FUSED PYRIDAZINE COMPOUNDS, PROCESS FOR THE PREPARATION OF THE SAME AND USES THEREOF

A compound represented by the formula: wherein Ring A is a ring represented by the formula: (wherein R is a hydrogen atom, a halogen atom, a hydrocarbon group optionally having a substituent, an acyl group or a hydroxy group having a substituent; R is a hydrogen atom, a halogen atom, a hydrocarbon group optionally having a substituent, an acyl group or a hydroxy group optionally having a substituent); Ar and Ar are independently an aromatic group optionally having a substituent, and may form a condensed ring group with an adjacent carbon atom; Ring B is a nitrogen-containing heterocycle optionally having a substituent; X and Y, whether identical or not, are a bond, an oxygen atom, S(O)p (p is an integer from 0 to 2), NR wherein R is a hydrogen atom or a lower alkyl group, or a divalent linear lower hydrocarbon group which may have a substituent, and which may contain 1 to 3 hetero atoms; R and R , whether identical or not, are a hydrogen atom, a halogen atom, a hydrocarbon group optionally having a substituent, an acyl group or a hydroxy group optionally having a substituent; R is a hydrogen atom, a hydroxy group which may be substituted by lower alkyl or a carboxyl group; provided that Ring B is not a heterocycle represented by the formula: wherein r is 0 or 1, or a salt thereof, or a pro-drug thereof exhibits anti-allergic activity, anti-histaminic activity and/or eosinophil chemotaxis-inhibiting activity, anti-inflammatory activity, anti-PAF (platelet-activating factor) activity, and the like, and is useful as an agent for preventing or treating asthma, allergic conjunctivitis allergic rhinitis, urticaria, atopic dermatitis, and the like.