Tacrolimus

Summary

Tacrolimus, also known as FK506, is a drug that causes immunosuppression and prevents transplant rejections. To achieve its effects, tacrolimus binds to FK506 Binding Protein (FKBP) creating a tacrolimus-FKBP complex. This complex then inhibits calcineurin, an enzyme important in the signalling for IL-2 production. By blocking IL-2 production, tacrolimus consequently results in reduced proliferation of all lymphocytes, but especially affects T-cells. Important side effects to note include neurotoxicity, nephrotoxicity, and hyperglycemia. 

Key Points

• Tacrolimus
  • Also called FK506
  • Immunosuppressant drug
    • Primarily used for transplant rejection prophylaxis
  • Mechanism
    • Inhibits calcineurin by forming a complex with FK506-binding protein (FKBP)
      • Note: Sirolimus also binds FKBP, but at a different site to form a different complex that inhibits mTOR (not calcineurin)
      • Blocks transcription and production of Interleukin-2 (IL-2)
    • Results in reduced proliferation of all lymphocytes (e.g. T cells)
  • Adverse Effects
    • Nephrotoxic
    • Diabetes
    • Neurotoxicity
    • No gingival hyperplasia or hirsutism (contrast vs. Cyclosporine)