The impact of tacrolimus exposure on extrarenal adverse effects in adult renal transplant recipients

Rituximab versus tacrolimus as corticosteroid-sparing therapy for children with steroid-dependent nephrotic syndrome: A systematic review and meta-analysis of randomized and nonrandomized controlled trials

Objectives

Prolonged use of corticosteroids induced complicated course in children with steroid-dependent nephrotic syndrome (SDNS), and the use of tacrolimus, a first-line alternative calcineurin inhibitor (CNI) agent was related to some unwanted adverse effects. Rituximab, a second alternative treatment has been proven to reliably reduce the number of relapses within 12 months with minimal adverse effects.

Materials and Methods

Our review follows Preferred Reporting Items for Systematic Review and Meta-analysis guidelines. All the databases were derived from MEDLINE, Proquest, EBSCOhost, Wiley, and Google Scholar within the past 11 years. The risk of bias was evaluated using the Revised Cochrane Risk of Bias Tool for Randomized Trials (RoB 2) and Risk of Bias in Non-Randomized Studies of Interventions. Meta-analysis used Review Manager (version 5.4) with a random effect model to obtain a pooled mean difference (MD) and odds ratio with 95% confidence intervals (CIs).

Results

Four studies were included based on our eligibility criteria, and only three were included in the quantitative analysis. Three studies had low and one study had a moderate risk of bias. Pooled data results indicated that Rituximab was superior to tacrolimus in reducing the number of patients with 1-2 relapses (MD = 0.44, [95% CI: 0.21-0.91]) and had higher eGFR values (MD = 6.67; [CI - 2.92-10.61]). However, Rituximab showed insignificant superiority compared to tacrolimus in reducing the number of patients with 3 relapses, sustained remission, cumulative steroid use, serum cholesterol, and serum albumin concentrations.

Conclusion

Rituximab exhibits more advantages in treating SDNS compared to tacrolimus, although the treatment options are highly individualized. Both regimens must also be weighed against their potential side effects to achieve a better overall health status.

Evaluation of Tacrolimus' Adverse Effects on Zebrafish in Larval and Adult Stages by Using Multiple Physiological and Behavioral Endpoints

Tacrolimus (FK506) is a common immunosuppressant that is used in organ transplantation. However, despite its importance in medical applications, it is prone to adverse side effects. While some studies have demonstrated its toxicities to humans and various animal models, very few studies have addressed this issue in aquatic organisms, especially zebrafish. Here, we assessed the adverse effects of acute and chronic exposure to tacrolimus in relatively low doses in zebrafish in both larval and adult stages, respectively. Based on the results, although tacrolimus did not cause any cardiotoxicity and respiratory toxicity toward zebrafish larvae, it affected their locomotor activity performance in light-dark locomotion tests. Meanwhile, tacrolimus was also found to slightly affect the behavior performance, shoaling formation, circadian rhythm locomotor activity, and color preference of adult zebrafish in a dose-dependent manner. In addition, alterations in the cognitive performance of the fish were also displayed by the treated fish, indicated by a loss of short-term memory. To help elucidate the toxicity mechanism of tacrolimus, molecular docking was conducted to calculate the strength of the binding interaction between tacrolimus to human FKBP12. The results showed a relatively normal binding affinity, indicating that this interaction might only partly contribute to the observed alterations. Nevertheless, the current research could help clinicians and researchers to further understand the toxicology of tacrolimus, especially to zebrafish, thus highlighting the importance of considering the toxicity of tacrolimus prior to its usage.

The association between tacrolimus exposure and tremor, headache and insomnia in adult kidney transplant recipients: A systematic review

PURPOSE

Tremor, headache and insomnia have been linked to the immunosuppressant, tacrolimus. The aim of this systematic review was to determine if there is a correlation between tacrolimus exposure and new-onset tremor, headache and insomnia experienced by adult kidney transplant recipients.

METHODS

PubMed, Embase, Cochrane Library and CINAHL databases were searched up to 11 April 2023 for published studies which reported on tacrolimus exposure in adult kidney transplant recipients, alongside information on treatment-emergent neurologic manifestations, including tremor, headache and insomnia. Review articles, case studies, conference abstracts and articles not published in English in peer-reviewed journals were excluded. The Physiotherapy Evidence Database and Newcastle-Ottawa Quality Assessment Scales were used to assess risk of bias. Extracted data was analysed via a narrative synthesis.

RESULTS

Eighteen studies involving 4030 patients in total were included in the final analysis. These comprised five randomised control trials and thirteen observational studies. Studies failed to find significant association between tacrolimus trough concentrations in whole blood and the incidence of neurologic side effects such as tremor, headache and insomnia; however, in one study the incidence of toxicity requiring a dose reduction increased with increasing, supratherapeutic targeted levels. Females, especially Black females, and older age were positively associated with the prevalence of neurologic adverse effects. Results were conflicting regarding whether extended-release formulations were associated with fewer neurologic complications than immediate-release formulations.

CONCLUSION

The varied study designs and criteria for reporting tremor, headache and insomnia impacted on the quality of the data for exploring the relationship between tacrolimus exposure and the onset of neurologic manifestations experienced after kidney transplantation. Studies that examine defined neurologic complications as the primary outcome, and that consider novel markers of tacrolimus exposure while assessing the potential contribution of multiple covariate factors, are required.

Bayesian optimization of tacrolimus exposure in stable kidney transplant patients

STUDY OBJECTIVE

The objective was to compare tacrolimus AUC0-12 determined by Non-Compartmental Analysis (NCA) using intensive sampling to Maximum a Posteriori-Bayesian (MAP-Bayesian) estimates from robust (n = 9 samples/subject) and sparse (n = 2 samples/subject) sampling in 67 stable KTRs and a validation group of similar patients.

DESIGN

This open-label, prospective, single center 12-h PK study included nine serial samples collected in KTRs to determine steady-state NCA tacrolimus AUC0-12 .

SETTING

This study was conducted at a single site within a large, urban hospital in the western New York area.

PATIENTS

This study described tacrolimus pharmacokinetics in stable kidney transplant recipients on maintenance tacrolimus therapy.

INTERVENTION

Robust and sparse AUC0-12 estimates by a MAP-Bayesian approach were obtained using the Advanced Dosing Solutions (AdDS) and ADAPT5 freeware. Limited sampling strategies were evaluated using the original population PK model (n = 67), which was also assessed using a validation group (n = 15). AUC0-12 agreement was tested by paired t-tests with intraclass correlation coefficient (ICC) and Bland Altman analysis.

MEASUREMENTS AND MAIN RESULTS

A total of 35 Black and 32 White stable KTRs (estimated glomerular filtration rate [eGFR] = 55.2 ± 15.7 mL/min/1.73m2 ) received the tacrolimus dose of 3.4 ± 1.7 mg/study with troughs of 6.8 ± 1.8 ng/mL. The NCA-AUC0-12 was 123.8 ± 33.6 μg·h/L compared to MAP-Bayesian estimates for Robust-AUC0-12 of 124.7 ± 33.3 μg·h/L and optimal 2-specimen Sparse-AUC0-12 of 119.7 ± 32.7 μg·h/L for the training group. Comparison of Robust-AUC0-12 to NCA-AUC0-12 had an ICC of 0.96 (p = 0.99) while comparison of Robust-AUC0-12 to Sparse-AUC0-12 using Pre-dose trough [C(t0h )] and 1 h [C(t1h )] resulted in an ICC of 0.93 (p = 0.014). In the validation group, 5 Black and 10 White KTRs (eGFR = 56.4 ± 16.8 mL/min/1.73m2 ) received a mean tacrolimus dose of 1.9 ± 1.2 mg/study with a trough of 6.0 ± 1.7 ng/mL. The validation group's NCA-AUC0-12 (88.4 ± 33.1 μg·h/L) was comparable to Robust-AUC0-12 (85.1 ± 33.8 μg·h/L, ICC = 0.93; p = 0.12) and Sparse-AUC0-12 determined from C(t0h ) and C(t4h ) (86.7 ± 33.9 μg·h/L, ICC = 0.91; p = 0.61).

CONCLUSION

MAP-Bayesian estimation for patient-specific AUC0-12 using sparse, two-specimen sampling is comparable to NCA and may enhance tacrolimus TDM in stable KTRs.

The Association of Tacrolimus Formulation on Cerebral Blood Flow and Cognitive Function

Calcineurin inhibitors are inherent vasoconstrictors. Cerebral vasoconstriction can reduce cerebral blood flow (CBF), and negatively impact cerebrovascular response (CVR) to exercise, and cognitive function. The once-daily extended-release (LCP) tacrolimus has fewer side effects than the immediate-release (IR) tacrolimus. The role of calcineurin inhibitors on CBF and the impact of specific formulations of tacrolimus on CBF, CVR, and cognitive function are unknown. In this pilot study, we evaluated whether changing from IR tacrolimus to LCP tacrolimus modulates CBF, CVR, or cognitive function in kidney transplant (KT) recipients.

Methods

We randomized (2:1) 30 stable KT recipients on IR tacrolimus to intervention (switch to LCP tacrolimus) and control (continue IR tacrolimus) arms. We measured CBF, CVR, and cognitive function at baseline and at 12 wk. We used ANCOVA to evaluate changes in outcome variables, with baseline values and study arm as covariates. We used descriptive statistics with mean changes in outcome variables to compare the 2 groups.

Results

Participants were 51 ± 13 y old. There was no difference in plasma tacrolimus levels at baseline and at 12 wk in the 2 arms. The changes in CBF, resting middle cerebral artery velocity, CVR, and cognitive function were more favorable in the intervention arm than in the control group.

Conclusions

Changing IR tacrolimus to LCP tacrolimus may improve CBF, cerebrovascular dynamics, and cognitive function in KT recipients. Larger studies are needed to confirm these results.

Immunogenicity of Recombinant Adeno-Associated Virus (AAV) Vectors for Gene Transfer

Recombinant adeno-associated viruses (AAVs) have emerged as promising gene delivery vehicles resulting in three US Food and Drug Administration (FDA) and one European Medicines Agency (EMA)-approved AAV-based gene therapies. Despite being a leading platform for therapeutic gene transfer in several clinical trials, host immune responses against the AAV vector and transgene have hampered their widespread application. Multiple factors, including vector design, dose, and route of administration, contribute to the overall immunogenicity of AAVs. The immune responses against the AAV capsid and transgene involve an initial innate sensing. The innate immune response subsequently triggers an adaptive immune response to elicit a robust and specific response against the AAV vector. AAV gene therapy clinical trials and preclinical studies provide important information about the immune-mediated toxicities associated with AAV, yet studies suggest preclinical models fail to precisely predict the outcome of gene delivery in humans. This review discusses the contribution of the innate and adaptive immune response against AAVs, highlighting the challenges and potential strategies to mitigate these responses, thereby enhancing the therapeutic potential of AAV gene therapy.

Machine Learning-Based Prediction Method for Tremors Induced by Tacrolimus in the Treatment of Nephrotic Syndrome

Tremors have been reported even with a low dose of tacrolimus in patients with nephrotic syndrome and are responsible for hampering the day-to-day work of young active patients with nephrotic syndrome. This study proposes a neural network model based on seven variables to predict the development of tremors following tacrolimus. The sensitivity and specificity of this algorithm are high. A total of 252 patients were included in this study, out of which 39 (15.5%) experienced tremors, 181 patients (including 32 patients who experienced tremors) were randomly assigned to a training dataset, and the remaining were assigned to an external validation set. We used a recursive feature elimination algorithm to train the training dataset, in turn, through 10-fold cross-validation. The classification performance of the classifer was then used as the evaluation criterion for these subsets to find the subset of optimal features. A neural network was used as a classification algorithm to accurately predict tremors using the subset of optimal features. This model was subsequently tested in the validation dataset. The subset of optimal features contained seven variables (creatinine, D-dimer, total protein, calcium ion, platelet distribution width, serum kalium, and fibrinogen), and the highest accuracy obtained was 0.8288. The neural network model based on these seven variables obtained an area under the curve (AUC) value of 0.9726, an accuracy of 0.9345, a sensitivity of 0.9712, and a specificity of 0.7586 in the training set. Meanwhile, the external validation achieved an accuracy of 0.8214, a sensitivity of 0.8378, and a specificity of 0.7000 in the validation dataset. This model was capable of predicting tremors caused by tacrolimus with an excellent degree of accuracy, which can be beneficial in the treatment of nephrotic syndrome patients.

Retrospective Analysis of the Risk Factors of Perioperative Bacterial Infection and Correlation with Clinical Prognosis in Kidney Transplant Recipients

Background

Infection remains a leading cause of morbidity and mortality in kidney transplant patients. This study aimed to investigate the risk factors of bacterial infection during the perioperative period of transplantation and the effects of infection on long-term clinical outcomes.

Methods

In total, 295 kidney transplantation recipients were included in this retrospective study and assigned to two groups: non-infected and infected. The tacrolimus concentration, pharmacogenomics, laboratory parameters, and clinical outcomes of both groups were evaluated.

Results

A relatively low incidence of urinary tract infection was observed in our cohort, and lung was identified as the most frequent site of infection. Gram-negative bacteria, such as Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae, were the most common infecting strains in kidney transplant recipients. Patients with diabetes showed greater susceptibility to infection. Compared with the non-infected group, tacrolimus concentration was significantly lower on day 7 and 14 in the infected group. White blood cell count, neutrophil count, and C-reactive protein (CRP) in the infected group were markedly higher post-transplantation, while albumin levels were lower relative to the non-infected group. ABCB1 (rs2032582) genotype showed clear associations with infection. Furthermore, the incidence of delayed graft function (DGF) and early acute rejection (AR) before infection was significantly greater in the infected group. Finally, early post-transplant infection was associated with a marked increase in the incidence of AR, post-transplant diabetes mellitus (PTDM), and secondary infection.

Conclusion

Pre-diabetes, longer duration of catheterization, lower albumin, higher CRP, tacrolimus concentration on the day 7 and 14, early AR before infection, and DGF were closely related to postoperative infection in kidney transplantation recipients. Moreover, bacterial infection during the perioperative period was closely associated with AR, PTDM and secondary infection.

Nephroprotective Plants: A Review on the Use in Pre-Renal and Post-Renal Diseases

Kidney diseases are expected to become the fifth leading cause of death by 2040. Several physiological failures classified as pre-, intra-, and post-renal factors induce kidney damage. Diabetes, liver pathologies, rhabdomyolysis, and intestinal microbiota have been identified as pre-renal factors, and lithiasis or blood clots in the ureters, prostate cancer, urethral obstructions, prostate elongation, and urinary tract infections are post-renal factors. Additionally, the nephrotoxicity of drugs has been highlighted as a crucial factor inducing kidney injuries. Due to the adverse effects of drugs, it is necessary to point to other alternatives to complement the treatment of these diseases, such as nephroprotective agents. Plants are a wide source of nephroprotective substances and can have beneficial effects in different levels of the physiological pathways which lead to kidney damage. In traditional medicines, plants are used as antioxidants, anti-inflammatories, diuretics, and anticancer agents, among other benefits. However, the mechanism of action of some plants empirically used remains unknown and scientific data are required to support their nephroprotective effects. The present work reviewed the plants with a beneficial effect on kidney diseases. The classification of nephroprotective plants according to the clinical definition of pre-renal, intrinsic, and post-renal factors is proposed to orient their use as complementary treatments.

Race and sex associations with tacrolimus pharmacokinetics in stable kidney transplant recipients

Study Objective

This study investigated race and sex differences in tacrolimus pharmacokinetics and pharmacodynamics in stable kidney transplant recipients.

Design and Setting

A cross‐sectional, open‐label, single center, 12‐h pharmacokinetic‐pharmacodynamic study was conducted. Tacrolimus pharmacokinetic parameters included area under the concentration‐time curve (AUC_0–12), AUC_0–4, 12‐h troughs (C_12 h), maximum concentrations (C_max), oral clearance (Cl), with dose‐normalized AUC_0–12, troughs, and C_max with standardized adverse effect scores. Statistical models were used to analyze end points with individual covariate‐adjustment including clinical factors, genotypic variants CYP3A5*3, CYP3A5*6, CYP3A5*7(CYP3A5*3*6*7) metabolic composite, and ATP binding cassette gene subfamily B member 1 (ABCB1) polymorphisms.

Patients

65 stable, female and male, Black and White kidney transplant recipients receiving tacrolimus and mycophenolic acid ≥6 months post‐transplant were evaluated.

Measurements and Main Results

Black recipients exhibited higher tacrolimus AUC_0–12 (Race: p = 0.005), lower AUC* (Race: p < 0.001; Race × Sex: p = 0.068), and higher Cl (Race: p < 0.001; Sex: p = 0.066). Greater cumulative (Sex: p < 0.001; Race × Sex: p = 0.014), neurologic (Sex: p = 0.021; Race × Sex: p = 0.005), and aesthetic (Sex: p = 0.002) adverse effects were found in females, with highest scores in Black women. In 84.8% of Black and 68.8% of White patients, the target AUC_0–12 was achieved (p = 0.027). In 31.3% of White and 9.1% of Black recipients, AUC_0–12 was <100 ng‧h/ml despite tacrolimus troughs in the target range (p = 0.027). The novel CYP3A5*3*6*7 metabolic composite was the significant covariate accounting for 15%–19% of tacrolimus variability in dose (p = 0.002); AUC_0–12 h* (p < 0.001), and Cl (p < 0.001).

Conclusions

Tacrolimus pharmacokinetics and adverse effects were different among stable kidney transplant recipient groups based upon race and sex with interpatient variability associated with the CYP3A5*3*6*7 metabolic composite. More cumulative, neurologic, and aesthetic adverse effects were noted among females. Tacrolimus regimens that consider race and sex may reduce adverse effects and enhance allograft outcomes by facilitating more patients to achieve the targeted AUC_0–12 h.

Effects of exercise training on immunological factors in kidney transplant recipients; a randomized controlled trial

The purpose of this study was to investigate the effects of a 12 week exercise training on the immune system of kidney transplant recipients. 23 kidney transplant recipients were randomly divided into two groups including control (n = 10) and training (n =13) groups. The training groups participated in the training for 10 weeks (three days a week; each day 60-90 minutes). The control group performed no regular exercise during this time. The blood samples were taken before and after 12 weeks. ELISA and Real-time PCR were used to evaluate cytokine profiles, including TNF-a, IL-6, IL-4, IL-31 and IL-35 as well as T-bet, GATA-3, RORYt and FOXP3, respectively. Finally, the data were analyzed, using paired T-test. ELISA results showed decreased levels of TNF- α, increased levels of IL-6 and no significant differences in the IL-35, IL-31 and IL-4 levels in the training group in comparison to the control group. Gene expression profiles showed significantly increased expression of T-bet and no changes in the GATA-3, RORYt and FOXP3 levels. According to these results, a moderate exercise including aerobic and resistance training could inhibit inflammatory cytokines and have beneficial effects on the immune system, but this issue needs further research.

Genetic Polymorphisms Affecting Tacrolimus Metabolism and the Relationship to Post-Transplant Outcomes in Kidney Transplant Recipients

Background

Tacrolimus is a key drug in kidney transplantation with a narrow therapeutic index. However, whether tacrolimus exposure variability affects clinical outcomes and adverse reactions remains unknown.

Objective

Our study investigated the factors that influence tacrolimus exposure in kidney transplantation recipients and the relationship between tacrolimus concentration and clinical outcomes and adverse reactions.

Settings and Methods

We examined the effect of tacrolimus concentration on clinical outcomes and adverse reactions in 201 kidney transplantation recipients, and identified clinical and pharmacogenetic factors that explain tacrolimus exposure.

Results

The CYP3A5 genotype was clearly associated with dose-adjusted trough blood tacrolimus concentrations (C₀/D), whereas no significant difference was observed in patients with the CYP3A4*1B, CYP3A4*22, ABCB1, ABCC2, POR*28 or PXR alleles. Clinical factors such as red blood cell count, hemoglobin, and albumin were the most useful influence factors affecting tacrolimus C₀/D. Besides, Wuzhi capsule increased tacrolimus C₀/D in kidney transplantation recipients. Furthermore, higher tacrolimus concentrations were associated with higher diarrhea and post-transplant diabetes mellitus (PTDM) risk but not with acute rejection and chronic allograft kidney dysfunction.

Conclusion

Clinical factors, medication, and CYP-enzyme polymorphisms accounted for tacrolimus concentration variability in kidney transplantation recipients. Furthermore, higher tacrolimus concentrations were associated with higher diarrhea and PTDM risk.

FK506-loaded PLGA nanoparticles improve long-term survival of a vascularized composite allograft in a murine model

Background

The side effects of life-long administration of FK506 limit the clinical practice of vascularized composite allografts (VCAs). This study aimed to evaluate the feasibility of FK506-loaded poly (lactic-co-glycolic acid) (PLGA) nanoparticles (FK506 NPs) for prolonging the long-term survival of VCAs and reducing the side effects of FK506.

Methods

PLGA nanoparticles loaded with FK506 were prepared by the solvent evaporation method. The characterization of FK506 NPs was evaluated by electron microscopy. To confirm the function and safety of FK506 NPs, these particles were administrated into rats by intraperitoneal injection. The survival time of the allograft, systemic concentration of FK506, anti-rejection activity, and side-effect of FK506 NPs were evaluated in a Brown Norway (BN)-to-Sprague Dawley (SD) epigastric VCA transplantation model.

Results

Compared with the nontreatment, PLGA control and FK506 groups, the median survival times (MST) of the FK506 NP groups were significantly prolonged. The FK506 NPs could maintain therapeutic drug concentration for 60 days. Moreover, cytokine concentrations, flow cytometry of regulatory T cells (Tregs) and histopathology of allografts revealed significantly prolonged immunosuppression by FK506 NPs. FK506 NPs also ameliorated FK506 nephrotoxicity.

Conclusions

FK506 NPs prolong the survival time of VCAs in a murine model with minimal nephrotoxicity, and provide a potential clinical strategy for ameliorating long-term side effects of immunosuppressive therapy.

Model-informed precision dosing to optimise immunosuppressive therapy in renal transplantation

Immunosuppressive therapy is pivotal for sustained allograft and patient survival after renal transplantation. However, optimally balanced immunosuppressive therapy is challenged by between-patient and within-patient pharmacokinetic (PK) variability. This could warrant the application of personalised dosing strategies to optimise individual patient outcomes. Pharmacometrics, the science that investigates the xenobiotic-biotic interplay using computer-aided mathematical modelling, provides options to describe and quantify this PK variability and enables identification of patient characteristics affecting immunosuppressant PK and treatment outcomes. Here, we review and critically appraise the available pharmacometric model-informed dosing solutions for the typical immunosuppressants in modern renal transplantation, to guide their initial and subsequent dosing.

Patient experiences of sleep in dialysis: systematic review of qualitative studies

RATIONALE AND OBJECTIVE

Sleep problems affect more than half of patients receiving dialysis and are associated with increased risk of mortality, cardiovascular events, depression and impaired functioning and quality of life. Symptoms such as fatigue and exhaustion may be attributed to sleep problems or sleep disorders, as well as the burden of kidney disease and treatment. This study aims to describe the patient perspectives on the reasons, impact and management of sleep problems in dialysis.

STUDY DESIGN

Systematic review and thematic synthesis of qualitative studies that report patient experience and perspectives on sleep in dialysis.

SETTING AND POPULATION

Patients receiving dialysis.

SEARCH STRATEGY AND SOURCES

MEDLINE, Embase, PsycINFO, CINAHL, reference lists and PhD dissertations were searched from inception to August 2019.

DATA EXTRACTION

All text from the results/conclusion of the primary studies.

ANALYTICAL APPROACH

Thematic synthesis.

RESULTS

We included 48 studies involving 1156 participants from 16 countries. We identified six themes: dominating demands of treatment (with subthemes of: demanding and relentless schedule, regret for wasted time); scheduling and control (managing sleep routines, napping and nocturnal sleep disruption, meditative aids); disruptions due to dialysis (unsettled sleep, hypervigilance and worry); symptoms depriving sleep (difficulty falling asleep, constant waking); overwhelmed and without choice (futility of sleep, uncontrollable exhaustion, restlessness is irrepressible); and as a coping mechanism (avoiding anxiety, alleviating symptoms, combating boredom).

LIMITATIONS

Most studies were conducted in high-income, English-speaking countries.

CONCLUSION

The treatment and symptom burden of dialysis disrupts and deprives patients of sleep, which leads to overwhelming and uncontrollable exhaustion. Better management of symptoms and effective strategies to manage sleep routines may improve sleep quality for better overall health in patients receiving dialysis.

Beyond Deterministic Models in Drug Discovery and Development

The model-informed drug discovery and development paradigm is now well established among the pharmaceutical industry and regulatory agencies. This success has been mainly due to the ability of pharmacometrics to bring together different modeling strategies, such as population pharmacokinetics/pharmacodynamics (PK/PD) and systems biology/pharmacology. However, there are promising quantitative approaches that are still seldom used by pharmacometricians and that deserve consideration. One such case is the stochastic modeling approach, which can be important when modeling small populations because random events can have a huge impact on these systems. In this review, we aim to raise awareness of stochastic models and how to combine them with existing modeling techniques, with the ultimate goal of making future drug-disease models more versatile and realistic.

Effect of Kaempferol on Tacrolimus-Induced Nephrotoxicity and Calcineurin B1 Expression Level in Animal Model

BACKGROUND

The kidneys are considered one of the most susceptible organs for adverse drug effects, particularly in post-transplant conditions. Tacrolimus (FK506), a calcineurin inhibitor immunosuppressant, is an essential component in the transplantation regimen. Despite that, nephrotoxicity is a severe drawback for its chronic utilization, where oxidative stress might be implicated. Kaempferol (KMF) is a natural flavonoid that has many adaptable biological activities, including antioxidant action.

OBJECTIVE

Exploring the KMF protective effect on FK506-induced nephrotoxicity and the underlying role of calcineurin B1.

METHODS

Twenty-four male albino-Wistar rats were randomly divided into three equal groups. The control group received solvents: propylene glycol, i.p. and 0.5% carboxymethyl cellulose, PO; FK506 group was injected with FK506 (0.6 mg/kg, i.p.), and FK506+KMF group was given FK506 (0.6 mg/kg, i.p.) and KMF (10 mg/kg, PO). The treatment regimen for all groups was once daily for 30 days. ELISA technique applied for measuring FK506 trough level and nephrotoxicity biomarkers in serum (cystatin C and urea) on days 15 and 30, and in kidney tissue homogenate (MDA and calcineurin B1) on day 30.

RESULTS

In FK506-treated rats, the FK506 trough level was 7.84 ± 1.31 ug/l on day 15 and 9.54 ± 1.45 ug/l on day 30. FK506 use has significantly (P<0.01) increased biomarkers levels of cystatin C (325% and 477%), urea (177% and 245%), MDA (1253%), except calcineurin B1 that has decreased (97%). The KMF combination has resulted in a significant reduction in the FK506 trough level by day 30 (6.79 ± 1.35 ug/l, P<0.01). KMF has significantly ameliorated the levels of cystatin C (46% and 73%, P<0.001), urea (38% and 68%, P<0.001), MDA (75%, P<0.001), and calcineurin B1 (1833%, P<0.05).

CONCLUSION

Oxidative stress and calcineurin B1 are contributing factors in FK506-induced nephrotoxicity. Hence, inhibition of calcineurin enzyme is not limited to the immune cells. KMF could be a novel nephroprotective antioxidant.

The impact of tacrolimus exposure on extrarenal adverse effects in adult renal transplant recipients

AIMS

Tacrolimus has been associated with notable extrarenal adverse effects (AEs), which are unpredictable and impact patient morbidity. The association between model-predicted tacrolimus exposure metrics and standardized extrarenal AEs in stable renal transplant recipients was investigated and a limited sampling strategy (LSS) was developed to predict steady-state tacrolimus area under the curve over a 12-h dosing period (AUC_ss,0-12h ).

METHODS

All recipients receiving tacrolimus and mycophenolic acid ≥6 months completed a 12-h cross-sectional observational pharmacokinetic-pharmacodynamic study. Patients were evaluated for the presence of individual and composite gastrointestinal, neurological, and aesthetic AEs during the study visit. The associations between AEs and tacrolimus exposure metrics generated from a published population pharmacokinetic model were investigated using a logistic regression analysis in NONMEM 7.3. An LSS was determined using a Bayesian estimation method with the same patients.

RESULTS

Dose-normalized tacrolimus AUC_ss,0-12h and apparent clearance were independently associated with diarrhoea, dyspepsia, insomnia and neurological AE ratio. Dose-normalized tacrolimus maximum concentration was significantly correlated with skin changes and acne. No AE associations were found with trough concentrations. Using limited sampling at 0, 2h; 0, 1, 4h; and 0, 1, 2, 4h provided a precise and unbiased prediction of tacrolimus AUC (root mean squared prediction error < 10%), which was not well characterized using trough concentrations only (root mean squared prediction error >15%).

CONCLUSIONS

Several AEs (i.e. diarrhoea, dyspepsia, insomnia and neurological AE ratio) were associated with tacrolimus dose normalized AUC_ss,0-12h and clearance. Skin changes and acne were associated with dose-normalized maximum concentrations. To facilitate clinical implementation, a LSS was developed to predict AUC_ss,0-12h values using sparse patient data to efficiently assess projected immunosuppressive exposure and potentially minimize AE manifestations.