Immune Monitoring of Mycophenolate Mofetil Activity in Healthy Volunteers Using Ex Vivo T Cell Function Assays

Abstract

Mycophenolate mofetil (MMF) is part of the standard immunosuppressive treatment after transplantation and usually given as “one-dose-fits-all” together with a calcineurin inhibitor (CNI). Although drug concentrations are frequently monitored, there is still a group of patients who experience side effects related to excessive or insufficient immune suppression. We therefore aimed to identify biomarkers that reflect the overall immune status of the patient and might support individualized dosing. We previously studied immune biomarkers for CNIs and aimed to investigate whether these are also suitable to monitor MMF activity. Healthy volunteers received a single dose of MMF or placebo, after which IMPDH enzymatic activity, T cell proliferation, and cytokine production were measured and compared to MPA (MMF’s active metabolite) concentration in three different matrices (plasma, peripheral blood mononuclear cells, and T cells). MPA concentrations in T cells exceeded those in PBMCs, but all intracellular concentrations correlated strongly with plasma concentrations. At clinically relevant MPA concentrations, IL-2 and IFN-γ production was mildly suppressed, while MPA T cell proliferation was strongly inhibited. Based on these data, it is expected that monitoring of T cell proliferation in MMF-treated transplantation patients may be a valid strategy to avoid excessive immune suppression.

Immune responsiveness in stable kidney transplantation patients: Complete inhibition of T‐cell proliferation but residual T‐cell activity during maintenance immunosuppressive treatment

“…We expected very limited levels of T‐cell proliferation (<1%) in renal transplantation patients on MMF therapy, based on previous data in healthy volunteers. 14 T‐cell proliferation was therefore only measured at two timepoints: pre‐dose ( C 0 , 0 h) and 2 h post‐dose ( C 2 ). As expected, at C 0 the percentage of proliferated T cells after stimulation was very low (0.25 ± 0.22%), and upon drug intake by the patients T‐cell proliferation was not further suppressed (Figure 3c ).…”

“…We expected very limited levels of T‐cell proliferation (<1%) in renal transplantation patients on MMF therapy, based on previous data in healthy volunteers 14 . T‐cell proliferation was therefore only measured at two timepoints: pre‐dose ( C 0 , 0 h) and 2 h post‐dose ( C 2 ).…”

“…We previously investigated several functional immune assays and their suitability in demonstrating the drug effect of CNIs and MMF in healthy volunteers. 14 , 15 , 16 In the current study, the selected immune assays were studied in kidney transplant patients. With both male and female patients, ages ranging from 32 to 78 and the time post‐transplantation ranging from 2 to 15.8 years, a heterogenous population of kidney transplantation patients participated in the study.…”

“…In previous studies, we showed that these immune assays could be used to measure the drug effect of CNIs (calcineurin A and tacrolimus) and MMF in healthy volunteers. 14 , 15 , 16 To evaluate if these assays are also suitable for monitoring drug activity in a clinical setting, we conducted an observational trial in kidney transplant recipients.…”

“…For the T‐cell‐based assays, whole blood was incubated with a T‐cell stimulus, after which T‐cell proliferation, T‐cell activation marker expression, and cytokine production were measured to study the residual T‐cell activity. In previous studies, we showed that these immune assays could be used to measure the drug effect of CNIs (calcineurin A and tacrolimus) and MMF in healthy volunteers 14–16 . To evaluate if these assays are also suitable for monitoring drug activity in a clinical setting, we conducted an observational trial in kidney transplant recipients.…”