The present invention relates to quinoxaline compound of the formula (I): wherein R1 is carbocyclyl or heterocyclyl, either of which is optionally substituted with 1, 2, 3, 4 or 5 R7; R2 is carbocyclyl or heterocyclyl, either of which is optionally substituted with 1, 2, 3, 4 or 5 R8; R3, R4, R5 and R6 are each independently hydrogen or R9; and R7, R8 and R9 are each independently selected from organic and inorganic substituents, their use in therapy of diseases, in particular diseases mediated by the tyrosine kinase activity of Janus kinases, including JAK-2 and JAK-3 kinases.