Pyrazole derivatives having a pyridazine and pyridine functionality

A compound represented by formula (I), or a salt of the compound:

• wherein Ar1 represents
• a pyridyl group having 1 to 3 substituents wherein the substituents are selected from the group consisting of C1-6 alkyl, halogeno, C1-6 alkoxy, C1-6 alkylamino, and di(C1-6 alkyl)amino groups, or
• a pyridazinyl group having 1 to 3 substituents wherein the substituents are selected from the group consisting of C1-6 alkyl, halogeno, C1-6 alkoxy, C1-6 alkylamino, and di(C1-6 alkyl) amino groups,
• Ar2 represents
• a pyridyl group which may have 1 to 3 substituents wherein the substituents are selected from the group consisting of C1-6 alkyl, halogeno, C1-6 alkoxy, C1-6 alkylamino, and di(C1-6 alkyl)amino groups, or
• a pyridazinyl group which may have 1 to 3 substituents wherein the substituents are selected from the group consisting of C1-6 alkyl, halogeno, C1-6 alkoxy, C1-6 alkylamino, and di(C1-6 alkyl)amino groups,
• wherein is one of Ar1 and Ar2 is pyridazine which may be substituted as defined herein and the other one of Ar1 and Ar2 is pyridine which may be substituted as defined herein,
• R1 is a group represented by formula (1):
• wherein ring structure A represents an azetidine ring, pyrrolidine ring, imidazolidine ring, pyrazolidine ring, piperidine ring, piperazine ring, morpholine ring, thiomorpholine ring, hexahydropyridazine ring, hexahydropyrimidine ring, homopiperazine ring, or oxazepane ring;
• X represents a carbonyl group;
• R3 represents 1 to 4 groups on ring structure A, R3 being selected from the group consisting of a hydrogen atom, a halogeno group, a hydroxyl group, a C1-6 alkoxy group, a C1-6 alkoxycarbonyl group, a carboxyl group, a sulfo group, a C1-6 alkylsulfonyl group, a C1-6 alkyl group which may have 1 or 2 substituents, an amino group which may have 1 or 2 substituents, a carbamoyl group which may have 1 or 2 substituents, a C1-6 acyl group, an aminosulfonyl group which may have 1 or 2 substituents, an oxo group, a hydroxyiminocarbonyl group, a C1-6 alkoxyiminocarbonyl group, and a substituted or non-substituted 3- to 6-membered spiro alicyclic alkyl group;
• and R2 represents a hydrogen atom, a halogeno group, or a C1-6 alkyl group which may have 1 or 2 substituents.