This invention relates to a group of trisubstituted and tetrasubstituted pteridine derivatives, their pharmaceutically acceptable salts, N-oxides, solvates, dihydro- and tetrahydro- derivatives and enantiomers, possessing unexpectedly desirable pharmaceutical properties, in particular which are highly active immunosuppressive agents, and as such are useful in the treatment in transplant rejection and/or in the treatment of certain inflammatory diseases. These compounds are also useful in preventing or treating cardiovascular disorders, allergic conditions, disorders of the central nervous system and cell proliferative disorders.