Overview of a 10-year experience on methods and compositions for inducing site-specific immunosuppression with topical immunosuppressants.

Methods and formulations have been successfully developed to bring about site-specific immune suppression of local T-cell-mediated immune responses involved in contact hypersensitivity, skin allograft rejection, and, putatively, autoimmune inflammatory conditions such as psoriasis. The induction of site-specific immune suppression results in reduced systemic pharmacology and toxicity. Certain formatulations have been devised that can effect dramatic transdermal drug delivery and systemic immunopharmacology. Local site-specific or systemic efficacy by transdermal delivery can be dependent upon carrier composition with respect to the hydrophilic/lipophilic nature of the solvent system, active principal solubilization, and concentration. Multiple classes of active immunosuppressive agents can be successfully combined to produce novel and extremely potent topical drugs. Specifically, either cyclosporine or rapamycin inhibit local inflammatory/immune responses by topical application to skin tissue in vivo. Rapamycin is particularly efficacious during the late local inflammatory/immune phase. Cyclosporine is particularly efficacious during the early local inflammatory-immune phase. Also, skin allograft survival may be prolonged via topical use of CyA, alone and in combination with other anti-inflammatory agents. This includes combined immunosuppressant and steroidal anti-inflammatory agents that can produce synergistic results. Systemic immunity in these instances is normal. Expression of MHC class I and MHC class II molecules is dramatically decreased in these CyA/steroid SITE-treated grafts. In summary, the induction of local immune suppression at the tissue site and focal responding immunocytes can result in surprising efficacy when used in conjunction with limited systemic administration, which could have significant immunologic and clinical ramifications.