Novel thrombopoietic agents.

Thrombocytopenia is a primary manifestation of immune thrombocytopenic purpura (ITP) and may occur as a result of hepatitis C, malignancy, and treatment with chemotherapy. There is a need for additional means to treat thrombocytopenia in these settings. Recombinant thrombopoietin-like agents became available after the cloning of thrombopoietin in 1994. In clinical trials, these agents showed some efficacy in chemotherapy-induced thrombocytopenia, but their use was ultimately discontinued due to the development of neutralizing antibodies that cross-reacted with endogenous thrombopoietin and caused thrombocytopenia in healthy blood donors and other recipients. Subsequently, "second-generation" thrombopoietic agents without homology to thrombopoietin were developed. In the past 5 years, these second-generation thrombopoeitic growth factors have undergone substantial clinical development and have demonstrated safety, tolerability and efficacy in subjects with ITP and hepatitis C-related thrombocytopenia. These completed studies, many of which are available only in abstract form, and other ongoing studies suggest that thrombopoietic agents will enhance the hematologist's ability to manage these and other causes of thrombocytopenia.