Romiplostim is a peptibody designed to evade the immune response to recombinant thrombopoietin and to stimulate the production of new platelets. The pathophysiology underlying primary immune thrombocytopenia (ITP) has shown that not only accelerated peripheral platelet destruction but also suppression of the production of new platelets can be responsible for the persistence of thrombocytopenia. Several prospective and well-designed trials have shown that weekly subcutaneous administration of romiplostim induces more durable platelet responses and less treatment failure compared with placebo or standard of care, not only in adult but also pediatric chronic ITP patients regardless of splenectomy status. Treatment with romiplostim also resulted in less use of rescue medication and permitted the majority of patients receiving concurrent ITP drugs to reduce or discontinue these therapies, avoiding further immunosuppression. Romiplostim has been shown to have overall a very favorable safety profile and to be well tolerated relative to other ITP treatments.