The present invention provides a compound having excellent JAK3 inhibitory activity and being useful as an active ingredient of an agent for treating and/or preventing various immune diseases including autoimmune diseases, inflammatory diseases, and allergic diseases. As a result of investigations with respect to novel condensed heterocyclic derivatives, the inventors have verified that a condensed pyridine compound has excellent JAK3 inhibitory activity, thereby completing the present invention. More specifically, it has been verified that since the compound according to the present invention has inhibitory activity against JAK3, the compound is useful as an active ingredient of an agent for treating or preventing diseases caused by undesirable cytokine signal transduction (e.g., rejection during live organ/tissue transplantation, autoimmune diseases, asthma, atopic dermatitis, rheumatism, psoriasis and atherosclerotic disease), or diseases caused by abnormal cytokine signal transduction (e.g., cancer and leukemia).
