Optimized liver-specific expression systems for FVIII and FIX

1. A nucleic acid expression cassette comprising a triple repeat of a liver-specific nucleic acid regulatory element, said triple repeat consisting of the nucleic acid fragment defined by SEQ ID NO:11 or a triple repeat of the nucleic acid fragment defined by SEQ ID NO:5, wherein a single nucleotide separates each nucleic acid fragment defined by SEQ ID NO:5; and a nucleic acid regulatory element comprising the nucleic acid fragment defined by SEQ ID NO: 12; wherein said triple repeat and said regulatory element are operably linked to a liver-specific promoter and a transgene.

2. The nucleic acid expression cassette according to claim 1 , wherein the liver-specific promoter is selected from the group consisting of: a minimal TTR promotor (TTRm), an AAT promoter, an albumin (ALB) promotor or minimal promoter, an apolipoprotein A1 (APOA1) promoter or minimal promoter, a complement factor B (CFB) promoter, a ketohexokinase (KHK) promoter, a hemopexin (HPX) promoter or minimal promoter, a nicotinamide N-methyltransferase (NNMT) promoter or minimal promoter, a carboxylesterase 1 (CES1) promoter or minimal promoter, a protein C (PROC) promoter or minimal promoter, an apolipoprotein C3 (APOC3) promoter or minimal promoter, a mannan-binding lectin serine protease 2 (MASP2) promoter or minimal promoter, a hepcidin antimicrobial peptide (HAMP) promoter or minimal promoter, or a serpin peptidase inhibitor, clade C (antithrombin), member 1 (SERPINC1) promoter or minimal promoter.

3. The nucleic acid expression cassette according to claim 1 , wherein said liver-specific promoter is the minimal TTR promotor (TTRm) as defined by SEQ ID NO:6.

4. The nucleic acid expression cassette according to claim 1 , wherein said liver-specific promoter is the AAT promoter as defined by SEQ ID NO:64.

5. The nucleic acid expression cassette according to claim 1 , comprising a regulatory element as defined by SEQ ID NO: 13 or SEQ ID NO:57, operably linked to the liver-specific promoter and the transgene.

6. The nucleic acid expression cassette according to claim 1 , wherein said transgene encodes for coagulation factor IX (FIX) or a coagulation factor FIX containing a hyper-activating mutation.

7. The nucleic acid expression cassette according to claim 1 , wherein said transgene encodes for coagulation factor VIII (FVIII) or a coagulation factor VIII having a deletion of the B domain.

8. The nucleic acid expression cassette according to claim 1 , comprising the combination of the nucleic acid regulatory element transthyretin enhancer (TTRe) defined by SEQ ID NO:12, and the liver-specific promoter TTRm, wherein said combination is encoded by SEQ ID NO:69.

9. The nucleic acid expression cassette according to claim 1 , further comprising a minute virus of mouse (MVM) intron.

10. The nucleic acid expression cassette according to claim 1 , further comprising a transcriptional termination signal derived from the bovine growth hormone polyadenylation signal (BGHpA), or derived from the Simian virus 40 polyadenylation signal (SV40 pA), or the synthetic polyadenylation signal as defined by SEQ ID NO:56.

11. A vector comprising the nucleic acid expression cassette according to claim 1 .

12. A method of treating hemophilia A or hemophilia B comprising transduction or transfection of the vector according to claim 11 into a subject, wherein the vector comprises a FVIII transgene for use in treating hemophilia A or the vector comprises a FIX transgene for use in treating hemophilia B.

13. The method according to claim 12 , wherein after transduction or transfection of the vector into a subject, levels of factor IX or FVIII in plasma are equal to or higher than the therapeutic threshold concentration of 10 mU/ml plasma in the subject are obtained.

14. The method according to claim 13 , wherein the transduction of a viral vector into the subject is done at a dose lower than 2×10 11 vg/kg.

15. The method according to claim 14 , wherein the transduction of the viral vector into the subject is done at a dose lower than or equal to 6×10 11 vg/kg, and wherein levels of factor IX or FVIII in plasma equal to or higher than the therapeutic concentration of 100 mU/ml are obtained in said subject; or wherein the transduction of the viral vector into the subject is done at a dose lower than or equal to 6×10 11 vg/kg, and wherein levels of factor IX or FVIII in plasma equal to or higher than the therapeutic concentration of 50 mU/ml are obtained in said subject; or wherein the transduction of the viral vector into the subject is done at a dose lower than or equal to 2×10 12 vg/kg, and wherein levels of factor IX or FVIII in plasma equal to or higher than the therapeutic concentration of 200 mU/ml are obtained in said subject; or wherein the transduction of the viral vector into the subject is done at a dose lower than or equal to 2×10 12 vg/kg, and wherein levels of factor IX or FVIII in plasma equal to or higher than the therapeutic concentration of 150 mU/ml are obtained in said subject.

16. A pharmaceutical composition comprising a vector according to claim 11 and a pharmaceutically acceptable carrier, optionally further comprising an active ingredient for treating hemophilia A when the transgene in said vector is FVIII; or an active ingredient for treating hemophilia B when the transgene in said vector is FIX.

17. The nucleic acid expression cassette according to claim 6 , wherein the coagulation factor FIX containing a hyper-activating mutation is encoded by SEQ ID NO:9.

18. The nucleic acid expression cassette according to claim 7 , wherein the B domain of the FVIII is replaced by a linker defined by SEQ ID NO:59.

19. The vector of claim 11 , wherein the vector is a viral vector.