Bone Marrow Transplantation (2003) 32, 399–404 & 2003 Nature Publishing Group All rights reserved 0268-3369/03 $25.00 www.nature.com/bmt

Pegfilgrastim, a sustained-duration form of filgrastim, significantly improves neutrophil recovery after autologous marrow transplantation in rhesus macaques

AM Farese1, B-B Yang2, L Roskos2, RB Stead2 and TJ MacVittie1

1Greenebaum Cancer Center, University of Maryland, Baltimore, MD, USA; and 2Amgen Inc., Thousand Oaks, CA, USA

Summary: Although effective, the daily dosing regimens have dis- advantages, such as variable patient compliance as well as Daily administration of filgrastim decreases the duration fluctuations in neutrophil counts, especially with regard to of severe neutropenia in the clinical setting. A sustained- multiple cycle chemotherapy regimens. Two new forms of duration form of filgrastim, pegfilgrastim, significantly G-CSF with sustained duration in vivo, pegfilgrastim and reduces scheduling protocols to a single injection per nartograstim (RO-258215), have shown that a single chemotherapy cycle while maintaining therapeutic effi- injection can sustain a dose- and time-dependent increase ciency. We examined the ability of a single injection of in neutrophil counts for as long as 7–10 days in humans.8,9 pegfilgrastim to significantly improve neutrophil recovery Furthermore, a single dose of pegfilgrastim improved following autologous bone marrow transplantation neutrophil recovery in rodent models of chemotherapy- (AuBMT) in rhesus macaques. On day 1, postmyeloabla- induced myelosuppression similar to that observed with tion (920 cGy x-irradiation) and AuBMT, animals re- daily injections of G-CSF.8,10 Both proteins have shown ceived either 0.1% autologous serum for 18 consecutive effective, dose-dependent mobilization of CD34+ cells in days (n ¼ 13), or single doses of pegfilgrastim via the normal human volunteers.8,9 Recent clinical trial results subcutaneous (s.c.) or intravenous (i.v.) route (300 or suggest that a single injection of pegfilgrastim is sufficient 100 lg/kg), or a single dose of filgrastim at 300 lg/kg to improve recovery from chemotherapy-induced neutro- via the s.c. or i.v. route, or filgrastim at 10 lg/kg via the penia.11–16 Pegfilgrastim, due to its favorable pharmaco- s.c. route (n ¼ 4) on a daily basis (range ¼ days 12–17). kinetics and sustained stimulatory effect on neutrophil Pharmacokinetic parameters and neutrophil recovery production, would improve concerns involving scheduling were assessed. A single dose of pegfilgrastim via the i.v. and compliance during multiple cycle cytotoxic therapy or s.c. route was as effective as daily filgrastim admin- and/or mobilization of stem cells.8,10,17 In order to further istration, resulting in significant improvement of neutro- explore the treatment efficiency of pegfilgrastim relative to phil recovery after myeloablation and ABuMT. Effective filgrastim, we investigated the ability of a single pegfilgras- pegfilgrastim plasma concentrations were maintained in tim injection schedule, via intravenous (i.v.) or subcuta- neutropenic animals until after the onset of hematopoietic neous (s.c.) route, to improve neutrophil recovery after recovery. Enhanced pharmacokinetics in AuBMT cohorts myeloablative conditioning and autologous bone marrow are consistent with self-regulating, neutrophil-mediated transplant (AuBMT) in rhesus macaques. We hypothesized clearance. that due to enhanced pharmacokinetics and predominant Bone Marrow Transplantation (2003) 32, 399–404. neutrophil-mediated clearance, a single dose of pegfilgras- doi:10.1038/sj.bmt.1704156 tim will be as efficient as daily filgrastim to correct Keywords: pegfilgrastim; neutrophil; rhesus; myelosup- neutropenia associated with myeloablative conditioning pression and AuBMT.

Therapeutic use of filgrastim (recombinant human methio- Materials and methods nyl G-CSF) or GM-CSF enhances recovery of neutrophils, reduces antibiotic support and risk of infection consequent Animals to cytotoxic treatment-induced myelosuppression or mye- loablative conditioning for stem cell transplantation.1–7 Male rhesus monkeys, Macaca mulatta, mean weight 3.570.2 kg, were housed in individual stainless-steel cages in conventional holding rooms in the Veterinary Resources Department at the University of Maryland, Greenebaum Correspondence: AM Farese, Greenebaum Cancer Center, University of Maryland, 655 West Baltimore St, Bressler Research Building, Room Cancer Center. Pharmacokinetic studies in normal rhesus 7-047, Baltimore, MD 21201, USA macaques (3–4 kg bw, male) were conducted by the Received 26 November 2002; accepted 1 April 2003 Immunochemistry Department, Covance Laboratories Pegfilgrastim enhances neutrophil recovery AM Farese et al 400 Inc., Vienna, VA. The animal facilities were accredited by cytokine measurement at 0.25, 0.5, 1, 2, 4, 6, and 8 h post the American Association for Accreditation of Laboratory dose on day 1 and at 24-h intervals from days 2–11. Animal Care. Monkeys were provided 10 air changes/h of 7 1 100% fresh air, conditioned to 72 2 F with a relative Autologous bone marrow transplantation (AuBMT).On 7 humidity of 50 20%, and were maintained on a 12-h light/ day 0, animals were myeloablated by TBI to 920 cGy. dark full spectrum light cycle, with no twilight. Monkeys Within 2 h of TBI, animals were infused with approxi- were provided with commercial primate chow (Harlan mately 1 Â 108 AuBM-MNC/kg bw. Beginning on day 1, Teklad, Madison, WI, USA), supplemented with fresh fruit the monkeys received either 0.1% autologous serum (AS) and tap water ad libitum. Research was conducted for 18 consecutive days (n ¼ 13), or single doses of according to the principles enunciated in the Guide for pegfilgrastim via the s.c. (300 mg/kg, n 4 or 100 mg/kg, 18 ¼ the Care and Use of Laboratory Animals, prepared by the n ¼ 3) or i.v. route (300 mg/kg, n ¼ 4 or 100 mg/kg, n ¼ 4), or Institute of Laboratory Animal Resources, National a single dose of filgrastim at 300 mg/kg (n ¼ 4) via the s.c. or Research Council. The research protocol was approved i.v. route, or filgrastim at 10 mg/kg via the s.c. route (n ¼ 4) by the Institutional Animal Care and Use Committee of the on a daily basis until ANC reached 3000/ml (range ¼ days University of Maryland, Greenebaum Cancer Center. 12–17).

Bone marrow harvest Pharmacokinetic analysis. Plasma samples for cytokine measurement were collected from the i.v. cohort preirradia- Rhesus monkeys were anesthetized by intramuscular (i.m.) s tion and at predose, 0.25, 0.5, 1, 2, 4, 6, and 8 h post dose injection of ketamine [Ketaset (10 mg/kg), Fort Dodge, on day 1 and at 24-h intervals from days 2 to 11. IA] plus buprenorphine (Buprenexs Injectable (0.3 mg/kg, i.m.) Rickett & Coleman Pharmaceuticals, Richmond, VA, USA). After sedation, approximately 30–40 ml of hepar- Clinical support inized bone marrow was harvested from the humeri and/or All animals received clinical support, which consisted of iliac crest. Low-density (o1.077 g/cm3) mononuclear cells (MNC) were separated using Histopaque (Sigma, St Louis, antibiotics and fresh irradiated whole blood and fluids, MO, USA) and resuspended in Iscove’s modified Dulbec- as needed. Gentamicin ((Elkin Sinn, an AH Robbins co’s medium (IMDM) (Gibco, Grand Island, NY, USA) subsidiary, Cherry Hill, NJ, USA); (10 mg/day, i.m., qd)) for i.v. infusion. was administered during the first 7 days of treatment and Baytrils ((Bayer Corporation, Shawnee Mission, KS, USA) (10 mg/kg i.m., qd)) was administered for the entire Irradiation period of antimicrobial treatment. The administration of antibiotics continued until the animal maintained a WBC Monkeys, after a prehabituation period, received total X s 1000/ml for three consecutive days and had attained an body irradiation (TBI) in Lucite restraining chairs. ANC X500/ml. Fresh, irradiated (1500 cGy 60Co) whole Approximately, 3–4 h after bone marrow harvest, the blood (approximately 30 ml/transfusion) from a random animals received TBI at a midline tissue dose of 920 cGy donor pool (monkeys of 410 kg) was administered when (250 kVp x-irradiation at 7 cGy/min). Each monkey re- the platelet count was o20 000/ml and the hematocrit was ceived a unilateral exposure of 460 cGy in the anterior– o18%. posterior position, and then was rotated 1801 at middose for completion of the 920 cGy exposure. Dosimetry was performed using paired 0.5 cm3 ionization chambers, with Hematologic evaluations calibration factors traceable to the National Institute of CBC. Peripheral blood was obtained from the saphenous Standards and Technology. vein to assay complete blood (Sysmex K-4500, Long Grove, IL, USA) and differential counts (Wright–Giemsa Recombinant cytokines Stain, Ames Automated Slide Stainer, Elkhart, IN, USA) for 45 days after TBI. These parameters were monitored for Filgrastim, recombinant human methionyl G-CSF, was 45 days post TBI and AuBMT. The duration of neutro- produced in Escherichia coli with a specific activity of penia (ANC o500/ml) and time to recovery (day ANC 8 1 Â 10 U/mg. Pegfilgrastim has a 20-kDa polyethylene reached X2000/ml after TBI), ANC nadir and antimicro- glycol (PEG) molecule covalently bound at the N-terminal bial requirements were assessed. The ANC nadir was the residue of rHumetG-CSF (filgrastim). Both proteins were first lowest observed or imputed ANC that occurred at least manufactured by Amgen Inc. (Thousand Oaks, CA, USA). 2 days after the first dose of study drug. The duration of neutropenia was estimated as the number of days that a Pegfilgrastim administration protocols subject had an observed or an imputed ANC below 500/ml. Any single observed ANC that was X500/ml and was Normal animal pharmacokinetic analysis. Normal animals immediately preceded and followed by ANC o500/ml was were intravenously administered single injections of pegfil- counted as a day of severe neutropenia. The time to grastim at 100 mg/kg. Peripheral blood samples were taken recovery was estimated as the number of days from study prior to and after administration of pegfilgrastim for day 1 until the day on which the first two consecutive determination of CBC and collection of plasma for observed or imputed ANC after the nadir were X2000/ml.

Bone Marrow Transplantation Pegfilgrastim enhances neutrophil recovery AM Farese et al 401 Statistical analysis Myeloablative conditioning with AuBMT The Normal Scores Test was used to make a pairwise Single administration of pegfilgrastim in the AuBMT comparison of the duration of neutropenia and to evaluate model. Intraverous (i.v.) or s.c. administration of pegfil- the statistical significance between the nadirs, time to grastim at 100 or 300 mg/kg on day 1 after AuBMT recovery and antimicrobial requirements. The exact significantly increased ANC recovery compared with the P-values were obtained. The test was carried out using placebo control (Po0.001). Pegfilgrastim administered via the software package StatXact (Cytel Software Corp., i.v. or s.c. route at 300 mg/kg significantly shortened the Cambridge, MA, USA). duration of neutropenia (2.5 and 2.3 days, respectively) vs control (11.2 days) (Po0.001), and significantly improved

Results 10000 Normal (n=3) Myeloablated and AuBMT (n=4) Pharmacokinetic of pegfilgrastim after s.c. and i.v. 1000 administration in normal and irradiated, AuBMT animals 100 The concentration–time and ANC-time profiles from the AuBMT monkeys were compared with those from the 10 normal rhesus monkeys after single i.v. administration of (ng/ml) 1

100 mg/kg pegfilgrastim. (Figure 1). The data for the normal 0.1 monkeys were from a study conducted previously by

Plasma pegfilgrastim conc. 0.01 Amgen Inc. While the mean Cmax value was lower for the AuBMT cohort (22007310 ng/ml, n ¼ 4) than for the 02468 7 normal monkeys (3930 380 ng/ml, n ¼ 3), the mean Time (day) post administration pegfilgrastim AUC value was higher for the AuBMT monkeys (46 30079200 ng h/ml, n ¼ 4) than for the normal monkeys 100 (29100 73100 ng h/ml, n ¼ 3). Pegfilgrastim was cleared from the circulation in 2 days in normal monkeys and in

/l) 10 8 days in the AuBMT monkeys. While the reason for the 9 difference in the Cmax values is not known, the lower clearance observed in the AuBMT monkeys is likely 1 because of a decrease in the G-CSF receptor-mediated (cells x 10 clearance secondary to the neutropenic condition. Pharma- cokinetic parameters were also evaluated for i.v. adminis- Absolute neutrophil count 0.1 tration of pegfilgrastim and filgrastim at the 300 mg/kg dose in the AuBMT cohorts. Pegfilgrastim exhibited nonlinear 02468 Time (day) post administration of pegfilgrastim in normal animals pk; the clearance value (CL) decreased from 2.2270.44 ml/ Time (day) post irradiation and AuBMT in myeloablated animals h/kg to 1.8070.32 ml/h/kg when the dose increased from 100 to 300 mg/kg (Table 1). As expected, the clearance Figure 1 (a, b). Mean (s.e.) plasma pegfilgrastim concentration- and ANC-time profiles in normal and AuBMT rhesus macaques. (a) The top values for pegfilgrastim were significantly lower than that panel are the mean (s.e.) plasma concentrations of pegfilgrastim in normal for filgrastim, 47.976.56 ml/h/kg in the AuBMT animals. animals (n ¼ 3) administered (100 mg/kg, i.v.) pegfilgrastim and AuBMT Therefore, systemic exposure after pegfilgrastim adminis- animals (n ¼ 4) administered pegfilgrastim (100 mg/kg, i.v.). Note that in the tration was higher than that for filgrastim administered i.v. AuBMT animals this occurred on day 1 after irradiation and AuBMT. (b) The bottom panel are the mean (s.e.) ANC values. In this panel, day 0 The respective T1/2 values for pegfilgrastim at 100 and refers to the time post administration of pegfilgrastim in the normal 300 mg/kg doses were 22.274.6 and 16.274.4 h, relative to animals and time after irradiation and AuBMT in the myeloablated 4.772.1 h for filgrastim. animals. Administration of pegfilgrastim occurred on day 1 post AuBMT.

Table 1 Pharmacokinetic mean values in rhesus macaques following i.v. administration of pegfilgrastim or filgrastim on day 1 after irradiation and AuBMT

Parameter Pegfilgrastim 100 mg/kg Pegfilgrastim 300 mg/kg Filgrastim 300 mg/kg n 444

Cmax (ng/ml) 2200 (310) 6180 (480) 3570 (990)

Tmax (h) 1.19(0.94) 0.44 (0.38) 0.31 (0.13)

T1/2 (h) 22.2 (4.6) 16.1 (4.4) 4.7 (2.1)

AUC(0–last) (ng h/ml) 46 300 (9200) 171 000 (31 000) 6340 (940)

Vc (ml/kg) 46.2 (6.5) 48.8 (3.9) 89.5 (26.1) CL (ml/h/kg) 2.22 (0.44) 1.80 (0.32) 47.9(6.5)

Cmax is the maximum observed serum concentration; Tmax is the time of Cmax; T1/2 is the terminal half-life; AUC(0–last) is the area under the concentrations– time curve from time 0 to the time of the last detectable concentration; Vc is the volume of distribution at the central compartment; and CL is the serum clearance after i.v. doses.

Bone Marrow Transplantation Pegfilgrastim enhances neutrophil recovery AM Farese et al 402 the ANC nadir (333 and 398/ml, respectively) vs control (63/ 135/ml, P ¼ 0.029). All other neutrophil-related parameters ml) (Po0.001). Pegfilgrastim at 300 mg/kg via the s.c. route were equivalent when comparing single administration of significantly shortened the time to recovery to ANC pegfilgrastim at 100 mg/kg on day 1 via either the i.v. or s.c. X2000/ml (10.3 days) vs control (19.8 days) (P ¼ 0.002), route with daily administration of filgrastim at 10 mg/kg. whereas the time to recovery via the i.v. route (19.5 days) When administered by either route at 300 mg/kg on day 1, was similar to that for the controls (Table 2). pegfilgrastim significantly improved the duration of neu- Pegfilgrastim administered via i.v. or s.c. route at 100 mg/ tropenia (P ¼ 0.029) and the ANC nadir (Pp0.029) as kg significantly shortened the duration of neutropenia (5.3 compared with daily administration of filgrastim at 10 mg/ and 4.0 days, respectively) and improved the ANC nadir kg/day; however, only s.c. administration of pegfilgrastim (301 and 192/ml, respectively) vs control (11.2 days, 63/ml) significantly improved the time to recovery to ANCX2000/ (Pp0.005). Neither i.v. nor s.c. administration of pegfil- ml(P ¼ 0.029) (Table 2, Figure 2). The daily administration grastim at this dose had a significant effect on the time to of filgrastim administered at 10 mg/kg/day until the ANC recovery to ANC X2000/ml (19.5 and 19.7 days, respec- X3000/ml (range 12–17 days) after AuBMT significantly tively) vs control (19.8 days)(Table 2, Figure 2). improved all neutrophil-related parameters vs the control Antibiotic requirements were significantly reduced after cohort (Table 2, Figure 2). pegfilgrastim was administered via the i.v. or s.c. route at either the 300 mg/kg dose (7.0, 5.8 days, respectively) or the Filgrastim administered on day 1 at 300 mg/kg via either 100 mg/kg dose (8.3, 10.7 days, respectively) vs the control route vs the placebo control cohort. Neutrophil-related cohort (15.3 days) (Pp0.021). parameters after i.v. administration of 300 mg/kg of filgrastim on day 1 were equivalent to those after treatment Single administration of pegfilgrastim vs single administra- with placebo, with the exception of a significantly longer tion of filgrastim. Pegfilgrastim administered at 300 or duration of neutropenia (19.5 days vs 11.2 days) (P ¼ 0.012) 100 mg/kg via i.v. or s.c. route significantly decreased the in the filgrastim-treated group. However, when filgrastim duration of neutropenia and antibiotic requirements and was administered at 300 mg/kg on day 1 via the s.c. route, significantly improved the ANC nadir vs a single dose of there was a significant improvement in the ANC nadir (125/ filgrastim administered via either i.v. or s.c. at 300 mg/kg ml vs 63/ml, P ¼ 0.037); the duration of neutropenia and X on day 1. The time to recovery to ANC 2000/ml was antibiotic requirements were equivalent, and there was a significantly improved (Pp0.05) after s.c. administration of significant delay in time to recovery to ANC X2000/ml pegfilgrastim at 300 mg/kg vs either i.v. or s.c. administra- (24.0 vs 19.9 days) (P ¼ 0.042) as compared to placebo tion of filgrastim at 300 mg/kg (Table 2). controls (Table 2, Figure 2).

Single administration of pegfilgrastim vs daily administration of filgrastim Discussion Pegfilgrastim administered at 100 mg/kg on day 1 via the s.c. route significantly improved the ANC nadir compared with Single i.v. or s.c. administration of pegfilgrastim, given daily administration of filgrastim at 10 mg/kg/day (301/ml vs within 20 h of myeloablative conditioning and AuBMT,

Table 2 Neutrophil-related parameters in autologous bone marrow transplanted rhesus monkeys treated with pegfilgrastim or filgrastim

Treatment n Duration of neutropenia (day) ANC nadir (cells/ml) Time to recovery (day) Antibiotic requirements (day) Placebo 13 11.270.7 63714 19.870.915.3 70.7a

i.v. Pegfilgrastim, 100 mg/kg 4 5.372.0a,b,c 192753a,b 19.570.3c 8.371.6a,b,c Pegfilgrastim, 300 mg/kg 4 2.570.6a,b,c,d 333747a,b,c,d 17.071.9c 7.071.4a,b,c Filgrastim, 300 mg/kg 4 19.575.5 6574 25.775.7 19.374.6

s.c. Pegfilgrastim, 100 mg/kg 3 4.071.2a,b,c 301739a,b,c,d 19.772.6 10.771.9a,b,c Pegfilgrastim, 300 mg/kg 4 2.370.9a,b,c,d 398793a,b,c,d 10.370.9a,b,c,d,e 5.871.9a,b,c Filgrastim, 300 mg/kg 4 12.070.7 125733a 24.070.0 15.570.3 Filgrastim, 10 mg/kg/d 4 6.071.4a 135732a 15.871.7a 9.370.9a

Monkeys were myeloablated with total body x-irradiation (TBI) to 920 cGy and within 2 h were transplanted with approximately 1 Â 108 AuBM MNCs per kilogram of body weight. Animals were treated, s.c., 0.1% autologous serum ( AS), filgrastim at 10 mg/kg, s.c., qd, on days 1–18 filgrastim at 300 mg/kg, s.c. or i.v. on day 1, pegfilgrastim at 100 mg/kg, s.c. or i.v. on day 1, or filgrastim at 300 mg/kg, s.c. or i.v. on day 1 post-TBI and AuBMT. The duration of neutropenia is defined as days of ANC o500/ml. Time to recovery is the number of days required for the ANC to reach X2,000/ml. Data are mean values7s.e.m. aStatistically different from control cohort (Pp0.037). bStatistically different from filgrastim 300 mg/kg, day 1 only, i.v. cohort (Pp0.05). cStatistically different from filgrastim 300 mg/kg, day 1 only, s.c. cohort (Pp0.05). dStatistically different from filgrastim 10 mg/kg, qd cohort (Pp0.029). eStatistically different from pegfilgrastim 100 mg/kg, day 1, i.v. or s.c. cohort (P=0.05).

Bone Marrow Transplantation Pegfilgrastim enhances neutrophil recovery AM Farese et al 403 a significantly improved neutrophil recovery relative to the 100.00 placebo control and the single i.v. or s.c. administration of filgrastim. Furthermore, the single dose of pegfilgrastim improved neutrophil recovery, similar to that noted with 10.00 daily administration of filgrastim. There was no improve- ment in neutrophil recovery after single, i.v. or s.c. l µ /

3 administration of filgrastim relative to the placebo control

10 1.00 × cohort. These results are consistent with prospective 0.50

ANC modeling and simulations based on pharmacokinetics and Pegfilgrastim 100 ug, iv pharmacodynamics noted in normal animals and Phase 1 Pegfilgrastim 100 ug, sc 0.10 12,19,20 19 Filgrastim 300 ug, iv clinical trials. Cheung et al suggested that the Filgrastim 300 ug, sc duration of action for pegfilgrastim during severe neutro- Placebo or 0.1% AS penia would be substantially longer than predicted by 0.01 normal animal models.19 Therefore, the radiation or 0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 Time (days) post irradiation and AuBMT chemotherapy-induced neutropenic phase would represent a condition of decreased G-CSF receptor-mediated clear- b 19 100.00 ance and thus provide for a longer response duration. The pk and pd data of pegfilgrastim in the AuBMT models presented herein support these suggestions. Significantly,

10.00 higher levels of pegfilgrastim were maintained in the neutropenic animals for the predicted 6–9days relative to 20 l the 3–4 days in nonmyelosuppressed animals. Roskos et al µ / 3 suggested that relative to G-CSF, the clearance of 10 1.00 × 0.50 pegfilgrastim is more efficiently regulated by neutrophils ANC Pegfilgrastim 300 ug, iv due to a reduction in the linear, neutrophil-independent Pegfilgrastim 300 ug, sc elimination pathway.20 Indeed, this study substantiates the 0.10 Filgrastim 300 ug, iv Filgrastim 300 ug, sc significant lower values for serum clearance and conse- Placebo or 0.1% AS quently terminal half-life values for pegfilgrastim than filgrastim. Therefore, during periods of chemotherapy- 0.01 0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 induced neutropenia, efficacious concentrations of pegfil- Time (days) post irradiation and AuBMT grastim are maintained until onset of hematopoietic recovery.20 c 100.00 Recently, several studies including early clinical trial results have suggested equivalent efficacy of pegfilgrastim and other peg-modified G-CSFs, relative to conventional, 10.00 daily administration of filgrastim in enhancing recovery of neutrophils following chemotherapy or radiation-induced 8,10–16,21 8 10 /L

3 myelosuppression. Molineux et al and Lord et al 1.00 have demonstrated that pegfilgrastim was effective as a

ANC x 10 0.50 single dose in reducing chemotherapy-induced neutropenia Pegfilgrastim 300 ug, iv 21 Pegfilgrastim 300 ug, sc in mice. Additionally, Farese et al have shown that a 0.10 Filgrastim 10 ug, sc single dose of peg-modified myelopoietin (leridistim), one Placebo or 0.1% AS of the dual IL-3/G-CSF receptor agonists, can improve postirradiation neutrophil recovery in nonhuman primates

0.01 in a manner equivalent to conventional daily dosing of 21 0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 leridistim. Recent clinical trials have shown that a single Time (Days) Post Irradiation and AuBMT dose of pegfilgrastim per chemotherapy cycle can reduce the Figure 2 (a–c) Effect of pegfilgrastim administration on peripheral blood duration of chemotherapy-induced neutropenia as safely ANC recovery following 920 cGy x-irradiation and AuBMT in rhesus and effectively as daily administered filgrastim.11,13–16 macaques. ANC recovery was observed in animals administered (a) Further evidence of the potential utility of pegfilgrastim Pegfilgrastim at 100 mg/kg i.v. (n ¼ 4) or s.c. (n ¼ 3) route, or filgrastim at 300 mg/kg via i.v. (n ¼ 4) or s.c. (n ¼ 4) route on day 1 after irradiation, or was shown in a recent phase III clinical trial comparing control autologous sera on days 1–18 (n ¼ 13) after irradiation and fixed-dose pegfilgrastim 6 mg/cycle with filgrastim adminis- AuBMT; (b) Pegfilgrastim at 300 mg/kg i.v. (n ¼ 4) or s.c. (n ¼ 3) route, or tered at 5 mg/kg/day.14 A 6 mg fixed dose of pegfilgrastim filgrastim at 300 mg/kg via i.v. (n ¼ 4) or s.c. (n ¼ 4) route on day 1 after per chemotherapy cycle showed efficacy comparable to that irradiation, or control autologous sera on days 1–18 (n ¼ 13) after irradiation and AuBMT; and (c) Pegfilgrastim at 300 mg/kg i.v. (n ¼ 4) or of daily filgrastim administration irrespective of patient s.c. (n ¼ 3) route, or filgrastim at 10 mg/kg daily (n ¼ 4) via s.c. administra- body weight. tion until the ANC reached 3000/ml (range 12–17 days), or control In summary, the clearance of pegfilgrastim is self- autologous sera on days 1–18 (n ¼ 13) after irradiation and AuBMT. regulated by neutrophils such that effective serum levels 7 Values are means s.e.m. are maintained over the duration of severe neutropenia and decrease with the onset of granulopoiesis. Furthermore, the stimulation of granulopoiesis by pegfilgrastim after

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Bone Marrow Transplantation