Effect of escalating doses of recombinant human granulocyte colony-stimulating factor (filgrastim) on circulating neutrophils in healthy subjects

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 (C_max ), time to reach C_max (t_max ), the area under the concentration-time curve (AUC), and elimination half-life. Pharmacodynamics were assessed by the maximum observed absolute neutrophil count effect (E_max ), t_max,E (time to reach E_max ), and the area under the effect of the absolute neutrophil count -time curve. The test/reference ratio (90% confidence intervals) of C_max of 0.992 (0.860-1.143), AUC_0-inf of 0.995 (0.891-1.111), E_max 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 t_max (∼4 hours), t_max,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 and Pharmacodynamics of a Proposed Pegfilgrastim Biosimilar MSB11455 Versus the Reference Pegfilgrastim Neulasta in Healthy Subjects: A Randomized, Double-blind Trial

PURPOSE

MSB11455 is a proposed biosimilar to the reference pegfilgrastim (Neulasta®). This pivotal equivalence study (NCT03251248) assessed the pharmacokinetic and pharmacodynamic equivalence of MSB11455 to the reference product.

METHODS

This 2-way, 2-sequence, group-sequential, crossover study was conducted in healthy subjects. Subjects received a single subcutaneous dose of MSB11455 or the reference product (both 6 mg/0.6 mL) on Day 1 of each study period. Pharmacokinetic and pharmacodynamic (absolute neutrophil count; ANC) samples were taken predose and up to day 16 post-dose. Non-compartmental parameters were calculated. Immunogenicity samples were taken pre-dose and up to day 84 after the first dose. Safety was assessed throughout the study.

FINDINGS

A total of 292 subjects were randomized to therapy and treated; 244 received both treatments. For all primary pharmacokinetic and pharmacodynamic parameters, 90% repeated confidence intervals of geometric means ratio of MSB11455 to the reference product were within the pre-defined equivalence range (80.00%-125.00%) for AUC_0-∞ (96.59-112.82); AUC_0-last (97.29-113.96), C_max (97.13-114.99), maximum observed effect on ANC (98.74-102.39), and area under the effect-time curve from time zero to time to last quantifiable concentration (97.30-100.23). Safety, tolerability, and immunogenicity were comparable between treatments. No filgrastim-specific neutralizing antibodies were detected with either treatment sequence.

IMPLICATIONS

Pharmacokinetic and pharmacodynamic equivalence of MSB11455 and the reference product was shown, with comparable immunogenicity, safety, and tolerability between treatments. The study supports the biosimilarity of MSB11455 to the reference product. ClinicalTrials.gov identifier: NCT03251248.

A physiological model of granulopoiesis to predict clinical drug induced neutropenia from in vitro bone marrow studies: with application to a cell cycle inhibitor

Neutropenia is one of the most common dose-limiting toxocities associated with anticancer drug therapy. The ability to predict the probability and severity of neutropenia based on in vitro studies of drugs in early drug development will aid in advancing safe and efficacious compounds to human testing. Toward this end, a physiological model of granulopoiesis and its regulation is presented that includes the bone marrow progenitor cell cycle, allowing for a mechanistic representation of the action of relevant anticancer drugs based on in vitro studies. Model development used data from previously reported tracer kinetic studies of granulocyte disposition in healthy humans to characterize the dynamics of neutrophil margination in the presence of endogenous granulocyte-colony stimulating factor (G-CSF). In addition, previously published data from healthy volunteers following pegfilgrastim and filgrastim were used to quantify the regulatory effects of support G-CSF therapies on granulopoiesis. The model was evaluated for the cell cycle inhibitor palbociclib, using an in vitro system of human bone marrow mononuclear cells to quantify the action of palbociclib on proliferating progenitor cells, including its inhibitory effect on G1 to S phase transition. The in vitro results were incorporated into the physiological model of granulopoiesis and used to predict the time course of absolute neutrophil count (ANC) and the incidence of neutropenia observed in three previously reported clinical trials of palbociclib. The model was able to predict grade 3 and 4 neutropenia due to palbociclib treatment with 86% accuracy based on in vitro data.

PF-06881893 (Nivestym™), a Filgrastim Biosimilar, Versus US-Licensed Filgrastim Reference Product (US-Neupogen®): Pharmacokinetics, Pharmacodynamics, Immunogenicity, and Safety of Single or Multiple Subcutaneous Doses in Healthy Volunteers

BACKGROUND

Three comparative clinical studies assessed the pharmacokinetics (PK), pharmacodynamics (PD), immunogenicity and safety of PF-06881893 (filgrastim-aafi; Nivestym™), a filgrastim biosimilar, versus US-licensed reference product (filgrastim; US-Neupogen^®) in healthy volunteers (HVs).

METHODS

Two separate open-label, crossover-design PK/PD studies were conducted: a single-dose study (n = 24) and a multiple-dose study (n = 60). In each study, HVs were randomized to Nivestym followed by US-Neupogen, or vice versa. Study drug (5 μg/kg) was administered subcutaneously as a single injection or as five consecutive daily injections. Primary PK and PD endpoints were area under the filgrastim serum concentration-time curve, maximum observed concentration, area under the effect curve (AUEC) for absolute neutrophil count (ANC), maximum observed ANC, AUEC for cluster of differentiation (CD)-34⁺ count, and maximum observed CD34⁺ count. In an open-label, parallel-design, non-inferiority, comparative immunogenicity study, HVs were randomized (n = 128/treatment) to Nivestym or US-Neupogen. The primary endpoint was the proportion of subjects with a negative baseline antidrug antibody (ADA) test result and one or more confirmed post-dose positive ADA result.

RESULTS

Overall demographics were as follows: female (n = 162/340); White (n = 274/340), Black (n = 58/340), and other (n = 8/340); age (18-65 years); and weight (50.8-96.5 kg). All primary PK and PD endpoints met the pre-specified criteria for PK and PD equivalence. The primary endpoint in the comparative immunogenicity study met pre-specified criteria for non-inferiority.

CONCLUSIONS

Nivestym demonstrated PK and PD equivalence in single and multiple subcutaneous-dose settings and non-inferiority for immunogenicity to US-Neupogen, with a comparable safety profile, supporting the demonstration of biosimilarity.

TRIAL REGISTRATION

ClinicalTrials.gov C1121002 (NCT02766647); C1121003 (NCT02766634); C1121012 (NCT02923791).

Quantitative Relationship Between AUEC of Absolute Neutrophil Count and Duration of Severe Neutropenia for G-CSF in Breast Cancer Patients

The aim of the study was to evaluate the quantitative relationship between duration of severe neutropenia (DSN, the efficacy endpoint) and area under effect curve of absolute neutrophil counts (ANC-AUEC, the pharmacodynamic endpoint), based on data from filgrastim products, a human granulocyte colony-stimulating factor (G-CSF). Clinical data from filgrastim product comparator and test arms of two randomized, parallel-group, phase III studies in breast cancer patients treated with myelosuppressive chemotherapy were utilized. A zero-inflated Poisson regression model best described the negative correlation between DSN and ANC-AUEC. The models predicted that with 10 × 10⁹ day/L of increase in ANC-AUEC, the mean DSN would decrease from 1.1 days to 0.93 day in Trial 1 and from 1.2 days to 1.0 day in Trial 2. The findings of the analysis provide useful information regarding the relationship between ANC and DSN that can be used for dose selection and optimization of clinical trial design for G-CSF.

Dexamethasone promotes granulocyte mobilization by prolonging the half-life of granulocyte-colony-stimulating factor in healthy donors for granulocyte transfusions

BACKGROUND

Granulocyte transfusion (GTX) is a potential approach to correcting neutropenia and relieving the increased risk of infection in patients who are refractory to antibiotics. To mobilize enough granulocytes for transfusion, healthy donors are premedicated with granulocyte-colony-stimulating factor (G-CSF) and dexamethasone. Granulocytes have a short circulatory half-life. Consequently, patients need to receive GTX every other day to keep circulating granulocyte counts at an acceptable level. We investigated whether plasma from premedicated donors was capable of prolonging neutrophil survival and, if so, which factor could be held responsible.

STUDY DESIGN AND METHODS

The effects of plasma from G-CSF/dexamethasone-treated donors on neutrophil survival were assessed by annexin-V, CD16. and CXCR4 staining and nuclear morphology. We isolated an albumin-bound protein using α-chymotrypsin and albumin-depletion and further characterized it using protein analysis. The effects of dexamethasone and G-CSF were assessed using mifepristone and G-CSF-neutralizing antibody. G-CSF plasma concentrations were determined by Western blot and Luminex analyses.

RESULTS

G-CSF/dexamethasone plasma contained a survival-promoting factor for at least 2 days. This factor was recognized as an albumin-associated protein and was identified as G-CSF itself, which was surprising considering its reported half-life of only 4.5 hours. Compared with coadministration of dexamethasone, administration of G-CSF alone to the same GTX donors led to a faster decline in circulating G-CSF levels, whereas dexamethasone itself did not induce any G-CSF, demonstrating a role for dexamethasone in increasing G-CSF half-life.

CONCLUSION

Dexamethasone increases granulocyte yield upon coadministration with G-CSF by extending G-CSF half-life. This observation might also be exploited in the coadministration of dexamethasone with other recombinant proteins to modulate their half-life.

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.

Granulocyte colony-stimulating factor (G-CSF) increases histone-complexed DNA plasma levels in healthy volunteers

Granulocyte colony-stimulating factor (G-CSF) is an activator of neutrophil granulocytes. Neutrophil extracellular traps are a defensive mechanism consisting of neutrophils, platelets, DNA, histones and antimicrobial proteins. This study was performed to determine whether G-CSF increases histone-complexed DNA in the plasma of healthy volunteers. In total, 51 healthy volunteers (25 males and 26 females) were treated with G-CSF (18 with 300 µg single dose i.v., 27 with 5 µg/kg s.c. for 4 days) and six participants received a placebo. Histone-complexed DNA was measured by enzyme immunoassay in plasma samples at predefined time points (0, 2, 4, 6, 24 h after single dose, day 1, day 2 and day 5 after repeated doses). Histone levels were quantified by Western blotting. A single dose of G-CSF rapidly increased hc-DNA by about 50 % (p < 0.05 for 2-24 h). After repeated doses the increase was even more pronounced: hc-DNA increased by about 50 % (3.0 ± 0.9, p < 0.001 after 24 h and about fourfold after 96 h (p < 0.001)). A statistical significant increase in histone levels was detected as early as 4 h after G-CSF injection (0.43 ± 0.2 vs. 1.08 ± 0.3 µg/ml; p = 0.034). In the placebo group no significant changes occurred. Moreover, significantly higher levels of hc-DNA were measured in male compared to female subjects (226 ± 43 vs. 84 ± 19, p < 0.001). G-CSF injection substantially increases hc-DNA levels in healthy volunteers. There is a significant gender difference in hc-DNA at the baseline.

Comparison of the pharmacokinetic and pharmacodynamic properties of two recombinant granulocyte colony-stimulating factor formulations after single subcutaneous administration to healthy volunteers

BACKGROUND AND OBJECTIVE

The aim of this randomized, single dose, two-period crossover study with two weeks wash-out period was the demonstration of bioequivalence of two recombinant human granulocyte colony-stimulating factor (rG-CSF) formulations after subcutaneous administration of 300μg comparing their pharmacokinetic (primary endpoints AUC0-24, AUC0-∞ and Cmax) and pharmacodynamic (primary endpoints ANC AUC0-72, ANC AUC0-∞ and ANCmax) profiles in healthy male subjects.

MATERIALS AND METHODS

A total of 36 (23.0±6.0 years, 76.6±7.2kg) healthy subjects were recruited. Using a 1:1 randomization ratio, subjects were randomly assigned to one of two possible treatment-sequence groups to receive the single dose of test formulation (Gp-02) and reference product (Neupogen™) concentrations were measured by enzyme-linked immunosorbent assay (ELISA) up to 24h and the Absolute Neutrophil Count (ANC) was determined using hematology analyzer Coulter STKS™ (Beckman Coulter) up to 72h after injection. The geometric mean of primary pharmacokinetic and pharmacodynamic variables were considered bioequivalent if the 90% confidence intervals (CI) would fall in the bioequivalence range of 80%-125%.

RESULTS

AUC0-24 (ratio of means 103.4, 90% CI: 95.6-111.9), AUC0-∞ (103.4, 90% CI: 95.7-111.7), Cmax (99.6, 90% CI: 89.0-111.4), ANC AUC0-72 (100.0, 90% CI: 96.6-103.5), ANC AUC0-∞ (100.8, 90% CI: 96.5-105.3), and ANCmax (100.2, 90% CI: 95.4-105.1) were determined. Single doses of test and reference formulations were well tolerated. The incidence of AEs was equally distributed across treatment groups with the most frequent AEs being headache, fever, and back pain.

CONCLUSIONS

The study results demonstrated the bioequivalence of Gp-02, a new formulation of filgrastim, and the reference product Neupogen™.

Preclinical and clinical phase I studies of a new recombinant Filgrastim (BK0023) in comparison with Neupogen®

Background

Filgrastim or methionyl-granulocyte colony-stimulating factor (Met-G-CSF), is a recombinant therapeutic protein widely used to treat severe neutropenia caused by myelosuppressive drugs in patients with nonmyeloid malignancies. In addition to its role in the regulation of granulopoiesis, treatment with G-CSF is considered the standard approach to mobilize CD34 positive (CD34⁺) mononuclear cells for reconstituting hemopoietic ability for bone marrow transplantation. An intended biosimilar filgrastim (coded BK0023) was produced in GMP conditions by E.coli fermentation according to an original recombinant process and showed physico-chemical properties and purity profile similar to Neupogen^®, a commercial preparation of filgrastim. The aim of the present study was to demonstrate the comparability of BK0023 to Neupogen^® in terms of both in vitro biological activities and in vivo toxicology, pharmacokinetics and pharmacodynamics.

Methods

Cell proliferation and radioligand binding assays were conducted in NFS-60 cells to compare the biological activity and functional interaction with the G-CSF receptor in vitro, while preclinical in vivo studies, including pharmacokinetics and pharmacodynamics after repeated dose were performed in normal and neutropenic rats. A phase I study was carried out in healthy male volunteers treated by multiple-dose subcutaneous administration of BK0023 and Neupogen^® to evaluate their pharmacodynamic effects as well as their pharmacokinetic and safety profile and to demonstrate their pharmacodynamic equivalence and pharmacokinetic bioequivalence.

Results

The results reported in this work demonstrate that BK0023 is comparable in terms of biological activity, efficacy and safety to Neupogen^®.

Conclusions

BK0023 has the same pharmacokinetic profile, efficacy and safety as the reference commercial filgrastim Neupogen^® and therefore could be further developed to become a convenient option to treat neutropenia in oncological patients.

Trial registration

Trial registration number (TRN): NCT01933971. Date of registration: Sept 6th 2013.

A rare but severe complication of filgrastim in a healthy donor: splenic rupture

BACKGROUND

Granulocyte-colony stimulating factor (G-CSF) is widely administered to donors who provide peripheral blood stem cells (PBSCs) for individuals who undergo hematopoietic stem cell transplants. G-CSF administration is associated with a small but definite risks of serious adverse events like splenic rupture.

CASE STUDY

In this case, we report a 40 year old women, a healthy donor for her sister who has aplastic anemia, who had sharp left upper abdominal pain on the forth mobilization day. The diagnosis at CT scan was splenic rupture; irregular intrasplenic low-attenuation areas consistent with ruptured spleen and perisplenic high density fluid. Her bidimensional spleen size was 16×6 cm.

RESULTS

She was followed conservatively. One month later the CT scan signs of rupture disappeared.

CONCLUSION

We must pay attention to this rare but serious adverse event during filgrastim use.

Pegfilgrastim administered in an abbreviated schedule, significantly improved neutrophil recovery after high-dose radiation-induced myelosuppression in rhesus macaques

Conventional daily administration of filgrastim is effective in reducing the duration of severe neutropenia and enhancing survival following lethal radiation, myelosuppressive cytotoxic therapy or myeloablation and stem cell transplantation. A sustained-duration form of filgrastim, pegfilgrastim has significantly simplified scheduling protocols after chemotherapy-induced neutropenia to a single injection while maintaining the therapeutic effectiveness of daily administration of filgrastim. We examined the ability of a single or double (weekly) administration of pegfilgrastim to significantly improve neutrophil recovery in a rhesus macaque model of severe radiation-induced myelosuppression. Animals were exposed to potentially lethal 6 Gy total-body X radiation. After irradiation all animals received supportive care and were administered either pegfilgrastim at 300 μg/kg on day 1 or day 1 and day 7 post exposure, or filgrastim at 10 μg/kg/day initiated on day 1 post exposure and continued daily through neutrophil recovery. Pharmacokinetic parameters and neutrophil-related values for duration of neutropenia, neutrophil nadir, time to recovery to an absolute neutrophil count ≥500/μL or ≥2000/μL, and days of antibiotic support were determined. Effective plasma concentrations of pegfilgrastim were maintained in neutropenic animals until after the onset of hematopoietic recovery, which is consistent with neutrophil-dependent properties of elimination. Administration of pegfilgrastim at day 1 and day 7 was most effective at improving neutrophil recovery compared to daily administration of filgrastim or a single injection of pegfilgrastim on day 1, after severe, radiation-induced myelosuppression in rhesus macaques.

Pharmacokinetic and -dynamic modelling of G-CSF derivatives in humans

Background

The human granulocyte colony-stimulating factor (G-CSF) is routinely applied to support recovery of granulopoiesis during the course of cytotoxic chemotherapies. However, optimal use of the drug is largely unknown. We showed in the past that a biomathematical compartment model of human granulopoiesis can be used to make clinically relevant predictions regarding new, yet untested chemotherapy regimen. In the present paper, we aim to extend this model by a detailed pharmacokinetic and -dynamic modelling of two commonly used G-CSF derivatives Filgrastim and Pegfilgrastim.

Results

Model equations are based on our physiological understanding of the drugs which are delayed absorption of G-CSF when applied to the subcutaneous tissue, dose-dependent bioavailability, unspecific first order elimination, specific elimination in dependence on granulocyte counts and reversible protein binding. Pharmacokinetic differences between Filgrastim and Pegfilgrastim were modelled as different parameter sets. Our former cell-kinetic model of granulopoiesis was essentially preserved, except for a few additional assumptions and simplifications. We assumed a delayed action of G-CSF on the bone marrow, a delayed action of chemotherapy and differences between Filgrastim and Pegfilgrastim with respect to stimulation potency of the bone marrow. Additionally, we incorporated a model of combined action of Pegfilgrastim and Filgrastim or endogenous G-CSF which interact via concurrent receptor binding. Unknown pharmacokinetic or cell-kinetic parameters were determined by fitting the predictions of the model to available datasets of G-CSF applications, chemotherapy applications or combinations of it. Data were either extracted from the literature or were received from cooperating clinical study groups. Model predictions fitted well to both, datasets used for parameter estimation and validation scenarios as well. A unique set of parameters was identified which is valid for all scenarios considered. Differences in pharmacokinetic parameter estimates between Filgrastim and Pegfilgrastim were biologically plausible throughout.

Conclusion

We conclude that we established a comprehensive biomathematical model to explain the dynamics of granulopoiesis under chemotherapy and applications of two different G-CSF derivatives. We aim to apply the model to a large variety of chemotherapy regimen in the future in order to optimize corresponding G-CSF schedules or to individualize G-CSF treatment according to the granulotoxic risk of a patient.

Population modeling of filgrastim PK-PD in healthy adults following intravenous and subcutaneous administrations

Filgrastim is a recombinant human granulocyte colony stimulating factor (G-CSF) that stimulates production of neutrophils. The objective of this analysis was to develop a pharmacokinetic (PK) and pharmacodynamic (PD) model to account for an increase in G-CSF clearance on multiple dosing because of an increase of the G-CSF receptor-mediated endocytosis. Data from 4 randomized studies involving healthy volunteers were used for analysis. Subjects received filgrastim (Neupogen) via subcutaneous (SC) and intravenous (IV) routes. Filgrastim was administered SC daily for 1 week at 2.5, 5, and 10 µg/kg doses and as single IV infusions (5 µg/kg over 0.5 hours) and SC (1 µg/kg) doses. PK data comprised serum concentration-time measurements and the blood absolute neutrophil count (ANC) was used for PD evaluations. Population nonlinear mixed-effect modeling was done using NONMEM VI (Version 6.1.0, Icon Development Solutions, Ellicott City, Maryland). The model depicted the decaying trend in C(max) values with repeated doses and an increase in ANC(max) values consistently with an increase in the G-CSF receptor pool. Simulated time courses of the total clearance exhibited an increasing pattern. The increase in filgrastim clearance on multiple dosing was attributed to the increased neutrophil count in the bone marrow and blood paralleled by an increase in the total G-CSF receptor density.

Development of a new G-CSF product based on biosimilarity assessment

BACKGROUND

Zarzio, a new recombinant human granulocyte colony-stimulating factor (filgrastim), was evaluated in healthy volunteers and neutropenic patients in phase I and III studies.

PATIENTS AND METHODS

Healthy volunteers in randomized, two-period crossover studies received single- and multiple-dose s.c. injections of 1 microg/kg (n = 24), 2.5 microg/kg (n = 28), 5 microg/kg (n = 28), or 10 microg/kg (n = 40), as well as single-dose i.v. infusions of 5 microg/kg (n = 26), of Zarzio or the reference product (Neupogen). Filgrastim serum levels were monitored; pharmacodynamic parameters were absolute neutrophil count (all studies) and CD34(+) cells (multiple-dose studies). Supportive efficacy and safety data were obtained from an open phase III study in 170 breast cancer patients undergoing four cycles of doxorubicin and docetaxel (Taxotere) chemotherapy, receiving Zarzio (300 or 480 microg) as primary prophylaxis of severe neutropenia.

RESULTS

The results of the studies in healthy volunteers confirm the comparability of the test and reference products with respect to their pharmacodynamics and pharmacokinetics. Confidence intervals were within the predefined equivalence boundaries. In the phase III study in breast cancer patients, the administration of Zarzio was efficacious and safe, triggering no immunogenicity.

CONCLUSION

The results of these studies demonstrate the biosimilarity of Zarzio with its reference product Neupogen.

Pharmacokinetic and pharmacodynamic modelling of the novel human granulocyte colony-stimulating factor derivative Maxy-G34 and pegfilgrastim in rats

OBJECTIVES

This study aims to compare pharmacokinetics and pharmacodynamics of pegfilgrastim, a pharmaceutical recombinant human granulocyte colony-stimulating factor (rhG-CSF), with that of a newly developed reagent, Maxy-G34. This comparison was performed using rat experiments and biomathematical modelling of granulopoiesis.

METHODS

Healthy rats and those with cyclophosphamide-induced neutropenia were treated with either pegfilgrastim or Maxy-G34 under various schedules. Time courses of absolute neutrophil count (ANC) and G-CSF serum level were measured and we constructed a combined pharmacokinetic/pharmacodynamic model of both drugs. Neutropenic episodes were assessed by experimental data and model simulations.

RESULTS

Both Pegfilgrastim and Maxy-G34 showed strong dose-dependent efficacy in reducing neutropenic episodes. However, time courses of ANC and G-CSF serum levels were markedly different. The biomathematical model showed good agreement with these data. We estimated that differences between the two drugs could be explained by lower bioavailability and reduced elimination of Maxy-G34. Based on the data and model interpolations, we estimated that Maxy-G34 is superior in reducing neutropenic episodes. Also, we predicted that G-CSF administration 48 h after cyclophosphamide would be superior to its administration after 2 or 24 h, for both derivatives.

CONCLUSION

Maxy-G34 is a highly potent drug for stimulation of neutrophil production in rats. By our modelling approach, we quantified differences between Maxy-G34 and pegfilgrastim, related to pharmacokinetic parameters. Model simulations can be used to estimate optimal dosing and timing options in the present preclinical rat model.

Effects of recombinant human granulocyte colony-stimulating factor (filgrastim) on ECG parameters in neutropenic patients: a single-centre, prospective study

BACKGROUND AND OBJECTIVE

Human granulocyte colony-stimulating factor (G-CSF) is a haematopoietic hormone that promotes the growth, proliferation, differentiation and maturation of neutrophil precursors. Filgrastim is a recombinant human G-CSF. Myocardial infarction, atrial fibrillation and arrhythmia have been reported in several patients with malignancy receiving filgrastim, but a causal relationship with the drug has not been established. The purpose of this study was to investigate the changes in ECG parameters in neutropenic patients during treatment with filgrastim.

METHODS

This was a single-centre, prospective study carried out in a hospital emergency room. Patients with neutropenia and malignancy who were required to receive filgrastim were eligible for the study. After a reference ECG had been obtained, filgrastim was administered to all patients at a dose of 5 microg/kg/day subcutaneously for 2 days. Follow-up ECGs were then obtained at 12-hourly intervals. Continuous telemetric monitoring was conducted throughout hospitalization.

RESULTS

Serial ECG parameters were compared in 102 patients. There were no statistically significant differences between baseline and follow-up ECG measurements of rhythm, P-wave duration, PR interval, QRS-wave duration, corrected QT (QTc) interval, ECG axis, premature supraventricular events, ventricular arrhythmia, R-wave progression, right bundle branch block or left bundle branch block. There was a significant reduction in mean heart rate in subsequent ECGs compared with baseline (p < 0.05).

CONCLUSION

This study did not demonstrate any ECG changes other than a significant reduction in mean heart rate in this selected population of neutropenic patients given 2 days' treatment with subcutaneous 5 microg/kg/day of filgrastim.

A pharmacokinetic model of filgrastim and pegfilgrastim application in normal mice and those with cyclophosphamide-induced granulocytopaenia

OBJECTIVES

Recombinant human granulocyte colony-stimulating factor (rhG-CSF) is widely used as treatment for granulocytopaenia during cytotoxic chemotherapy; however, optimal scheduling of this pharmaceutical is unknown. Biomathematical models can help to pre-select optimal application schedules but precise pharmacokinetic properties of the pharmaceuticals are required at first. In this study, we have aimed to construct a pharmacokinetic model of G-CSF derivatives filgrastim and pegfilgrastim in mice.

METHODS

Healthy CD-1 mice and those with cyclophosphamide-induced granulocytopaenia were studied after administration of filgrastim and pegfilgrastim in different dosing and timing schedules. Close meshed time series of granulocytes and G-CSF plasma concentrations were determined. An ordinary differential equations model of pharmacokinetics was constructed on the basis of known mechanisms of drug distribution and degradation.

RESULTS

Predictions of the model fit well with all experimental data for both filgrastim and pegfilgrastim. We obtained a unique parameter setting for all experimental scenarios. Differences in pharmacokinetics between filgrastim and pegfilgrastim can be explained by different estimates of model parameters rather than by different model mechanisms. Parameter estimates with respect to distribution and clearance of the drug derivatives are in agreement with qualitative experimental results.

CONCLUSION

Dynamics of filgrastim and pegfilgrastim plasma levels can be explained by the same pharmacokinetic model but different model parameters. Beause of a strong clearance mechanism mediated by granulocytes, granulocytotic and granulocytopaenic conditions must be studied simultaneously to construct a reliable model. The pharmacokinetic model will be extended to a murine model of granulopoiesis under chemotherapy and G-CSF application.

A glycosylated recombinant human granulocyte colony stimulating factor produced in a novel protein production system (AVI-014) in healthy subjects: a first-in human, single dose, controlled study

Background

AVI-014 is an egg white-derived, recombinant, human granulocyte colony-stimulating factor (G-CSF). This healthy volunteer study is the first human investigation of AVI-014.

Methods

24 male and female subjects received a single subcutaneous injection of AVI-014 at 4 or 8 mcg/kg. 16 control subjects received 4 or 8 mcg/kg of filgrastim (Neupogen, Amgen) in a partially blinded, parallel fashion.

Results

The Geometric Mean Ratio (GMR) (90% CI) of 4 mcg/kg AVI-014/filgrastim AUC(0–72 hr) was 1.00 (0.76, 1.31) and Cmax was 0.86 (0.66, 1.13). At the 8 mcg/kg dose, the AUC(0–72) GMR was 0.89 (0.69, 1.14) and Cmax was 0.76 (0.58, 0.98). A priori pharmacokinetic bioequivalence was defined as the 90% CI of the GMR bounded by 0.8–1.25. Both the white blood cell and absolute neutrophil count area under the % increase curve AUC(0–9 days) and Cmax (maximal % increase from baseline)GMR at 4 and 8 mcg/kg fell within the 0.5–2.0 a priori bound set for pharmacodynamic bioequivalence. The CD 34+ % increase curve AUC(0–9 days) and Cmax GMR for both doses was ~1, but 90% confidence intervals were large due to inherent variance, and this measure did not meet pharmacodynamic bioequivalence. AVI-014 demonstrated a side effect profile similar to that of filgrastim.

Conclusion

AVI-014 has safety, pharmacokinetic, and pharmacodynamic properties comparable to filgrastim at an equal dose in healthy volunteers. These findings support further investigation in AVI-014.

Splenic rupture, secondary to G-CSF use for chemotherapy induced neutropenia: a case report and review of literature

Introduction

Chemotherapy Induced neutropenia is a frequent and serious complication of cytotoxic cancer treatment.

Granulocyte colony stimulating factors (G-CSF) are frequently used to counter neutropenia, attempt rapid recovery of patients and allow for continuation of treatment without compromise on dose, especially in curative malignancies. Generally regarded as safe, G-CSF use has been very rarely reported to have resulted in serious side effects, such as, splenic rupture.

Case presentation

We are reporting a case of a twenty years old man, who was being treated for T cell acute lymphoblastic leukemia and received colony stimulating factors for treatment of severe neutropenia and suffered from splenic rupture, He was treated with splenectomy.

Conclusion

Although extremely rare, splenic rupture can be a serious and sometimes life threatening complication of high dose colony stimulating factors therapy.

Hematologic effects of subcutaneous administration of recombinant human granulocyte colony-stimulating factor (filgrastim) in healthy alpacas

OBJECTIVE

To determine the effects of SC administration of filgrastim on cell counts in venous blood and bone marrow of healthy adult alpacas.

ANIMALS

10 healthy alpacas.

PROCEDURES

Alpacas were randomly assigned to receive treatment with filgrastim (5 microg/kg, SC; n=5) or an equivalent volume of physiologic saline (0.9% NaCl) solution (5) once a day for 3 days. Blood samples were obtained via jugular venipuncture 1 day prior to treatment and once a day for 5 days commencing 24 hours after the first dose was administered. Complete blood counts were performed for each blood sample. Bone marrow aspirates were obtained from the sternum of each alpaca 48 hours before the first treatment was administered and 72 hours after the third treatment was administered. Myeloid-to-erythroid cell (M:E) ratio was determined via cytologic evaluation of bone marrow aspirates.

RESULTS

In filgrastim-treated alpacas, substantial increases in counts of WBCs and neutrophils were detected within 24 hours after the first dose was administered. Band cell count and percentage significantly increased 24 hours after the second dose. Counts of WBCs, neutrophils, and band cells remained high 48 hours after the third dose. Red blood cell counts and PCV were unaffected. The M:E ratio also increased significantly after treatment with filgrastim.

CONCLUSIONS AND CLINICAL RELEVANCE

Filgrastim induced rapid and substantial increases in numbers of circulating neutrophils and M:E ratios of bone marrow in healthy alpacas. Therefore, filgrastim may be useful in the treatment of camelids with impaired bone marrow function.

Murine megakaryocyte progenitor cells and their susceptibility to suppression by G-CSF

In agar cultures of mouse bone marrow cells, mega-karyocyte colony-forming cells exhibited shorter survival times than granulocyte-macrophage progenitor cells when initially cultured in the absence of stimulating factors. Initiation of cultures with G-CSF improved the survival times of granulocyte-macrophage progenitor cells and those of megakaryocyte progenitor cells. Paradoxically, G-CSF was found to consistently inhibit megakaryocyte colony formation stimulated by erythropoietin or by stem cell factor plus interleukin-3 (IL-3) plus erythropoietin. G-CSF was a less-consistent inhibitor of megakaryocyte colonies stimulated by thrombopoietin or IL-3. Analysis of the response of marrow cells from mice with the deletion of the genes encoding CIS, SOCS-1, SOCS-2, SOCS-3, SOCS-5, SOCS-6, or SOCS-7 indicated that the inhibitory SOCS proteins, with the possible exception of SOCS-3, were not involved in the G-CSF-initiated suppression of megakaryocyte colony formation.

Bioequivalence of two recombinant granulocyte colony-stimulating factor formulations in healthy male volunteers

To evaluate the equivalence of the pharmacokinetic, pharmacodynamic and safety properties of two recombinant G-CSF formulations in healthy male volunteers, a standard 2-way randomized crossover double-blind study, with a 3 week washout period, was conducted. A single 300 microg G-CSF dose was administered subcutaneously. Hebervital (Heber Biotec, Havana, formulation A) and Neupogen (Hoffmann-La Roche S.A, formulation B) were compared. Twenty-four healthy male volunteers were included. The serum G-CSF level was measured by enzyme immunoassay (EIA) during the first 36 h after administration. Absolute neutrophils (ANC), white blood cells (WBC) and CD34+ cells counts were the pharmacodynamic variables measured up to 120 h. Other clinical and laboratory determinations were used as safety criteria. The pharmacokinetic parameters for formulation A and B were very close to each other (i.e. AUC, 235.9 vs 270.0 ng.h/ml; C(max), 29.2 vs 33.4 ng/ml; T(max), 4.2 vs 4.7 h; half-life, 3.2 vs 2.8 h; CL, 260.9 vs 277.2 ml/h; V(d), 1.2 vs 1.1 l; and MRT, 7.58 vs 7.38 h). The confidence intervals for the means ratio of all these parameters were within or very close to the 0.8-1.25 acceptance range. The pharmacodynamics showed high similarity since ANC and WBC had the same profiles for both products and no differences were detected for the estimated parameters. The CD34+ cells count increments were evident for both formulations in a similar way as well. The treatments were well tolerated. Registered adverse events were similar; back/spine pain was the most frequent. According to the overall results these formulations could be considered as clinically comparable.

Modelling Human Granulopoiesis under Poly-chemotherapy with G-CSF Support

Cytotoxic drugs administered in polychemotherapy cause a characteristic neutropenic period depending on the schedule of the drugs, which can partly be prevented by G-CSF growth factor support. To quantify these effects and to gain a deeper insight into the dynamics of bone marrow recovery after such suppressing and stimulating disturbances, we construct a biomathematical compartment model of human granulopoiesis under polychemotherapy with G-CSF support. The underlying assumptions and mathematical techniques used to obtain the model are explained in detail. A large variety of biological and clinical data as well as knowledge from a model of murine haematopoiesis are evaluated to construct a physiological model for humans. Particular emphasis is placed on estimating the influence of chemotherapeutic drugs on the granulopoietic system. As a result, we present an innovative method to estimate the bone marrow damage caused by cytotoxic drugs with respect to single identifiable cell stages only on the basis of measured peripheral blood leukocyte dynamics. Conversely, our model can be used in a planning phase of a clinical trial to estimate the haematotoxicity of regimens based on new combinations of drugs already considered and with or without growth factor support.

A computational model of human granulopoiesis to simulate the hematotoxic effects of multicycle polychemotherapy

Moderate intensification of conventional multicycle chemotherapy has recently been shown to improve treatment results in malignant lymphomas and might prove to be beneficial also in other malignancies. However, the feasibility of such regimens is mainly limited by their granulopoietic toxicity. To identify and quantify the basic cell kinetic mechanisms of damage and stimulation caused by cytotoxic drugs and recombinant human granulocyte colony-stimulating factor (rhG-CSF), respectively, we developed a mathematical model of human granulopoiesis that allows simulation of leukocyte concentration profiles under 10 different multicycle polychemotherapy regimens with varying drug composition, dosage, and scheduling, including rhG-CSF assistance. Clinical data on leukocyte profiles were obtained from large numbers of patients treated within several multicenter trials. Simulation studies show that the leukocyte profiles of all regimens can be appropriately fitted using one single set of assumptions and parameters for the cell kinetic effects of cytotoxic drugs and rhG-CSF. Furthermore, the model can be used to explain the interindividual heterogeneity of hematotoxicity by a differential chemosensitivity, which might be useful in drug scheduling for specific risk groups. It is demonstrated that the model can be used to design and to select new drug schedules for subsequent clinical trial testing.

Synergistic and inhibitory interactions in the in vitro control of murine megakaryocyte colony formation

The formation of megakaryocyte colonies in agar cultures of murine bone marrow or spleen cells can be stimulated by the addition of interleukin-3 (IL-3), erythropoietin (EPO), thrombopoietin (TPO), or IL-6. However, greater numbers of colonies developed if combinations of two or more of these stimuli were used, particularly combinations including stem cell factor, with maximal numbers of colonies developing with the combination of stem cell factor plus IL-3 plus EPO. The data indicate that most committed progenitor cells in the megakaryocyte lineage were unusual in that they required stimulation by two or more hematopoietic growth factors. In tests using a range of growth factors, G-CSF was exceptional in that it consistently specifically inhibited megakaryocyte colony formation stimulated by EPO, TPO, or IL-6 but not that stimulated by IL-3. The mechanisms involved in this inhibitory action of G-CSF are unknown, but the inhibitory action could be of relevance for the dose-dependent lowering of platelet levels observed in some subjects injected with G-CSF.

Kinetics of G-CSF-induced granulocyte mobilization in healthy subjects: effects of route of administration and addition of dexamethasone

BACKGROUND

Granulocyte donors are frequently given G-CSF with or without dexamethasone approximately 18 hours before apheresis to increase cell yields. The purpose of this study was to assess the kinetics of G-CSF plus dexamethasone neutrophil mobilization to determine whether the neutrophils can be mobilized and collected the same day.

STUDY DESIGN AND METHODS

Sixteen subjects were given four separate mobilization regimens: IV G-CSF (5 microg/kg), subcutaneous G-CSF (5 microg/kg), IV G-CSF (5 microg/kg) plus oral dexamethasone (8 mg), and subcutaneous G-CSF (5 microg/kg) plus oral dexamethasone (8 mg). Blood cell counts were measured before and after G-CSF administration.

RESULTS

Following all four mobilization regimens, neutrophil counts fell 0.5 hour after the mobilizing agents were given, rose above baseline levels at Hour 2, and increased further with each time interval to Hour 8. In the absence of dexamethasone at Hours 2 through 8, there was no difference in neutrophil counts by subcutaneous or IV G-CSF administration routes. The addition of dexamethasone enhanced mobilization of neutrophils from Hours 3 through 24. Through Hour 8, there was no difference in the degree of mobilization among the subcutaneous G-CSF plus dexamethasone and the IV G-CSF plus dexamethasone regimens. However, at Hour 24, neutrophil counts were sustained at higher levels with subcutaneous G-CSF plus dexamethasone than with IV G-CSF plus dexamethasone.

CONCLUSIONS

Granulocyte mobilization response to subcutaneous G-CSF plus dexamethasone is sustained at peak levels for 8 to 24 hours after coadministration of the two drugs. There was no advantage to giving G-CSF intravenously.

Estimation of rhG-CSF absorption kinetics after subcutaneous administration using a modified Wagner-Nelson method with a nonlinear elimination model

The clearance of recombinant human granulocyte-colony stimulating factor (rhG-CSF) is known to decrease with dose increase, and to be saturable. The average clearance after intravenous administration will be lower than that after subcutaneous administration. Therefore, the apparent absolute bioavailability with subcutaneous administration calculated from the AUC ratio is expected to be an underestimate. The absorption pharmacokinetics after subcutaneous administration was examined using the results of the bioequivalency study between two rhG-CSF formulations with a dose of 2 microg/kg. The analysis was performed using a modified Wagner-Nelson method with the nonlinear elimination model. The apparent absolute bioavailability for subcutaneous administration was 56.9 and 67.5% for each formulation, and the ratio between them was approximately 120%. The true absolute bioavailability was, however, estimated to be 89.8 and 96.9%, respectively, and the ratio was approximately 108%. The absorption pattern was applied to other doses, and the predicted clearance values for subcutaneous and intravenous administrations were then similar to the values for several doses reported in the literature. The underestimation of bioavailability was around 30%, and the amplification of difference was 2.5 times, from 8 to 20%, because of the nonlinear pharmacokinetics. The neutrophil increases for each formulation were identical, despite the different bioavailabilities. The reason for this is probably that the amount eliminated through the saturable process, which might indicate the amount consumed by the G-CSF receptor, was identical for each formulation.

Biopharmaceutical drug development: Filgrastim (r-metHuG-CSF) use in patients with HIV infection

Hematopoietic growth factors are well known to increase neutrophil counts and support the administration of myelotoxic and myelosuppressive therapies, especially chemotherapies. Filgrastim (r-metHuG-CSF) has been used in the setting of HIV disease to treat neutropenia and HIV-associated neutrophil defects. This article reviews the biology, product characteristics, and preclinical and clinical development of Filgrastim. Emphasis is given on the use of Filgrastim in the setting of HIV infection and AIDS.