Pharmacokinetics and Hematological Effects of the PEGylated Thrombopoietin Peptide Mimetic GW395058 in Rats and Monkeys After Intravenous or Subcutaneous Administration

Abstract

GW395058, a potent PEGylated peptide human thrombopoietin receptor (HuTPOr) agonist in vitro, is being evaluated for the treatment of thrombocytopenia. GW395058 shares no sequence homology with TPO. In this report the pharmacokinetics and hematological effects of GW395058 in rats and monkeys are described. Doses eliciting thrombocytosis in rodents (2 or 10 µg/kg s.c.) produced insufficient plasma concentration data for pharmacokinetic parameter estimate calculations. At higher i.v. doses in rats (500, 1,000 or 2,000 µg/kg) serum t 1/2 (half-life) values were >20 h, and the area under the concentration time curve increased proportionally with dose. In cynomolgus monkeys GW395058 plasma t 1/2 values ranged from 37 to 68 h after s.c. or i.v. dosing, and similar values were observed in rhesus monkeys following s.c. dosing. Rat platelet counts increased following 2 (1.6-fold) or 10 µg/kg (fourfold) s.c. doses. Cynomolgus and rhesus monkey platelet counts did not change significantly at comparable s.c. doses, but did increase slightly (<twofold) in cynomolgus monkeys following a 25 µg/kg s.c. dose and twofold following a 100 µg/kg s.c. dose. Because the plasma t 1/2 of GW395058 is long in mouse, rat, dog, and monkey, yet the dose required to double platelet levels in monkeys is 50-fold that required in rats, differences in hematological responses may be due to interspecies differences in the interaction of GW395058 with the TPOr. Stem

Cloning and Expression of Human Stem Cell Factor Fused with Thrombopoietin Mimetic Peptide in Escherichia coli

“…It was anticipated that the cytokine/mimetic peptide fusion proteins would induce less immunogenic response than the fused cytokines. Studies showed that the N-terminal PEGylation improved the potency of TMP (de Serres et al 1999), indicating that the attachment of a large molecule to the N-terminus does not prevent the interaction of TMP with its receptor. Therefore, TMP was fused through its amino termini to the SCF by a flexible peptide linker.…”

Thrombopoietin regulates IEX-1 gene expression through ERK-induced AML1 phosphorylation

“…The TPO mimetic peptide GW395058 38,39 was synthesized by Genosys Biotechnologies (The Woodlands, TX). Recombinant human EPO and stem cell factor (SCF) were from Boehringer-Mannheim (Mannheim, Germany) and PromoCell (Heidelberg, Germany).…”

The molecular and cellular biology of thrombopoietin: the primary regulator of platelet production

“…Although a nity of the EPO-mimetic peptide (EMP) was about three logs less than EPO itself (Wrighton et al, 1996), the TPO mimetic peptide (TMP) a nity was remarkably close to that of the native hormone (Cwirla et al, 1997). Injection of 2 mg/kg of a polyethylene glycol modi®ed TMP resulted in doubling of the platelet count, and 10 mg/kg tripled or quadrupled the count (de Serres et al, 1999). The e ects in monkeys were not quite as impressive and a much higher dose was required to double the platelet counts, but the TMP has also been shown to protect animals from severe thrombocytopenia following chemotherapy (Case et al, 2000).…”