treated with voxelotor 900 mg per day for 6 months. All patients who received multiple doses of voxelotor for ≥28 days experienced hematologic improvements including increased Hb and reduction in hemolysis and percentage of sickled red cells, supporting the potential of voxelotor to serve as a disease-modifying therapy for SCD. Voxelotor was well tolerated with no treatment-related serious adverse events and no evidence of tissue hypoxia. These trials were registered at www.clinicaltrials.gov as #NCT02285088 and #NCT03041909.

Avatrombopag maleate for the treatment of periprocedural thrombocytopenia in patients with chronic liver disease.

Avatrombopag maleate (Doptelet; Dova Pharmaceuticals) is an oral, small-molecule second-generation thrombopoietin (TPO) receptor agonist under development for the treatment of thrombocytopenia. Recently approved by the U.S. Food and Drug Administration (FDA) for the treatment of periprocedural thrombocytopenia in patients with chronic liver disease on the basis of the results of two phase III trials, it is currently under investigation for treatment of immune thrombocytopenia (two randomized trials demonstrating efficacy have already been completed), chemotherapy-induced thrombocytopenia and perioperative thrombocytopenia in patients undergoing major surgical procedures. This review will evaluate the preclinical pharmacology, pharmacokinetics, clinical studies, safety, indications and drug interactions of avatrombopag, with a focus on its use for the treatment of periprocedural thrombocytopenia in patients with chronic liver disease.

Pharmacokinetic-pharmacodynamic modelling of neutrophil response to G-CSF in healthy subjects and patients with chemotherapy-induced neutropenia.

AIM: The objective of the present study was to use pharmacokinetic-pharmacodynamic modelling to characterize the effects of chemotherapy on the granulopoietic system and to predict the absolute neutrophil counts (ANCs) for patients with chemotherapy-induced neutropenia treated with filgrastim and pegfilgrastim. METHODS: Data were extracted from 10 phase I-III studies conducted in 110 healthy adults, and 618 adult and 52 paediatric patients on chemotherapy following administration of filgrastim or pegfilgrastim. The structural model accounted for ANC dynamics and the effects of filgrastim and pegfilgrastim, chemotherapy and corticosteroids. The impact of neutrophils on drug disposition was based on a drug receptor-binding model that assumed quasi-equilibrium and stimulation of the production and maturation of neutrophils upon treatment. The chemotherapy and corticosteroid effects were represented by kinetic-pharmacodynamic-type models, where chemotherapy stimulated elimination of neutrophil precursors at the mitotic stage, and corticosteroids stimulated neutrophil production. RESULTS: The systemic half-lives of filgrastim (2.6 h) and pegfilgrastim (10.1 h) were as expected. The effective half-life of chemotherapy was 9.6 h, with a 2-day killing effect. The rate of receptor elimination from mitotic compartments exhibited extreme interindividual variability (% coefficient of variation >200), suggesting marked differences in sensitivity to chemotherapy effects on ANCs. The stimulatory effects of pegfilgrastim were significantly greater than those of filgrastim. Model qualification confirmed the predictive capability of this model. CONCLUSION: This qualified model simulates the time course of ANC in the absence or presence of chemotherapy and predicts nadir, time to nadir and time of recovery from different grades of neutropenia upon treatment with filgrastim and pegfilgrastim.

Safety and Biosimilarity of ior®LeukoCIM Compared to Neupogen® Based on Toxicity, Pharmacodynamic, and Pharmacokinetic Studies in the Sprague-Dawley Rat.

This study examined the safety, pharmacodynamic and pharmacokinetic similarity of the human recombinant filgrastim products ior®LeukoCIM and Neupogen® following a 28-day repeated subcutaneous dose administration in male and female Sprague-Dawley rats with a 14-day recovery period. Safety profiling was based on clinical observations, clinical pathology, and pathology findings for control rats dosed with vehicle and rats dosed either with 15, 75, and 150 µg/kg of ior®LeukoCIM or with 150 µg/kg of Neupogen®. The major adverse treatment-related clinical finding was mild to severe swelling of the hock-joint (tarsal joint) and hind limb, alone or accompanied with lameness which was more prominent in males and which had a similar frequency of occurrence for both ior®LeukoCIM and Neupogen®. All adverse findings were fully reversible. As expected, ior®LeukoCIM and Neupogen® both increased white blood cell and neutrophil levels in rats and to a similar extent for high-dose ior®LeukoCIM and Neupogen®. The pharmacokinetics of filgrastim following dosing with ior®LeukoCIM were well behaved and comparable for high-dose ior®LeukoCIM and Neupogen®. The results of this study imply that ior®LeukoCIM and Neupogen® had similar safety profiles, pharmacodynamic responses, and pharmacokinetic profiles that suggest they are biosimilar.

A phase III, randomized, non-inferiority study comparing the efficacy and safety of biosimilar filgrastim versus originator filgrastim for chemotherapy-induced neutropenia in breast cancer patients.

OBJECTIVES:: To compare the efficacy and safety of two filgrastim formulations for controlling chemotherapy-induced neutropenia and to evaluate the non-inferiority of the test drug relative to the originator. METHODS:: This phase III non-inferiority study had a randomized, multicenter, and open-label design. The patients were randomized at a ratio of 1:1 with a follow-up period of 6 weeks for each patient. In both study arms, filgrastim was administered subcutaneously at a daily dose of 5 mg/kg body weight. The primary endpoint was the rate of grade 4 neutropenia in the first treatment cycle. The secondary endpoints were the duration of grade 4 neutropenia, the generation of anti-filgrastim antibodies, and the rates of adverse events, laboratory abnormalities, febrile neutropenia, and neutropenia of any grade. RESULTS:: The primary efficacy analysis demonstrated the non-inferiority of the test drug compared with the originator drug; the upper limit of the 90% confidence interval (CI) for the rate of neutropenia between the two groups (12.61%) was lower than the established margin of non-inferiority. The two treatments were similar with respect to the secondary endpoints and safety. CONCLUSION:: The efficacy and safety profile of the test drug were similar to those of the originator product based on the rate of grade 4 neutropenia in the first treatment cycle. This study supports Anvisa's approval of the first biosimilar drug manufactured by the Brazilian industry (Fiprima¯).

A phase III, randomized, non-inferiority study comparing the efficacy and safety of biosimilar filgrastim versus originator filgrastim for chemotherapy-induced neutropenia in breast cancer patients

OBJECTIVES: To compare the efficacy and safety of two filgrastim formulations for controlling chemotherapy-induced neutropenia and to evaluate the non-inferiority of the test drug relative to the originator. METHODS: This phase III non-inferiority study had a randomized, multicenter, and open-label design. The patients were randomized at a ratio of 1:1 with a follow-up period of 6 weeks for each patient. In both study arms, filgrastim was administered subcutaneously at a daily dose of 5 mg/kg body weight. The primary endpoint was the rate of grade 4 neutropenia in the first treatment cycle. The secondary endpoints were the duration of grade 4 neutropenia, the generation of anti-filgrastim antibodies, and the rates of adverse events, laboratory abnormalities, febrile neutropenia, and neutropenia of any grade. RESULTS: The primary efficacy analysis demonstrated the non-inferiority of the test drug compared with the originator drug; the upper limit of the 90% confidence interval (CI) for the rate of neutropenia between the two groups (12.61%) was lower than the established margin of non-inferiority. The two treatments were similar with respect to the secondary endpoints and safety. CONCLUSION: The efficacy and safety profile of the test drug were similar to those of the originator product based on the rate of grade 4 neutropenia in the first treatment cycle. This study supports Anvisa’s approval of the first biosimilar drug manufactured by the Brazilian industry (Fiprima¯).

A cell-level model of pharmacodynamics-mediated drug disposition.

We aimed to develop a cell-level pharmacodynamics-mediated drug disposition (PDMDD) model to analyze in vivo systems where the PD response to a drug has an appreciable effect on the pharmacokinetics (PK). An existing cellular level model of PD stimulation was combined with the standard target-mediated drug disposition (TMDD) model and the resulting model structure was parametrically identifiable from typical in vivo PK and PD data. The PD model of the cell population was controlled by the production rate k in and elimination rate k out which could be stimulated or inhibited by the number of bound receptors on a single cell. Simulations were performed to assess the impact of single and repeated dosing on the total drug clearance. The clinical utility of the cell-level PDMDD model was demonstrated by fitting published data on the stimulatory effects of filgrastim on absolute neutrophil counts in healthy subjects. We postulated repeated dosing as a means of detecting and quantifying PDMDD as a single dose might not be sufficient to elicit the cellular response capable of altering the receptor pool to visibly affect drug disposition. In the absence of any PD effect, the model reduces down to the standard TMDD model. The applications of this model can be readily extended to include chemotherapy-induced cytopenias affecting clearance of endogenous hematopoietic growth factors, different monoclonal antibodies and immunogenicity effects on PK.

Confirmation of Biosimilarity in a Pharmacokinetic/Pharmacodynamic Study in Healthy Volunteers for an Analytically Highly Similar Pegfilgrastim.

A phase 1 pharmacokinetic (PK) and pharmacodynamic (PD) study was conducted to demonstrate similarity of a proposed pegfilgrastim biosimilar to its reference product. In a single-dose, randomized, assessor-blinded, 2-way crossover, active-controlled PK/PD study, 66 healthy adults received the proposed pegfilgrastim biosimilar and US-licensed pegfilgrastim reference product. Primary end points were pegfilgrastim AUCt and Cmax (PK), and absolute neutrophil count AUECt and Emax (PD). Safety and immunogenicity were also measured. Fifty-six subjects completed both arms of the study. Mean pegfilgrastim concentration-time profile for both products was similar, with the 90% confidence intervals (CI) of the relative mean ratio for the primary end points falling within the predefined acceptance criteria of 80%-125% (91.7%-116.1% and 86.7%-110.2% for AUCt and Cmax , respectively). PD similarity was also demonstrated by the 95%CI of the relative mean ratio of the primary end point parameters within the predefined acceptance margins of 80%-125% (96.0%-101.6% and 92.6%-100.1% for AUECt and Emax , respectively). No statistically meaningful PK/PD differences were observed. No clinically meaningful safety or immunological differences were observed with the proposed pegfilgrastim biosimilar that were not previously identified with the reference product. The proposed pegfilgrastim biosimilar product is highly similar to the reference product with regard to PK/PD.

Totality of the evidence at work: The first U.S. biosimilar.

On March 6(th) 2015, the Food and Drug Administration (FDA) approved filgrastim-sndz (Zarxio) as the first biosimilar in the United States (US) for all indications of the reference product. Filgrastim-sndz is a biosimilar of Amgen's Neupogen and is mainly used to treat neutropenia in cancer patients receiving chemotherapy. This article presents a summary of the analytical and clinical studies submitted by Sandoz and describes how the information was integrated to provide the 'totality of the evidence' leading to the approval of the biosimilar.

Ethnopharmacology, phytochemistry, and biological activities of Cymbopogon citratus (DC.) Stapf extracts.

Cymbopogon citratus is a widely distributed perennial herb belonging to the Poaceae family and has been extensively consumed for its medicinal, cosmetic, and nutritional effects for centuries. A large number of reports have been published describing the pharmacological, biological, and therapeutic actions of this herb. In this review, we summarized the literatures on related studies (up to January, 2014) that highlighted the pharmacologic and biological effects of the major phytochemicals isolated from C. citratus extracts and its essential oil. The components of the essential oils found in C. citratus have a similar pharmacokinetic properties, including absorption, distribution, metabolism, and excretion. They are quickly absorbed following oral, pulmonary, and dermal administration. Based on the published reports, it can also be inferred that, after absorption from the small intestine, some phytochemicals in C. citratus can undergo oxidation, glucuronidation, sulfation, and/or O-methylation. Excretion is through urine, feces and/or expired volatiles. The biotransformation reactions of C. citratus bioactive constituents are essential for its relatively safe consumption and therapeutic applications. The data available so far warrant further studies evaluating C. citratus pharmacokinetics. Reliable pharmacokinetic data in humans would be critical for a better understanding of the the systemic handling of C. citratus.

Eltrombopag in patients with chronic liver disease.

INTRODUCTION: Thrombocytopenia may represent a barrier to optimal management of chronic liver disease patients undergoing invasive procedures, or who need to be treated with interferon-based antiviral therapy. Eltrombopag is a thrombopoietic drug that acts upon binding thrombopoietin receptor and stimulates megakaryocytopoiesis and platelet production. AREAS COVERED: A summary of the preclinical studies and of studies carried out in patients with chronic liver disease with eltrombopag are presented in this paper. Data are based on abstracts from journal articles and international conferences found in a PubMed search of literature published up to November 2012. EXPERT OPINION: Eltrombopag has shown to be capable of reducing the need for platelet transfusion in thrombocytopenic patients with advanced liver disease undergoing invasive procedures and help increase the sustained virological response rate to interferon-based antiviral therapy in patients with chronic hepatitis C who were poor candidates to treatment because of thrombocytopenia. In chronic liver disease patients, the possible benefits of eltrombopag administration should be accurately weighed against the adverse events profile of the drug due to possible concerns regarding the occurrence of thromboembolic events and the potential for decompensation of chronic liver disease.

Cardiovascular safety of anagrelide in healthy subjects: effects of caffeine and food intake on pharmacokinetics and adverse reactions.

BACKGROUND: Essential thrombocythaemia (ET) is a rare clonal myeloproliferative disorder characterized by a sustained elevation in platelet count and megakaryocyte hyperplasia. Anagrelide is used in the treatment of ET, where it has been shown to reduce platelet count. Anagrelide is metabolized by cytochrome P450 (CYP) 1A2, and previous studies of the effect of food on the bioavailability and pharmacokinetics of anagrelide were conducted prior to the identification of the active metabolite, 3-hydroxyanagrelide. OBJECTIVES: The objectives of this study were to determine the effect of food and caffeine on the pharmacokinetics of anagrelide and its active metabolite, 3-hydroxyanagrelide, to monitor electrocardiogram (ECG) parameters following drug administration, and to document the relationship between palpitations, ECG changes and caffeine intake METHODS: Thirty-five healthy subjects who received 1 mg of anagrelide following either a 10-h fast or within 30 min of a standardized breakfast, including two cups of coffee, were studied. RESULTS: Time to maximum (peak) plasma concentration (C(max)) of anagrelide was 4.0 h in the fed and 1.5 h in the fasted group (p < 0.05); similar results were observed for 3-hydroxyanagrelide. The mean C(max) of anagrelide was 4.45 ± 2.32 ng/mL and 5.08 ± 2.99 ng/mL in the fed/caffeine and fasted groups, respectively; peak concentrations were higher for 3-hydroxyanagrelide in both the fed/caffeine and fasted groups. The most frequent adverse events (AEs) were headache (60 %) and palpitations (40 %). There were no serious AEs and all ECGs were normal, although significant reductions in PR interval, QRS length and QT interval were observed in both groups. Heart rate increased after anagrelide administration in both fed/caffeine and fasted states (p < 0.01); however, increased heart rate was significantly more frequent in the fed/caffeine state than in the fasted state (p < 0.001 for heart rate increase in the first hour after drug administration). There was a trend towards a greater heart rate increase in subjects reporting palpitations than in those without (mean heart rate ± SD at 1 h: 10.1 ± 6.4 vs. 8.0 ± 8.4 beats/min [p = 0.35]; at 4 h: 12.7 ± 7.5 vs. 9.1 ± 8.8 beats/min [p = 0.10], respectively). CONCLUSION: We conclude that food/caffeine delayed absorption of anagrelide. Anagrelide was generally well tolerated and had small effects on ECG parameters and heart rate. Caffeine may be implicated in a higher increase in heart rate and increased frequency of palpitations observed following administration of anagrelide with food/caffeine versus fasting.

Pharmacokinetics and tolerability of anagrelide hydrochloride in young (18 - 50 years) and elderly (≥ 65 years) patients with essential thrombocythemia.

OBJECTIVE: To ascertain the role of patient age as an influencing factor in the pharmacokinetics of anagrelide and to clarify whether different dosing is required in young (18 - 50 years) vs. elderly (≥ 65 years) patients with essential thrombocythemia (ET). METHOD: This Phase II, multicenter, open-label study compared the pharmacokinetics, pharmacodynamics and tolerability of anagrelide and its active metabolite, 3-hydroxy-anagrelide, in young and elderly patients with ET. Three days prior to pharmacokinetic assessment, patients divided their normal daily anagrelide into a structured twice-daily dosing (BID) schedule. Serial blood samples were obtained for pharmacokinetic and pharmacodynamic analysis over a 12-h dosing interval. Anagrelide and 3-hydroxy-anagrelide plasma concentrations were normalized to a common dose (1 mg BID) to control for dosing differences between patients. Patients were monitored routinely for adverse events (AEs) and vital signs. RESULTS: A total of 24 patients (12 young; 12 elderly) completed the study. The dose-normalized anagrelide maximum observed plasma concentration (Cmax) and area under the plasma concentration vs. time curve over one dosing interval (AUCτ), were higher in elderly patients compared with young patients (Cmax: 3.63 vs. 2.66 ng/ml; p = 0.09, AUCτ: 10.3 vs. 6.4 ng×h/ml; p = 0.01). In contrast, the dose-normalized 3-hydroxy-anagrelide Cmax and AUCτ were lower in the elderly patients when compared with young patients (Cmax: 4.19 vs. 7.26 ng/ml; p = 0.02, AUCτ: 17.4 vs. 27.6 ng×h/ml; p = 0.03). No significant difference was observed in the geometric mean terminal half-life (t1/2) of anagrelide in elderly and young patients (1.4 vs. 1.3 h, respectively; p = 0.38), whereas the geometric mean t1/2 of 3-hydroxy-anagrelide was significantly longer in the elderly patients compared with the young patients (3.5 vs. 2.7 h, respectively; p = 0.01). There were no significant differences in platelet count or vital signs between the age groups. Anagrelide was well tolerated; there were no serious AEs or AEs that led to withdrawal from the study. CONCLUSIONS: To conclude, the differences observed in anagrelide and 3-hydroxy-anagrelide pharmacokinetics do not justify using a different dosing regimen in young vs. elderly patients with ET.

A lower starting dose of eltrombopag is efficacious in Japanese patients with previously treated chronic immune thrombocytopenia.

BACKGROUND: Eltrombopag is an oral, non-peptide thrombopoietin receptor agonist that has shown efficacy and safety in chronic immune thrombocytopenia (ITP). However, ethnic differences in eltrombopag exposure have been reported: area under the curve exposure to eltrombopag was 87% greater among ITP patients of East Asian descent than among ITP patients of non-East Asian ITP descent. OBJECTIVES: To evaluate the efficacy and safety of eltrombopag by using, in Japanese ITP patients, lower starting (12.5 mg) and maximum (50 mg) doses of eltrombopag than the standard starting (50 mg) and maximum (75 mg) doses approved in the USA and Europe. PATIENTS: We examined 23 Japanese patients with previously treated chronic ITP with a platelet count of < 30,000 µL(-1) in a multicenter study comprising a randomized, double-blind, placebo-controlled phase for 6-week evaluation (15 eltrombopag, and eight placebo) and an open-label phase for 6-month evaluation (23 eltrombopag). RESULTS AND CONCLUSIONS: The response rate (platelet count of ≥ 50,000 µL(-1) ) at week 6 of the 6-week double-blind phase was 60% in eltrombopag-treated patients and 0% in placebo-treated patients. Ten of 23 patients (43.5%) responded for ≥ 75% of predefined assessment visits during the 6-month open-label phase. Notably, 22% (5/23) of patients responded to 12.5 mg of eltrombopag, which was administered within the first 3 weeks of eltrombopag treatment. Bleeding decreased with eltrombopag treatment as compared with baseline. Eltrombopag was generally well tolerated; one patient experienced a transient ischemic attack on day 9. Eltrombopag (12.5-50 mg) is effective for the management of Japanese patients with chronic ITP (NCT00540423).

Clinical pharmacokinetics, platelet response, and safety of eltrombopag at supratherapeutic doses of up to 200 mg once daily in healthy volunteers.

This was a double-blind, placebo-controlled, randomized, parallel, dose-escalation study to assess the pharmacokinetics, platelet response, safety, and tolerability of supratherapeutic doses of eltrombopag (100 mg, 150 mg, and 200 mg once daily) administered for 5 days to 33 healthy adult volunteers. Plasma eltrombopag concentrations accumulated between days 1 and 5, with average increases of 66% to 81% for area under the plasma concentration-time curve from time zero to the end of the 24-hour dosing interval (AUC(0-τ)) and 32% to 45% for maximum observed plasma concentration (C(max)) across doses. After 5 days of dosing, AUC(0-τ) was dose-proportional and C(max) was less than dose-proportional over eltrombopag 100 to 200 mg with slope estimates (90% confidence intervals) of 0.92 (0.45-1.39) and 0.76 (0.29-1.22), respectively. Platelet counts peaked at day 14, and maximum change from baseline platelet count increased dose-dependently, with mean platelet count increases of 14, 67, 107, and 150 Gi/L for placebo and eltrombopag 100 mg, 150 mg, and 200 mg, respectively. There was no notable difference in day 14 mean platelet aggregation between eltrombopag (59 to 74%) and placebo (67%), although this was not tested statistically. There was no notable difference in adverse event frequency across eltrombopag doses. Eltrombopag pharmacokinetics and platelet response were dose-dependent, and doses up to 200 mg/d were well tolerated, with safety profiles similar to placebo.

Pharmacokinetic modelling of pentoxifylline and lisofylline after oral and intravenous administration in mice.

The aim of this study was to develop pharmacokinetic models for pentoxifylline (PTX) and the R(-)-enantiomer of the PTX metabolite 1, lisofylline (LSF), in order to identify some factors influencing the absorption of these compounds from the intestines and to clarify mechanisms involved in their non-linear pharmacokinetics. Serum samples were collected after oral and intravenous administration of PTX and LSF to male CD-1 mice at two different doses. In addition, both compounds under investigation were coadministered with a modulator of drug transporters, verapamil, and an inhibitor of cytochrome P450 (CYP) 3A4, ketoconazole. Pharmacokinetic analysis revealed that a one-compartment model with Michaelis-Menten type absorption and elimination best described the pharmacokinetics of PTX, whereas the LSF concentration-time data were adequately fitted to a two-compartment model with a first-order absorption and Michaelis-Menten type elimination process. Both coadministered compounds significantly decreased the area under the concentration-time curve from 0 to 60 min calculated for PTX and increased the value of this parameter for LSF. The results of this study indirectly suggest that saturation of drug transport across intestinal cells and elimination from the central compartment may be responsible for the non-linear pharmacokinetics of PTX, whereas in the case of LSF, the dose dependency in the pharmacokinetics is solely related to the elimination from the central compartment. It seems that the observed changes in PTX and LSF concentrations after coadministration with verapamil and ketoconazole may be clinically significant, especially after chronic treatment, however further studies are necessary to assess the importance of these interactions in humans.

Interconversion and tissue distribution of pentoxifylline and lisofylline in mice.

The aim of this study was to assess the interconversion pharmacokinetics and tissue distribution of pentoxifylline and the active (R)-enantiomer of its metabolite M1, lisofylline in male CD-1 mice. Both compounds were administered intravenously at a dose of 50 mg/kg on two separate occasions. Serum and tissues were collected at different time points following drug administration. In addition, the (S)-enantiomer of M1 was administered to a group of mice and serum samples were obtained. Analyte concentrations were measured by chiral HPLC. All serum concentration versus time data were fitted simultaneously to a pharmacokinetic model incorporating interconversion processes of parent drug and metabolites. The estimated conversion clearance of (-)-(R)-M1 to pentoxifylline (CL21) was six times greater than that for the reverse process (CL12). The interconversion of pentoxifylline and (+)-(S)-M1 was faster as reflected by the values of conversion clearances CL13 and CL31 which were approximately 16 and 7 times greater in comparison with the corresponding clearances for the interconversion of pentoxifylline and (-)-(R)-M1. When fitting pharmacokinetic data of both parent compounds to a one-compartment model, the values of elimination clearances assessed were close to those obtained on the basis of the interconversion model. After administration of pentoxifylline, tissue-to-serum AUC ratios ranged from 0.1 for liver and lungs to 0.32 for brain tissue. Serum levels of its metabolite, (-)-(R)-M1 were very low, whereas its tissue levels exceeded serum concentrations. The highest value of metabolite-to-parent AUC ratio (4.98) was observed in lungs. When (-)-(R)-M1 was given as a parent drug, tissue-to-serum AUC ratios in liver, kidney, and lungs were very close and ranged from 0.64 to 0.72. At the same time, levels of its metabolite, pentoxifylline were relatively low both in serum and all tissues studied. In consequence, metabolite-to-parent AUC ratios did not exceed the value of 0.27. In conclusion, reversible metabolism plays a modest role in the disposition of pentoxifylline and (-)-(R)-M1. It seems that pentoxifylline has less favourable pharmacokinetic properties than (-)-(R)-M1 due to lower concentrations attained in target organs. High levels of (-)-(R)-M1 observed after pentoxifylline administration in certain tissues such as liver or lungs suggest that pentoxifylline may constitute an effective prodrug for (-)-(R)-M1 in these organs.