Comparison of biological activity and safety of recombinant canine erythropoietin with that of recombinant human erythropoietin in clinically normal dogs

Objective - To determine whether recombinant canine erythropoietin (rcEPO) stimulates erythropoiesis in dogs without causing the immunogenicity problem (ie, erythroid hypoplasia) associated with recombinant human erythropoietin (rhEPO). Animals - 13 clinically normal dogs. Procedure - Dogs were randomly assigned to 2 groups; 1 group (n = 6) received rhEPO, whereas the other group (7) received rcEPO. Both groups received SC injections of diluent for 4 weeks before initiating treatment with erythropoietin (100 U/kg of body weight, SC, 3 times/wk). Hematocrit, and absolute reticulocyte count were monitored weekly, CBC were done monthly, and bone marrow aspirates for cytologic evaluation were obtained before and at 4, 8, 16, and 24 weeks during treatment. Results - Weekly mean Hct and absolute reticulocyte count increased in both groups of dogs during the first 2 weeks of treatment. For dogs receiving rhEPO, precipitous decreases in reticulocyte number and more gradual decreases in Hct were associated with development of erythroid hypoplasia. Dogs receiving rhEPO developed erythroid hypoplasia by week 4 (n = 4), 8 (1), or 16 (1). With cessation of rhEPO treatment after diagnosis of erythroid hypoplasia, RBC production recovered 5 to 11 weeks (median, 7 weeks) later. In contrast, rcEPO treatment caused sustained increases in Hct and reticulocytosis. None of the dogs receiving rcEPO developed erythroid hypoplasia. Conclusions - rcEPO stimulated erythrocyte production in clinically normal dogs during a 24-week period without causing the erythroid hypoplasia encountered in rhEPO-treated dogs. Clinical Relevance - Because rcEPO did not cause erythroid hypoplasia, rcEPO may represent an improved option, compared with rhEPO, for treatment of erythropoietin-dependent anemia in dogs.