PK of itacitinib on day 1 and day 7 stratified by concomitant CYP3A4 inhibitor use in relation to the concentration needed to inhibit IL-6- or TPO-induced STAT phosphorylation by 50%. Data are shown as mean ± standard error of the mean. *Only 6 patient samples were available for analysis at the first time point (baseline). IC₅₀, half maximal inhibitory concentration; TPO, thrombopoietin.