Pyrrolo[3,2-d] pyrimidine derivatives for the treatment of viral infections and other diseases

1. A method of treating viral hepatitis in a subject in need thereof, the method comprising activating TLR7 and/or TLR8 in the subject by administering to the subject a therapeutically effective amount of a compound of formula (I):

or a pharmaceutically acceptable salt or solvate thereof;

wherein:

R 1 is selected from the group consisting of H, fluorine, and methyl;

R 2 is selected from the group consisting of H, halogen, and C 1-3 alkyl;

R 3 is C 1-6 alkyl optionally substituted by aryl wherein said aryl is optionally substituted by one or more substituents independently selected from the group consisting of aryloxy, halogen, aryl, alkylamino, dialkylamino, C 1-6 alkyl, —CO 2 H, —C(O)OC 1-6 alkyl, —CONH 2 ,—CN, and C 1-6 alkoxy;

or R 3 is C 1-6 alkyl optionally substituted by C 1-6 alkene, C 3-7 cycloalkyl or C 3-7 heterocycloalkyl;

or R 3 is C 1-6 alkyl optionally substituted by C 1-6 alkoxy, wherein said C 1-6 alkoxy is optionally substituted by aryl; and

R 4 is C 1-8 alkyl optionally substituted by one or more substituents independently selected from the group consisting of hydroxyl, C 1-6 alkoxy, C 1-6 alkyl, C 3-7 cycloalkyl, C 2-6 alkenyl, aryl, heteroaryl, and C 3-7 cycloalkyl, wherein said heteroaryl and said C 3-7 cycloalkyl are optionally further substituted by C 1-6 alkyl;

with the proviso that 2-amino, 4-(N-butylamino)-5-(alphamethylbenzyl)pyrrolo[3,2-d] pyrimidine is excluded.

2. The method of claim 1 wherein R 3 is methyl optionally substituted by aryl.

3. The method of claim 1 wherein each of R 3 and R 4 is independently 1-3 alkyl substituted by aryl.

4. The method of claim 1 wherein R 1 is fluorine and R 2 is hydrogen.

5. A method of treating viral hepatitis in a subject in need thereof, the method comprising activating TLR7 and/or TLR8 in the subject by administering to the subject a therapeutically effective amount of a pharmaceutical composition comprising a compound of claim 1 , or a pharmaceutically acceptable salt or solvate thereof, together with one or more pharmaceutically acceptable excipients, diluents or carriers.

6. A method of treating viral hepatitis in a subject in need thereof, the method comprising activating TLR7 and/or TLR8 in the subject by administering to the subject a therapeutically effective amount of a compound selected from the group consisting of:

or a pharmaceutically acceptable salt thereof.

7. A method of activating human TLR7 and/or TLR8 in a subject, comprising administering to the subject an effective amount of a compound of formula (I):

or a pharmaceutically acceptable salt or solvate thereof;

wherein:

R 1 is selected from the group consisting of H, fluorine, and methyl;

R 2 is selected from the group consisting of H, halogen, and C 1-3 alkyl;

R 3 is C 1-6 alkyl optionally substituted by aryl wherein said aryl is optionally substituted by one or more substituents independently selected from the group consisting of aryloxy, halogen, aryl, alkylamino, dialkylamino, C 1-6 alkyl, —CO 2 H, —C(O)OC 1-6 alkyl, —CONH 2 ,—CN, and C 1-6 alkoxy;

or R 3 is C 1-6 alkyl optionally substituted by C 1-6 alkene, C 3-7 cycloalkyl or C 3-7 heterocycloalkyl;

or R 3 is C 1-6 alkyl optionally substituted by C 1-6 alkoxy, wherein said C 1-6 alkoxy is optionally substituted by aryl; and

R 4 is C 1-8 alkyl optionally substituted by one or more substituents independently selected from the group consisting of hydroxyl, C 1-6 alkoxy, C 1-6 alkyl, C 3-7 cycloalkyl, C 2-6 alkenyl, aryl, heteroaryl, and C 3-7 cycloalkyl, wherein said heteroaryl and said C 3-7 cycloalkyl are optionally further substituted by C 1-6 alkyl;

with the proviso that 2-amino, 4-(N-butylamino)-5-(alphamethylbenzyl)pyrrolo[3,2-d] pyrimidine is excluded.

8. A method of activating human TLR7 and/or TLR8 in a subject, comprising administering to the subject an effective amount of a compound selected from the group consisting of:

or a pharmaceutically acceptable salt thereof.

9. The method of claim 7 wherein R 3 is methyl optionally substituted by aryl.

10. The method of claim 7 wherein each of R 3 and R 4 is independently 1-3 alkyl substituted by aryl.

11. The method of claim 7 wherein R 1 is fluorine and R 2 is hydrogen.

12. A method of activating human TLR7 and/or TLR8 in a subject, comprising administering to the subject an effective amount of a pharmaceutical composition comprising the compound of claim 7 , or a pharmaceutically acceptable salt or solvate thereof, together with one or more pharmaceutically acceptable excipients, diluents or carriers.