AbstractThe allergic mediator release inhibitor CI‐949 [5‐methoxy‐3‐(1‐methylethoxy)‐1‐phenyl‐N‐1H‐tetwol‐5‐yl‐1H‐indole‐2‐carboxamide, L‐arginine salt] was evaluated for its effects on human neutrophil functions. CI‐949 (100 μM) inhibited spontaneous migration and chemotaxis toward f‐met‐leu‐phe (FMLP) by 49.1% and 45.8%, respectively. At the same concentration, CI‐949 inhibited the phagocytosis of serum‐opsonized zymosan (SOZ) by 39.0%. CI‐949 inhibited leukotriene B4and thromboxane B2release in response to SOZ with IC50S of 2.0 μM and 3.3 μM, while inhibiting the response to FMLP with IC50s of 1.7 and 2.0 μM. CI‐949 also inhibited myeloperoxidase release from primary lysosomal granules in response to the following stimuli with the respective IC50s (μM): C5a (40.3); FMLP (34.4): SOZ (21.4); concanavalin A (Con A) (3.9); and calcium ionophore A23187 (91.2). In contrast, CI‐949 inhibited lysozyme release from secondary granules in response to SOZ and Con A with IC50S of 99.3 and 56.1 μM, while inhibiting the response to C5a, FMLP, and A23187 by 41.2%, 52.4%, and 10.0%, respectively, at 100 μM. CI‐949 (100 μM) had no inhibitory effect against lysozyme release in response to L‐α‐1,2 dioctanoylglycerol (DiC8), or phorbol 12‐myristate 13‐acetate (PMA). CI‐949 inhibited superoxide anion generation stimulated by FMLP and Con A with IC50S of 33.9 and 25.8 μM, while inhibiting the response to C5a, SOZ, and A23187 by 36.6%, 24.8%, and 14.1% and having no effect on the response to DIC8or PMA at 100 μM. These results demonstrate preferential inhibition of arachidonic acid metabolism and degranulation of primary lysosomal granules by CI‐949 with selectivity for stimuli which promote intracellular calcium mobilization or calcium influx.