A compound of formula (I): ** Formula ** in which A represents ** Formula ** in which the asterisks indicate the bond that is attached to the pyridine group of Formula (I)； R1 represents cyclopentyl； R2 represents methyl and R4 represents ethyl or chlorine； or R2 represents methoxy, and R4 represents chlorine； R3 represents -OCH2COOH, -OCH2CH2CH2COOH, -OCH2CONHCH2CH2OH, -OCH2CH2CH2CONHCH2CH2OH, - OCH2- (CH2) n-NH- (CH2) m-COOH, -OCH2- (CH2) nN (CH3) - (CH2) m-COOH - [(azetidin-3-carboxylic acid) -1-yl] -ethoxy, 2 - [(pyrrolidin-3-carboxylic acid) -1-yl] -ethoxy, 3 - [(azetidin-3-carboxylic acid) -1 -il] -propoxy, 3 - [(pyrrolidin-3- carboxylic acid) -1-yl] -propoxy, -OCH2CH (OH) -CH2NH-CH2COOH, -OCH2CH (OH) -CH2NH-CH2CH2COOH, - OCH2CH (OH) -CH2N (CH3) -CH2COOH, -OCH2CH (OH) -CH2N (CH3) -CH2CH2COOH, 3 - [(azetidin-3- carboxylic acid) -1-yl] -2-hydroxy-propoxy, 2-hydroxy-3- [(pyrrolidin-3-carboxylic acid) -1-yl] -propoxy, -OCH2- (CH2) n-NHCH2CH2OH, -OCH2- (CH2) n-NH-CH (CH2OH) 2, -OCH2- (CH2) n -NH-CH2CH (OH) -CH2OH, -OCH2CH (OH) -CH2NH CH2CH2OH, -OCH2CH (OH) -CH2NH-CH (CH2OH) 2, -OCH2- (CH2) k-NH-CO-CH2OH, -OCH2- (CH2) n-NH-COCH2COOH, -OCH2- (CH2) n-NH-CO-CH2CH2COOH, -OCH2CH (OH) -CH2NH-CO- (CH2) nCOOH, -OCH2- (CH2) n- N (CH3) -CO-CH2OH, -OCH2- (CH2) nN (CH3) -CO-CH2COOH or -OCH2- (CH2) nN (CH3) -CO-CH2CH2COOH； n represents, independently, 1 or 2； m represents, independently, 1, 2 or 3； and k represents 1 or 2； or a salt thereof.Un compuesto de fórmula (I):**Fórmula** en la que A representa**Fórmula** en las que los asteriscos indican el enlace que está unido al grupo piridina de Fórmula (I)； R1 representa ciclopentilo； R2 representa metilo y R4 representa etilo o cloro； o R2 representa metoxi, y R4 representa cloro； R3 representa -OCH2COOH, -OCH2CH2CH2COOH, -OCH2CONHCH2CH2OH, -OCH2CH2CH2CONHCH2CH2OH, - OCH2-(CH2)n-NH-(CH2)m-COOH, -OCH2-(CH2)n-N(CH3)-(CH2)m-COOH, 2-[(ácido azetidin-3-carboxílico)-1-il]-etoxi, 2-[(ácido pirrolidin-3-carboxílico)-1-il]-etoxi, 3-[(ácido
