Ascomycin is primarily used in the development of immunosuppressive drugs, particularly in preventing organ transplant rejection. It acts by inhibiting T-cell activation through binding to immunophilins, thereby suppressing the immune response. Due to this mechanism, it serves as a lead compound for derivatives like pimecrolimus, which is used topically to treat inflammatory skin conditions such as atopic dermatitis. Its potent anti-inflammatory properties without causing significant skin atrophy make it valuable in dermatology. Additionally, ascomycin and its analogs are being investigated for potential applications in treating autoimmune diseases and neurodegenerative disorders due to their neuroprotective and immunomodulatory effects.