Compound of formula wherein: the symbol - - - represents a single or a double bond; Y is oxygen or guanidinoimino when - - - in position 3 is a double bond; Y is hydroxy, OR 4 or SR 4, when - - - in position 3 is a single bond and can have an alpha or beta configuration; R is an unsubstituted or substituted 3-furyl or 4-pyridazinyl group; R 1 is hydrogen; methyl; ethyl or n-propyl substituted by OH or NR 5 R 6; R 2 is hydrogen or together to R 3 is a bond of an oxirane ring; R 3 is hydrogen or together to R 2 is a bond of an oxirane ring; R 4 is hydrogen; methyl; C2-C6 alkyl or C3-C6 alkenyl or C2-C6 acyl, these alkyl, alkenyl and acyl groups being unsubstituted or substituted by a quaternary ammonium group or one or more OR 7, NR 8 R 9, formyl, amidino, guanidinoimino or by NR 8 R 9 and hydroxy; R 5, R 6 are independently hydrogen; methyl; C2-C6 alkyl unsubstituted or substituted by one NR 10 R 11, or NR 10 R 11 and hydroxy, or R 5 and R 6 taken together with the nitrogen atom form an unsubstituted or substituted saturated or unsaturated penta- or hexa-monoheterocyclic ring, optionally containing another heteroatom chosen from oxygen or sulfur or nitrogen; R 7 is hydrogen, methyl or C2-C4 alkyl, this alkyl being unsubstituted or substituted by one or more NR 10 R 11 or by NR 10 R 11 and hydroxy; R 8, R 9 are independently hydrogen; methyl; C2-C6 alkyl or C3-C6 alkenyl, these alkyl and alkenyl groups being unsubstituted or substituted by one or more NR 10 R 11, or NR 10 R 11 and hydroxy, or R 8 and R 9 taken together with the nitrogen atom form an unsubstituted or substituted saturated or unsaturated penta- or hexa-monoheterocyclic ring, optionally containing another heteroatom chosen from oxygen or sulfur or nitrogen, or R 8 is hydrogen and R 9 is amidino; or NR 8 R 9 represents propargylamino, R 10, R 11 are independently hydrogen, C1-C6 alkyl, or R 10 and R 11, taken together with the nitrogen atom form a saturated or unsaturated penta- or hexa-monoheterocyclic ring; for the prevention or treatment of a disease due to organ fibrosis selected from the group consisting of: kidney fibrosis; heart fibrosis; pancreas fibrosis; lung fibrosis; vascular vessel fibrosis; bone marrow fibrosis, liver fibrosis; or organ fibrosis due to systemic sclerosis. the symbol - - - represents a single or a double bond; Y is oxygen or guanidinoimino when - - - in position 3 is a double bond; Y is hydroxy, OR 4 or SR 4, when - - - in position 3 is a single bond and can have an alpha or beta configuration; R is an unsubstituted or substituted 3-furyl or 4-pyridazinyl group; R 1 is hydrogen; methyl; ethyl or n-propyl substituted by OH or NR 5 R 6; R 2 is hydrogen or together to R 3 is a bond of an oxirane ring; R 3 is hydrogen or together to R 2 is a bond of an oxirane ring; R 4 is hydrogen; methyl; C2-C6 alkyl or C3-C6 alkenyl or C2-C6 acyl, these alkyl, alkenyl and acyl groups being unsubstituted or substituted by a quaternary ammonium group or one or more OR 7, NR 8 R 9, formyl, amidino, guanidinoimino or by NR 8 R 9 and hydroxy; R 5, R 6 are independently hydrogen; methyl; C2-C6 alkyl unsubstituted or substituted by one NR 10 R 11, or NR 10 R 11 and hydroxy, or R 5 and R 6 taken together with the nitrogen atom form an unsubstituted or substituted saturated or unsaturated penta- or hexa-monoheterocyclic ring, optionally containing another heteroatom chosen from oxygen or sulfur or nitrogen; R 7 is hydrogen, methyl or C2-C4 alkyl, this alkyl being unsubstituted or substituted by one or more NR 10 R 11 or by NR 10 R 11 and hydroxy; R 8, R 9 are independently hydrogen; methyl; C2-C6 alkyl or C3-C6 alkenyl, these alkyl and alkenyl groups being unsubstituted or substituted by one or more NR 10 R 11, or NR 10 R 11 and hydroxy, or R 8 and R 9 taken together with the nitrogen atom form an unsubstituted or substituted saturated or unsaturated penta- or hexa-monoheterocyclic ring, optionally containing another heteroatom chosen from oxygen or sulfur or nitrogen, or R 8 is hydrogen and R 9 is amidino; or NR 8 R 9 represents propargylamino, R 10, R 11 are independently hydrogen, C1-C6 alkyl, or R 10 and R 11, taken together with the nitrogen atom form a saturated or unsaturated penta- or hexa-monoheterocyclic ring; for the prevention or treatment of a disease due to organ fibrosis selected from the group consisting of: kidney fibrosis; heart fibrosis; pancreas fibrosis; lung fibrosis; vascular vessel fibrosis; bone marrow fibrosis, liver fibrosis; or organ fibrosis due to systemic sclerosis.