Fused thiophone derivatives and drugs containing the same as the active ingredient

The present invention relates to a fused thiophene derivative of the formula (I) (wherein all the symbols are defined as described in the specification) and an inhibitor of producing interleukin-6 and/or interleukin-12 comprising the said derivative as an active ingredient.A fused thiophene derivative of the formula (I) is useful as an agent for the prevention and/or treatment of various inflammatory diseases, sepsis, multiple myeloma, plasma cell leukemia, osteoporosis, cachexia, psoriasis, nephritis, renal cell carcinoma, Kaposi's sarcoma, rheumatoid arthritis, gammopathy, Castleman's disease, atrial myxoma, diabetes mellitus, autoimmune diseases, hepatitis, multiple sclerosis, colitis, graft versus host immune diseases, infectious diseases.