When MPN RBCs were pre-treated with the ABCG2 inhibitor KO143 prior to adding ruxolitinib, there was a significant decrease in PS-positive RBCs with an average of 16% (range: 6–25%, p = 0.021) (Figure 3B,C) showing that active ABCG2 potentiates ruxolitinib-induced PS exposure on MPN RBCs and suggesting that ruxolitinib influx is reduced when the ABCG2 transporter is blocked. The gene discussed is ABCG2; the disease is myeloproliferative disorder.