Chronic Preclinical Safety Evaluation of Hematide^™, a PEGylated Peptidic Erythropoiesis Stimulating Agent, in Monkeys.

Hematide, a synthetic PEGylated peptidic compound specifically binds and activates the erythropoietin receptor thereby stimulating erythropoiesis. To support chronic clinical dosing requirements, a comprehensive safety program was undertaken including a 9-month IV Cynomolgus monkey toxicology study. Four groups, composed of 16 male and 16 females in the vehicle-control and high dose groups and 8 male and 8 females in the low and mid-dose groups, received 0, 0.2, 2, and 20 mg/kg Hematide IV Q3W for up to 9 months followed by a 14-week recovery. An interim sacrifice was conducted on days 90 and 195. Clinical observations including ophthalmologic examinations, body weight, and food consumption were recorded. Clinical pathologic evaluations, organ weight, histopathologic, and ECG examinations were performed. Toxicokinetics and anti-Hematide antibodies were also assessed. Unscheduled deaths included 3 high-dose animals on Days 79, 104 and 207. Chronic administration was associated with polycythemia that was time and dose-dependent. There were no gender-related differences. At Day 90, the average Hgb levels for males were 13.9, 17.0, 21.7, and 23.3 g/dL for 0, 0.2, 2.0, and 20 mg/kg, respectively, corresponding to Hgb increases, over controls, of 3.1, 7.8, and 9.4 g/dL. Thereafter, Hgb values maintained peak levels. At Day 279, for the males, the average Hgb levels were 13.7, 15.5, 21.9, and 23.0 g/dL for 0, 0.2, 2.0, and 20 mg Hematide/kg, respectively, corresponding to Hgb increases, over controls, of 1.8, 8.2, and 9.3 g/dL. During the recovery period, hematology values steadily decreased to values more similar to controls. By Day 372, approximately fourteen weeks after the final dose of Hematide, for males, the average Hgb levels were 12.7, and 11.7 g/dL for 0 and 20 mg/kg, respectively. The findings in the three high dose animals that died prior to sacrifice indicated that the cause of death was secondary to hemodynamic changes that were attributed to exaggerated polycythemia induced by very high and repeated Hematide doses. Effects on the micro-vasculature of several organ sections (brain, kidney, liver, lung, spleen, and gastro-intestinal tract) were observed for monkeys dosed at ≥ 2.0 mg/kg. The return to normalcy from suspected test article related lesions was generally complete in monkeys euthanized after a 14-week recovery period for the 20.0 mg/kg group except for effects on choroid plexus and kidneys which were still detectable. Hematide displayed a sustained plasma level following intravenous administration in monkeys. At all dose levels and dosing intervals, increases in AUC values were greater than dose proportional, indicating a deviation from linear kinetics over the dose range studied. Apparent half-life (t_1/2) at steady state (Day 106) ranged from ~30 h at the low dose to ~90 h at the high dose. Three of 32 monkeys in the 20 mg/kg group were deemed likely positive for anti-Hematide antibodies but the antibodies were not cross-reactive with erythropoietin. No antibodies were detected in the low and medium dose groups. No difference in pharmacology and toxicology profiles were observed in the 3 antibody-positive monkeys compared to antibody-negative monkeys. In conclusion, Hematide is a potent ESA with prolonged half-life and this study supports chronic clinical administration for the correction of anemia associated with chronic kidney disease and cancer.