SC99 is an orally active, selective STAT3 inhibitor targeting JAK2-STAT3 pathway. SC99 docks into the ATP-binding pocket of JAK2. SC99 inhibits phosphorylation of JAK2 and STAT3 with no effects on the other kinases associated with STAT3 signaling. SC99 inhibits platelet activation, aggregation and displays potent anti-myeloma, anti-thrombotic activities.