CLINICAL CONTROVERSY ON THE EFFECT OF TOPICAL CYCLOSPORINE - WHAT IS THE TARGET SITE

In recent years attempts have been made to treat T-cell-mediated skin diseases with topical therapeutics. Based on clinical data on the local treatment of recalcitrant erosive lichen planus (LP) with ciclosporin (CS) we discuss in vitro and in vivo studies on percutaneous absorption of CS, drug localization and drug metabolism in the skin as well as clinical data. Clinically relevant immunosuppressive activity depends not only on drug distribution in the target organ skin. The inhibition of T cell response is also dependent upon T cell subsets involved and the activation stage of the T cell. There are different proportions in T cell subpopulations during different evolutional stages of LP. Thus responsiveness to therapy with this drug may depend on the disease activity. Furthermore lymphocyte migration throughout various organs in the body including skin depend on a variety of molecular and cellular interactions. Whether local CS is sufficient to inhibit these interactions or to inactivate already activated T cells remains unclear. Assuming that the T lymphocyte is the target site for CS, local therapy reaches only a small fraction of the T cell population. This may be insufficient, and a systemic inhibition of helper/inducer T lymphocyte function is needed for successful therapy. With CS and with other drugs it seems that percutaneous absorption is not the only key to variable clinical responses to topical therapy.