Vamifeport improved deformability of RBCs in hypoxia, reduced the adhesion of blood cells to microvasculature, and prevented inflammation-triggered vaso-occlusion in HbSS mice. (A) No change in the point of sickling of RBCs in HbSS mice; measurement of point of sickling is not applicable (n.a.) to HbAA mice. Reduced severity of sickling shown as a decrease in ΔEI (B) and lowered EI at minimal oxygenation (EI_min) (C) with a minor change in the EI at maximal oxygenation (EI_max) (D). (E and F) Scanning electron microscopy analysis revealed RBCs with improved membrane morphology in HbSS mice treated with vamifeport compared with vehicle. Representative intravital microscopy images showing marked blood stasis (vaso-occlusion) in capillaries of vehicle-treated Townes mice (arrows show firmly adherent cells) (G), reduced blood cell adhesion in capillaries of vamifeport-treated HbSS mice (H), the number of adherent blood cells (I), and the percentage of vessels with normal blood flow (J). In average, 12 to 35 vessels per mouse in each group were analyzed. Results are presented as mean ± standard deviation (n = 4-7 mice per group). Analysis was performed by using one-way analysis of variance with Dunnett’s multiple comparison of all groups vs the HbSS vehicle group: *P < .05, **P < .01, ***P < .001. a.u., arbitrary units; BID, twice daily; FU, fluorescence units.