Novel, selective inhibitor of interleukin-5 (IL-5) (IC50 = 0.45 - 1 mM). Inhibits IL-5-prolonged eosinophil survival and IL-5-induced tyrosine phosphorylation of JAK2 without inhibiting GM-CSF-mediated effects. Inhibits antigen-induced eosinophil and lymphocyte recruitment in rat airways in vivo, without affecting peripheral blood or bone marrow leukocytes.