Although the thrombopoietin receptor was discovered in 1991 and thrombopoietin (TPO) was purified in 1994, the development of a clinically useful TPO was hampered by the appearance of neutralizing antibodies to some forms of recombinant TPO. However, in 2008 two new drugs that mimic the effect of TPO became available to treat thrombocytopenia. Romiplostim is a TPO peptide mimetic given by subcutaneous injection that activates the TPO receptor by binding to the distal hematopoietic receptor domain just like TPO. Eltrombopag is a TPO nonpeptide mimetic administered orally that activates the TPO receptor by binding to the transmembrane domain. Both increase the platelet count in healthy humans as well as in >80% of patients with immune thrombocytopenic purpura (ITP). Although initially restricted to the second-line treatment of ITP, both agents could help treat many thrombocytopenic disorders. Both agents are well tolerated, with mild headache being the most common complaint. Potential long-term complications include thrombosis, increased bone marrow reticulin, rebound worsening of thrombocytopenia upon discontinuation, and increased blast formation. Ongoing studies should establish the incidence of these complications and determine the efficacy of these new agents in a variety of other thrombocytopenic conditions.

中文翻译：

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血小板生成素和血小板生成素模拟物在血小板减少症的治疗中。

尽管在1991年发现了血小板生成素受体，并在1994年纯化了血小板生成素（TPO），但对某些形式的重组TPO的中和抗体的出现阻碍了临床上有用的TPO的发展。但是，2008年有两种模仿TPO作用的新药可用于治疗血小板减少症。Romiplostim是通过皮下注射给予的TPO肽模拟物，与TPO一样，它通过与远端造血受体域结合而激活TPO受体。Eltrombopag是一种口服的TPO非肽模拟物，通过与跨膜结构域结合来激活TPO受体。两者都会增加健康人以及免疫血小板减少性紫癜（ITP）患者中80％以上的血小板数量。尽管最初仅限于ITP的二线治疗，两种药物均可帮助治疗许多血小板减少症。两种药物都具有良好的耐受性，轻度头痛是最常见的不适。长期的潜在并发症包括血栓形成，骨髓网状蛋白增加，停药后血小板减少的反弹恶化以及成胚细胞增多。正在进行的研究应确定这些并发症的发生率，并确定这些新药在多种其他血小板减少性疾病中的疗效。