Use of Nuclear Factor of Activated T Cell-Regulated Gene Expression for Monitoring Immunosuppression with Extended-Release Tacrolimus after Liver Transplantation—A Proof of Concept.

Background: There is a narrow therapeutic window for immunosuppression using calcineurin inhibitors. Drug trough levels do not reflect immunosuppression and should be replaced by pharmacodynamic monitoring. This prospective cohort study was designed to evaluate the effect of an extended-release formulation of tacrolimus (LCP Tac) on the nuclear factor of activated T cell-regulated gene expression (NFAT-RGE). Methods: The expression of interleukin-2, interferon-γ, granulocyte-macrophage colony-stimulating factor, and three reference genes was measured. Samples from 23 patients at defined time points in the first year after liver transplantation were analyzed using a droplet digital polymerase chain reaction. Results: All samples were within the targeted trough levels of LCP Tac, and their LCP Tac peak levels and residual NFAT-RGE showed a strong inverse correlation (r = −0.8). Most importantly, there was an individual immunosuppressive response to the LCP Tac. The mean individual trough effect of LCP Tac on the three target genes when all time points were pooled was 33% (26–56%) in patients without infection and 81% (53–95%) in those with infection (p < 0.011). The mean individual peak effect was 48% (44–64%) in patients without infection and 91% (90–94%) in those with infection (p < 0.001). Conclusions: Thus, tailored immunosuppression based on residual NFAT-RGE could prevent infections associated with over-immunosuppression early after liver transplantation. [ABSTRACT FROM AUTHOR]