This phases Ⅲ trials is divided into two stages,Ⅲa and Ⅲb.The aim of Ⅲa is to evaluate the optimal dosing dose of genetically modified recombinant human IL-11 (mIL-11) in a multicenter randomized self-control trial involving 60 cancer patients undergoing chemotherapy.The aim of Ⅲb is to evaluate the efficacy and safety of genetically modified recombinant human IL-11 (mIL-11), using rhIL-11 as an active control, in a multicenter randomized trial involving 240 cancer patients undergoing chemotherapy.

The investigators recently developed a mutant form of rhIL-11 with improved stability. In in vitro experimental systems, mIL-11 was shown to endure chemical and proteolytic stresses more effectively, while retaining the biological activity of the original rhIL-11. The improved stability of mIL-11 was also demonstrated in the comparative pharmacokinetic study of subcutaneously delivered mIL-11 and rhIL-11 in the rodent and primate models. Based on its improved pharmacokinetic and pharmacodynamic features. In Phase II study shows that mIL-11 is well tolerated and has thrombopoietic activity equivalent to one third of the clinical dose of rhIL-11, indicating the potential of mIL-11 for use in the treatment of CIT. This study is a phase III, single-blinded, randomized,multicenter,cross-over study designed to evaluate optimal dosing dose and efficacy and safety of mIL-11 on CIT patients receiving suitable chemotherapeutic regimen for treating cancer.

Inclusion Criteria:

• histological verification of malignancy at the time of initial diagnosis；
• Patients (age,18-75 years) receiving chemotherapy, who had experienced platelet counts below 75×10^9/L；
• patients were required to have adequate bone marrow,hepatic, and renal functions at the time of study entry；
• ECOG ≤2；
• patients to have normal laboratory findings:while white blood count >3.0×10^9/L,platelet count ≥100×10^9/L, and AST and/or ALT lesser than 2.5 times the upper limit of the normal value；
• The estimated life expectancy of the patient was more than 3 months.

Exclusion Criteria:；

• patients who received total body irradiation；
• patients with childbearing potential；
• patients who were breast-feeding or pregnant