STA 21 selectively inhibits signal transducers and activators of transcription 3 (Stat3), which is transcription factor that is often found to be constitutively active in human breast cancer (1). It also inhibits osteoclastogenesis in mice and humans (2). In addition, STA 21 has been shown to attenuates the development and progression of inflammation in collagen antibody-induced arthritis and therefore, this compound may be used to develop therapeutic strategies to treat rheumatoid arthritis (3).