Biochemical and immunologic mechanisms in atopic dermatitis: new targets for emerging therapies.

The immunologic and pharmacophysiologic features of atopic dermatitis have stimulated research seeking to identify relevant effector cells and mediators that characterize chronic skin inflammation. The theory that unifies the various abnormalities associated with atopic dermatitis suggests that hematopoietic cells carrying abnormal genetic expressions of atopy cause clinical disease once they infiltrate the skin and mucosa. The proposed underlying mechanism may be either abnormalities in cyclic nucleotide regulation of marrow-derived cells or allergenic overstimulation that causes secondary abnormalities. The primacy of one mechanism over the other remains unresolved, but this does not obviate their value in identifying two novel therapeutic targets: phosphodiesterase inhibition and immune-intervention alternatives to corticosteroids. New type IV phosphodiesterase inhibitors are proving promising in topical formulations, as are inhibitors of calcineurin, such as FK506 and SDZ ASM 981, an ascomycin macrolactam derivative that in early clinical research appears to offer the potency of a corticosteroid without its adverse side effects. The promising clinical trial profiles of these new topical agents may result in alternative therapies providing potent anti-inflammatory activity without the adverse effects that limit corticosteroid use.