Use of (R)-penciclovir triphosphate for the manufacture of a medicament for the treatment of viral diseases

1 . A method of treatment of:

i) HIV-1 infections in mammals, including humans; or

ii) HBV infections in mammals, including humans;

which method comprises the administration to the human in need of such treatment, an effective amount of the (R)-enantiomer of the triphosphate of a compound of formula (A):

or a pharmaceutically acceptable salt thereof.

2 . Use of the (R)-enantiomer of the triphosphate of a compound of formula (A):

or a pharmaceutically acceptable salt thereof;

in the manufacture of a medicament for the treatment of HIV-1 infections or HBV infections.

3 . A pharmaceutical composition for the treatment of HIV-1 infections or HBV infections comprising the (R)-enantiomer of the triphosphate of a compound of formula (A):

or a pharmaceutically acceptable salt thereof,

and a pharmaceutically acceptable carrier.

4 . A method, composition, or use according to claim 1 , 2 , or 3 wherein the (R)-PCV-TP is in the form of a bioprecursor which is a derivative of (R)-PCV-MP which liberates intracellularly (R)-PCV-MP which is in turn converted to (R)-PCV-TP.

5 . A compound which is bioprecursor of (R)-PCV-TP, for use in the method, use, or composition according to claim 1 , 2 , 3 , or 4 .

6 . A compound which is bioprecursor of (R)-PCV-TP, which is a derivative of (R)-PCV-MP.

7 . A compound according to claim 6 , which is selected from the following:

PL-ASOR derivative;

phospholipid derivative;

(R)-MP Bis(POM) derivative;

(R)-MP diphenyl ester derivative;

dimyristoylglycerol diphosphate derivative.