Pacritinib appears to elicit significant spleen responses in patients with the “myelodepletive phenotype” of MF or cytopenic MF, which has been associated with anemia, thrombocytopenia, JAK2 V617F variant allele frequencies below 50%, and smaller spleen size [53, 54]; efficacy in this subgroup, associated with a poor prognosis, may be attributed to the inhibitory activity of pacritinib on IRAK1 [37]. This evidence concerns the gene JAK2 and anemia.