A double-blind, randomized, placebo-controlled phase I/II study to evaluate the safety and tolerability of eltrombopag olamine, a thrombopoietin receptor agonist, administered for 6 months as oral tablets once daily in adult subjects with advanced MDS, sAML/MDS, or de novo AML. Study medication may be increased up to 300 mg (150 mg maximum dose for East Asian subjects), based upon individual platelet counts and bone marrow blast counts.