A series of fused bicyclic pyridine and pyrazine derivatives, substituted directly on the pyridine or pyrazine ring by a functional group attached via a sulphur-containing linkage, being selective inhibitors of P13 kinase enzymes, are accordingly of benefit in medicine, for example in the treatment of inflammatory, autoimmune, cardiovascular, neurodegenerative, metabolic, oncological, nociceptive or ophthalmic conditions.
