Adenosine deaminase inhibitor

An adenosine derivative represented by the following formula or a pharmaceutically acceptable salt thereof:

• ##STR14## wherein R.sub.1 b and R.sub.2 b are the same and each is methyl or ethyl;
• Rb and Xb is hydrogen or methyl;
• and
• at least one of Rb and Xb is methyl.

An adenosine derivative represented by the following formula or a pharmaceutically acceptable salt thereof:

• ##STR15## wherein one of R.sub.1 c and R.sub.2 c is methyl and the other is hydrogen;
• when Xc is hydrogen, Rc is iodo;
• and
• when Xc is methyl, Rc is bromo or iodo.

A pharmaceutical composition comprising:

• (a) at least one adenosine deaminase inhibitor comprising at least one of the compounds represented by the formula (I) or a pharmaceutically effective salt thereof:
• ##STR17## wherein each of R.sub.1, R.sub.2 and R.sub.3 may be the same or different and R.sub.1, R.sub.2 and R.sub.3 is hydrogen or alkyl, at least one of R.sub.1, R.sub.2 and R.sub.3 being an alkyl;
• R is hydrogen, alkyl, alkenyl, alkynyl, hydroxyalkynyl, alkoxy, phenyl, hydroxy, amino, alkylamino, phenylamino or halogen;
• and
• X is hydrogen, alkyl, alkynyl, allyl, methallyl, cycloalkyl, an alkyl having one or more hydroxy groups, phenyl, substituted phenyl, alkyl having one or more phenyl groups, alkyl having one or more substituted phenyl groups, bicycloalkyl, naphthalkyl, acenaphthylenylalkyl or a group represented by Formula (II) or Formula (III):
• ##STR18## wherein Z is hydrogen, hydroxy or lower alkoxy;
• Q is hydrogen or hydroxy;
• A is --CH.sub.2 --, --O--, --S-- or a single bond forming a five-membered ring;
• Y is --(CH.sub.2).sub.n -- or a single bond;
• n is an integer from 1 to 3;
• and
• (b) adenosine or at least one therapeutically useful adenosine analogous drug which is different from (a) and which is metabolized or deaminated by adenosine deaminase;
• as active ingredients wherein said adenosinedeaminase inhibitor inhibits loss of activity of said adenosine or said adenosine analogous drug.