A compound of formula (I) wherein: - one of the groups Grepresents a nitrogen atom or a group CRand the other represents a group CR； - Grepresents a nitrogen atom or a group CR； - Rrepresents a group selected from hydrogen atoms, halogen atoms, Calkyl groups which may be optionally substituted by 1, 2 or 3 substituents selected from halogen atoms and hydroxy groups, and Ccycloalkyl groups which may be optionally substituted by 1, 2 or 3 substituents selected from halogen atoms and hydroxy groups； - Rrepresents a group selected from hydrogen atoms, halogen atoms, hydroxyl groups, Calkyl groups which may be optionally substituted by 1, 2 or 3 substituents selected from halogen atoms and hydroxy groups, Calkoxyl groups which may be optionally substituted by 1, 2 or 3 substituents selected from halogen atoms and hydroxy groups, and Ccycloalkyl groups which may be optionally substituted by 1, 2 or 3 substiluents selected from halogen atoms and hydroxy groups； R, Rand Rindependently represent groups selected from hydrogen atoms, halogen atoms, Calkyl groups which may be optionally substituted by 1,2 or 3 substituents selected from halogen atoms and hydroxy groups, and Calkoxy groups which may be optionally substituted by 1, 2 or 3 substituents selected from halogen atoms and hydroxy groups； - Rrepresents a group selected from hydrogen atoms, halogen atoms, hydroxyl groups, Calkyl groups which may be optionally substituted by 1, 2 or 3 substituents selected from halogen atoms and hydroxy groups, and Calkoxy groups which may be optionally substituted by 1, 2 or 3 substituents selected from halogen atoms and hydroxy groups, and Ccycloalkoxy groups which may be optionally substituted by 1, 2 or 3 substituents selected from halogen atoms and hydroxy groups； - one of the groups Gand Gis a nitrogen atom and the other is a CH group； - M is a hydrogen atom or an pharmaceutically acceptable cation with the proviso that, when at least one of the groups Rand Rrepresent a hydrogen ato
