Individually tailored immunosuppression: is there a role for biomarkers?

Therapeutic drug monitoring (TDM) of immunosuppressive drugs has evolved over the last few decades. The use of liquid chromatography–tandem mass spectrometry, for example, now provides robust and highly specific quantification in the clinical laboratory. Nevertheless, the measurement of immunosuppressive drug concentrations, even if carried out accurately and precisely, does not sufficiently reflect theeffectsoftheapplieddrugsonimmunecells,because of theconsiderable interindividualvariationinthesensitivity to suppression of immune function. Irreversible chronic allograft rejection and the long-term side effects of immunosuppressive therapy are still major limiting factors in transplantation medicine. In this context, pharmacodynamic (PD) biomarkers are a potential key for further optimization of immunosuppressive therapy.