Eltrombopag stimulates megakaryopoiesis in CD34⁺ BM-MNC cells from MDS/AML patients. (A) Number of Mk CD41a-expressing cells upon Eltrombopag treatment of CD34⁺ BM-MNC from MDS/AML patients (n = 5). Immunomagnetically enriched CD34⁺ BM-MNC were seeded in liquid cultures containing BSA, insulin, transferrin, hrIL-3, hrIL-6, hrSCF, hrFLT3L, and human low-density lipoproteins. Cells were incubated with either 0 or 3 μg/mL Eltrombopag, or 100 ng/mL hrTPO alone, or a combination of 3 μg/mL Eltrombopag and 20 ng/mL hrTPO for 5 days. CD41a⁺ cells were assessed by FACS analysis. The fold of change of CD41a⁺ cells in comparison with 100 ng/mL hrTPO-treated cultures of 5 individual patients is shown. Four of the 5 samples were treated with the combination of Eltrombopag plus TPO (one patient data not analyzed [n/a]). (B) Representative FACS histogram plot of cells upon incubation with either 0 or 3 μg/mL Eltrombopag, 100 ng/mL TPO alone, or 3 μg/mL Eltrombopag and 20 ng/mL hrTPO. (C) Eltrombopag increases the number of Mk colonies in cultures of CD34⁺ BM-MNC from MDS/AML patients. CD34⁺ BM-MNC were seeded in semisolid collagen-based medium containing hrIL-3, hrIL-6, hrSCF, hrFLT3L, and human low-density lipoproteins. Cultures were supplemented with either 0 or 3 μg/mL Eltrombopag, 100 ng/mL hrTPO alone, or 3 μg/mL Eltrombopag in combination with 20 ng/mL hrTPO. Mk colonies were enumerated after 12 days of culture. The fold of change compared with 100 ng/mL hrTPO-treated CD34⁺ cells is shown (n = 5). (D) Mk colony morphology of Mk colonies derived from healthy persons' and MDS/AML patients' BM-MNC. (E) Differential colony counts of Mk progenitor-derived colonies after 12 days of culture in the presence of either 0 or 3 μg/mL Eltrombopag, 100 ng/mL hrTPO alone, or 3 μg/mL Eltrombopag in combination with 20 ng/mL hrTPO. Colonies from bipotent Mk progenitors, immature Mk progenitors, and mature Mk progenitors were scored. The fold change compared with cells cultured in presence of 100 ng/mL hrTPO is shown. Results from 5 individual patients are shown.