Inhibitors of FLAP such as MK-886 and MK-591
which is a structural analogue of MK-886, have no direct
activity on 5-LO but antagonizes FLAP thus preventing
the translocation of the enzyme to the membrane
[55]. MK886 is a highly selective compound with no
effects of prostaglandin synthesis. MK886 inhibits antigen-
induced bronchoconstriction in Ascaris-sensitive
squirrel monkeys [56, 57]. MK-591 [58] inhibits LTB4
synthesis ex-vivo by up to 90% and urinary LTE4 by
>80% at 24 h, with a half-life of 6 h [59]. Although
FLAP antagonists REV5091 and WY50295 were shown
to be active in vitro and in animals, they were inactive
in inhibiting leukotriene synthesis in volunteers [60, 61].
BAY-X-1005 inhibits anti-immunoglobulin E(IgE) challenge
in human airways in vitro [62].