There is provided compounds of formula (I), wherein R
1
, R
2
, R
3
and R
4
have meanings given in the description (and which compounds are optionally substituted as indicated in the description), and pharmaceutically-acceptable esters, amides, solvates or salts thereof, which compounds are useful in the treatment of diseases in which inhibition of a protein or lipid kinase (e.g. a PIM family kinase, such as PIM-1, PIM-2 and/or PIM-3) is desired and/or required, and particularly in the treatment of cancer or a proliferative disease. There is also provided combinations comprising the compounds of formula (I).