JAK2 and Splenomegaly: Similar to ruxolitinib/LTT462, dual JAK2/ERK1/2 inhibition by 60 mg/kg ruxolitinib bid and 30 mg/kg MK-8353 bid enhanced MPN phenotype correction in the MPLW515L model including reduction of splenomegaly, leukocytosis and thrombocytosis.