Presently 2 licensed agents romiplostim and eltrombopag.
Highly effective in immune thrombocytopenia, even in refractory disease a response rate of 75% can be expected.
Responses in immunne thrombocytopenia with these agents generally are not seen until one-two weeks of treatment, depending on the dose of the drugs.
A minimum of 4-6 weeks of treatment at the highest dose levels to establish a patient as unresponsive to these agents.
The best candidates for such therapy have undergoing splenectomy and particularly if they have also received rituximab.
Thrombopoietic growth factor therapy can induce reticulin fibrosis in the bone marrow.
Reticulin fibrosis has been observed in trials of romiplostim and eltrombopag.
Data suggest that a minority of patients treated with romiplsotim and eltrombopag may develop bone marrow fibrosis within one year of initiating therapy, and that this fibrosis may be reversible after short-term treatment.
At present, the risk of bone marrow fibrosis is unknown.
At least monthly monitoring blood cell counts and peripheral blood smear is indicated in all patients on these agents, and if morphologic abnormalities or cytopenias are noted, a bone marrow biopsy with staining for reticulin and collagen is recommended.