XGRAF-2 Capsules XGRAF-2 contains Tacrolimus (FK506), a potent macrolide immunosuppressant. Tacrolimus binds intracellularly to the FK506-binding protein-12 (FKBP-12), forming a complex that selectively inhibits calcineurin, a calcium- and calmodulin-dependent serine-threonine phosphatase. Inhibition of calcineurin prevents the dephosphorylation and nuclear translocation of Nuclear Factor of Activated T-cells (NFAT), blocking the transcription of genes encoding interleukin-2 (IL-2), interferon-gamma, and other pro-inflammatory cytokines essential for T-cell activation and proliferation. XGRAF-2 is indicated for the prophylaxis of organ rejection in patients receiving allogeneic kidney, liver, or heart transplants, as well as for the treatment of organ rejection in patients resistant to other immunosuppressive therapies.