Kathryn W. Woodburn

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

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 [14C]-labeled peginesatide. Mass balance, tissue distribution and metabolism were evaluated following IV administration of 5 mg·kg−1 [14C]-peginesatide, with tissue distribution also evaluated by quantitative whole-body autoradiography (QWBA) following an IV dose of 17 mg·kg−1 [14C]-peginesatide. 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. Biodistribution to bone marrow and extramedullary hematopoietic sites, and to highly vascularized lymphatic and excretory tissues occurred. A predominant degradation event to occur in vivo was the loss of one PEG chain from the branched PEG moiety to generate mono-PEG. Renal excretion was the primary mechanism (41%) of elimination, with parent molecule (67%) the major moiety excreted. In conclusion, elimination of [14C]-peginesatide-derived radioactivity was extended, retention preferentially occurred at sites of erythropoiesis (bone marrow), and urinary excretion was the primary elimination route.

Chronic preclinical safety evaluation of Hematide, a pegylated peptidic erythropoiesis stimulating agent in monkeys.

Hematide is a synthetic peptide-based, pegylated erythropoiesis stimulating agent in clinical development for treatment of anemia. In this study, hematide administration was associated with time and dose-dependent polycythemia in monkeys. Hematide is a synthetic peptide-based, pegylated erythropoiesis stimulating agent in clinical development for treatment of anemia. To support chronic clinical dosing requirements, a 9-month repeat dose IV monkey safety study was undertaken. Animals received 0, 0.2, 2 or 20 mg/kg hematide IV every three weeks for nine months followed by a 14-week recovery. Hematide administration was associated with time and dose-dependent polycythemia. Histological findings were related to exaggerated pharmacology that was secondary to the administration of an erythropoiesis stimulating agent to a normocythemic animal. In conclusion, these results support the use of repeated administration of hematide for the correction of anemia.

Preclinical Safety and Pharmacology of Hematide™, a Peptidic Erythropoiesis Stimulating Agent (ESA), in Rats and Monkeys

The pharmacology, toxicokinetics, and safety of HematideTM, a synthetic peptidic erythropoiesis-stimulating agent (ESA), were characterized. Hematide was given intravenously (0, 0.5, 5, and 50 mg/kg) weekly for five weeks with a 6- (rat) and 12-week (monkey) recovery period. The pharmacological action of Hematide resulted in polycythemia. Histopathology consistent with drug-induced exaggerated pharmacology was observed primarily in rats. Secondary sequelae resulting from pronounced polycythemia was considered the cause of deaths in rats and a single high-dose monkey. Toxicokinetic analysis indicated prolonged exposure. In conclusion, Hematide is a potent ESA and the safety and efficacy profile support clinical development.

Chronic Pharmacological and Safety Evaluation of Hematide™, a PEGylated Peptidic Erythropoiesis-Stimulating Agent, in Rodents

Hematide™ is a synthetic peptide-based, PEGylated erythropoiesis-stimulating agent, which is being developed for the chronic treatment of anaemia associated with chronic renal failure. To support the safety of long-term dosing of chronic renal failure patients, a comprehensive toxicology programme was implemented including rat subchronic and chronic studies. Rats were administered 0, 0.1, 1 and 10 mg/kg of Hematide every 3 weeks for 3 months via subcutaneous injection or for 6 months via intravenous injection. The dosing period was followed by a 6-week follow-up period. The primary pharmacology of Hematide resulted in erythroid polycythemia as measured by elevated haemoglobin levels that were time-and dose-dependent. The pharmacology profiles were similar regardless of administration route. For example, for male rats at Day 90, subcutaneous dosing resulted in haemoglobin increases of 2.7, 4.5 and 6.9 g/dl for 0.1, 1 and 10 mg Hematide/kg respectively, compared to 2.8, 5.7 and 7.4 g/dl increases for intravenous dosing. Histopathological changes were related to the prolonged severe polycythemia induced in normocythemic animals administered an erythropoiesis-stimulating agent. The findings included extramedullary haematopoiesis in the spleen and liver, bone marrow hypercellularity and organ congestion. Microscopic findings were reversible, demonstrating a return towards control findings within 6 weeks following cessation of dosing. Systemic exposures, based on both area under the curve (AUC) and maximum concentration (Cmax), were substantially greater for intravenous than subcutaneous administration. No Hematide-specific antibodies were detected. In conclusion, Hematide is a potent erythropoiesis-stimulating agent, and the studies provide support for the safety of clinical development, including chronic dosing, for the treatment of anaemia associated with chronic renal failure.

Peginesatide Clearance, Distribution, Metabolism, and Excretion in Monkeys Following Intravenous Administration

Peginesatide, a polyethylene glycol (PEG)ylated peptide-based erythropoiesis-stimulating agent, stimulates the erythropoietin receptor dimer that governs erythropoiesis. Studies were designed to determine the erythropoietic response, pharmacokinetics (PK), tissue distribution, metabolism, and excretion of peginesatide in nonhuman primates following a single i.v. dose. The PK profile of peginesatide (0.1–5 mg/kg) is characterized by low, dose-dependent plasma clearance; small volume of distribution; and long half-life. The peginesatide PK profile following a single i.v. dose is consistent with the sustained erythropoiesis. Biodistribution quantitative whole-body autoradiography demonstrated high peginesatide levels in bone marrow (i.e., primary hematopoietic site) as well as other known hematopoietic sites persisting through at least 3 weeks at 2.1 mg/kg. Microautoradiography analysis at 48 hours postdose revealed uniform and high distribution of radioactivity in the bone marrow and splenic red pulp with less extensive distribution in the renal cortex (glomeruli, associated ducts, interstitial cells). Radioactivity in the kidney was most prominent in the outer medullary and papillary interstitium. At 2 weeks after dosing, cumulative radioactivity recovery in the urine and feces was 60 and 7% of the administered dose, respectively, with most of the radioactivity associated with the parent molecule. In conclusion, the PK characteristics are consistent with a PEGylated peptide of a 45-kDa molecular mass, specifically low volume of distribution and long half-life. Drug was localized principally to hematopoietic sites, and nonspecific tissue retention was not observed. The nonhuman primate data indicate that peginesatide is metabolically stable and primarily excreted in the urine.

Genotoxic assessment and toxicity evaluation of peginesatide in CByB6F1 hybrid mice.

Peginesatide is a PEGylated, investigational, peptide-based erythropoiesis-stimulating agent (ESA) that was designed and engineered to stimulate specifically the erythropoietin receptor dimer that governs erythropoiesis. Clinical use of peginesatide is anticipated to result in chronic dosing in chronic kidney disease (CKD) patients, and the nonclinical data to support development should include an evaluation of carcinogenic potential evaluation. Peginesatide was not mutagenic or clastogenic in a standard genotoxicity battery of tests. Doses for a rasH2 transgenic mouse carcinogenicity assay were defined in a 28-day study in the wild-type littermates of the rasH2 transgenic mouse strain, using intravenous doses of 1–25 mg/kg on days 1 and 22. The findings were consistent with exaggerated pharmacology, including polycythemia, with associated increases in hemoglobin level and extramedullary hematopoiesis and bone marrow hypercellularity.

A subchronic murine intravenous pharmacokinetic and toxicity study of Hematide™, a PEGylated peptidic erythropoiesis-stimulating agent

The subchronic toxicity of Hematide™, a synthetic PEGylated peptidic erythropoiesis-stimulating agent (ESA), was evaluated in CD-1 mice at intravenous doses of 0, 1, 5, 25, and 125 mg/kg administered once every 3 weeks for 3 months. Hematide displayed sustained plasma levels with reduced clearance and prolonged half-lives up to 59.4 hours that translated into sustained, pronounced polycythemia, bone marrow hyperplasia, and splenic and liver extramedullary hematopoiesis. Toxicological findings were considered to be secondary to exaggerated pharmacology, rather than a direct drug effect, and included mortality at ≥25 mg/kg/dose. The no-observed-adverse-effect-level was determined to be 5 mg/kg.

Peri‐ and postnatal rodent development of Hematide, an erythropoiesis‐stimulating agent

BACKGROUND Aperi- and postnatal reproduction toxicity study was conducted in rats treated with Hematide, a synthetic PEGylated peptidic erythropoiesis stimulating agent (ESA). METHODS Hematide, at IV doses of 0, 0.5, 3, and 15 mg/kg, was administered from implantation through lactation on gestation days (GDs) 5 and 18 and lactation day (LD) 13. RESULTS Hematide induced pronounced polycythemia in all Hematide-treated dams. On LDs 2 and 21, hemoglobin (Hgb) increases above control levels were 3.1, 5.2, and 5.0 g/dL and 4.1, 5.1, and 5.5 g/dL at the 0.5, 3, and 15 mg/kg/dose, respectively. There were no effects on parturition, lactation, or maternal behavior in the F0 generation female rats. A slight decrease in pup viability on postpartum days 2-4 and lower body weights and/or body weight gain for the F1 generation were associated with pronounced polycythemia and decreases in maternal body weight gain and/or food consumption at > or =3 mg/kg/dose. Hematide fetal exposure was negligible. No Hematide effect, other than on growth and survival, was noted on developmental, functional, mating, and fertility end points in the F1 generation rats, and no effect on litter or fetal parameters was observed in the F2 generation. The maternal no-observed-adverse-effect level (NOAEL) for Hematide was 0.5 mg/kg, and the NOAEL for parturition and maternal behavior was 15 mg/kg. The NOAEL for F1 pup viability and growth was 0.5 mg/kg/dose. CONCLUSIONS In conclusion, the Hematide-associated adverse findings were attributed to exaggerated erythropoiesis (pronounced and prolonged polycythemia) resulting from administration of an ESA to pregnant animals.