Rapamycin for Immunosuppression and B Cell Modulation Post Stem Cell Transplant for Acute Lymphoblastic Leukemia (ALL)

Rapamycin (RAPA, RapamuneR) (sirolimus) is an immunosuppressive agent that was approved by the FDA in 1999. It is a macrocyclic lactone that is structurally similar to Tacrolimus (FK506) and binds to the same intracellular protein as FK506, FKBP1,2,3, but it has an entirely different mechanism of action and a different principal target protein. The target of the RAPA: FKBP complex is the mammalian target of rapamycin (mTOR). Unlike the calcineurin inhibitors cyclosporine (CSA) and - FK506, RAPA exerts its effects by inhibiting growth factor-driven transduction signals in the T-cell response to alloantigen, thus preventing proliferation among T and B lymphocytes3,4.