Naphthyridine deratives or salts thereof

A naphthyridine compound represented by the following general formula (1):

• wherein R3 is selected from the group consisting of hydrogen atom;
• lower alkyl groups;
• halogeno-lower-alkyl groups;
• phenyl groups;
• lower alkoxy groups;
• hydroxyl group;
• amino group;
• halogen atoms;
• trifluoromethyl group;
• amino protecting groups represented by NRaCORb wherein Ra and Rb are independently a hydrogen atom, a lower alkyl group, a cycloalkyl group or a phenyl group;
• lower acyloxy groups;
• nitro group;
• cyano group;
• amino protecting groups represented by NRaRb wherein Ra and Rb are independently a hydrogen atom, a lower alkyl group, a cycloalkyl group or a phenyl group;
• lower alkylsulfonylamino groups;
• lower alkoxycarbonyl groups;
• carboxyl group;
• lower acyl groups;
• carbamoyl group;
• aminocarbonyl groups represented by CONRaRb wherein Ra and Rb are independently a hydrogen atom, a lower alkyl group, a cycloalkyl group or a phenyl group;
• amninocarbonyl groups represented by COJ wherein J is a substituted or unsubstituted pyrrolidino, piperidino, piperazino, homopiperazino or morpholino group;
• lower alkylsulfonyl groups;
• amino protecting groups represented by NRaCOORb wherein Ra and Rb are independently a hydrogen atom, a lower alkyl group, a cycloalkyl group or a phenyl group;
• and hydroxyl-lower-alkyl groups, a combination of R1 and R2 forms through the saturated or unsaturated carbon-carbon bond a cyclic group which may contain 1 to 3 heteroatoms selected from nitrogen atom, oxygen atom and sulfur atom and may have a substituent selected from the group consisting of lower alkyl groups;
• phenyl group;
• lower alkoxy groups;
• hydroxyl group;
• amino group;
• halogen atoms;
• trifluoromethyl group;
• amino protecting groups represented by NRaCORb wherein Ra and Rb are independently a hydrogen atom, a lower alkyl group, a cycloalkyl group or a phenyl group;
• lower acyloxy groups;
• nitro group;
• cyano group;
• amino protecting groups represented by NRaRb wherein Ra and Rb are independently a hydrogen atom, a lower alkyl group, a cycloalkyl group or a phenyl group;
• lower alkylsulfonylamino groups;
• lower alkoxycarbonyl groups;
• carboxyl group;
• lower acyl groups;
• carbamoyl group;
• aminocarbonyl groups represented by CONRaRb wherein Ra and Rb are independently a hydrogen atom, a lower alkyl group, a cycloalkyl group or a phenyl group;
• aminocarbonyl groups represented by COJ wherein J is a substituted or unsubstituted pyrrolidino, piperidino, piperazino, homopiperazino or morpholino group;
• lower alkylsulfonyl groups;
• oxo group;
• amino protecting groups represented by NRaCOORb wherein Ra and Rb are independently a hydrogen atom, a lower alkyl group, a cycloalkyl group or a phenyl group;
• and hydroxyl-lower-alkyl groups,
• X and Y are independently a methylene chain represented by —(CH2)n— wherein n is 0 to 3,
• Z is a phenyl group, a phenylalkyl group or a phenylalkenyl group, each of which may have one or more substituents selected from the group consisting of lower alkyl groups, phenyl group, lower alkoxy groups, hydroxyl group, amino group, halogen atoms and trifluoromethyl group,
• A is a hydrogen atom, a lower alkyl group or a lower alkoxy group, and
• G is a hydrogen atom, a lower alkyl group, a lower alkoxy group, a phenylalkyl group or an acyl group represented by —C(═O)XZ, —C(═O)CH(R1)(Z) or —C(═O)C(R1)(R2)(Z) wherein X, Z, R1 and R2 are as defined above, or a pharmacologically acceptable salt thereof.