Study On Long-term Toxic Effect And Immunogenicity Of Recombinant EPO-Fc In Rhesus Monkeys

Recombinant EPO-Fc is a new biopharmaceutical intended to correct anaemia due to chronic renal failure, cancer and so on. This new product of recombinant EPO is a fusion protein of human EPO, peptides and F component of human IgG, which is derived from Chinese hamster ovary cell (CHO). There have been no reports on the evaluation of its preclinical long-term toxicity and immunogenicity. The 24-week repeated dose toxicity study in rhesus monkeys were conducted to evaluate the toxicity of recombinant EPO-Fc and the potential immunogenicity by determing the anti- EPO-Fc antibody in serum.Twenty four monkeys were randomly divided into 4 groups to receive the dose of 8, 25, 80μg·kg^-1 of EPO-Fc by subcutaneous injection once a week for 24 weeks. On dosing termination, two third of the animals in each group were subjected to full necropsy with gross pathologic evaluation of target tissues .Organs were removed, weighed and individual organ weight: body weight ratios were calculated. Tissue samples were obtained and processed for histopathologic examination.The rest were killed after another 8 weeks recovery. Body weights, body temperature cageside observations hematology, clinical chemistry, ECG, bone marrow, ophthalmology and antibody formation were examined in different time points in administration period and recovery period.The results indicated that RBC and RET were significantly increased, which was followed by the increase of HCT and HGB in high and medium dose groups, It was considered to be the pharmacological effect of EPO-Fc. The antibodies for EPO-Fc were first found in one animal in low dose group after 2 weeks dosing and in most animals treated with EPO-Fc after 18 weeks dosing. They were determined as neutralizing antibody by cell-based bioassay. There were no mortalities or overt sign of clinical toxicity present in any of control or EPO-Fc treated animals. No vomiting and twithing were observed in administration and recovery period; the luster of fur was fine and no piloerection. Appetite, weight increase and body temperature all kept normal. No abnormalities were found in the examinations of clinical chemistry, ECG, bone marrow, and ophthalmology as compared to control group. At necropsy, no treatment-related findings were evident on gross pathological examination of the EPO-Fc treated monkeys. There were no pathologic findings that could be directly related to treatment with EPO-Fc. In conclusion, EPO-Fc shows no significantly toxic effect in rhesus monkeys. However, it has immunogenicity to develop antibody which can partly neutralize the activity of EPO. The safety dosage of EPO-Fc for rhesus monkeys is 80μg·kg^-1.