Totrombopag is an orally bioavailable, nonpeptide, small-molecule thrombopoietin receptor agonist. It induces proliferation and differentiation of megakaryocytes and progenitor cells, ultimately increasing the production of platelets. Totrombopag has been investigated in healthy volunteers in a phase 1, single-blind, randomized fashion to cause a dosedependent increase in platelet count with demonstrated safety. There were no serious adverse events, no significant changes in laboratory or cardiovascular safety parameters and there was no observed relationship between the incidence or severity of adverse events and dose. Most adverse events were mild in intensity and self-limiting. Totrombopag was developed for the treatment of immune thrombocytopenic purpura.