A compound of following formula: in which: - X represents a -CH- group or a nitrogen atom, - R 1 represents a hydrogen atom, a halogen atom, preferably a chlorine atom, a (C 1 -C 6)alkyl group, preferably a methyl group, a -CN group or a -CF 3 group, - R 2 represents a hydrogen atom, a (C 1 -C 6)alkyl group, an aryl-(C 1 -C 6)alkyl group, preferably a benzyl, or a -COR 21 group with R 21 representing a (C 1 -C 6)alkyl group or an aryl group, - R 3 represents a (C 1 -C 6)alkyl group, preferably a methyl group, an aryl-(C 1 -C 6)alkyl group or a -COR 31 group with R 31 representing a (C 1 -C 6)alkyl group or an aryl group, - R 41, R 42, R 43 and R 44 represent independently of each other a hydrogen atom; a halogen atom; -OR 45; -SR 45; -NR 45 R 46; -NO 2; or a (C 1 -C 6)alkyl group optionally substituted by one or more substituents selected from among a halogen atom, - OR 45, -SR 45, -NR 45 R 46 and -NO 2, with R 45 and R 46 representing independently of each other a hydrogen atom, a (C 1 -C 6)alkyl group, a -CF 3 group or a -COR 47 group with R 47 representing a (C 1 -C 6)alkyl group or an aryl group, - R 5 and R 6 represent a hydrogen atom or form together a -CR 51 =CR 52 -CR 53 =CR 54 - chain with R 51, R 52, R 53 and R 54 representing independently of each other a hydrogen atom; a halogen atom; -OR 55; -SR 55; -NR 55 R 56; -NO 2; or a (C 1 -C 6)alkyl group optionally substituted by one or more substituents selected from among a halogen atom,-OR 55, -SR 55, -NR 55 R 56 and -NO 2, with R 55 and R 56 representing independently of each other a hydrogen atom, a (C 1 -C 6)alkyl group, a -CF 3 group or a -COR 57 group with R 57 representing a (C 1 -C 6)alkyl group or an aryl group, or a pharmaceutically acceptable salt thereof, characterised in that, when X represents a nitrogen atom, R 1 represents a chlorine atom, a -CN group or a -CF 3 group, or R 5 and R 6 form together a -CR 51 =CR 52 -CR 53 =CR 54 - chain. - X represents a -CH- group or a nitrogen atom, - R 1 represents a hydrogen atom, a halogen atom, preferably a chlorine atom, a (C 1 -C 6)alkyl group, preferably a methyl group, a -CN group or a -CF 3 group, - R 2 represents a hydrogen atom, a (C 1 -C 6)alkyl group, an aryl-(C 1 -C 6)alkyl group, preferably a benzyl, or a -COR 21 group with R 21 representing a (C 1 -C 6)alkyl group or an aryl group, - R 3 represents a (C 1 -C 6)alkyl group, preferably a methyl group, an aryl-(C 1 -C 6)alkyl group or a -COR 31 group with R 31 representing a (C 1 -C 6)alkyl group or an aryl group, - R 41, R 42, R 43 and R 44 represent independently of each other a hydrogen atom; a halogen atom; -OR 45; -SR 45; -NR 45 R 46; -NO 2; or a (C 1 -C 6)alkyl group optionally substituted by one or more substituents selected from among a halogen atom, - OR 45, -SR 45, -NR 45 R 46 and -NO 2, with R 45 and R 46 representing independently of each other a hydrogen atom, a (C 1 -C 6)alkyl group, a -CF 3 group or a -COR 47 group with R 47 representing a (C 1 -C 6)alkyl group or an aryl group, - R 5 and R 6 represent a hydrogen atom or form together a -CR 51 =CR 52 -CR 53 =CR 54 - chain with R 51, R 52, R 53 and R 54 representing independently of each other a hydrogen atom; a halogen atom; -OR 55; -SR 55; -NR 55 R 56; -NO 2; or a (C 1 -C 6)alkyl group optionally substituted by one or more substituents selected from among a halogen atom,-OR 55, -SR 55, -NR 55 R 56 and -NO 2, with R 55 and R 56 representing independently of each other a hydrogen atom, a (C 1 -C 6)alkyl group, a -CF 3 group or a -COR 57 group with R 57 representing a (C 1 -C 6)alkyl group or an aryl group, or a pharmaceutically acceptable salt thereof, characterised in that, when X represents a nitrogen atom, R 1 represents a chlorine atom, a -CN group or a -CF 3 group, or R 5 and R 6 form together a -CR 51 =CR 52 -CR 53 =CR 54 - chain.