Used primarily as an immunosuppressive agent in organ transplantation to prevent rejection, especially in kidney, liver, and heart transplants. It suppresses T-cell activity by inhibiting calcineurin, thereby reducing the immune response. Also used in the treatment of autoimmune diseases such as severe psoriasis, rheumatoid arthritis, and atopic dermatitis. Its acetate form improves solubility and stability in pharmaceutical formulations, making it suitable for oral and topical delivery systems. Widely applied in research to study immune system regulation and cellular signaling pathways involving T-lymphocytes.