Background: Mycophenolic acid (MPA) is a widely used immunosuppressant to prevent acute rejection in kidney transplant recipients (KTRs). However, clinical significance of MPA therapeutic drug monitoring for predicting its efficacy or toxicity have shown inconsistent results. We investigated the correlation of MPA trough concentration (MPA C₀) with transplant outcomes and adverse events after kidney transplantation (KT).

Methods: This study included consecutive 70 KTRs who received MPA with tacrolimus and steroid. All the enrolled KTRs prospectively measured MPA C₀ which was determined monthly by using particle-enhanced turbidimetric inhibition immunoassay until 12 months and clinical data were collected at each time point. Correlations between MPA dose and MPA C₀ were analyzed with Pearson's correlation. Clinical endpoints were biopsy-proven acute rejection (BPAR), graft and patient survival, any cytopenia, severe gastrointestinal symptoms including persistent diarrhea, and severe infections. To determine the effect of MPA C₀ on the clinical endpoints, we performed logistic regression analysis in three-divided periods after KT; 0-3, 4-6, and 7-12 months.

Results: MPA C₀ was not correlated with MPA dose during the study period (r=0.112, p=0.354). From 0 to 3 month, MPA C₀ of patients with leukopenia was significantly higher than that of patients without leukopenia (3.81±0.74 mg/L vs. 2.82±1.13 mg/L; p=0.015). In the same period, MPA C₀ was significantly higher in patients with anemia compared to patients without anemia (4.14±1.20 mg/L vs. 2.90±1.09 mg/L, p=0.017). In logistic regression analysis, MPA C₀ was associated with leukopenia (OR: 2.65; 95% CI: 1.10- 6.41; p=0.03) and anemia (OR: 2.23; 95% CI: 1.21-4.21; p=0.01). MPA C₀ of 3.73 mg/L and 3.00 mg/L best predicted leukopenia and anemia, respectively. However, there were no significant associations of MPA C₀ with clinical outcomes including BPAR.

Conclusions: MPA dose was not correlated with MPA C₀ in KTRs. High MPA C₀ increased the risk of leukopenia and anemia in the early transplant period. Therefore, therapeutic drug monitoring of MPA could be recommended to reduce MPA-related toxicity after KT.

CITATION INFORMATION: Kim C.-D, Cho J.-H, Kim K, Kim M, Do W, Yang Y, Yim T, Hwang I, Lee J.-H, Jung H.-Y, Choi J.-Y, Park S.-H, Kim Y.-L. Clinical Significance of Mycophenolic Acid Therapeutic Drug Monitoring in Kidney Transplant Recipients. Am J Transplant. 2016;16 (suppl 3).

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