Absorption, distribution, metabolism and excretion of peginesatide, a novel erythropoiesis-stimulating agent, in rats

1. The pharmacokinetics(PK) (absorption, distribution, metabolism, excretion) of peginesatide.a synthetic, PEGylated, investigational, peptide-based erythropoiesis-stimulating agent (ESA), was evaluated in rats. The PK profile was evaluated at 0.1-5 mg·kg(−1) IV using unlabeled or [(14)C]-labeled peginesatide. Mass balance, tissue distribution and metabolism were evaluated following IV administration of 5 mg·kg(−1) [(14)C]-peginesatide, with tissue distribution also evaluated by quantitative whole-body autoradiography (QWBA) following an IV dose of 17 mg·kg(−1)[(14)C]-peginesatide. 2. Plasma clearance was slow and elimination was biphasic with unchanged peginesatide representing >90% of the total radioactivity of the total radioactive exposure. Slow uptake of the radiolabeled compound from the vascular compartment into the tissues was observed. 3. Biodistribution to bone marrow and extramedullary hematopoietic sites, and to highly vascularized lymphatic and excretory tissues occurred. 4. A predominant degradation event to occur in vivo was the loss of one PEG chain from the branched PEG moiety to generate mono-PEG. 5. Renal excretion was the primary mechanism (41%) of elimination, with parent molecule (67%) the major moiety excreted. 6. In conclusion, elimination of [(14)C]-peginesatide-derived radioactivity was extended, retention preferentially occurred at sites of erythropoiesis (bone marrow), and urinary excretion was the primary elimination route.