Quiflapon (MK-591) causes cell apoptosis. Quiflapon is a selective and specific 5-lipoxygenase-activating protein (FLAP) inhibitor (IC50: 1.6 nM in a FLAP binding assay) and is also an effective and orally active Leukotriene biosynthesis (LT) inhibitor (IC50: 3.1 and 6.1 nM in intact human and elicited rat PMNLs, respectively).

Quiflapon is an effective inhibitor of leukotriene (LT) biosynthesis in the human, squirrel monkey, and rat whole blood (IC50: 510, 69, and 9 nM, respectively). Quiflapon has a high affinity for 5-lipoxygenase activating protein (FLAP) as evidenced by an IC50 value of 1.6 nM in a FLAP binding assay and inhibition of the photoaffinity labeling of FLAP by two different photoaffinity ligands. However, Quiflapon has no effect on rat 5-lipoxygenase. The inhibition of activation of 5-lipoxygenase was shown through inhibition of the translocation of the enzyme from the cytosol to the membrane in human PMNLs[1].

Pups were treated with either vehicle or Quiflapon(10, 20, or 40 mg/kg; daily for days 1-4, 5-9, or 10-14) subcutaneously. On day 14, the lungs were inflated, fixed, and stained for histopathological and morphometric analyses. Inhibition of antigen-induced bronchoconstriction by Quiflapon is observed in inbred rats pretreated with methysergide, Ascaris-challenged squirrel monkeys, and Ascaris-challenged sheep (early and late phase response) [1]. Hyperoxia groups treated with Quiflapon untreated hyperoxia groups displayed definite evidence of aberrant alveolarization but no inflammation[2].