Pre-clinical toxicokinetics and safety study of M₂ES, a PEGylated recombinant human endostatin, in rhesus monkeys

PEGylated recombinant human endostatin (M₂ES) exhibited prolonged serum half-life and enhanced antitumor activity when compared with endostatin. A non-clinical study was performed to evaluate the toxicokinetics and safety of M₂ES in rhesus monkeys. After intravenous (IV) infusions of M₂ES at a dose level of 3, 10, and 30mg/kg in rhesus monkeys, the concentration-time curves of M₂ES were best fitted to a non-compartment model, and area under the curve (AUC) was positively correlated with the dosage. M₂ES had a tendency to accumulate in vivo following successive IV infusions. Serum anti-M₂ES IgG antibodies were generated quickly during IV administration, and the antibody level in serum did not significantly decrease after four-week recovery period. Animals administered IV infusions twice weekly (M₂ES at 10 or 30mg/kg body weight per day) for 3months developed mild or moderate vacuolation of proximal tubule epithelial cell in proximal convoluted tubule of kidney, but this adverse-effect was reversible. In summary, M₂ES was well tolerated and did not cause any serious toxicity. These pre-clinical safety data contribute to the initiation of the ongoing clinical study.