This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
[{'content': 'Tarcolimus belong to which class of drug? \nSelect and explain. \nA. Calcineurin inhibitor, B. m TOR inhibitor, C. Hypoxathine inhibitor, D. Inosine inhibitor', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Reference: Katzung, Basic & Clinical Pharmacology, 13th ed., Pg. 1402.\nTacrolimus (FK 506) is an immunosuppressant macrolide antibiotic produced by Streptomyces tsukubaensis. It is not chemically related to cyclosporine, but their mechanisms of action are similar. Both drugs bind to cytoplasmic peptidylprolyl isomerases that are abundant in all tissues. While cyclosporine binds to cyclophilin, tacrolimus binds to the immunophilin FK-binding protein (FKBP). Both complexes inhibit calcineurin, which is necessary for the activation of the T-cell-specific transcription factor NF-AT.', 'role': 'assistant'}]