A series of thiazolo[5,4-d]pyrimidine derivatives of formula (I) or an N-oxide thereof, or a pharmaceutically acceptable salt or solvate thereof: (I) Q represents a group of formula (Qa), (Qb), (Qc), (Qd) or (Qe) are beneficial in the treatment and/or prevention of various human ailments, including inflammatory, autoimmune and oncological disorders; viral diseases; and organ and cell transplant rejection.