Effects of the Stat3 inhibitor S3I-201 (NSC74859) in mice expressing JAK2-V617F and carrying a knockout allele for Stat1. Mice were randomized into groups of 6 animals at 6 weeks after transplantation. (A) Platelet counts, (B) spleen weight, and (C) megakaryocyte percentages in Scl;V617F;Stat1^+/+, Scl;V617F;Stat1^−/+, and Scl;V617F;Stat1^−/− mice after dosing the mice for 14 days: intravenous injection every 2 days with S3I-201 (5 mg/kg) or vehicle. *P < .05 was considered significant.