Clinical pharmacology of immunosuppressive drugs: year 2000--time for alternatives

Perspectives in immunosuppressive drug therapy have changed rapidly in the past few years with the appearance on the market of several new entities. Used for organ transplantation, bone-marrow transplantation and more recently in some auto-immune diseases, the usual classical scheme consisting of corticoids, azathioprine (1970) and cyclosporin (1980), with or without an induction period with antilymphocyte antibodies, has varied little except for the monoclonal antibody OKT3. The considerable evolution due to the introduction of cyclosporin almost twenty years ago has reached its limits. The new perspectives offer two aspects: (1) on one hand, the specificity of each compound: tacrolimus, Prograf, Fujisawa; mycophenolate mofetyl (MMF), CellCept, Roche; cyclosporin, Neoral, Novartis; basiliximab, Simulect, Novartis; and dacliximab, Zenapax, Roche; monoclonal humanized antibodies, rapamycine or sirolimus, Rapamune, Wyeth; or its derived form RAD Novartis; (2) on the other hand, all these products represent alternatives to the present scheme in a field where coprescription is the rule. These alternatives encounter one main difficulty: the evaluation and the organization of the different possible combinations have to be done within a small series of patients. It is essential to note that the market authorizations have been given on the basis of a precise scheme of dosage regimen from the pivotal studies and that extrapolation from these conditions, in particular choice of the doses, has required thorough reflection. These recent developments need optimization between an improvement of immunosuppression and a higher risk for infection and malignancy.