[Development and pre-clinical aspects of pimecrolimus]

Pimecrolimus for the treatment of inflammatory skin disease

Pimecrolimus (SDZ ASM 981, Elidel ) is an ascomycin macrolactam derivative and a cell-selective inhibitor of inflammatory cytokines specifically developed to treat inflammatory skin diseases. Pimecrolimus combines high anti-inflammatory activity in the skin with a low potential to impair systemic immune reactions. Multi-centre studies have proved the efficacy and safety of pimecrolimus cream in patients with atopic dermatitis (AD) and confirmed that it is suitable for short-term treatment and long-term management of AD in adults, children and infants as young as 3 months. Topical application in humans is not associated with the atrophogenic side effects observed with corticosteroids. Pimecrolimus blood levels remained consistently low after repeated topical application and no clinically relevant drug-related systemic adverse events have been reported among the 8000 patients treated in clinical trials so far. Short-term, Phase I/II and Phase II trials of pimecrolimus administered orally in psoriasis and AD have shown that this drug is highly effective in a dose-dependent manner in patients with these diseases and has high safety profile. This finding is confirmed by pharmacogenomic blood analysis. Available data thus indicates that pimecrolimus, in both the cream and oral formulations, may represent a new option for the treatment of inflammatory skin diseases.

Novel pharmacological approaches in the treatment of psoriasis

Progress in the understanding of psoriasis as a T-cell mediated inflammatory disease has led to the development of new immunomodulatory therapies. Currently the main focus is on the so-called biologics (or biological agents), including fusion proteins, monoclonal antibodies, cytokines and selective receptors. They mainly target single steps in the complex cascade of humoral and cellular inflammatory immuno-mechanisms that finally lead to the accelerated growth of epidermal and vascular cells in the psoriatic lesions. The most promising and advanced biological agents are discussed along with their influence on the critical pathophysiological steps in psoriasis, including depletion of T cells, blockade of initial T-cell activation and T-cell receptor (TCR) stimulation, blockade of costimulatory signals and T-cell proliferative signals as well as restoration of the T helper type 1 (Th1)/Th2 balance by diminishing type 1 cytokines and administration of type 2 cytokines. In addition to the biological agents, further development of 'classical' dermatological therapies, such as retinoids, or the discovery of new indications for non-dermatological agents contribute to the novel pharmacological approaches in the treatment of psoriasis.

Pimecrolimus - an anti-inflammatory drug targeting the skin

Pimecrolimus is the most recent member of calcineurin inhibitors available for the therapy for inflammatory skin diseases. It targets T-cells and mast cells and inhibits the production and release of cytokines and other inflammatory mediators, as well as the expression of signals essential for the activation of inflammatory T-lymphocytes. Pimecrolimus has a cell-selective mode of action. In contrast to corticosteroids, it does not affect, e.g., Langerhans'cells/dendritic cells (LC/DC), as demonstrated in vitro with human monocyte-derived DC and in vivo with epidermal LC in mice, nor human primary fibroblasts. As shown in vitro with human skin and by comparison of clinical pharmacokinetic data from patients with atopic dermatitis, pimecrolimus permeates less through skin than tacrolimus and much less than corticosteroids. It, thus, has a lower potential for transcutaneous resorption after topical administration, resulting in a lower risk of systemic effects. Pimecrolimus has high anti-inflammatory activity in animal models of skin inflammation, including a model reflecting neurogenic inflammation, but a more favourable balance of anti-inflammatory vs. immunosuppressive activity than tacrolimus. Pimecrolimus does not affect sensitization in a murine model of allergic contact dermatitis and has a lower potency in various models of immunosuppression after systemic administration, compared to tacrolimus. In conclusion, the results of preclinical studies show that pimecrolimus has a selective pharmacological profile, suited for effective and safe treatment for inflammatory skin diseases.