CP-96021 hydrochloride is a potent and orally active antagonist of leukotriene D4 (LTD4)/platelet activating factor receptor (Kis: 34 nM and 37 nM).

LTC4:34 nM (Ki), PAF receptor:37 nM (Ki)

In vivo, CP-96021 inhibits iv LTD4- and iv PAF-induced bronchoconstriction in guinea pigs (ED50s: 0.46 and 0.16 mg/kg p.o.). CP-96021 effectively blocks the combined airway obstructive effects of endogenously released PAF and LTD4 stimulated by aerosolized antigen challenge in guinea pigs (ED50s: 1.8 mg/kg p.o.).