... purity. water not more than 0.5%. Sirolimus (INN/USAN), also known as rapamycin, is an immunosuppressant drug used to prevent rejection ... -cells by inhibiting their response to interleukin-2(IL-2). Rapamycin also inhibits the activity of the protein, mTOR, (mammalian ... target of rapamycin) which functions in a signaling pathway to promote tumor growth ...