Pyridinone compounds for use in photodynamic therapy

1. A compound of formula (I) or any salt thereof:

wherein

R 1 is a C 1 -C 6 alkyl group,

R 2 is H or a C 1 -C 6 alkyl group,

R 3 is H or a C 1 -C 6 alkyl group, and

n is an integer from 0 to 5.

2. The compound according to claim 1 which is a salt of formula (Ia) or a salt of formula (Ib):

wherein

R 1 , R 2 , R 3 and n are as defined in claim 1 ; and

each X − is independently selected from monovalent counterions.

3. The compound according to claim 2 , wherein X − is Cl − .

4. The compound according to claim 1 , wherein R 1 is ethyl, R 2 and R 3 are H, and n is 1.

5. The compound according to claim 1 which is a salt of formula (Ic):

6. A pharmaceutical composition comprising the compound according to claim 1 and a pharmaceutically acceptable carrier.

7. The pharmaceutical composition according to claim 6 , wherein the compound is a salt of formula (Ic):

8. A process for making the compound according to claim 1 , the method comprising the step of:

(a) reacting a compound of formula (II) with a compound of formula (III) via an esterification reaction to form a compound of formula (IV);

in accordance with the following reaction scheme:

wherein

R 1 , R 2 , R 3 and n are as defined in claim 1 ; and

R PG1 and R PG2 are protecting groups.

9. The process according to claim 8 , further comprising the step of:

(b1) deprotecting the compound of formula (IV) to give a compound of formula (I);

in accordance with the following reaction scheme:

10. The process according to claim 8 , further comprising the step of:

(b2) deprotecting the compound of formula (IV) in the presence of acid H + X − to give a salt of formula (Ia);

in accordance with the following reaction scheme:

11. The process according to claim 8 , further comprising the step of:

(b3) deprotecting the compound of formula (IV) in the presence of acid H + X − to give a salt of formula (Ib);

in accordance with the following reaction scheme:

12. A method for treating or assisting the treatment of a proliferative, skin, inflammatory, or infectious condition in a subject in need thereof by photodynamic therapy, the method comprising:

(a) administering to the subject a compound of formula (I) or any salt thereof:

wherein

R 1 is a C 1 -C 6 alkyl group,

R 2 is H or a C 1 -C 6 alkyl group,

R 3 is H or a C 1 -C 6 alkyl group, and

n is an integer from 0 to 5;

and

(b) exposing a region of the subject containing the compound to light, thereby treating the subject.

13. The method according to claim 12 , wherein the compound of formula (I) is a salt of formula (Ia) or a salt of formula (Ib):

wherein

R 1 , R 2 , R 3 and n are as defined in claim 12 ; and

each X − is independently selected from monovalent counterions.

14. The method according to claim 13 , wherein X − is Cl − .

15. The method according to claim 12 , wherein R 1 is ethyl, R 2 and R 3 are H, and n is 1.

16. The method according to claim 12 , wherein the subject is a human or an animal.

17. The method according to claim 12 , wherein the proliferative condition is cancer.

18. The method according to claim 17 , wherein the cancer is a skin cancer or an internal cancer.

19. The method according to claim 17 , wherein the cancer is leukemia and the treatment comprises bone marrow purging.

20. The method according to claim 12 , wherein the skin, inflammatory, or infectious condition is scleroderma, lichen sclerosus, psoriasis, warts, chronic wounds, acne, a microbial infection, a viral infection, a parasitic infestation, or rheumatoid arthritis.

21. The method according to claim 12 , wherein the condition is cosmetic.

22. The method according to claim 12 , wherein the compound is a salt of formula (Ic):

23. The method according to claim 22 , wherein the subject is a human or an animal.

24. The method according to claim 23 , wherein the proliferative condition is cancer.

25. The method according to claim 24 , wherein the cancer is a skin cancer or an internal cancer.