Quiflapon sodium (MK-591 sodium) is a selective and specific 5-Lipoxygenase-activating protein (FLAP) inhibitor. Quiflapon sodium is an orally active Leukotriene biosynthesis inhibitor. Induces apoptosis. In Vitro: Quiflapon sodium (MK591) and SB203580 are able to block SEB-induced human PBMC cell proliferation. Quiflapon sodium (MK591) down regulates three genes [for cathepsin L, IL-17 and guanylate binding protein (GBP)-2] that are up regulated by SEB^[1]. Quiflapon sodium (MK591) undergoes apoptosis within hours of treatment. Quiflapon sodium also induces rapid activation of the stress kinase, c-Jun N-terminal kinase (JNK), which plays an important role in the apoptosis process. Quiflapon sodium triggers apoptosis in prostate cancer cells without inhibition of PI3K-Akt, or ERK. Moreover, Quiflapon sodium and LY294002 exert synergistic effect in inducing apoptosis in prostate cancer cells^[2]. Quiflapon sodium (MK591) influences cAMP response element-binding protein but not Sp1^[4]. In Vivo: Hyperoxia groups of mice treated with Quiflapon sodium (MK591) (20, 40 mg/kg) show alveolarization that resembles that of room air controls while untreated hyperoxia groups show definite evidence of aberrant alveolarization but no inflammation^[3]. Comparison of the Aβ-immunopositive areas between the placebo and Quiflapon sodium (MK591) (320 mg/kg)-treated group reveals a statistically significant reduction of the amyloid burden in the treated mice. Quiflapon sodium also has a significant reduction in brain levels of IL-1β. Mice treated with Quiflapon sodium show a statistically significant decrease in the steady-state levels of total CREB and its phosphorylated form at Ser133^[4].