Mycophenolic acid concentrations in peripheral blood mononuclear cells are associated with the incidence of rejection in renal transplant recipients

A validated UPLC-MS/MS method for the quantification of immunosuppressive drugs in peripheral blood mononuclear cells using liquid-liquid extraction with low temperature purification without complex pretreatment steps

Immunosuppressive drugs (ISDs) are given to avoid the allograft rejection after transplantation. The concentrations of ISDs should be closely monitored owing to their wide inter-individual variability in its pharmacokinetics and narrow therapeutic window. Currently, the whole blood concentration measurement is the major approach of therapeutic drug monitoring of clinical ISDs in organ transplantation. Its correlation with the efficacy of ISDs remains elusive. While the acute rejection after transplantation may occur even when whole-blood ISDs concentrations are within the target range. Since the site of action of ISDs are within the lymphocyte, direct measurement of drug exposure in target cells may more accurately reflect the clinical efficacy of ISDs. Although several methods have been developed for the peripheral blood mononuclear cells (PBMCs) extraction and drug concentration measurement, the complex pre-processing has limited the study of the relationship between intracellular ISDs concentrations and the occurrence of rejection. In this study, the extraction of ISDs in PBMCs was carried out by the liquid-liquid extraction with low temperature purification, without centrifugation. The lower limit of quantitation were 0.2 ng/mL for cyclosporine A, tacrolimus and sirolimus, 1.0 ng/mL for mycophenolic acid, and the within-run and between-run coefficient of variations were both less than 12.4 %. The calibration curves of mycophenolic acid had a linear range (ng/mL): 1.0-128.0 (r2 = 0.9992). The calibration curves of other three ISDs had a linear range (ng/mL): 0.2-20.48 (r2 > 0.9956). A total of 157 clinical samples were analyzed by the UPLC-MS/MS for ISDs concentration in blood or plasma ([ISD]blood or plasma) and the concentration within PBMCs ([ISD]PBMC). Although there was strong association between [ISD]PBMC and [ISD]blood or plasma, the large discrepancies between concentration within [ISD]blood or plasma and [ISD]PBMC were observed in a small proportion of clinical samples. The developed method with short analysis time and little amounts of blood sample can be successfully applied to therapeutic drug monitoring of ISDs in PBMCs for analysis of large numbers of clinical samples and is helpful to explore the clinical value of ISDs concentration in PBMCs.

Mycophenolate-induced colitis in a patient with lupus nephritis: a case report and review of the literature

BACKGROUND

Mycophenolate mofetil (MMF) is an immunosuppressive drug that is frequently prescribed to patients with rheumatological diseases. MMF's side effects include abdominal discomfort, nausea, vomiting, and other gastro-intestinal side effects, which typically appear in the first few months of treatment. However, late-onset diarrhea does not rule out the presence of MMF-induced colitis, which can be misdiagnosed since it is linked to a broad range of histopathological characteristics, including alterations that resemble inflammatory bowel disease, graft-versus-host disease, and ischemia. The differences in treatment response may be explained by the complexity of the histopathologic characteristics.

CASE PRESENTATION

Here we present a case of a 29-year-old Arabian female with lupus nephritis who started on MMF as induction therapy. In two months, the patient was presented to the Emergency Department with diarrhea and manifestations of severe dehydration. Infectious diseases and adverse drug events were suspected, so the patient was admitted for further workup, and MMF was stopped. The patient was diagnosed with MMF-induced colitis based on colonoscopy and histological findings. Fourteen days after stopping MMF, she was within her baseline.

CONCLUSION

The purpose of this paper is to report a case of early-onset MMF-induced colitis in a patient with lupus nephritis who had started MMF as induction therapy. A review of the available literature on this uncommon immunosuppressive effect is also presented.

Dynamic Monitoring of Intracellular Tacrolimus and Mycophenolic Acid Therapy in Renal Transplant Recipients Using Magnetic Bead Extraction Combined with LC-MS/MS

BACKGROUND

Tacrolimus (TAC) and mycophenolic acid (MPA) are commonly used immunosuppressive therapies after renal transplant. Our objective was to quantify TAC and MPA concentrations in peripheral blood mononuclear cells (PBMCs) using liquid chromatography tandem mass spectrometry (LC-MS/MS) and to evaluate and validate the performance of the methodology. A prospective follow-up cohort study was conducted to determine whether intracellular concentrations were associated with adverse outcomes in renal transplants.

METHODS

PBMCs were prepared using the Ficoll separation technique and purified with erythrocyte lysis. The cells were counted using Sysmex XN-3100 and then packaged and frozen according to a 50 µL volume containing 1.0 × 106 cells. TAC and MPA were extracted using MagnaBeads and quantified using an LC-MS/MS platform. The chromatography was run on a reversed-phase Waters Acquity UPLC BEH C18 column (1.7 µm, 50 mm × 2.1 mm) for gradient elution separation with a total run time of 4.5 min and a flow rate of 0.3 mL/min. Mobile phases A and B were water and methanol, respectively, each containing 2 mM ammonium acetate and 0.1% formic acid. Renal transplant recipients receiving TAC and MPA in combination were selected for clinical validation and divided into two groups: a stable group and an adverse outcome group. The concentrations were dynamically monitored at 5, 7, 14, and 21 days (D5, D7, D14, and D21) and 1, 2, 3, and 6 months (M1, M2, M3, and M6) after operation.

RESULTS

Method performance validation was performed according to Food and Drug Administration guidelines, showing high specificity and sensitivity. The TAC and MPA calibration curves were linear (r2 = 0.9988 and r2 = 0.9990, respectively). Both intra-day and inter-day imprecision and inaccuracy were less than 15%. Matrix effects and recoveries were satisfactory. The TAC and MPA concentrations in 304 "real" PBMC samples from 47 renal transplant recipients were within the calibration curve range (0.12 to 16.40 ng/mL and 0.20 to 4.72 ng/mL, respectively). There was a weak correlation between PBMC-C0TAC and WB-C0TAC (p < 0.05), but no correlation was found for MPA. The level of immunosuppressive intra-patient variation (IPV) was higher in PBMC at 77.47% (55.06, 97.76%) than in WB at 34.61% (21.90, 49.85%). During the dynamic change in C0TAC, PBMC-C0TAC was in a fluctuating state, and no stable period was found. PBMC-C0TAC did not show a significant difference between the stable and adverse outcome group, but the level of the adverse outcome group was generally higher than that of the stable group.

CONCLUSIONS

Compared with conventional therapeutic drug monitoring, the proposed rapid and sensitive method can provide more clinically reliable information on drug concentration at an active site, which has the potential to be applied to the clinical monitoring of intracellular immunosuppressive concentration in organ transplantation. However, the application of PBMC-C0TAC in adverse outcomes of renal transplant should be studied further.

The combination of exposure to Tacrolimus, mycophenolic acid, Inosine 5'-Monophosphate Dehydrogenase activity and inhibition in the first week define early histological outcomes in renal transplant recipients

Therapeutic drug monitoring is routine for Tacrolimus, while levels are not routinely monitored for mycophenolic acid (MPA). This study investigated the effect of early post-transplant pharmacokinetics (PK) of MPA and Tacrolimus along with the pharmacodynamics (PD) of MPA on biopsy-proven acute rejection (BPAR) after renal transplantation. A prospective PK/PD study with limited sampling (three blood samples) was conducted in renal transplant recipients on week 1, around Day 6 (n = 42) and at the 3rd-month biopsy on Day 90 (n = 23). The partial exposures (area under curve [AUC]_0-3.5 h ) of both MPA and Tacrolimus obtained during the first week were more predictive of rejection (combined clinical and subclinical rejection) by Day 90 than their trough concentrations or Day 90 exposures. Patients with rejection had significantly worse renal function (eGFR) and a comparatively lower exposure to MPA during the first post-transplant week. The lower MPA exposure was also associated with sub-optimal inosine monophosphate dehydrogenase (IMPDH) inhibition in patients with rejection, and the probability of rejection was higher in the presence of an increased pre-transplant IMPDH activity. A composite of parameters, including MPA exposure and IMPDH activity was found to predict acute rejection and may be beneficial along with tacrolimus monitoring early after renal transplantation.

Individualization of Mycophenolic Acid Therapy through Pharmacogenetic, Pharmacokinetic and Pharmacodynamic Testing

Mycophenolic acid (MPA) is a widely used immunosuppressive agent and exerts its effect by inhibiting inosine 5′-monophosphate dehydrogenase (IMPDH), the main regulating enzyme of purine metabolism. However, significant unexplained differences in the efficacy and tolerability of MPA therapy pose a clinical challenge. Therefore, broad pharmacogenetic, pharmacokinetic, and pharmacodynamic approaches are needed to individualize MPA therapy. In this prospective cohort study including 277 renal transplant recipients, IMPDH2 rs11706052 SNP status was assessed by genetic sequencing, and plasma MPA trough levels were determined by HPLC and IMPDH enzyme activity in peripheral blood mononuclear cells (PBMCs) by liquid chromatography–mass spectrometry. Among the 277 patients, 84 were identified with episodes of biopsy-proven rejection (BPR). No association was found between rs11706052 SNP status and graft rejection (OR 1.808, and 95% CI, 0.939 to 3.479; p = 0.076). Furthermore, there was no association between MPA plasma levels and BPR (p = 0.69). However, the patients with graft rejection had a significantly higher predose IMPDH activity in PBMCs compared to the controls without rejection at the time of biopsy (110.1 ± 50.2 vs. 95.2 ± 45.4 pmol/h; p = 0.001), and relative to the baseline IMPDH activity before transplantation (p = 0.042). Our results suggest that individualization of MPA therapy, particularly through pharmacodynamic monitoring of IMPDH activity in PBMCs, has the potential to improve the clinical outcomes of transplant patients.

Association Between the Intracellular Tacrolimus Concentration in CD3 + T Lymphocytes and CD14 + Monocytes and Acute Kidney Transplant Rejection

BACKGROUND

Intracellular tacrolimus concentration in peripheral blood mononuclear cells (PBMCs) (TAC [PBMC] ) has been proposed to better represent its active concentration than its whole blood concentration. As tacrolimus acts on T lymphocytes and other white blood cells, including monocytes, we investigated the association of tacrolimus concentration in CD3 + T lymphocytes (TAC [CD3] ) and CD14 + monocytes (TAC [CD14] ) with acute rejection after kidney transplantation.

METHODS

From a total of 61 samples in this case-control study, 28 samples were obtained during biopsy-proven acute rejection (rejection group), and 33 samples were obtained in the absence of rejection (control group). PBMCs were collected from both cryopreserved (retrospectively) and freshly obtained (prospectively) samples. CD3 + T lymphocytes and CD14 + monocytes were isolated from PBMCs, and their intracellular tacrolimus concentrations were measured.

RESULTS

The correlation between tacrolimus whole-blood and intracellular concentrations was poor. TAC [CD3] was significantly lower than TAC [CD14] (median 12.8 versus 81.6 pg/million cells; P < 0.001). No difference in TAC [PBMC] (48.5 versus 44.4 pg/million cells; P = 0.82), TAC [CD3] (13.4 versus 12.5 pg/million cells; P = 0.28), and TAC [CD14] (90.0 versus 72.8 pg/million cells; P = 0.27) was found between the rejection and control groups. However, freshly isolated PBMCs showed significantly higher TAC [PBMC] than PBMCs from cryopreserved samples. Subgroup analysis of intracellular tacrolimus concentrations from freshly isolated cells did not show a difference between rejectors and nonrejectors.

CONCLUSIONS

Differences in TAC [CD3] and TAC [CD14] between patients with and without rejection could not be demonstrated. However, further optimization of the cell isolation process is required because a difference in TAC [PBMC] between fresh and cryopreserved cells was observed. These results need to be confirmed in a study with a larger number of patients.

Inosine monophosphate dehydrogenase activity and mycophenolate pharmacokinetics in children with nephrotic syndrome treated with mycophenolate mofetil

Some studies have shown that the area under the concentration-time curve (AUC) of mycophenolic acid (MPA) should be higher for children with nephrotic syndrome (NS) than after renal transplantation. The pharmacodynamic aspect of MPA, the activity of inosine monophosphate dehydrogenase (IMPDH), has not been studied in children with NS. The study included 21 children (4-16 years) with NS treated with mycophenolate mofetil. MPA and its glucuronide plasma concentrations were determined using validated high-performance liquid chromatography (HPLC-UV). The separate HPLC-UV method was applied for IMPDH activity determination. The variability was expressed by the coefficient of variation (CV). IMPDH activity and MPA concentration (C_trough ) before the morning dose amounted to 29.95 μmol·s^-1 ·mol^-1 AMP (range, 6.71-98.60 μmol·s^-1 ·mol^-1 AMP) and 1.72 μg/mL (range, 0.39-4.34 μg/mL), respectively, whereas the area under the effect-time curve from 0 to 4 h and MPA AUC_0-4 were 130.36 μmol·s^-1 ·mol^-1 AMP∙h (range, 23.58-306.57 μmol·s^-1 ·mol^-1 AMP∙h) and 24.63 μg·h/mL (range, 12.21-67.48 μg·h/mL), respectively. IMPDH activity decreased concomitantly with MPA concentration increase, however, the variability of the pharmacodynamic parameters was greater than of the pharmacokinetics. The median degree of maximum IMPDH inhibition was 61%. MPA C_trough and predicted AUC were lower than in our previous study. Only a few MPA pharmacokinetic parameters correlated with the pharmacodynamics. IMPDH activity did not correlate with children's age and did not differ between boys and girls. MPA clearance was the highest in younger children (median 10.54 L/m² /h) and cholesterol correlated negatively with children's age (r=-0.659, p=0.003). IMPDH minimum activity and the degree of maximum IMPDH inhibition were similar to those obtained in renal transplant recipients. IMPDH activity does not undergo developmental or gender-specific regulation in children with NS. MPA underexposure might be more frequent in younger children, especially with high cholesterol and triglycerides levels due to high MPA clearance.

Pharmacokinetics and pharmacodynamics profiles of enteric-coated mycophenolate sodium in female patients with difficult-to-treat lupus nephritis

Relapsed or resistant lupus nephritis (LN) is considered a difficult-to-treat type of LN, and enteric-coated mycophenolate sodium (EC-MPS) has been used in this condition. Therapeutic drug monitoring using the area under the plasma mycophenolic acid concentration from 0 to 12 h postdose (MPA-AUC_0-12h ) ≥45 μg.h/ml is a useful approach to achieve the highest efficiency. This study assessed EC-MPS's pharmacokinetic (PK) and pharmacodynamic (PD) profiles and investigated an optimal level of the single time point of plasma MPA concentration. Nineteen biopsy-proven patients with class III/IV LN received 1440 mg/day of EC-MPS for 24 weeks. PK (maximum plasma MPA concentration [C_max ], time to C_max , and MPA-AUC_0-12h ) and PD (activity of inosine-5'-monophosphate dehydrogenase [IMPDH]) parameters were measured at weeks 2, 8, 16, and 24. We found that IMPDH activity decreased from baseline by 31-42% within 2-4 h after dosing, coinciding with the increased plasma MPA concentration. MPA-AUC_0-12h ≥45 μg.h/ml was best predicted by a single time point MPA concentration at C0.5, C2, C3, C4, and C8 (r²  = 0.516, 0.514, 0.540, 0.611, and 0.719, respectively), independent of dose, albumin, urine protein/creatinine ratio, and urinalysis. The MPA-C0.5 cutoff of 2.03 g/ml yielded the highest overall sensitivity of 85% and specificity of 88.2% in predicting MPA-AUC_0-12h ≥45 μg.h/ml. A single timepoint of plasma MPA-C0.5 ≥2.03 μg/ml may help guide EC-MPS adjustment to achieve adequate drug exposure. Further study of EC-MPS used to validate this cutoff is warranted.

Personalized Therapy for Mycophenolate: Consensus Report by the International Association of Therapeutic Drug Monitoring and Clinical Toxicology

ABSTRACT

When mycophenolic acid (MPA) was originally marketed for immunosuppressive therapy, fixed doses were recommended by the manufacturer. Awareness of the potential for a more personalized dosing has led to development of methods to estimate MPA area under the curve based on the measurement of drug concentrations in only a few samples. This approach is feasible in the clinical routine and has proven successful in terms of correlation with outcome. However, the search for superior correlates has continued, and numerous studies in search of biomarkers that could better predict the perfect dosage for the individual patient have been published. As it was considered timely for an updated and comprehensive presentation of consensus on the status for personalized treatment with MPA, this report was prepared following an initiative from members of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology (IATDMCT). Topics included are the criteria for analytics, methods to estimate exposure including pharmacometrics, the potential influence of pharmacogenetics, development of biomarkers, and the practical aspects of implementation of target concentration intervention. For selected topics with sufficient evidence, such as the application of limited sampling strategies for MPA area under the curve, graded recommendations on target ranges are presented. To provide a comprehensive review, this report also includes updates on the status of potential biomarkers including those which may be promising but with a low level of evidence. In view of the fact that there are very few new immunosuppressive drugs under development for the transplant field, it is likely that MPA will continue to be prescribed on a large scale in the upcoming years. Discontinuation of therapy due to adverse effects is relatively common, increasing the risk for late rejections, which may contribute to graft loss. Therefore, the continued search for innovative methods to better personalize MPA dosage is warranted.

Assessment of pharmacokinetic mycophenolic acid clearance models using Monte Carlo numerical analysis

Previously, we performed population pharmacokinetic analysis and indicated age, mycophenolate mofetil (MMF)/mycophenolic acid (MPA) daily dose, and presence of nifedipine in patient therapy as significant predictors of MPA apparent clearance (CL/F) variability. This study aimed to determine the reliability of previously published population pharmacokinetic models derived from similar studies. Furthermore, this study investigated correspondence between chosen population models from the literature.By means of the Monte Carlo simulation method, pharmacokinetic models from different studies are simulated and analysed in the range of standard deviations of measured system parameters as well as the range of observed model parameters taken from the comparison studies.The 1000 numerical simulations were performed for every analysed model in order to calculate the most possible MPA CL/F values according to the expected values from the performed experiment. Fitting our results with other models showed how the presence of nifedipine makes difference in MPA CL/F values.By testing the data from selected studies into our model, a similar range of expected CL/F values was obtained, which may confirm the validity of our model. The results of our population pharmacokinetic study are partially applicable in models by other researchers.

Establishment of a Liquid Chromatography-Tandem Mass Spectrometry Method for the Determination of Immunosuppressant Levels in the Peripheral Blood Mononuclear Cells of Chinese Renal Transplant Recipients

BACKGROUND

Monitoring immunosuppressant levels, such as mycophenolic acid (MPA), cyclosporin A (CsA), and tacrolimus (TAC), in peripheral blood mononuclear cells (PBMCs) could be useful in organ transplant patients administered individualized therapy. The authors developed a liquid chromatography-tandem mass spectrometry assay technique to simultaneously determine immunosuppressant levels in PBMCs and assess their pharmacokinetics in Chinese renal allograft recipients.

METHODS

PBMCs were isolated from the whole blood of 27 Chinese renal transplant patients using Ficoll-Paque Plus solution, and cell number was determined; acetonitrile treatment for protein precipitation, and gradient elution was performed on an Agilent Eclipse XDB-C18 column (3.5 μm, 2.1 × 100 mm) with mobile phase: water and methanol (containing 2 mM ammonium formate); flow rate: 0.3 mL·min.

RESULTS

The calibration curves of MPA, CsA, and TAC had a linear range (ng·mL): 0.098-39.2 (r = 0.9987), 0.255-102 (r = 0.9969), and 0.028-11.2 (r = 0.9993), respectively. The extraction effects, matrix effects, and mean relative recovery of these immunosuppressants were 70.4%-93.2%, 72.7%-96.5%, and 90.1%-112.4%, respectively. The within-day and between-day coefficients of variation were <15%. The AUC0-12 of MPA in PBMCs correlated well with those in plasma. The level of MPA, CsA, and TAC in PBMCs might be more stable during dosing interval.

CONCLUSIONS

The derived liquid chromatography-tandem mass spectrometry assay is suitable for simultaneously monitoring different immunosuppressants in PBMCs. Pharmacokinetic of MPA, CsA, and TAC displayed considerable interindividual variability. Intracellular monitoring of immunosuppressants may facilitate individualized therapy for renal allograft recipients.

Pharmacodynamic assessment of mycophenolic acid in resting and activated target cell population during the first year after renal transplantation

Aims

To explore the pharmacodynamics of mycophenolic acid (MPA) through inosine monophosphate dehydrogenase (IMPDH) capacity measurement and purine levels in peripheral blood mononuclear cells (PBMC) longitudinally during the first year after renal transplantation (TX).

Methods

PBMC were isolated from renal recipients 0–4 days prior to and 6–9 days, 5–7 weeks and 1 year after TX (before and 1.5 hours after dose). IMPDH capacity and purine (guanine and adenine) levels were measured in stimulated and nonstimulated PBMC.

Results

Twenty‐nine patients completed the follow‐up period, of whom 24 received MPA. In stimulated PBMC, the IMPDH capacity (pmol 10⁻⁶ cells min⁻¹) was median (interquartile range) 127 (95.8–147) before TX and thereafter 44.9 (19.2–93.2) predose and 12.1 (4.64–23.6) 1.5 hours postdose across study days after TX. The corresponding IMPDH capacity in nonstimulated PBMC was 5.71 (3.79–6.93), 3.35 (2.31–5.62) and 2.71 (1.38–4.08), respectively. Predose IMPDH capacity in nonstimulated PBMC increased with time, reaching pre‐TX values at 1 year. In stimulated PBMC, both purines were reduced before (median 39% reduction across days after TX) and after (69% reduction) dose compared to before TX. No alteration in the purine levels was observed in nonstimulated PBMC. Patients needing dose reductions during the first year had lower pre‐dose IMPDH capacity in nonstimulated PBMC (1.87 vs 3.00 pmol 10⁻⁶ cells min⁻¹, P = .049) at 6–9 days.

Conclusion

The inhibitory effect of MPA was stronger in stimulated PBMC. Nonstimulated PBMC became less sensitive to MPA during the first year after TX. Early IMPDH capacity appeared to be predictive of dose reductions.

Optimizing Mycophenolic Acid Exposure in Kidney Transplant Recipients: Time for Target Concentration Intervention

The immunosuppressive agent mycophenolate is used extensively in kidney transplantation, yet dosing strategy applied varies markedly from fixed dosing ("one-dose-fits-all"), to mycophenolic acid (MPA) trough concentration monitoring, to dose optimization to an MPA exposure target (as area under the concentration-time curve [MPA AUC0-12]). This relates in part to inconsistent results in prospective trials of concentration-controlled dosing (CCD). In this review, the totality of evidence supporting mycophenolate CCD is examined: pharmacological characteristics, observational data linking exposure to efficacy and toxicities, and randomized controlled trials of CCD, with attention to dose optimization method and exposure achieved. Fixed dosing of mycophenolate consistently leads to underexposure associated with rejection, as well as overexposure associated with toxicities. When CCD is driven by pharmacokinetic calculation to a target concentration (target concentration intervention), MPA exposure is successfully controlled and clinical benefits are seen. There remains a need for consensus on practical aspects of mycophenolate target concentration intervention in contemporary tacrolimus-containing regimens and future research to define maintenance phase exposure targets. However, given ongoing consequences of both overimmunosuppression and underimmunosuppression in kidney transplantation, impacting short- and long-term outcomes, these should be a priority. The imprecise "one-dose-fits-all" approach should be replaced by the clinically proven MPA target concentration strategy.

Identification of anti-flaviviral drugs with mosquitocidal and anti-Zika virus activity in Aedes aegypti

Zika virus (ZIKV), an emerging arbovirus belonging to the genus Flavivirus, is transmitted by Aedes mosquitoes. ZIKV infection can cause microcephaly of newborn babies and Guillain-Barré syndrome in adults. Because no licensed vaccine or specific antiviral treatment is available for ZIKV infection, the most commonly used approach to control the spread of ZIKV is suppression of the mosquito vector population. A novel proposed strategy to block arthropod virus (arbovirus) transmission is based on the chemical inhibition of virus infection in mosquitoes. However, only a few drugs and compounds have been tested with such properties. Here we present a comprehensive screen of 55 FDA-approved anti-flaviviral drugs for potential anti-ZIKV and mosquitocidal activity. Four drugs (auranofin, actinomycin D (Act-D), bortezomib and gemcitabine) were toxic to C6/36 cells, and two drugs (5-fluorouracil and mycophenolic acid (MPA)) significantly reduced ZIKV production in C6/36 cells at 2 μM and 0.5 μM, respectively. Three drugs (Act-D, cyclosporin A, ivermectin) exhibited a strong adulticidal activity, and six drugs (U18666A, retinoic acid p-hydroxyanilide (4-HPR), clotrimazole, bortezomib, MPA, imatinib mesylate) significantly suppressed ZIKV infection in mosquito midguts. Some of these FDA-approved drugs may have potential for use for the development of ZIKV transmission-blocking strategies.

Mycophenolic acid concentrations in peripheral blood mononuclear cells are associated with the incidence of rejection in renal transplant recipients

AIMS

Although therapeutic drug monitoring of plasma mycophenolic acid (MPA) concentrations has been recommended to individualize dosage in transplant recipients, little is known regarding lymphocyte concentrations of MPA, where MPA inhibits inosine monophosphate dehydrogenase (IMPDH). This study investigated the utility of measuring predose MPA concentrations in peripheral blood mononuclear cells (C_0C ) and predose IMPDH activity, as predictors of graft rejection in renal transplant recipients.

METHODS

Forty-eight patients commencing mycophenolate mofetil (1 g twice daily) in combination with tacrolimus and prednisolone were recruited. Blood was collected for determination of trough total (C_0P ) and unbound (C_0u ) plasma MPA concentrations. Peripheral blood mononuclear cells were isolated for determination of C_0C and IMPDH activity. The incidence of rejection within 2 days of sample collection was determined histologically and classified according to the Banff 2007 criteria.

RESULTS

There was no association between MPA C_0C and C_0P (r_s  = 0.28, P = 0.06), however, MPA C_0C were weakly correlated with MPA C_0u (r_s  = 0.42, P = 0.013). Multivariate analysis indicated that MPA C_0C was the only covariate independently associated with rejection (FDR-adjusted P = 0.033). The receiver operating characteristic area under the curve (AUC) for the prediction of severe rejection using MPA C_0C was 0.75 (P = 0.013), with 73% sensitivity and specificity at a C_0C threshold of 0.5 ng 10^-7 cells. However, predose IMPDH activity was not a predictor of rejection (P > 0.15).

CONCLUSIONS

MPA C_0C measurement within the early post-transplant period may be useful to facilitate early titration of MPA dosing to significantly reduce rejection.