A model of myelosuppression with thrombocytopenia was produced in monkey by i.v. administration of carboplatin to the evaluate effects of rhIL-11 treatment in monkeys. Following myelosuppression, rhIL-11 was subcutaneously injected for 19 consecutive days at the dose of 50 or 100 micro g/kg. In myelosuppressed monkeys treated with rhIL-11, peripheral blood platelet started to drop at the day 8 after the administration of carboplatin, and reaching the nadir between the day 12 - 14, the decrease in blood platelet was less severe compared with untreated monkeys; peripheral blood platelet began to recovery on day 11 - 13 (D14 - D16) after rhIL-11 treatment, and reached or surpassed the baseline value before carboplatin administration after 13 - 15 days rhIL-11 treatment. Blood platelet counts remained high level after discontinuation of rhIL-11 administration and returned to baseline after 4 days. The results demonstrated that rhIL-11 has a significant thrombopoietic activity, it can reduce the severity of thrombocytopenia as well as shorten the duration of thrombocytopenia caused by myeloablastive agents, and is likely to become an effective agent against thrombocytopenia induced by chemotherapy.

Hematological effects of rhIL-11 on normal and myelosuppressed male BALB/c mice were observed. Mice were subcutaneously injected with rhIL-11 for 7 consecutive days, at the dose of 200 or 400 micro g/kg per day, peripheral blood platelet counts were moderately elevated on 5 days after administration and returned to base level within 4 days after discontinuation of injection. In myelosuppressed mice, treatment with rhIL-11 significantly ameliorated the degree of thrombocytopenia, the recovery of thrombocytopenia was also significantly accelerated at the dose range of 100 - 400 micro g/kg per day, and blood platelet counts reached pre-irradiated level after 13 - 15 days of treatment. The magnitudes of platelet count elevation were similar among groups of 100, 200 and 400 micro g/kg per day, although recovery appeared earlier in group of 400 micro g/kg per day. Significant increases in CFU-Meg were observed both in normal and myelosuppressed mice. Our results suggest that rhIL-11 promotes the increase of peripheral blood platelets both in normal and myelosuppressed mice, and can be used as a potential therapeutic agent for thrombocytopenia induced by chemotherapy.