Crystalline forms of (6R)-L-erythro-tetrahydrobiopterin dihydrochloride

1. A pharmaceutical tablet formulation comprising a purified crystalline polymorph of (6R)-L-erythro-tetrahydrobiopterin dihydrochloride, form B, which exhibits a characteristic X-ray powder diffraction pattern comprising characteristic peaks expressed in d-values (Å): 8.7±0.1-0.2° (vs), 5.63±0.1-0.2° (m), 4.76±0.1-0.2° (m), 4.40±0.1-0.2° (m), 4.00±0.1-0.2° (s), 3.23±0.1-0.2° (s) and 3.11±0.1-0.2° (vs); or which exhibits a characteristic X-ray powder diffraction pattern substantially as exhibited in FIG. 2 ; and polyvinylpyrrolidone as a pharmaceutically acceptable ingredient and/or dicalcium phosphate as an excipient, wherein the polyvinylpyrrolidone is a biologically degradable polymer which may be linear, branched or crosslinked.

2. A pharmaceutical tablet formulation comprising a purified crystalline polymorph of (6R)-L-erythro-tetrahydrobiopterin dihydrochloride, form B, which exhibits a characteristic X-ray powder diffraction pattern comprising characteristic peaks expressed in d-values (Å): 8.7±0.1-0.2° (vs), 6.9±0.1-0.2° (w), 5.90±0.1-0.2° (vw), 5.63±0.1-0.2° (m), 5.07±0.1-0.2° (m), 4.76±0.1-0.2° (m), 4.40±0.1-0.2° (m), 4.15±0.1-0.2° (w), 4.00±0.1-0.2° (s), 3.95±0.1-0.2° (m), 3.52±0.1-0.2° (m), 3.44±0.1-0.2° (w), 3.32±0.1-0.2° (m), 3.23±0.1-0.2° (s), 3.17±0.1-0.2° (w), 3.11±0.1-0.2° (vs), 3.06±0.1-0.2° (w), 2.99±0.1-0.2° (w), 2.96±0.1-0.2° (w), 2.94±0.1-0.2° (m), 2.87±0.1-0.2° (w), 2.84±0.1-0.2° (s), 2.82±0.1-0.2° (m), 2.69±0.1-0.2° (w), 2.59±0.1-0.2° (w) and 2.44±0.1-0.2° (w); and polyvinylpyrrolidone as a pharmaceutically acceptable ingredient and/or dicalcium phosphate as an excipient, wherein the polyvinylpyrrolidone is a biologically degradable polymer which may be linear, branched or crosslinked.

3. A pharmaceutical tablet formulation comprising a purified crystalline polymorph of (6R)-L-erythro-tetrahydrobiopterin dihydrochloride, form B, which exhibits a characteristic X-ray powder diffraction pattern substantially as exhibited in FIG. 2 ; and polyvinylpyrrolidone as a biologically degradable polymeric binder and/or dicalcium phosphate as an excipient.

4. The pharmaceutical tablet formulation according to claim 1 , wherein the purified crystalline polymorph of (6R)-L-erythro-tetrahydrobiopterin dihydrochloride is of at least about 98% purity by high performance liquid chromatography.

5. A process for preparing a pharmaceutical tablet formulation according to claim 1 comprising

(a) providing a purified crystalline polymorph of form B of (6R)-L-erythro-tetrahydrobiopterin dihydrochloride of at least about 98% purity by high performance liquid chromatography, and

(b) mixing the purified crystalline polymorph with polyvinylpyrrolidone and/or dicalcium phosphate.

6. A pharmaceutical tablet formulation prepared by the process of claim 5 .

7. A pharmaceutical tablet formulation according to claim 1 , further comprising folate alone or together with arginine.

8. A pharmaceutical tablet formulation according to claim 1 , further comprising a lubricant, a vitamin and a sugar.

9. A pharmaceutical tablet formulation according to claim 2 , further comprising a lubricant, a vitamin and a sugar.

10. A pharmaceutical tablet formulation according to claim 3 , further comprising a lubricant, a vitamin and a sugar.

11. A pharmaceutical tablet formulation according to claim 1 , wherein the polyvinylpyrrolidone is a biologically degradable crosslinked polymer.

12. A pharmaceutical tablet formulation according to claim 2 , wherein the polyvinylpyrrolidone is a biologically degradable crosslinked polymer.

13. A pharmaceutical tablet formulation according to claim 3 , wherein the polyvinylpyrrolidone is a biologically degradable crosslinked polymer.

14. The pharmaceutical tablet formulation according to claim 2 , wherein the purified crystalline polymorph of (6R)-L-erythro-tetrahydrobiopterin dihydrochloride is of at least about 98% purity by high performance liquid chromatography.

15. The pharmaceutical tablet formulation according to claim 3 , wherein the purified crystalline polymorph of (6R)-L-erythro-tetrahydrobiopterin dihydrochloride is of at least about 98% purity by high performance liquid chromatography.

16. The pharmaceutical tablet formulation according to claim 1 , wherein the formulation comprises polyvinylpyrrolidone and dicalcium phosphate.

17. The pharmaceutical tablet formulation according to claim 2 , wherein the formulation comprises polyvinylpyrrolidone and dicalcium phosphate.

18. The pharmaceutical tablet formulation according to claim 3 , wherein the formulation comprises polyvinylpyrrolidone and dicalcium phosphate.

19. The pharmaceutical tablet formulation according to claim 1 , wherein form B exhibits a characteristic X-ray powder diffraction pattern with the following characteristic peaks expressed in d-values (Å): 8.7 (vs), 5.63 (m), 4.76 (m), 4.40 (m), 4.00 (s), 3.23 (s) and 3.11 (vs).

20. The pharmaceutical tablet formulation according to claim 2 , wherein form B exhibits a characteristic X-ray powder diffraction pattern with the following characteristic peaks expressed in d-values (Å): 8.7 (vs), 6.9 (w), 5.90 (vw), 5.63 (m), 5.07 (m), 4.76 (m), 4.40 (m), 4.15 (w), 4.00 (s), 3.95 (m), 3.52 (m), 3.44 (w), 3.32 (m), 3.23 (s), 3.17 (w), 3.11 (vs), 3.06 (w), 2.99 (w), 2.96 (w), 2.94 (m), 2.87 (w), 2.84 (s), 2.82 (m), 2.69 (w), 2.59 (w) and 2.44 (w).

21. The pharmaceutical tablet formulation according to claim 19 , wherein the formulation comprises polyvinylpyrrolidone and dicalcium phosphate.

22. The pharmaceutical tablet formulation according to claim 20 , wherein the formulation comprises polyvinylpyrrolidone and dicalcium phosphate.