MK-0591 is a FLAP inhibitor (IC 50 = 1.6 nM), blocking LTB4 (IC 50 = 6 nM) without affecting 5-LO (IC 50 > 4 µM). In squirrel monkeys, it prevents airway resistance increases and dynamic compliance decreases (0.3 and 1 mg/kg). In a rat glomerulonephritis model, it reduces proteinuria and maintains renal LTC4 synthase activity (60 mg/kg). Additionally, it induces apoptosis in LNCaP prostate cancer cells (8 µM).