Specific Inhibition of AKT with ARQ 092, an Orally-Available Selective AKT Inhibitor, Attenuates Acute Vaso-Occlusive Events in Sickle Cell Disease

Previous studies have identified the Ser/Thr protein kinase, AKT, as a therapeutic target for thromboinflammatory diseases. Recently, we have shown that the basal levels of AKT phosphorylation were significantly increased in neutrophils and platelets isolated from sickle cell disease (SCD) patients compared with those cells from healthy donors and that specific inhibition of AKT2 impaired neutrophil-endothelial cell and neutrophil-platelet interactions in venules of Berkeley (SCD) mice (Li et al. J Clin Invest 2014; Barazia et al. Blood 2015). Although our results suggest that AKT2 inhibition may be a novel therapy to treat a vaso-occlusive crisis in SCD patients, no AKT2 specific inhibitor is available in clinic. Using ARQ 092, an orally-available, allosteric AKT inhibitor that is currently in Phase I clinical trials in oncology indications and AKT-driven overgrowth disease, Proteus syndrome, here we report that specific inhibition of AKT attenuates the adhesive function of neutrophils and platelets from sickle cell disease (SCD) patients in vitro and heterotypic cell-cell interactions in the Berkeley mouse model of SCD in vivo. Studies using neutrophils and platelets isolated from SCD patients revealed that treatment with 50-500 nM ARQ 092 significantly blocks αMβ2 integrin function in neutrophils and reduces P-selectin exposure and glycoprotein Ib/IX/V-mediated agglutination in platelets. Consistently, treatment of isolated platelets and neutrophils with ARQ 092 inhibited heterotypic cell-cell aggregation under shear conditions. Using in vivo real-time fluorescence intravital microscopy, we demonstrated that short-term oral administration of ARQ 092 (100 mg/kg body weight) or hydroxyurea (HU, 250 mg/kg body weight), a main therapy for the treatment of SCD, diminishes neutrophil-endothelial cell and neutrophil-platelet interactions in venules of Berkeley mice challenged with TNF-α to induce a vaso-occlusive crisis. Co-administration of HU and ARQ 092 further reduced the adhesive function of neutrophils in venules and neutrophil transmigration into alveoli, inhibited the expression of E-selectin and intercellular adhesion molecule-1 (ICAM-1) in the cremaster vessel wall, and improved survival in these mice. Ex vivo studies in Berkeley mice suggested that co-administration of HU and ARQ 092 efficiently blocks neutrophil and platelet activation and reactive oxygen species generation. The synergistic effects of both inhibitors resulted from increased NO production by HU and specific inhibition of AKT by ARQ 092. Our results provide important evidence that ARQ 092 has potential as a novel drug to be developed to prevent or treat the acute vaso-occlusive complications in SCD patients.