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Japanese Journal of Clinical Oncology Advance Access originally published online on April 24, 2009
Japanese Journal of Clinical Oncology 2009 39(7):425-430; doi:10.1093/jjco/hyp038
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© The Author (2009). Published by Oxford University Press. All rights reserved

A Pharmacokinetic and Dose Escalation Study of Pegfilgrastim (KRN125) in Lung Cancer Patients with Chemotherapy-induced Neutropenia

Nobuyuki Yamamoto1, Ikuo Sekine2, Kazuhiko Nakagawa3, Minoru Takada4, Masahiro Fukuoka3, Yusuke Tanigawara5 and Nagahiro Saijo6

1 Division of Thoracic Oncology, Shizuoka Cancer Center, Shizuoka
2 Division of Internal Medicine, National Cancer Center Hospital
3 Department of Medical Oncology, Kinki University School of Medicine
4 Division of Internal Medicine, Kinki-chuo Chest Medical Center, Osaka
5 Department of Hospital Pharmacy, Keio University School of Medicine, Tokyo
6 Internal Medicine and Thoracic Oncology, National Cancer Center Hospital East, Chiba, Japan

For reprints and all correspondence: Nobuyuki Yamamoto, Division of Thoracic Oncology, Shizuoka Cancer Center, 1007 Shimonagakubo Nagaizumi-cho, Sunto-gun, Shizuoka 411-8777, Japan. E-mail: n.yamamoto{at}scchr.jp

Received September 30, 2008; accepted March 22, 2009


   Abstract
TOP
 Abstract
INTRODUCTION
 PATIENTS AND METHODS
 RESULTS
 DISCUSSION
 Funding
 Conflict of interest statement
 Acknowledgements
 References
 
Objective: The aim of this study was to investigate the safety, pharmacokinetic and pharmacodynamic profiles of pegfilgrastim (KRN125), a long-acting granulocyte colony-stimulating factor, in lung cancer patients with chemotherapy-induced neutropenia.

Methods: Eighteen Japanese lung cancer patients who had experienced severe neutropenia (absolute neutrophil counts <0.5 x 109 cells/l) were enrolled. Six patients were sequentially enrolled in each pegfilgrastim dose cohort (dose levels of 30, 60 or 100 µg/kg). Patients received the same chemotherapy regimen as in their previous cycle and pegfilgrastim was injected subcutaneously the day after chemotherapy ended in each treatment cycle. Pharmacokinetic, pharmacodynamic and safety analyses were performed.

Results: Dose-limiting toxicity and serious adverse events related to pegfilgrastim were not observed in any patients. Pegfilgrastim antibodies were not detected. Maximum serum concentrations and area under the serum concentration–time curves of pegfilgrastim were dependent on the pegfilgrastim dose in a non-linear manner. Of the 18 patients, severe neutropenia occurred in 4 (22.2%), and, of these, 1 patient (5.5%) required rescue treatment by filgrastim.

Conclusions: A single dose of pegfilgrastim increases the serum concentration of pegfilgrastim for several days in a dose-dependent manner and is not associated with significant toxicity. Good efficacy of pegfilgrastim for the prevention of severe neutropenia was observed at all dose levels. Based on these data, further studies are warranted to determine the recommended dose of pegfilgrastim for Japanese patients with chemotherapy-induced neutropenia.

Key Words: pegfilgrastim • subcutaneous • pharmacokinetics • neutropenia


   INTRODUCTION
TOP
 Abstract
 INTRODUCTION
PATIENTS AND METHODS
 RESULTS
 DISCUSSION
 Funding
 Conflict of interest statement
 Acknowledgements
 References
 
Filgrastim [recombinant methionyl human granulocyte colony-stimulating factor (G-CSF)] was approved for use in Japan and in the USA in 1991 and has been widely used for the prevention and treatment of neutropenia in Japan, the USA and other countries. In 1994, the American Society of Clinical Oncology published evidence-based clinical practice guidelines for the use of hematopoietic colony-stimulating factors (1). Thus, G-CSFs have become standard therapy for neutropenia caused by various chemotherapies and diseases. Daily subcutaneous injections are required for filgrastim therapy in most indications, however, and this is a burden for both patients and medical personnel.

Pegfilgrastim is a polyethylene glycol (PEG)-derived form of filgrastim. PEG-conjugated proteins have decreased plasma clearance, with a resultant increase in their plasma half-life (2). Based on the features of PEG-conjugated proteins, pegfilgrastim was designed to prolong the half-life of filgrastim and to decrease the number of injections required.

Several clinical studies have been conducted in the USA to investigate the indications for pegfilgrastim for chemotherapy-induced neutropenia in patients with various solid tumors (e.g. lung cancer, breast cancer and malignant lymphoma) (3–8). Dose range studies in breast cancer patients led to a recommended dose of 100 µg/kg or 6 mg/body per chemotherapeutic cycle of pegfilgrastim for chemotherapy-induced neutropenia (4) and revealed non-inferiority against standard filgrastim treatment in two independent comparative studies (5,6). Based on these results, pegfilgrastim was approved and has been available on the market in the USA, EU and other western countries.

On the other hand, there are few clinical data available for Japanese cancer patients. Anticancer chemotherapies and the supportive care required are not always the same among countries. In Japan, the indication for G-CSF in chemotherapy for solid tumors such as non-small cell lung cancer and breast cancer is limited to secondary prophylaxis or salvage therapy for severe or febrile neutropenia, but all the clinical studies of pegfilgrastim conducted in the USA were in primary prophylaxis settings. Therefore, an evaluation of preliminary information on the safety, pharmacodynamic and pharmacokinetic properties of pegfilgrastim in a conventional Japanese chemotherapeutic setting is essential for the introduction of pegfilgrastim to Japan. Therefore, we conducted this dose-escalation study to investigate the safety, pharmacokinetic and pharmacodynamic profiles of pegfilgrastim in Japanese lung cancer patients with chemotherapy-induced neutropenia.


   PATIENTS AND METHODS
TOP
 Abstract
 INTRODUCTION
 PATIENTS AND METHODS
RESULTS
 DISCUSSION
 Funding
 Conflict of interest statement
 Acknowledgements
 References
 
Patient Population
The institutional review boards of the participating hospitals reviewed and approved the protocol, amendments and informed consent form, and all patients gave written informed consent before being enrolled into the study. Patients were eligible for the study if they were 20–74 years of age, had a diagnosis of lung cancer receiving neutropenic chemotherapy [nadir absolute neutrophil count (ANC) <0.5 x 109 cells/l] and recovered to ANC of >1.5 x 109 cells/l. Patients had an Eastern Cooperative Oncology Group (ECOG) performance status of no more than 2. Patients also had to have adequate renal and hepatic function (total bilirubin within 1.5 x upper normal limit and serum creatinine within 2.0 mg/dl) and life expectancy of >3 months. Patients were excluded from the study if they had a history of bone marrow transplantation or stem cell transplantation. Patients were excluded from the study if they were scheduled to have the chemotherapy dose reduced due to neutropenia. Patients with uncontrollable infectious disease, primary hematologic disease such as myelodysplastic syndrome, aplastic anemia and sickle cell anemia, and pregnant and lactating women were excluded from the study. Radiation therapy against >20% of bone marrow was prohibited within 4 weeks of the study enrollment.

Overall Study Design
This was a multicenter, open-label, group sequential dose-escalation study to obtain preliminary information on the safety, pharmacokinetic and pharmacodynamic properties of pegfilgrastim. There were three sequentially enrolled pegfilgrastim cohorts (dose levels of 30, 60 and 100 µg/kg) of six patients each. All patients received a single subcutaneous dose of pegfilgrastim the day after chemotherapy ended in each treatment cycle.

Dose-limiting toxicities were defined as uncontrollable adverse events with a severity of more than Grade 2 as judged by National Cancer Institute common toxicity criteria version 2.0 (NCI-CTC ver.2) with a possible relationship to treatment with pegfilgrastim. When all six patients in each cohort completed Cycle 1, investigators had to confirm that the incidence of dose-limiting toxicities was less than two patients in the same cohort before proceeding to the next dose level.

Treatment and Observation Schedule
After enrollment, patients received the same chemotherapy regimen as for their previous chemotherapy cycle in which severe neutropenia had occurred, and were administered pegfilgrastim subcutaneously the day after chemotherapy ended (secondary prophylactic administration of pegfilgrastim) for each treatment cycle.

In Cycle 1, which was a 21-day post-chemotherapy cycle, blood sampling for pharmacokinetic analyses were performed pre-dose (just before pegfilgrastim administration), 1, 2, 4, 8 and 24 h post-dose on day 1, which was the day after chemotherapy ended, and further samples were collected 48, 96, 144, 192, 240 and 312 h after pegfilgrastim administration. Serum was separated and stored at –20°C until analyzed.

Complete blood cell counts (WBC count, RBC count, hemoglobin level, hematocrit and platelet count) and body temperature were monitored three times a week during Cycle 1. Biochemistry panels were performed on days 1, 8 and 15; and serum samples for antibody testing were taken on day 1. In Cycles 2, 3 and 4, CBC, biochemistry and other laboratory tests were conducted weekly and antibodies were tested at the end of each cycle.

Analytical Methods
The analysis of serum pegfilgrastim concentrations was conducted at Mitsubishi Kagaku Bio-clinical Laboratories Inc. (Tokyo, Japan) and determined using the Quantikine® Human G-CSF Immunoassay (ELISA) kit (R&D Systems, Minneapolis, MN, USA). In validation tests, the intra-assay accuracy and precision for spiked samples ranged from –12.0% to 3.4% and 4.0% to 9.8%, and the inter-assay accuracy and precision ranged from –6.7% to 2.6% and 7.8% to 8.8%, respectively. The lower limit of quantification was 0.2 ng/ml. The inter-assay precision criterion for clinical serum samples was within ± 20%.

Pharmacokinetic Analysis
Serum samples were analyzed using an ELISA that does not distinguish pegfilgrastim from endogenous G-CSF. Thus, serum concentrations of pegfilgrastim for pharmacokinetic analysis were calculated by subtracting the pre-dose serum concentration of G-CSF from all post-dose concentrations for each subject to adjust for the baseline G-CSF level.

Pharmacokinetic parameters of pegfilgrastim after a single-dose administration during Cycle 1 were determined using non-compartmental analysis using WinNonlin (Pharsight Corporation, Mountain View, CA, USA). The maximum serum concentration (Cmax) and the time to reach maximum serum concentration (tmax) were obtained directly from the baseline-corrected concentration–time data. The apparent elimination rate constant at the terminal phase ({lambda}z) was estimated by linear regression analysis from the terminal log-linear declining phase to the last detectable concentration. The elimination half-life (t1/2) was calculated as t1/2 = ln(2)/{lambda}z. The area under the serum concentration–time curve (AUC) from zero to time t, AUC0–t, was obtained by the linear trapezoidal rule. The AUC from zero to infinity, AUC0–{infty}, was calculated as AUC0–t + Ct/{lambda}z, where Ct was the serum concentration at the last detectable time point. The apparent clearance, CL/f, was calculated as dose/AUC0–{infty}.

Safety Analysis
Patients were interviewed and examined daily during Cycle 1 and weekly during Cycles 2, 3 and 4. All adverse events reported were recorded in a case report form, with investigators determining the severity and whether they were caused by the study drug. The toxicities, which were categorized by MedDRA/J Coding Systems version 7.0 and graded by NCI-CTC ver.2, were summarized by frequencies and percent.

Study Termination and Rescue Treatment
The study treatment period was continued until there was a change in the chemotherapeutic regimen (including dose reduction or skipping) or the fourth cycle of the treatment phase. Additional administration of filgrastim was allowed in the case of insufficient neutrophil recovery (e.g. >5 consecutive days of Grade 4 neutropenia) at the discretion of the physician in charge.

Study Drug
Pegfilgrastim comprises the protein filgrastim (recombinant methionyl human G-CSF) to which a PEG molecule is covalently bound to the N-terminal residue. Pegfilgrastim was supplied in single-use vials (1.0 ml containing KRN125 10 mg/ml) from Kirin Brewery Co. Ltd (Tokyo, Japan).

Pharmacodynamic Analysis
This was a pilot study of the use of pegfilgrastim in Japanese patients with cancer. ANC was calculated as ANC (x109 cells/l) = % neutrophil x WBC. The maximum observed ANC (ANCmax) was obtained directly from the ANC–time data. Summary statistics for ANCs were calculated for each cohort, and pharmacokinetic/pharmacodynamic analyses were performed to compare with each pegfilgrastim group.


   RESULTS
TOP
 Abstract
 INTRODUCTION
 PATIENTS AND METHODS
 RESULTS
DISCUSSION
 Funding
 Conflict of interest statement
 Acknowledgements
 References
 
Patient Population
Eighteen patients were enrolled into the trial. The 6 women and 12 men ranged in age from 23 to 74 years (median, 63 years) (Table 1). There was no significant difference in patient background among the three cohorts. Fourteen patients had non-small cell lung cancer and four patients had small cell lung cancer. The most commonly used chemotherapeutic regimen (n = 9) was a combination regimen of carboplatin and paclitaxel.


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  		Table 1. Patient demographics

 
Duration of Pegfilgrastim Treatment
All patients completed at least one treatment cycle, 10 patients completed two cycles, 4 patients completed three cycles and 3 patients completed four cycles. The main reason for terminating the study treatment was due to the need to change the chemotherapeutic regimen. There was no study discontinuation due to pegfilgrastim toxicity.

Pharmacokinetics
The serum concentration–time curves for pegfilgrastim are shown in Fig. 1 and the pharmacokinetic parameters are summarized in Table 2. In Cycle 1, Cmax and AUC0–{infty} increased with an increase in the dose of pegfilgrastim, and clearance decreased as the dose was increased. The pharmacokinetics of pegfilgrastim showed a non-linear profile within the dose range evaluated in this study. Serum concentrations of pegfilgrastim began to decrease after day 3 at the end of chemotherapy and returned to baseline levels on day 15.


Figure 1
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  		Figure 1. Median granulocyte colony-stimulating factor (G-CSF) serum concentrations of KRN125 after a single subcutaneous injection at dose of 30, 60 or 100 µg/kg.

 

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  		Table 2. Pharmacokinetic parameters

 
Safety
No dose-limiting toxicities were observed at any dose level and tolerability of pegfilgrastim up to 100 µg/kg was confirmed. The adverse events observed during this study are common to cancer chemotherapies (Table 3). Clinical adverse events attributed to the study drug were limited to mild-to-moderate events. There was no apparent relationship between pegfilgrastim dose and the frequency of adverse events. No seroreactivity was detected. Almost all patients had transient decreases in platelets and WBC.


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  		Table 3. Adverse drug reaction occurring in >10% of patients

 
Neutrophil Response
Average ANCs before the start of chemotherapy in Cycle 1 were 2.87, 4.39 and 3.24 x 109 cells/l in the groups receiving pegfilgrastim 30, 60 or 100 µg/kg, respectively. As expected, all groups had a rapidly increased ANC, which peaked at 16.6 x 109, 19.0 x 109 and 21.1 x 109 cells/l in the groups receiving pegfilgrastim 30, 60 or 100 µg/kg, respectively, 3 days after pegfilgrastim administration, followed by an ANC nadir. The average ANC nadir was 3.56, 2.11 and 3.12 x 109 cells/l in the cohorts receiving pegfilgrastim 30, 60 or 100 µg/kg, respectively, and the ANC returned to baseline values by the beginning of the next cycle (Fig. 2). The incidence of severe neutropenia was one patient in the 30 µg/kg cohort, one patient in the 60 µg/kg cohort and two patients in the 100 µg/kg cohort (Table 4).


Figure 2
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  		Figure 2. Average absolute neutrophil count (ANC) after a single injection of KRN125. Each point is the average with the standard error indicated by bars.

 

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  		Table 4. Incidence of Grade 3/4 neutropenia

 
There was one episode of neutropenic fever (body temperature >38°C and ANC <1.0 x 109 cells/l) and this patient, who received 60 µg/kg pegfilgrastim, required filgrastim rescue because of prolonged severe neutropenia. There was no apparent relationship between pegfilgrastim dose and ANC nadir or ANCmax.


   DISCUSSION
TOP
 Abstract
 INTRODUCTION
 PATIENTS AND METHODS
 RESULTS
 DISCUSSION
Funding
 Conflict of interest statement
 Acknowledgements
 References
 
An analysis of the pharmacokinetic data and safety of pegfilgrastim administration in lung cancer patients receiving myelosuppressive chemotherapy in the USA confirmed that pegfilgrastim is tolerable up to 300 µg/kg (3). The pharmacokinetic parameters were also calculated (3), revealing a non-linear profile between 30 and 300 µg/kg, and a neutrophil recovery effect was observed at the dose level of 30 µg/kg. The target population in the previous study, however, was patients without previous chemotherapies who received pegfilgrastim as primary prophylaxis. Such a patient population does not have seriously damaged bone marrow function. In Japan, the majority of patients receiving G-CSF administration with solid tumors such as lung cancer are not treated with filgrastim as a primary prophylaxis, but rather as a secondary prophylaxis or rescue treatment for severe or febrile neutropenia. In such a population, the degree of bone marrow damage might be different from that in the USA study and it is possible that the safety, pharmacokinetic and pharmacodynamic properties of pegfilgrastim are therefore not the same.

Good tolerability of pegfilgrastim was confirmed and unexpected toxicities were not observed in the present study. Most adverse events were reported as chemotherapy-related events by the investigators and there was no clear relationship between the dose of pegfilgrastim and the incidence or severity of the adverse events. Complaints of arthralgia, back pain and headache were attributed to pegfilgrastim and tended to be similar to complaints reported in other clinical studies of pegfilgrastim or filgrastim (9). In the previous study of US patients, a decrease in platelets was reported (3). It is not clear, however, whether this abnormal value was attributed to the study drug because a decrease in platelets might also be caused by myelosuppression due to concomitant chemotherapies.

The original aim of the pegylation of filgrastim was to prolong its half-life by decreasing its serum clearance. Previous data indicate that pegfilgrastim has a 10-fold longer half-life (40.4–52.9 h for pegfilgrastim versus 3.37 h for filgrastim) and decreased serum clearance (12.3–24.6 mL/h/kg for pegfilgrastim versus 39.6 mL/h/kg for filgrastim) (3). The pharmacokinetics of pegfilgrastim had a non-linear profile. This is explained mainly by the saturation of receptors on neutrophils at higher pegfilgrastim doses, resulting in a decreased rate of receptor-mediated clearance of the growth factor (3,10). The pharmacokinetic variables obtained from our study are not markedly different from the results of Johnston et al. (3), despite the fact that patients had already received at least one cycle of myelosuppressive chemotherapy and chemotherapeutic regimens were not the same as in their study.

There was no dose relationship with ANC recovery. This might be mainly due to the intensity of the chemotherapeutic regimens that the patients received. Among several studies conducted outside of Japan, there were differences in the incidence and duration of severe neutropenia according to cancer type or chemotherapeutic regimen (3–8). As observed in our study, a trial in patients with thoracic tumors demonstrated no apparent dose relationship (3).

The results of the present study indicate that the tolerability and pharmacokinetic and pharmacodynamic profiles of pegfilgrastim in Japanese cancer patients are similar to those reported for cancer patients in the USA. A dose-determining study is currently underway in Japanese patients receiving myelosuppressive chemotherapies.


   Funding
TOP
 Abstract
 INTRODUCTION
 PATIENTS AND METHODS
 RESULTS
 DISCUSSION
 Funding
Conflict of interest statement
 Acknowledgements
 References
 
This study was sponsored by Kirin Brewery Company, Limited.


   Conflict of interest statement
TOP
 Abstract
 INTRODUCTION
 PATIENTS AND METHODS
 RESULTS
 DISCUSSION
 Funding
 Conflict of interest statement
Acknowledgements
 References
 
None declared.


   Acknowledgements
TOP
 Abstract
 INTRODUCTION
 PATIENTS AND METHODS
 RESULTS
 DISCUSSION
 Funding
 Conflict of interest statement
 Acknowledgements
References
 
The authors thank all the investigators and patients who participated in this study.


   References
TOP
 Abstract
 INTRODUCTION
 PATIENTS AND METHODS
 RESULTS
 DISCUSSION
 Funding
 Conflict of interest statement
 Acknowledgements
 References
 
1 Ozer H, Armitage JO, Bennett CL, Crawford J, Demetri GD, Pizzo PA, et al. 2000 update of recommendations for the use of hematopoietic colony-stimulating factors: evidence-based, clinical practice guidelines. J Clin Oncol (2000) 18:3538–85.

2 Delgado C, Francis GE, Fisher D. The uses and properties of PEG-linked proteins. Crit Rev Ther Drug Carrier Syst (1992) 9:249–304.[Web of Science][Medline]

3 Johnston E, Crawford J, Blackwell S, Bjurstrom T, Lockbaum P, Roskos L, et al. Randomized, dose-escalation study of SD/01 compared with daily filgrastim in patients receiving chemotherapy. J Clin Oncol (2000) 18:2522–28.[Abstract/Free Full Text]

4 Holms FA, Johnes SE, O'Shaughnessy J, Vukelja S, George T, Savin M, et al. Comparable efficacy and safety profiles of once-per-cycle pegfilgrastim and daily injection filgrastim in chemotherapy-induced neutropenia: a multicenter dose-finding study in women with breast cancer. Ann Oncol (2002) 13:903–9.[Abstract/Free Full Text]

5 Holms FA, O'Shaughnessy J, Vukelja S, Jones SE, Shogan J, Savin M, et al. Blinded randomized, multicenter study to evaluate single administration pegfilgrastim once per cycle versus daily filgrastim as an adjunct to chemotherapy in patients with high-risk stage II or stage III/IV breast cancer. J Clin Oncol (2002) 20:727–31.[Abstract/Free Full Text]

6 Green MD, Koelbl H, Baselga J, Galid A, Guillem V, Gascon P, et al. A randomized double-blind multicenter phase III study of fixed-dose single-administration pegfilgrastim versus daily filgrastim in patients receiving myelosuppressive chemotherapy. Ann Oncol (2003) 14:29–35.[Abstract/Free Full Text]

7 Vose JM, Crump H, Lazarus H, Emmanouilides C, Schenkein D, Moore J, et al. Randomized, multicenter, open-label study of pegfilgrastim compared with daily filgrastim after chemotherapy for lymphoma. J Clin Oncol (2003) 21:514–9.[Abstract/Free Full Text]

8 Grigg A, Solal-Celigny P, Hoskin P, Taylor K, McMillan A, Forstpointner R, et al. Open-label, randomized study of pegfilgrastim vs. daily filgrastim as an adjunct to chemotherapy in elderly patients with non-Hodgkin's lymphoma. Leuk Lymphoma (2003) 44:1503–8.[Medline]

9 Kubista E, Glaspy J, Holmes FA, Green MD, Hackett J, Neumann T. Bone pain associated with once-per-cycle pegfilgrastim is similar to daily filgrastim in patients with breast cancer. Clin Breast Cancer (2003) 3:391–8.[CrossRef][Medline]

10 Roskos LK, Yank B, Schwab G, Lockbaum P, Molineux G, Johnston E, et al. A cytokinetic model of r-metHUG-CSF-SD/01 mediated granulopoiesis and ‘self-regulation’ of SD-01, elimination in non-small cell lung cancer patients. Blood (1998) 92:507a. (abstr 2085).


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This Article
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