A Single Dose of Pegylated Leridistim Significantly Improves Neutrophil Recovery in Sublethally Irradiated Rhesus Macaques ANN M. FARESE,a DANIEL B. CASEY,a ROY M. VIGNEULLE,a NED R. SIEGEL,b RORY F. FINN,b JON A. KLOVER,b WALTER G. SMITH,b JOHN P. MCKEARN,b THOMAS J. MACVITTIEa a
University of Maryland, Greenebaum Cancer Center, Baltimore, Maryland, USA; b Pharmacia Corp., St. Louis, Missouri, USA Key Words. Leridistim · Myelopoietin · Myelosuppression · Rhesus · Neutrophil
A BSTRACT Leridistim, a member of the myelopoietin family of dual receptor agonists that binds interleukin-3 and GCSF receptors, has been shown to enhance hematopoietic activity in rhesus monkeys above that observed with either cytokine alone or in combination. This study demonstrated the ability of a pegylated form of leridistim (peg-leridistim), administered s.c., as a single- or two-dose regimen separated by 4 or 7 days, to significantly improve neutrophil recovery following radiation-induced myelosuppression. Rhesus macaques were total body x-irradiated (250 kVp, TBI) to 600 cGy. Following TBI, two groups received peg-leridistim (n = 5) or leridistim (n = 4) at a dose of 600 µg/kg on day 1, while two other groups
(both n = 4) received peg-leridistim at 200 µg/kg on day 1 and day 4, or day 1 and day 7. The irradiation controls (n = 7) received 0.1% autologous serum for 18 days. All pegleridistim treatment schedules significantly improved all neutrophil-related parameters following TBI as compared with nontreated controls and were equivalent in effect when compared among themselves. Administration of a single high dose or two separate lower doses of pegleridistim significantly improved neutrophil regeneration, in a manner equal to that of conventional daily or abbreviated every-other-day administration of leridistim in this nonhuman primate model of severe myelosuppression. Stem Cells 2001;19:514-521
INTRODUCTION Leridistim, a member of the myelopoietin family of dual receptor agonists that binds interleukin-3 (IL-3) and GCSF receptors, has been shown to enhance hematopoietic activity in myelosuppressed nonhuman primates. Multilineage hematopoiesis was stimulated above that observed with either cytokine alone or in combination when leridistim was administered in daily (qd) or every other day (qod) schedules for 18 days [1, 2]. The favorable pharmacodynamic profile exhibited by the abbreviated, qod administration of leridistim suggested that further alteration in its pharmacokinetic properties by addition of polyethylene glycol may significantly enhance its therapeutic utility from both standpoints of patient compliance and administration schedule. Recently, a new pegylated form (SD-01) of filgrastim (rmet-HuG-CSF) has been shown to have a sustained
concentration in vivo [3-5]. SD-01 has demonstrated enhanced ability to mobilize peripheral blood progenitors and increase neutrophil recovery in chemotherapy-treated mice or rhesus macaques following radiation-induced myelosuppression or bone marrow transplantation when administered as a single or two separate injections relative to standard, daily injections of filgrastim [3-5]. The potential to reduce the effective administration schedule of therapeutic cytokines will offer significant advantages in treatment scheduling as well as allow for further insights into stimulating hematopoietic regeneration subsequent to cytotoxic therapy or stem cell transplantation. We report herein on the relative therapeutic efficacy of peg-leridistim administered as a single or two separate injections to stimulate hematopoietic recovery in rhesus macaques following high-dose sublethal irradiation.
Correspondence: Ann M. Farese, M.S., University of Maryland, Greenebaum Cancer Center, 655 West Baltimore Street, BRB 7-049, Baltimore, Maryland USA, 21201; Telephone: 410-328-5347; Fax: 410-328-5488; e-mail:
[email protected] Received July 3, 2001; accepted for publication July 10, 2001. ©AlphaMed Press 1066-5099/2001/$5.00/0
STEM CELLS 2001;19:514-521
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Farese, Casey, Vigneulle et al. MATERIALS AND METHODS Animals Male rhesus monkeys, Macaca mulatta, mean weight 4.35 ± 0.32 kg, were housed in individual stainless steel cages in conventional holding rooms at the Veterinary Resources Department at the Greenebaum Cancer Center in animal facilities accredited by the American Association for Accreditation of Laboratory Animal Care (http://www. aaalac.org). Monkeys were provided 10 air changes/hour of 100% fresh air, conditioned to 72° ± 2°F with a relative humidity of 50% ± 20% and maintained on a 12-hour light/dark full spectrum light cycle, with no twilight. Monkeys were provided with commercial primate chow, supplemented with fresh fruit and tap water ad libitum. Research was conducted according to the principles enunciated in the Guide for the Care and Use of Laboratory Animals [6], prepared by the Institute of Laboratory Animal Resources, National Research Council (http://www.nas.edu/nrc). Irradiation Monkeys, following a prehabituation period, were unilaterally irradiated in Lucite® restraining chairs with 250 kVp x-radiation at 13 cGy/minute in the posterior-anterior position, rotated 180° at the mid-dose (300 cGy) to the anterior-posterior position for completion of the total 600 cGy midline tissue exposure. Dosimetry was performed using paired 0.5 cm3 ionization chambers, with calibration factors traceable to the National Institute of Standards and Technology. Clinical Support All animals received clinical support that consisted of antibiotics, fresh irradiated whole blood, and fluids as needed. Gentamicin (Elkin Sinn, an AH Robbins subsidiary; Cherry Hill, NJ) (10 mg/day, i.m., qd) was administered during the first 7 days of treatment, and Baytril® (Bayer Corporation; Shawnee Mission, KS; http://www. bayerus.com) (10 mg/day i.m., qd) was administered for the entire period of antimicrobial treatment. The administration of antibiotics continued until the animal maintained a WBC ≥1,000/µl for 3 consecutive days and had attained an ANC ≥500/µl [7, 8]. Fresh, irradiated (1,500 cGy Co-60) whole blood (approximately 30 ml/transfusion) from a random donor pool (monkeys of >10 kg) was administered when the platelet (PLT) count was
