Additionally, phospho-MEK showed under-expression after KNK437 treatment, and this was more pronounced in samples from PV patients (ratio in PV without treatment: 63.17; ratio in PV with KNK437, 50 μM: 23.58) vs. ET patients (ratio in ET without treatment: 66.19; ratio in ET with KNK437, 50 μM: 59.82). Here, MAP2K7 is linked to essential thrombocythemia.