Compounds chosen from the 4-aminoindole derivatives of formula, the addition salts thereof, mesomers thereof, and solvates thereof: in which: R 1 represents: - a hydrogen atom; - a linear or branched saturated C 1 -C 6 alkyl radical, optionally interrupted with an oxygen atom or a radical NR 7, optionally substituted with a radical chosen from OH and NR 7 R 8; R 2 and R 3, which may be identical or different, represent: - a hydrogen atom; - a C 1 -C 6 and preferably C 1 -C 4 alkyl radical, optionally substituted with one or more hydroxyl radicals; - a carboxyl radical; - a radical CONR 7 R 8; R 4 and R 5, which may be identical or different, represent: - a hydrogen atom; - a C 1 -C 6 alkyl radical; R 6 represents: - a linear or branched C 1 -C 6 alkyl radical, optionally interrupted with a radical NR 9, and/or optionally substituted with one or more radicals, which may be identical or different, chosen from OH and NR 7 R 8; - a carboxyl radical; - a C 1 -C 10 alkyl carboxylate; - a radical CONR 7 R 8; - a C 1 -C 10 (poly)hydroxyalkyloxy; - a radical (poly)(C 1 -C 10)alkoxy(C 1 -C 10)alkyloxy; - a radical O-Ak-NR 9 R 10 with Ak = linear C 1 -C 8 or branched C 3 -C 8 divalent alkylene radical, optionally interrupted with one or more oxygen atoms and/or groups NR 7; R 7 and R 8, which may be identical or different, represent: - a hydrogen atom; - a C 1 -C 8 alkyl radical optionally substituted with one or more hydroxyl radicals; R 9 and R 10, which may be identical or different, represent a linear or branched, saturated or unsaturated C 1 -C 4 alkyl; R 9 and R 10 may form, with the nitrogen that bears them, a saturated or unsaturated 5- to 8-membered heterocycle, one of the chain members possibly being an oxygen atom or a radical NR 11 with R 11 = H or C 1 -C 4 alkyl, optionally substituted with one or more radicals chosen from OH and NR 7 R 8; with the exception of the following two compounds: R 1 represents: - a hydrogen atom; - a linear or branched saturated C 1 -C 6 alkyl radical, optionally interrupted with an oxygen atom or a radical NR 7, optionally substituted with a radical chosen from OH and NR 7 R 8; - a hydrogen atom; - a linear or branched saturated C 1 -C 6 alkyl radical, optionally interrupted with an oxygen atom or a radical NR 7, optionally substituted with a radical chosen from OH and NR 7 R 8; R 2 and R 3, which may be identical or different, represent: - a hydrogen atom; - a C 1 -C 6 and preferably C 1 -C 4 alkyl radical, optionally substituted with one or more hydroxyl radicals; - a carboxyl radical; - a radical CONR 7 R 8; - a hydrogen atom; - a C 1 -C 6 and preferably C 1 -C 4 alkyl radical, optionally substituted with one or more hydroxyl radicals; - a carboxyl radical; - a radical CONR 7 R 8; R 4 and R 5, which may be identical or different, represent: - a hydrogen atom; - a C 1 -C 6 alkyl radical; - a hydrogen atom; - a C 1 -C 6 alkyl radical; R 6 represents: - a linear or branched C 1 -C 6 alkyl radical, optionally interrupted with a radical NR 9, and/or optionally substituted with one or more radicals, which may be identical or different, chosen from OH and NR 7 R 8; - a carboxyl radical; - a C 1 -C 10 alkyl carboxylate; - a radical CONR 7 R 8; - a C 1 -C 10 (poly)hydroxyalkyloxy; - a radical (poly)(C 1 -C 10)alkoxy(C 1 -C 10)alkyloxy; - a radical O-Ak-NR 9 R 10 with Ak = linear C 1 -C 8 or branched C 3 -C 8 divalent alkylene radical, optionally interrupted with one or more oxygen atoms and/or groups NR 7; - a linear or branched C 1 -C 6 alkyl radical, optionally interrupted with a radical NR 9, and/or optionally substituted with one or more radicals, which may be identical or different, chosen from OH and NR 7 R 8; - a carboxyl radical; - a C 1 -C 10 alkyl carboxylate; - a radical CONR 7 R 8; - a C 1 -C 10 (poly)hydroxyalkyloxy; - a radical (poly)(C 1 -C 10)alkoxy(C 1 -C 10)alkyloxy; - a radical O-Ak-NR 9 R 10 with Ak = linear C 1 -C 8 or branched C 3 -C 8 divalent alkylene radical, optionally interrupted with one or more oxygen atoms and/or groups NR 7; R 7 and R 8, which may be identical or different, represent: - a hydrogen atom; - a C 1 -C 8 alkyl radical optionally substituted with one or more hydroxyl radicals; - a hydrogen atom; - a C 1 -C 8 alkyl radical optionally substituted with one or more hydroxyl radicals; R 9 and R 10, which may be identical or different, represent a linear or branched, saturated or unsaturated C 1 -C 4 alkyl; R 9 and R 10 may form, with the nitrogen that bears them, a saturated or unsaturated 5- to 8-membered heterocycle, one of the chain members possibly being an oxygen atom or a radical NR 11 with R 11 = H or C 1 -C 4 alkyl, optionally substituted with one or more radicals chosen from OH and NR 7 R 8; with the exception of the following two compounds: