The present invention describes novel compounds, or their pharmaceutically acceptable salts, pharmaceutical compositions containing them, and their medical uses. The compounds of the invention have activity as Janus kinase (JAK) inhibitors and are useful in the in the treatment or control of inflammation, auto-immune diseases, cancer, and other disorders and indications where modulation of JAK would be desirable. Also described herein are methods of treating inflammation, auto-immune diseases, cancer, and other conditions susceptible to inhibition of JAK by administering a compound herein described.