How cyclosporin reduces mycophenolic acid exposure by 40% while other calcineurin inhibitors do not

Pharmacology of drugs used in autoimmune dermatopathies in cats and dogs: A narrative review

Immunosuppressive drugs are the mainstay of treatment for many feline and canine autoimmune skin diseases, either as monotherapy or in combination with other drugs. Treatment with these drugs is often lifelong and may have long-term consequences on the affected animal's overall quality-of-life. Clinicians need to understand the pharmacology of immunosuppressants in planning and executing the treatment regimen for the best possible clinical outcome, as well as reducing the risk of adverse effects. This review paper will focus on the mechanism of action, pharmacokinetics and pharmacodynamics, clinical uses and adverse effects of immunosuppressive drugs used to treat autoimmune dermatoses in cats and dogs. These include glucocorticoids, ciclosporin A, azathioprine, chlorambucil, mycophenolate mofetil, oclacitinib and Bruton's tyrosine kinase inhibitors.

Clinical validation of two volumetric absorptive microsampling devices to support home-based therapeutic drug monitoring of immunosuppression

AIMS

Dried blood volumetric absorptive microsamples (VAMS) may facilitate home-based sampling to enhance therapeutic drug monitoring after transplantation. This study aimed to clinically validate a liquid chromatography-tandem mass spectrometry assay using 2 VAMS devices with different sampling locations (Tasso-M20 for the upper arm and Mitra for the finger). Patient preferences were also evaluated.

METHODS

Clinical validation was performed for tacrolimus and mycophenolic acid by comparison of paired VAMS and venipuncture samples using Passing-Bablok regression and Bland-Altman analysis. Conversion of mycophenolic acid VAMS to serum concentrations was evaluated using haematocrit-dependent formulas and fixed correction factors defined a priori. Patients' perspectives, including useability, acceptability and feasibility, were also investigated using established questionnaires.

RESULTS

Paired samples (n = 50) were collected from 25 kidney transplant recipients. Differences for tacrolimus whole-blood concentration were within ±20% for 86 and 88% of samples from the upper arm and fingerstick, respectively. Using correction factors of 1.3 for the upper-arm and 1.47 for finger-prick samples, 84 and 76% of the paired samples, respectively, were within ±20% for mycophenolic acid serum concentration. Patient experience surveys demonstrated limited pain and acceptable useability of the upper-arm device.

CONCLUSIONS

Tacrolimus and mycophenolic acid can be measured using 2 common VAMS devices with similar analytical performance. Patients are supportive of home-based monitoring with a preference for the Tasso-M20 device.

Management of kidney transplant recipients for primary care practitioners

Patients with kidney transplants have a significant co-morbidity index, due to a high number of pre-existing conditions and use of immunosuppression medications. These patients are at higher risk of developing conditions such as hypertension, dyslipidemia, post-transplant diabetes, cardiovascular events, and anemia. Moreover, they are particularly susceptible to infections such as urinary tract infections or pyelonephritis, cancers, and gastrointestinal complications such as diarrhea, which in turn may be attributed to medication adverse effects or infectious causes. Along with these concerns, meticulous management of electrolytes and allograft function is essential. Prior to prescribing any new medications, it is imperative to exercise caution in identifying potential interactions with immunosuppression drugs. This review aims to equip primary care practitioners to address these complex issues and appropriate methods of delivering care to this rapidly growing highly susceptible group.

Therapeutic drug monitoring of mycophenolic acid and clinical outcomes of lupus nephritis: a systematic review and meta-analysis

INTRODUCTION

Mycophenolic acid (MPA) is a primary immunosuppressive agent used in the treatment of lupus nephritis (LN). While therapeutic drug monitoring (TDM) of MPA is well established in organ transplantation, its role in LN treatment remains uncertain. Our objective was to review and summarise current knowledge on TDM of MPA in the LN treatment.

METHODS

A systematic search was conducted in the online databases, specifically targeted patients diagnosed with LN receiving MPA treatment. The included studies had to report both MPA pharmacokinetic parameters and renal outcomes. A random-effects model meta-analysis was conducted to assess the relationship between clinical responses and MPA pharmacokinetics.

RESULTS

A total of 1507 studies were initially screened, resulting in the inclusion of 16 studies for meta-analysis, encompassing 433 patients. The response group exhibited significantly higher MPA area under the concentration-time curve (AUC) compared with the non-response group (51.44±21.73 mg·h/L vs 30.30±16.24 mg·h/L). The weighted mean difference (WMD) of MPA-AUC between responders and non-responders was 16.83 mg·h/L (95% CI 10.59 to 23.06; p<0.001). Similarly, trough concentration (C0) of MPA showed a strong association with renal response, evidenced by C0 values of 2.50±1.73 mg/L in the response group vs 1.51±1.33 mg/L in the non-response group (WMD 1.37 mg/L; 95% CI 0.77 to 1.97; p<0.001). There was no significant relationship identified between MPA-AUC and adverse events.

CONCLUSION

This meta-analysis emphasised the meaningful correlation between MPA AUC and C0 with renal response in LN treatment. Randomised controlled trials are necessary to validate this approach and determine its superiority over fixed dosing in the context of LN treatment.

Drug-Drug Interaction Between Cannabidiol, Cyclosporine, and Mycophenolate Mofetil: A Case Report

Kidney transplantation remains the optimal therapy for many patients with end-stage kidney disease (ESKD). Chronic pain is one of the most common and distressing symptoms among patients with ESKD, and its treatment is a complex and challenging task to accomplish. The benefits of cannabidiol (CBD) in chronic pain treatment have been reported recently. Cannabidiol is metabolized by cytochrome P450, mainly CYP3A4 and CYP2C19, and can also undergo direct conjugation via UDP-glucuronosyltransferase enzymes, with a growing body of evidence suggesting it is also a potent inhibitor or inducer of these pathways. Cannabidiol was also found to be a potent inhibitor of carboxylesterases in vitro. Because cytochrome P450 enzymes and carboxylesterases are also responsible for the clearance and activation of immunosuppressants, respectively, drug-drug interactions are likely to occur. Here, we report a pharmacokinetic drug interaction between CBD and cyclosporine and mycophenolate mofetil in a patient with ESKD with a kidney transplantation. It is thus crucial to take into account these interactions and monitor drug levels to avoid drug toxicity or a lack of efficacy. This study is in accordance with the guidelines of the Declaration of Helsinki and the Declaration of Istanbul.

Management of Lupus Nephritis: New Treatments and Updated Guidelines

Management of lupus nephritis has evolved considerably over the past years. Here, we provide a comprehensive review of clinical trials that form the basis for the Kidney Disease: Improving Global Outcomes and EULAR/ERA-EDTA updated guidelines and present day trials that will change the landscape of lupus nephritis therapy in years to come. In addition, we highlight the issues related to cost of therapy, resistant disease, and downstream adverse effects of specific therapies.

Mycophenolate Mofetil Dose Adjustment in Pediatric Kidney Transplant Recipients

BACKGROUND

The Immunosuppressant Bayesian Dose Adjustment web site aids clinicians and pharmacologists involved in the care of transplant recipients; it proposes dose adjustments based on the estimated area under the concentration-time curve (AUCs). Three concentrations (T 20 min , T 1 h , and T 3 h ) are sufficient to estimate mycophenolic acid (MPA) AUC 0-12 h in pediatric kidney transplant recipients. This study investigates mycophenolate mofetil (MMF) doses and MPA AUC values in pediatric kidney transplant recipients, and target exposure attainment when the proposed doses were followed, through a large-scale analysis of the data set collated since the inception of the Immunosuppressant Bayesian Dose Adjustment web site.

METHODS

In this study, 4051 MMF dose adjustment requests, corresponding to 1051 patients aged 0-18 years, were retrospectively analyzed. AUC calculations were performed in the back office of the Immunosuppressant Bayesian Dose Adjustment using published Bayesian and population pharmacokinetic models.

RESULTS

The first AUC request was posted >12 months posttransplantation for 41% of patients. Overall, only 50% had the first MPA AUC 0-12 h within the recommended 30-60 mg.h/L range. When the proposed dose was not followed, the proportion of patients with an AUC in the therapeutic range for MMF with cyclosporine or tacrolimus at the subsequent request was lower (40% and 45%, respectively) than when it was followed (58% and 60%, respectively): P = 0.08 and 0.006, respectively. Furthermore, 3 months posttransplantation, the dispersion of AUC values was often lower at the second visit when the proposed doses were followed, namely, P = 0.03, 0.003, and 0.07 in the 4 months-1 year, and beyond 1 year with <6-month or >6-month periods between both visits, respectively.

CONCLUSIONS

Owing to extreme interindividual variability in MPA exposure, MMF dose adjustment is necessary; it is efficient at reducing such variability when based on MPA AUC.

Significant Effects of Renal Function on Mycophenolic Acid Total Clearance in Pediatric Kidney Transplant Recipients with Population Pharmacokinetic Modeling

BACKGROUND AND OBJECTIVES

Mycophenolic acid (MPA) is an immunosuppressant commonly prescribed in pediatric kidney transplantation to prevent graft rejection. Large variabilities in MPA plasma exposures have been observed in this population, which could result in severe adverse effects. The majority of the MPA pharmacokinetic data have been reported in adult populations, whereas information in pediatric patients is still very limited. The objective of this study was to establish a novel, nonlinear mixed-effects model for MPA and investigate the clinical variables affecting MPA population pharmacokinetics in pediatric kidney transplant recipients.

METHODS

Data were collected retrospectively from pediatric kidney transplant patients (≤ 18 years when MPA concentrations were initially collected; on oral administration of mycophenolate mofetil) in Calgary, Alberta, Canada. Nonlinear mixed-effect modeling was conducted using stochastic approximation expectation-maximization in Monolix 2021R2 (Lixoft SAS, France) to determine population pharmacokinetic estimates, interindividual variabilities, and interoccasional variabilities. Covariate models were constructed using the Model Proposal function in Monolix in conjunction with a systematic stepwise inclusion/elimination protocol. The best model was selected based on objective function values, relative standard errors, goodness-of-fit plots, prediction-corrected visual predictive checks, and numerical predictive checks.

RESULTS

A total of 50 pediatric kidney transplant patients (25 female) with 219 MPA plasma concentration-time profiles were included. The average age (± standard deviation) and posttransplant time for the sample population were 12.8 ± 4.8 years and 762 ± 1160 days, respectively. The majority of study subjects (i.e., > 85% based on all occasions) were co-administered tacrolimus. A two-compartment, first-order absorption with lag time and linear elimination structural model with lognormal distributed proportional residual errors best described the MPA concentration-time data. The absorption rate constant (2.52 h-1 or 0.042 min-1), lag time (0.166 h or 9.96 min), volumes of distributions of the central (22.8 L) and peripheral (216 L) compartments, and intercompartment clearance (17.6 L h-1 or 0.293 L min-1) were consistent with literature values; whereas total MPA clearance (0.72 L h-1 or 0.012 L min-1) was relatively reduced, likely due to the general lack of cyclosporine interactions and the stabilized graft functions from significantly longer posttransplant time in our sample population. Of the clinical variables tested, only estimated glomerular filtration rate (eGFR) was identified a significant covariate affecting total MPA clearance with a positive, exponential relationship. The final population pharmacokinetic model was successfully evaluated/validated using a variety of complementary methods.

CONCLUSION

We have successfully constructed and validated a novel population pharmacokinetic model of MPA in pediatric kidney transplant patients. A positive, nonlinear relationship between eGFR and total MPA clearance identified in our model is likely attributed to multiple concurrent mechanisms, which warrant further systematic investigations.

KDOQI US Commentary on the 2021 KDIGO Clinical Practice Guideline for the Management of Glomerular Diseases

The KDIGO 2021 Clinical Practice Guideline for the Management of Glomerular Diseases represents the first update to this set of recommendations since the initial set of KDIGO guideline recommendations was published in 2012. The pace of growth in our molecular understanding of glomerular disease has quickened and a number of newer immunosuppressive and targeted therapies have been introduced since the original set of guideline recommendations, making such an update necessary. Despite these updates, many areas of controversy remain. In addition, further updates since the publication of KDIGO 2021 have occurred which this guideline does not encompass. With this commentary, the KDOQI work group has generated a chapter-by-chapter companion opinion article that provides commentary specific to the implementation of the KDIGO 2021 guideline in the United States.

Clinical Evidence on the Purported Pharmacokinetic Interactions between Corticosteroids and Mycophenolic Acid

Corticosteroids (steroids) are commonly used concurrently with mycophenolic acid (MPA) as the first-line immunosuppression therapy for the prevention of rejection in solid organ transplantations. Steroids are also commonly administered with MPA in various autoimmune disorders such as systemic lupus erythematosus and idiopathic nephrotic syndrome. Despite various review articles having suggested the presence of pharmacokinetic interactions between MPA and steroids, definitive data have not yet been demonstrated. The aim of this Current Opinion is to critically evaluate the available clinical data and propose the optimal study design for characterising the MPA-steroid pharmacokinetic interactions. The PubMed and Embase databases were searched for relevant clinical articles in English as of September 29, 2022, where a total of 8 papers have been identified as supporting and 22 as non-supporting the purported drug interaction. To objectively evaluate the data, novel assessment criteria to effectively diagnose the interaction based on known MPA pharmacology were formulated, including the availability of independent control groups, prednisolone concentrations, MPA metabolite data, unbound MPA concentrations, and the characterisations of entero-hepatic recirculation and MPA renal clearance. Overall, the majority of the identified corticosteroid data were pertaining to prednisone or prednisolone. Our assessment indicated that no conclusive mechanistic data supporting the interaction are available in the current clinical literature, and further studies are required to quantify the effects/mechanisms of steroid-tapering or withdrawal on MPA pharmacokinetics. This current opinion provides justification for further translational investigations, as this particular drug interaction has the potential to exert significant adverse outcomes in patients prescribed MPA.

Adult liver transplantation for the advanced clinical practitioner: an overview

Liver transplantation (LT) is a major surgical undertaking but, in a carefully selected population, it provides excellent outcomes in terms of prolongation of life and improvements in quality of life. This article outlines the processes of referral, assessment, operative course and post-transplant complications of LT, in the UK context. Specific consideration is also given to immunosuppressive medications and considerations around their prescription. The role of the advanced clinical practitioner (ACP) in primary or secondary care may focus on identifying potential candidates for transplantation and ensuring timely discussion and referral. Thus, a familiarity with eligibility criteria, and where to access this information, is important for all ACPs. Additionally, the increasing numbers of transplants performed in the UK mean that there is a large population of post-transplant patients in the wider community. These patients may present to healthcare services with a variety of issues relating to their LT, where early recognition and treatment has the potential to have major impacts on patient, or graft, function and longevity. Due to this, early discussions with specialist transplant centres is advised.

BK Virus Nephropathy in Kidney Transplantation: A State-of-the-Art Review

BK virus maintains a latent infection that is ubiquitous in humans. It has a propensity for reactivation in the setting of a dysfunctional cellular immune response and is frequently encountered in kidney transplant recipients. Screening for the virus has been effective in preventing progression to nephropathy and graft loss. However, it can be a diagnostic and therapeutic challenge. In this in-depth state-of-the-art review, we will discuss the history of the virus, virology, epidemiology, cellular response, pathogenesis, methods of screening and diagnosis, evidence-based treatment strategies, and upcoming therapeutics, along with the issue of re-transplantation in patients.

Voclosporin: a novel calcineurin inhibitor for the treatment of lupus nephritis

INTRODUCTION

Lupus nephritis (LN) is a severe manifestation of systemic lupus erythematosus. Standard-of-care immunosuppressive therapies achieve poor complete renal response (CRR) rates, with considerable toxicity. This article reviews voclosporin, a novel oral calcineurin inhibitor (CNI) approved for treatment of adults with active LN by the US Food and Drug Administration (the FDA) in January 2021.

AREAS COVERED

: This review summarizes the chemical properties, pharmacokinetics, and pharmacodynamics of voclosporin, and its efficacy and safety in LN, based on literature review covering PubMed searches, manufacturers' websites and documents produced by the FDA.

EXPERT OPINION

: Voclosporin is a CNI with a consistent pharmacokinetic-pharmacodynamic relationship resulting from enhanced calcineurin binding and reduced drug and metabolite load. This profile permits therapeutic efficacy in LN at a dose associated with relatively low calcineurin inhibition, and therefore a potentially improved safety profile. Pivotal trials demonstrated a significant benefit of adding voclosporin to standard therapy, with rapid reduction in proteinuria, and a clinically meaningful and significantly higher CRR rate at 1 year. At approved doses for LN, potential advantages of voclosporin versus historical experience with CNIs include lack of need for therapeutic drug monitoring, benign metabolic, lipid and electrolyte profile, and no impact on mycophenolate mofetil levels.

Reduced Enterohepatic Recirculation of Mycophenolate and Lower Blood Concentrations are Associated with the Stool Bacterial Microbiome After Hematopoietic Cell Transplantation

BACKGROUND

Mycophenolate mofetil (MMF) is an important immunosuppressant used after allogeneic hematopoietic cell transplant (HCT). MMF has a narrow therapeutic index and blood concentrations of mycophenolic acid (MPA), the active component of MMF, are highly variable. Low MPA concentrations are associated with risk of graft vs host disease (GvHD) while high concentrations are associated with toxicity. Reasons for variability are not well known and may be due, at least in part, to the presence of β-glucuronidase producing bacteria in the gastrointestinal tract which enhance MPA enterohepatic recirculation (EHR) by transforming MPA metabolites formed in the liver back to MPA.

OBJECTIVE

To determine if individuals with high MPA EHR have a greater abundance of β-glucuronidase producing bacteria in their stool and higher MPA concentrations relative to those with low EHR.

STUDY DESIGN

We conducted a pharmacomicrobiomics study in 20 adult HCT recipients receiving a myeloablative or reduced intensity preparative regimen. Participants received MMF 1g IV every 8 hours with tacrolimus. Intensive pharmacokinetic sampling of mycophenolate was conducted before hospital discharge. Total MPA, MPA glucuronide (MPAG) and acylMPAG were measured. EHR was defined as a ratio of MPA area under the concentration-versus-time curve (AUC)_4-8 to MPA AUC_0-8. Differences in stool microbiome diversity and composition, determined by shotgun metagenomic sequencing, were compared above and below the median EHR (22%, range 5-44%).

RESULTS

Median EHR was 12% and 29% in the low and high EHR groups, respectively. MPA troughs, MPA AUC_4-8 and acylMPAG AUC_4-8/AUC_0-8, were greater in the high EHR group vs low EHR group [1.53 vs 0.28 mcg/mL, p = 0.0001], [7.33 vs 1.79 hr*mcg/mL, p = 0.0003] and [0.33 vs 0.24 hr*mcg/mL, p = 0.0007], respectively. MPA AUC_0-8 was greater in the high EHR than the low EHR group and trended towards significance [22.8 vs. 15.3 hr*mcg/mL, p=0.06]. Bacteroides vulgatus, stercoris and thetaiotaomicron were 1.2-2.4 times more abundant (p=0.039, 0.024, 0.046, respectively) in the high EHR group. MPA EHR was positively correlated with B. vulgatus (⍴=0.58, p≤0.01) and B. thetaiotaomicron (⍴=0.46, p<0.05) and negatively correlated with Blautia hydrogenotrophica (⍴=-0.53, p<0.05). Therapeutic MPA troughs were achieved in 80% of patients in the high EHR group and 0% in the low EHR. There was a trend towards differences in MPA AUC_0-8 and MPA C_ss mcg/mL in high vs. low EHR groups (p=0.06).

CONCLUSION

MPA EHR was variable. Patients with high MPA EHR had greater abundance of Bacteroides species in stool and higher MPA exposure than patients with low MPA EHR. Bacteroides may therefore be protective from poor outcomes such as graft vs host disease but in others it may increase the risk of MPA adverse effects. These data need to be confirmed and studied after oral MMF.

Significant Correlations between p-Cresol Sulfate and Mycophenolic Acid Plasma Concentrations in Adult Kidney Transplant Recipients

BACKGROUND AND OBJECTIVES

Mycophenolic acid (MPA) is a commonly prescribed life-long immunosuppressant for kidney transplant recipients. The frequently observed large variations in MPA plasma exposure may lead to severe adverse outcomes; therefore, characterizations of contributing factors can potentially improve the precision dosing of MPA. Our group recently reported the potent inhibitory effects of p-cresol (a protein-bound uremic toxin that can be accumulated in kidney transplant patients) on the hepatic metabolism of MPA in human in vitro models. Based on these data, the hypothesis for this clinical investigation was that a direct correlation between p-cresol and MPA plasma exposure should be evident in adult kidney transplant recipients.

METHODS

Using a prospective and observational approach, adult kidney transplant recipients within the first year after transplant on oral mycophenolate mofetil (with tacrolimus ± prednisone) were screened for recruitment. The exclusion criteria were cold ischemia time > 30 h, malignancy, pregnancy, severe renal dysfunction (i.e., estimated glomerular filtration rate, eGFR, < 10 mL/min/1.73 m²), active graft rejection, or MPA intolerance. Patients' demographic and biochemistry data were collected. Total and free plasma concentrations of MPA, MPA glucuronide (MPAG), and total p-cresol sulfate (the predominant, quantifiable form of p-cresol in the plasma) were quantified using validated assays. Correlational and categorical analyses were performed using GraphPad Prism.

RESULTS

Forty patients (11 females) were included: donor type (living/deceased: 20/20), induction regimen (basiliximab/thymoglobulin/basiliximab followed by thymoglobulin: 35/3/2), post-transplant time (74 ± 60 days, mean ± standard deviation), age (53.7 ± 12.4 years), bodyweight (79.8 ± 18.5 kg), eGFR (51.9 ± 18.0 mL/min/1.73 m²), serum albumin (3.6 ± 0.5 g/dL), prednisone dose (18.5 ± 13.2 mg, n = 33), and tacrolimus trough concentration (9.4 ± 2.4 µg/L). Based on Spearman analysis, significant control correlations supporting the validity of our dataset were observed between total MPA trough concentration (C₀) and total MPAG C₀ (correlation coefficient [R] = 0.39), ratio of total MPAG C₀-to-total MPA C₀ and post-transplant time (R = - 0.56), total MPAG C₀ and eGFR (R = - 0.35), and p-cresol sulfate concentration and eGFR (R = - 0.70). Our primary analysis indicated the novel observation that total MPA C₀ (R = 0.39), daily dose-normalized total MPA C₀ (R = 0.32), and bodyweight-normalized total MPA C₀ (R = 0.32) were significantly correlated with plasma p-cresol sulfate concentrations. Consistently, patients categorized with elevated p-cresol sulfate concentrations (i.e., ≥ median of 3.2 µg/mL) also exhibited increased total MPA C₀ (by 57 % vs those below median), daily dose-normalized total MPA C₀ (by 89 %), and bodyweight-normalized total MPA C₀ (by 62 %). Our secondary analyses with MPA metabolites, unbound concentrations, free fractions, and MPA metabolite ratios supported additional potential interacting mechanisms.

CONCLUSION

We have identified a novel, positive association between p-cresol sulfate exposure and total MPA C₀ in adult kidney transplant recipients, which is supported by published mechanistic in vitro data. Our findings confirm a potential role of p-cresol as a significant clinical variable affecting the pharmacokinetics of MPA. These data also provide the justifications for conducting subsequent full-scale pharmacokinetic-pharmacodynamic studies to further characterize the cause-effect relationships of this interaction, which could also rule out potential confounding variables not adequately controlled in this correlational study.

The global burden of heterogeneity of lupus erythematosus interventional trials

To explore bias in lupus erythematosus (LE) randomized clinical trials (RCTs) and to help the development of benchmarks for future trials and management. We searched systematically three databases and three registries to summarize the interventional randomized clinical trials (RCTs) and identify factors associated with participant loss. Trials which examined pharmacological interventions with control group were included and a meta-analysis was carried out by using fixed and random effects models to calculate risk ratio of participant loss in the intervention and control groups. A total of 481 trials with 68,582 participants met our inclusion criteria, organ specific interventional studies along with trials that address quality of life attributes and geopolitical disparities are missing or lagging behind. 90 trials were involved in the meta-analyses, the withdrawal ratio between intervention and control groups was distinctly influenced by national income of the trial-conducted country. In high income countries, the withdrawal ratio was relatively constant, while for trials conducted in low and middle income countries, the results were altered by trial registration, year of start, number of centers, number of participants, and primary outcome identification. Moreover, the comparability of participants was also worrying, trial location and registration status altered basal participant adherence. Our study reveals the unexpectedly huge heterogeneity brought by national income and trial registration in lupus RCTs worldwide. To maintain the fundamental repeatability and referenceability of LE RCTs, rigorously designed single-country trials with diverse inclusion criteria are needed.

Recent lessons learned from population pharmacokinetic studies of mycophenolic acid: physiological, genomic, and drug interactions leading to the prediction of drug effects

INTRODUCTION

Mycophenolic acid (MPA) is a widely used immunosuppressant in transplantation and autoimmune disease. Highly variable pharmacokinetics have been observed with MPA, but the exact mechanisms remain largely unknown.

AREAS COVERED

The current review provided a critical, comprehensive update of recently published population pharmacokinetic/dynamic models of MPA (n=16 papers identified from PubMed and Embase, inclusive from January 2017 to August 2021), with specific emphases on the intrinsic and extrinsic factors influencing the pharmacology of MPA. The significance of the identified covariates, potential mechanisms, and comparisons to historical literature have been provided.

EXPERT OPINION

While select covariates affecting the population pharmacokinetics of MPA are consistently observed and mechanistically supported, some variables have not been regularly reported and/or lacked mechanistic explanation. Very few pharmacodynamic models were available, pointing to the need to extrapolate pharmacokinetic findings. Ideal models of MPA should consist of: i) utilizing optimal sampling points to allow the characterizations of absorption, re-absorption, and elimination phases; ii) characterizing unbound/total MPA, MPA metabolites, plasma/urinary concentrations, and genetic polymorphisms to facilitate mechanistic interpretations; and iii) incorporating actual outcomes and pharmacodynamic data to establish clinical relevance. We anticipate the field will continue to expand in the next 5 to 10 years.