Disclosed are sulfonamide analogues of galiellactone of formula (I) as STAT3-inhibitors for use in the treatment of a STAT3 signaling related disorder, e.g. solid cancers, hematological cancers, benign tumors, hyperproliferative diseases, inflammations, autoimmune diseases, graft or transplant rejections, delayed physiological function of grafts or transplants, neurodegenerative diseases and viral infections. The sulfonamide comprises a cyclic substituent.
