Clinical Pharmacokinetics of Once-Daily Tacrolimus in Solid-Organ Transplant Patients

Combating Alcohol Adduct Impurity in Immunosuppressant Drug Product Manufacturing: A Scientific Investigation for Enhanced Process Control

OBJECTIVE

This research aims to elucidate critical impurities in process validation batches of tacrolimus injection formulations, focusing on identification and characterization of previously unreported impurity at RRT 0.42, identified as the tacrolimus alcohol adduct. The potential root causes for the formation of new impurity was determined using structured risk assessment by cause and effect fishbone diagram. The primary objective was to propose mitigation plan and demonstrate the control of impurities with 6 month accelerated stability results in development batches.

METHODS

The investigation utilizes method validation and characterization studies to affirm the accuracy of quantifying the tacrolimus alcohol adduct. The research methodology employed different characterization techniques like rotational rheometer, ICP‒MS, MALDI-MS, 1H NMR, 13C NMR, and DEPT-135 NMR for structural elucidation. Additionally, the exact mass of the impurity is validated using electrospray ionization mass spectra.

RESULTS

Results indicate successful identification and characterization of the tacrolimus alcohol adduct. The study further explores the transformation of Tacrolimus monohydrate under various conditions, unveiling the formation of Tacrolimus hydroxy acid and proposing the existence of a novel degradation product, the Tacrolimus alcohol adduct. Six-month data from development lots utilizing Manufacturing Process II demonstrate significantly lower levels of alcohol adducts.

CONCLUSIONS

Manufacturing Process II, selectively locates Tacrolimus within the micellar core of HCO-60, this prevent direct contact of ethanol with Tacrolimus which minimizes impurity alcohol adduct formation. This research contributes to the understanding of tacrolimus formulations, offering ways to safeguard product integrity and stability during manufacturing and storage.

CYP3A5*3 and CYP3A4*22 Cluster Polymorphism Effects on LCP-Tac Tacrolimus Exposure: Population Pharmacokinetic Approach

The aim of the study is to develop a population pharmacokinetic (PopPK) model and to investigate the influence of CYP3A5/CYP3A4 and ABCB1 single nucleotide polymorphisms (SNPs) on the Tacrolimus PK parameters after LCP-Tac formulation in stable adult renal transplant patients. The model was developed, using NONMEM v7.5, from full PK profiles from a clinical study (n = 30) and trough concentrations (C0) from patient follow-up (n = 68). The PK profile of the LCP-Tac formulation was best described by a two-compartment model with linear elimination, parameterized in elimination (CL/F) and distributional (CLD/F) clearances and central compartment (Vc/F) and peripheral compartment (Vp/F) distribution volumes. A time-lagged first-order absorption process was characterized using transit compartment models. According to the structural part of the base model, the LCP-Tac showed an absorption profile characterized by two transit compartments and a mean transit time of 3.02 h. Inter-individual variability was associated with CL/F, Vc/F, and Vp/F. Adding inter-occasion variability (IOV) on CL/F caused a statistically significant reduction in the model minimum objective function MOFV (p < 0.001). Genetic polymorphism of CYP3A5 and a cluster of CYP3A4/A5 SNPs statistically significantly influenced Tac CL/F. In conclusion, a PopPK model was successfully developed for LCP-Tac formulation in stable renal transplant patients. CYP3A4/A5 SNPs as a combined cluster including three different phenotypes (high, intermediate, and poor metabolizers) was the most powerful covariate to describe part of the inter-individual variability associated with apparent elimination clearance. Considering this covariate in the initial dose estimation and during the therapeutic drug monitoring (TDM) would probably optimize Tac exposure attainments.

Tacrolimus loaded nanostructured lipid carriers using Moringa oleifera seed oil: design, optimization and in-vitro evaluations

The proposed research aims to develop Tacrolimus-loaded nanostructured lipid carriers (TAC-loaded NLCs) to overcome poor aqueous solubility and dissolution rate to enhance its oral absorption. A central composite design was used to optimise the amount of Poloxamer 188 and D-α-Tocopherol-polyethylene-glycol-succinate (TPGS). The optimised TAC-loaded NLCs contain stearic acid (250 mg), Moringa oleifera (MO) seed oil (50 mg), TAC (Tacrolimus: 10 mg), TPGS (60 mg), and Poloxamer 188 (1% w/v) with a mean diameter of 393.3 ± 29.68 nm, a zeta potential of -18.3 ± 6.19 mV, high entrapment efficiency (92.12 ± 1.14% w/w), and desirability (0.989). TAC-loaded NLCs showed ∼12 times higher drug dissolution efficiency, while in-vitro anti-inflammatory studies showed ∼1.8 times lower IC50 (half-maximal inhibitory concentration) than TAC suspension. The lyophilised TAC-loaded NLCs were found to be stable after 3 months. Thus, the present study concludes the successful encapsulation of TAC in NLCs made of stearic acid and MO seed oil.

Safety and Efficacy of Conversion to Once-Daily Tacrolimus from Twice-Daily Tacrolimus in Pediatric Liver Transplant Recipients

BACKGROUND

Nonadherence to immunosuppression is the most common cause of late acute rejection in pediatric liver transplant (LT) recipients. A prolonged-release once-daily tacrolimus formulation was developed to improve adherence and long-term allograft survival.

METHODS

We screened 179 pediatric LT recipients who converted from twice-daily tacrolimus (TD-TAC) to once-daily tacrolimus (OD-TAC) between February 2011 and September 2019.

RESULTS

One hundred seventy-nine recipients converted to OD-TAC and were followed for 18 months. 152 OD-TAC-converted recipients (84.9%) experienced uneventful follow-up, while 21 recipients showed LFT elevation. Four recipients had biopsy-proven acute rejection within six months of conversion, all of which were successfully treated with steroid pulse. 166 recipients (92.7%) remain on OD-TAC and 13 (7.3%) were switched back to TD-TAC. The mean tacrolimus trough level significantly decreased three months following conversion (3.14 ± 1.9 ng/mL) compared with pre-conversion levels (3.69 ± 1.98 ng/mL). Mean tacrolimus trough levels remained unchanged from 3 months to 12 months following conversion. Percent coefficient of variation of tacrolimus trough levels decreased significantly from 32.5 ± 16.4 ng/mL to 27.5 ± 15.6 ng/mL after conversion to OD-TAC, reflecting a decrease in variation of tacrolimus trough levels following conversion.

CONCLUSIONS

Conversion to OD-TAC in pediatric LT recipients with stable graft function is safe and effective.

LEVEL OF EVIDENCE

Level IV.

Intestinal Permeability in Patients Early after Kidney Transplantation Treated with Two Different Formulations of Once-Daily Tacrolimus

Adequate tacrolimus blood exposure is crucial in the early post-renal transplant period and a gut epithelial barrier integrity may play a role. We prospectively investigated several markers of intestinal permeability in recent kidney transplant recipients (KTRs) treated with different tacrolimus extended-release formulations. Within each of the 49 KTR pairs that received grafts from the same donor, an early randomized conversion was performed from twice-daily (Prograf) to once-daily tacrolimus formulation: Advagraf or Envarsus. Plasma zonulin, calprotectin, circulating lipopolysaccharide (LPS), LPS-binding protein (LBP), intestinal fatty acid binding protein (FABP-2), and CD-14 levels were measured. There was no difference in the recipient age, dialysis vintage, BMI, and residual diuresis between Advagraf and Envarsus groups. FABP-2 and LPS levels were significantly associated with tacrolimus trough level, 3-h level, and area under the curve (AUC) in the Envarsus but not in the Advagraf group. AUC was independently increased by LPS and decreased by age, FABP-2 concentration, and the use of Envarsus formulation as compared with Advagraf. Functional changes of gastrointestinal tract in patients treated with Envarsus may influence intestinal tacrolimus absorption to a greater extent than in Advagraf-treated KTRs and may lead to inadequate variability of tacrolimus exposure early after kidney transplantation.

Comparative Study of 2 Extended-Release Tacrolimus Formulations in Kidney Transplantation

BACKGROUND

During the 1900s, tacrolimus became the mainstay immunosuppressive agent to prevent rejection after kidney transplant. Subsequently, an extended-release tacrolimus (ER-Tac) formulation was developed to improve adherence, and its generic version has been marketed over the last years. This study examines the differences in efficacy and safety between the generic ER-Tac (Conferoport) and the reference brand-name drug (Advagraf).

METHODS

Prospective, randomized and parallel single-center study (May 2020 to June 2021) with 52 kidney transplant recipients who were randomly assigned to 1 of the following groups: study group (Conferoport, n = 31) and control group (Advagraf, n = 21). The variables of interest were collected and analyzed to compare tacrolimus efficacy and safety between them. Demographic characteristics of the patients and clinical donor data were homogeneous in both groups (P > .05).

RESULTS

No statistically significant differences were found among treatments regarding dosage used, levels, creatinine, and proteinuria (P > .05), with these variables presenting a downward trend during follow-up and, consequently, the improvement of graft function. Analyses also revealed the absence of differences concerning the incidence of acute rejection and intrapatient variability (coefficient of variation) throughout the first year of evolution between both formulations (P > .05). A total of 5 graft losses occurred, 2 resulting from patient death.

CONCLUSIONS

In our experience, we found no significant differences between the measured parameters in relation to the efficacy and safety profile of both drugs, with generic ER-Tac being an alternative comparable with the reference brand-name ER-Tac.

HCV-positive kidney transplant patients treated with direct-acting antivirals maintain stable medium-term graft function despite persistent reduction in tacrolimus trough levels

Background/aim:

Direct-acting antivirals (DAAs) have improved the treatment of HCV-positive kidney transplant recipients (KTRs). However, their medium-term follow-up effects on graft function are conflicting. This study aimed to analyze how the interplay between DAAs, calcineurin inhibitors (CNI), and HCV eradication impacts 12-month kidney graft function.

Methods:

This double-center retrospective study with a prospective follow-up enrolled 35 KTRs with HCV treated with DAAs for 12 weeks. We compared three parameters: estimated glomerular filtration rate (eGFR), 24-h proteinuria, and CNI trough levels at three time points: baseline, end of treatment (EOT), and 12 months later.

Results:

Kidney allograft function remained stable when comparing baseline and 12-month post-treatment values of eGFR (60.7 versus 57.8 ml/min; p = 0.28) and 24-h proteinuria (0.3 versus 0.2 g/24 h; p = 0.15), while tacrolimus (Tac) trough levels underwent a statistically significant decline (6.9 versus 5.4 ng/ml; p = 0.004). Using an ongoing triple Tac-based maintenance therapy as a conservative measure, a dose escalation of Tac was applied only in seven patients. No variation in CyA and mTOR levels was detected.

Conclusion:

DAA therapy is safe and effective in HCV-positive KTRs. It also produces a persistent significant reduction in Tac trough levels that does not influence graft function at 12 months.

A Potential Route to Reduce Ischemia/Reperfusion Injury in Organ Preservation

The pathophysiological process of ischemia and reperfusion injury (IRI), an inevitable step in organ transplantation, causes important biochemical and structural changes that can result in serious organ damage. IRI is relevant for early graft dysfunction and graft survival. Today, in a global context of organ shortages, most organs come from extended criteria donors (ECDs), which are more sensitive to IRI. The main objective of organ preservation solutions is to protect against IRI through the application of specific, nonphysiological components, under conditions of no blood or oxygen, and then under conditions of metabolic reduction by hypothermia. The composition of hypothermic solutions includes osmotic and oncotic buffering components, and they are intracellular (rich in potassium) or extracellular (rich in sodium). However, above all, they all contain the same type of components intended to protect against IRI, such as glutathione, adenosine and allopurinol. These components have not changed for more than 30 years, even though our knowledge of IRI, and much of the relevant literature, questions their stability or efficacy. In addition, several pharmacological molecules have been the subjects of preclinical studies to optimize this protection. Among them, trimetazidine, tacrolimus and carvedilol have shown the most benefits. In fact, these drugs are already in clinical use, and it is a question of repositioning them for this novel use, without additional risk. This new strategy of including them would allow us to shift from cold storage solutions to cold preservation solutions including multitarget pharmacological components, offering protection against IRI and thus protecting today's more vulnerable organs.

Tacrolimus dose adjustment is not necessary in dose to dose conversion from a twice daily to a prolonged release once daily dose form

Twice daily TAC (BID TAC) and prolonged released once daily dose tacrolimus (OD TAC) have different pharmacokinetic (PK) profiles in kidney transplant (KT) recipients. Precise dose adjustment recommendations when converting from BID TAC to OD TAC remain inconclusive. A single center, PK study was conducted in stable KT recipients taking constant doses of TAC, mycophenolic acid, and prednisolone. The area under the concentration-time curve (AUC) 0-24 and C_trough were measured before and 4 weeks after 1:1 conversion from BID TAC to OD TAC without subsequent dose adjustment. A 90% confidence interval (CI) of geometric mean ratio (GMR) of OD TAC/BID TAC within the range of 0.9-1.11 was utilized to indicate equivalence of the narrow therapeutic index drugs. The roles of CYP3A5 genotypic polymorphism on PK parameters were also assessed. There were 20 patients with median time since transplantation of 18 months. The mean of CKD-EPI eGFR was 60.7 ± 16.43 mL/min/1.73 m². The median total daily TAC dose of 0.058 mg/kg/day. The geometric means (%CV) of AUC_0-24 of OD and BID TAC were 205.16 (36.4%) and 210.3 (32.5%) ng/mL × h, respectively, with a GMR of 0.98 (90%CI 0.91-1.04). The geometric means (%CV) of C_trough of OD TAC and BID TAC were 5.43 (33.1%) and 6.09 (34.6%) ng/mL, respectively. The GMR of C_trough was 0.89 (90%CI 0.82-0.98), which was below 0.9. The newly calculated target C_trough level of OD TAC was 4.8-6.2 ng/mL. The best abbreviated AUC_0-24 was AUC = 0.97(C0) + 5.79(C6) + 18.97(C12) - 4.26. The GMR AUC_0-24 was within the range of 0.9-1.11 irrespective of CYP3A5 genotypic polymorphism while the GMR of C_trough was below 0.9 only in the CYP3A5 expressor patients. The 1:1 conversion from BID TAC to OD TAC without subsequent dose adjustment provided similar AUC_0-24 regardless of CYP3A5 genotypic polymorphism. However, the C_trough was lower in the CYP3A5 expressor group. Therefore, it is not necessary to routinely increase the OD TAC dose after conversion.Trial registration: Thai Clinical Trials Registry (TCTR20210715002).

Tacrolimus-Induced Diffuse Coronary Artery Spasm

Prinzmetal angina, also known as vasospastic angina, is defined as an intermittent focal or diffuse coronary artery narrowing, which is often associated with transient ST-segment elevation on an electrocardiogram. Also, it could be associated with an atherosclerotic lesion at the site of the spasm. Vasospastic angina might be induced by medications, most commonly with cocaine and other examples which include catecholamines such as epinephrine, norepinephrine, isoproterenol, dopamine, and dobutamine. Parasympathomimetic agents include acetylcholine, methacholine, and pilocarpine. It is rarely caused by tacrolimus. The clinical evaluation includes an electrocardiogram and echocardiogram. The confirmed diagnosis is done by coronary angiography. Cardiac catheterization is indicated in such cases to rule out coronary artery disease.

Body composition is associated with tacrolimus pharmacokinetics in kidney transplant recipients

Purpose

A population pharmacokinetic (popPK) model may be used to improve tacrolimus dosing and minimize under- and overexposure in kidney transplant recipients. It is unknown how body composition parameters relate to tacrolimus pharmacokinetics and which parameter correlates best with tacrolimus exposure. The aims of this study were to investigate which body composition parameter has the best association with the pharmacokinetics of tacrolimus and to describe this relationship in a popPK model.

Methods

Body composition was assessed using bio-impedance spectroscopy (BIS). Pharmacokinetic analysis was performed using nonlinear mixed effects modeling (NONMEM). Lean tissue mass, adipose tissue mass, over-hydration, and phase angle were measured with BIS and then evaluated as covariates. The final popPK model was evaluated using goodness-of-fit plots, visual predictive checks, and a bootstrap analysis.

Results

In 46 kidney transplant recipients, 284 tacrolimus concentrations were measured. The base model without body composition parameters included age, plasma albumin, plasma creatinine, CYP3A4 and CYP3A5 genotypes, and hematocrit as covariates. After full forward inclusion and backward elimination, only the effect of the phase angle on clearance (dOFV =  − 13.406; p < 0.01) was included in the final model. Phase angle was positively correlated with tacrolimus clearance. The inter-individual variability decreased from 41.7% in the base model to 34.2% in the final model. The model was successfully validated.

Conclusion

The phase angle is the bio-impedance spectroscopic parameter that correlates best with tacrolimus pharmacokinetics. Incorporation of the phase angle in a popPK model can improve the prediction of an individual’s tacrolimus dose requirement after transplantation.

Supplementary information

The online version contains supplementary material available at 10.1007/s00228-022-03323-0.

Possible Tacrolimus-Related Neuropsychiatric Symptoms: One Year After Allogeneic Hematopoietic Cell Transplantation: A Case Report

Tacrolimus is a calcineurin inhibitor (CNI), an immunosuppressive agent used to prevent graft versus host disease following allogeneic hematopoietic cell transplantation (HCT). Side-effects of tacrolimus treatment include neuropsychiatric symptoms, for example, affective disturbances, psychosis, and akinetic mutism. The onset of side-effects is independent of tacrolimus blood concentration and can occur years after treatment initiation. To our knowledge, case-reports describing tacrolimus-induced neuropsychiatric symptoms following HCT are sparse. This article reports the case of a 60-year-old woman with T-cell prolymphocytic leukemia, who developed memory loss, affective disturbances, and delusions, 1-year after HCT, and tacrolimus treatmentinitiation. Upon hospital admission, she was motionless and mute, albeit easily roused. The routine physical examination was without pathological findings. Blood work and microbiological analyses of blood and cerebrospinal fluid were normal. The neuroimaging showed chronic structural changes without relation to the debut of neuropsychiatric symptoms. Tacrolimus was discontinued on suspicion of tacrolimus-induced neuropsychiatric symptoms. The patient recovered within 48 hours of discontinuation. She was switch to prednisone treatment, and there has been no reemergence of neuropsychiatric symptoms since.

A single-center, open-label, randomized cross-over study to evaluate the pharmacokinetics and bioavailability of once-daily prolonged-release formulations of tacrolimus in de novo liver transplant recipients

BACKGROUND

The narrow therapeutic window of tacrolimus (Tac) requires intense drug monitoring to achieve adequate efficacy while minimizing dose-related toxicities. Once-daily formulations of Tac (LCP-Tac and PR-Tac) have been recently designed for higher bioavailability and a more consistent exposure over time, as opposed to the twice-daily, administered immediate-release formulation of Tac (IR-Tac).

METHODS

This single-center, open-label, randomized cross-over pharmacokinetic (PK) study compares extended-release LCP-Tac with the prolonged-release formulation of tacrolimus (PR-Tac) in adult de novo liver transplant recipients. Eligible patients were screened and randomized 1:1 to the two treatment arms up to 30 days after liver transplantation. Patients were administered either LCP-Tac or PR-Tac for 14 days followed by another 14-day time interval of the other once-daily Tac medication. A 24hr-PK profile was obtained at the end of each time interval.

RESULTS

Nine patients (45%) completed the study resulting in a total of 18 Tac PK profiles. Overall, the profile of the mean concentrations indicated a flattened kinetic of LCP-Tac compared to PR-Tac, especially in the first 3 h after drug intake. The average cumulative dose per day to achieve equivalent trough levels was approximately 25% lower for LCP-Tac (8.7 mg) than for PR-Tac (11.7 mg). LCP-Tac resulted in a longer tmax and fewer peak-to-trough fluctuations compared to PR-Tac.

CONCLUSION

Despite methodological weaknesses that limit the conclusions, we have found a more consistent drug exposure for LCP-Tac in de novo LT recipients. LCP-Tac demonstrated a greater bioavailability compared to PR-Tac.

Therapeutic Drug Monitoring Strategies for Envarsus in De Novo Kidney Transplant Patients Using Population Modelling and Simulations

INTRODUCTION

Tacrolimus, the cornerstone of transplantation immunosuppression, is a narrow therapeutic index drug with a low and highly variable bioavailability. Therapeutic drug monitoring based on trough level assessment is mandatory in order to target a personalised exposure and avoid both rejection and toxicity. Population pharmacokinetic (POPPK) models might be a useful tool for improving early attainment of target range by guiding initial doses until steady state is reached and trough levels can be reliably used as surrogate marker of exposure. Here we present the first POPPK for predicting the initial doses of the once-daily prolonged release tacrolimus Envarsus (LCPT) in adult kidney recipients.

METHODS

The model was developed exploiting the data from a recent pharmacokinetic randomised clinical study, in which 69 de novo kidney recipients, 33 of whom treated with LCPT, underwent an intensive blood sampling strategy for tacrolimus including four complete pharmacokinetic profiles.

RESULTS

The complex and prolonged absorption of LCPT is well described by the three-phase model that incorporates body weight and CYP3A5 genotype as significant covariates accounting for a great proportion of the inter-patient variability: in particular, CYP3A5*1/*3 expressors had a 66% higher LCPT clearance. We have then generated by simulation a personalised dosing strategy based on the model that could improve the early attainment of therapeutic trough levels by almost doubling the proportion of patients within target range (69.3% compared to 36.1% with the standard body weight-based approach) on post-transplantation day 4 and significantly reduce the proportion of overexposed patients at risk of toxicity.

CONCLUSIONS

A POPPK model was successfully developed for LCPT in de novo kidney recipients. The model could guide a personalised dosing strategy early after transplantation. For the model to be translated into clinical practice, its beneficial impact of earlier attainment of therapeutic trough levels should be demonstrated on hard clinical outcomes in further studies.

Effects of fasting on solid organ transplant recipients during Ramadan - a practical guide for healthcare professionals

Fasting in the month of Ramadan is an obligatory act for healthy adult Muslims. It requires abstinence from food and drink from dawn to sunset. Although there are exemptions from fasting, many patients are keen to fulfil what they see as a religious obligation, even if this may be against medical advice in some cases. Solid organ transplant (SOT) recipients often ask healthcare professionals for advice on fasting. Studies on the effect of fasting in transplant patients have all been done in the Middle East and North Africa where the average fasting duration is between 12 and 14 hours. In comparison, in temperate regions in the summer, fasting duration can be as long as 20 hours. Fasting when patients have to take immunosuppression 12 hours apart with little time variation poses unique challenges. In this review, current literature is reviewed, and a decision-making tool has been developed to assist clinicians in discussing the risks of fasting in transplant recipients, with consideration also given to circumstances such as the COVID-19 pandemic. Our review highlights that SOT recipients wishing to fast should undergo a thorough risk assessment, ideally 3 months before Ramadan. They may require medication changes and a plan for regular monitoring of graft function and electrolytes in order to fast safely. Recommendations have been based on risk tiers (very high risk, high risk and low/moderate risk) established by the International Diabetes Federation and the Diabetes and Ramadan International Alliance. Patients in the 'very high risk' and 'high risk' categories should be encouraged to explore alternative options to fasting such as winter fasting or Fidyah. Those in the 'low/moderate' category may be able to cautiously fast with guidance from their clinician. Prior to the commencement of Ramadan, all patients must receive up-to-date education on sick-day rules, instructions on when to terminate their fast or abstain from fasting.

Association of CYP3A5 polymorphisms and parathyroid hormone with blood level of tacrolimus in patients with end-stage renal disease

Because tacrolimus is predominantly metabolized by CYP3A, the blood concentration/dose (C/D) ratio is affected by CYP3A5 polymorphism. Parathyroid hormone (PTH) expression increases in secondary hyperparathyroidism, which is frequently associated with end‐stage renal disease. Recently, PTH has been shown to downregulate CYP3A expression at mRNA level. In this study, we examined the influence of CYP3A5 polymorphism on and association of serum intact‐PTH (iPTH) level with blood tacrolimus concentration in patients with end‐stage renal disease just before kidney transplantation. Forty‐eight patients who satisfied the selection criteria were analyzed. Subjects were classified into two phenotype subgroups: CYP3A5 expressor (CYP3A5*1/*1 and *1/*3; n = 15) and CYP3A5 nonexpressor (CYP3A5*3/*3; n = 33). The blood tacrolimus C/D (per body weight) ratio was significantly lower in CYP3A5 expressors than that in CYP3A5 nonexpressors. A significant positive correlation was found between tacrolimus C/D and iPTH concentrations (r = 0.305, p = 0.035), and the correlation coefficient was higher after excluding 20 patients co‐administered CYP3A inhibitor or inducer (r = 0.428, p = 0.023). A multiple logistic regression analysis by stepwise selection identified CYP3A5 polymorphism and serum iPTH level as significant factors associated with tacrolimus C/D. These results may suggest the importance of dose design considering not only the CYP3A5 phenotype but also serum iPTH level when using tacrolimus in patients who undergo renal transplantation.

Glycol chitosan-based tacrolimus-loaded nanomicelle therapy ameliorates lupus nephritis

Background

Recently, we developed hydrophobically modified glycol chitosan (HGC) nanomicelles loaded with tacrolimus (TAC) (HGC-TAC) for the targeted renal delivery of TAC. Herein, we determined whether the administration of the HGC-TAC nanomicelles decreases kidney injury in a model of lupus nephritis. Lupus-prone female MRL/lpr mice were randomly assigned into three groups that received intravenous administration of either vehicle control, an equivalent dose of TAC, or HGC-TAC (0.5 mg/kg TAC) weekly for 8 weeks. Age-matched MRL/MpJ mice without Fas^lpr mutation were also treated with HGC vehicle and used as healthy controls.

Results

Weekly intravenous treatment with HGC-TAC significantly reduced genetically attributable lupus activity in lupus nephritis-positive mice. In addition, HGC-TAC treatment mitigated renal dysfunction, proteinuria, and histological injury, including glomerular proliferative lesions and tubulointerstitial infiltration. Furthermore, HGC-TAC treatment reduced renal inflammation and inflammatory gene expression and ameliorated increased apoptosis and glomerular fibrosis. Moreover, HGC-TAC administration regulated renal injury via the TGF-β1/MAPK/NF-κB signaling pathway. These renoprotective effects of HGC-TAC treatment were more potent in lupus mice compared to those of TAC treatment alone.

Conclusion

Our study indicates that weekly treatment with the HGC-TAC nanomicelles reduces kidney injury resulting from lupus nephritis by preventing inflammation, fibrosis, and apoptosis. This advantage of a new therapeutic modality using kidney-targeted HGC-TAC nanocarriers may improve drug adherence and provide treatment efficacy in lupus nephritis mice.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00857-w.

Predicting drug release and degradation kinetics of long-acting microsphere formulations of tacrolimus for subcutaneous injection

Today, tacrolimus represents a cornerstone of immunosuppressive therapy for liver and kidney transplants and remains subject of preclinical and clinical investigations, aiming at the development of long-acting depot formulations for subcutaneous injection. One major challenge arises from establishing in vitro-in vivo correlations due to the absence of meaningful in vitro methods predictive for the in vivo situation, together with a strong impact of multiple kinetic processes on the plasma concentration-time profile. In the present approach, two microsphere formulations were compared with regards to their in vitro release and degradation characteristics. A novel biorelevant medium provided the physiological ion and protein background. Release was measured using the dispersion releaser technology under accelerated conditions. A release of 100% of the drug from the carrier was achieved within 7 days. The capability of the in vitro performance assay was verified by the level A in vitro-in vivo correlation analysis. The contributions of in vitro drug release, drug degradation, diffusion rate and lymphatic transport to the absorption process were quantitatively investigated by means of a mechanistic modelling approach. The degradation rate, together with release and diffusion characteristics provides an estimate of the bioavailability and therefore can be a guide to future formulation development.

Comparison of the Impact of Pharmacogenetic Variability on the PK of Slow Release and Immediate Release Tacrolimus Formulations

Tacrolimus-modified release formulations allow for once-daily dosing, and adherence is better compared to the twice-daily immediate release formulation. When patients are switched from one formulation to another, variable changes in drug concentrations are observed. Current data suggest that the changes in drug exposure are larger in patients who express the CYP3A5 enzyme (CYP3A5 *1/*3 or *1/*1) compared to nonexpressers (CYP3A5*3/*3). Possibly, these differences are due to the fact that in the upper region of the small intestine CYP3A activity is higher, and that this expression of CYP3A decreases towards the more distal parts of the gut. Modified release formulations may therefore be subject to a less presystemic metabolism. However, the full implications of pharmacogenetic variants affecting the expression and function of drug transporters in the gut wall and of enzymes involved in phase I and phase II metabolism on the different formulations are incompletely understood, and additional studies are required. Conclusions: In all patients in whom the formulation of tacrolimus is changed, drug levels need to be checked to avoid clinically relevant under- or overexposure. In patients with the CYP3A5 expresser genotype, this recommendation is even more important, as changes in drug exposure can be expected.

Diagnosis and management of oral ulcerations associated with mycophenolate mofetil in kidney transplantation

AIMS

The final diagnosis of oral mucosal ulcerations in solid organ transplant recipients represents a challenge. We describe a unique case of oral ulceration related to mycophenolate mofetil (MMF) toxicity, 11 years after kidney transplantation, whose dose reduction was sufficient to resolve it.

METHODS AND RESULTS

A 54-year-old female patient, who underwent kidney transplantation 11 years ago, presents multiple ulcers on the buccal mucosa bilaterally, soft palate and tongue dorsum, for 8 months, with moderate pain. The diagnosis of oral ulcerations associated with MMF therapy was assumed by excluding infection and malignancy diagnosis. After MMF dose reduction, the oral ulcers healed utterly.

CONCLUSIONS

MMF toxicity manifested as oral ulcers. Reduction or discontinuation of MMF therapy should be considered in a patient with refractory oral ulcers and a negative workup for other causes.

Meeting Regulatory Requirements for Drugs with a Narrow Therapeutic Index: Bioequivalence Studies of Generic Once-Daily Tacrolimus

Despite growing clinical confidence in generics and their potential to reduce long-term healthcare costs, the transplant community have had real concerns about the use of generic immunosuppressants. One such immunosuppressant is tacrolimus, a cornerstone of lifelong treatment for patients who have undergone a solid organ transplant. Tacrolimus has a narrow therapeutic index (NTI), giving rise to questions about the potential for clinically relevant altered drug exposure. Its use in transplant patients also gives rise to questions about the most discriminative subject population for bioequivalence studies. The recognised need for stringent criteria to support approval of generic drugs with an NTI led the European Medicines Association and Health Canada to provide detailed information on requirements for bioequivalence studies and introduce tighter bioequivalence limits for these drugs, including tacrolimus. The aim of this article is to illustrate how regulatory guidance is implemented during the clinical development of generic immunosuppressants, using a generic, once-daily prolonged-release formulation of tacrolimus as an example.

Oral generic tacrolimus initiation and substitution in the Medicaid population: a new user cohort study

OBJECTIVE

Although existing studies have compared clinical efficacy and pharmacokinetics of generic with brand tacrolimus, little is known about generic tacrolimus utilization patterns or factors predicting generic substitution. This study examines associations between patient-level factors and generic tacrolimus initiation or substitution among new users of oral generic or brand-name tacrolimus.

METHODS

This new user retrospective cohort study identified 374 beneficiaries who initiated generic or brand tacrolimus treatment, using 100% Medicaid administrative claims data from 11 states in 2011-2012. Outcomes were generic tacrolimus initiation and substitution within 12 months of treatment initiation. Multivariable logistic regression and Cox proportional hazards models were used to identify factors associated with generic tacrolimus initiation and substitution.

RESULTS

Two-thirds of oral tacrolimus new users initiated generic tacrolimus. Patients who were older age and black were significantly more likely to initiate generic tacrolimus (adjusted odds ratio [AOR] = 1.02, 95% confidence interval [CI] = 1.001-1.03; AOR = 2.54, 95% CI = 1.40-4.62; respectively). Patients with more concomitant prescriptions, more comorbidities, or higher initial daily dosage had significantly lower likelihoods of initiating generic tacrolimus (AOR = 0.93, 95% CI = 0.87-0.99; AOR = 0.87, 95% CI = 0.77-0.99; AOR = 0.96, 95% CI = 0.93-0.993). Among brand tacrolimus new users, 23.6% substituted with generics within 12 months, and an addition of prior hospitalization or unit of initial daily dosage increment was associated with 35% (subdistribution hazard ratio [SHR] = 1.35, 95% CI = 1.02-1.76) or 2% (SHR = 1.02, 95% CI = 1.00-1.04) increase in likelihood of generic substitution, respectively.

CONCLUSIONS

Understanding associations between patient-level factors with generic tacrolimus initiation and substitution could help practitioners and policymakers monitor treatment effect and facilitate generic tacrolimus utilization.

Maintenance Immunosuppression in Solid Organ Transplantation: Integrating Novel Pharmacodynamic Biomarkers to Inform Calcineurin Inhibitor Dose Selection

Calcineurin inhibitors, the primary immunosuppressive therapy used to prevent alloreactivity of transplanted organs, have a narrow therapeutic index. Currently, treatment is individualized based on clinical assessment of the risk of rejection or toxicity guided by trough concentration monitoring. Advances in immune monitoring have identified potential markers that may have value in understanding calcineurin inhibitor pharmacodynamics. Integration of these markers has the potential to complement therapeutic drug monitoring. Existing pharmacokinetic-pharmacodynamic (PK-PD) data is largely limited to correlation between the biomarker and trough concentrations at single time points. Immune related gene expression currently has the most evidence supporting PK-PD integration. Novel biomarker-based approaches to pharmacodynamic monitoring including development of enhanced PK-PD models are proposed to realize the full clinical benefit.

Tacrolimus therapeutic efficacy in post-liver transplant patients with Cytochrome P450 3A5 (CYP3A5) genetic polymorphisms

Genetic polymorphisms of CYP3A5 have been pointed out as factors that influenciates tacrolimus immunosuppressive efficacy in post liver transplant patients. This study aims to review the literature on the influence of cytochrome P450 3A5 (CYP3A5) genetic polymorphisms of tacrolimus in post-liver transplant patients. This study is a literature review. A combination of the descriptors "tacrolimus", "liver transplant", "cytochrome P-450 CYP3A inhibitors" and "genetic polymorphism" were used in the databases PubMed, Cochrane Library, Scopus and Scielo, being evaluated only studies between 2009 and 2019 in English, Portuguese or Spanish. A total of six studies, each from a different population were summarized. Initially, the pharmacological aspects of tacrolimus were discussed, including details on its pharmacodynamics, pharmacokinetics and toxicity After that, we analyzed the studies that correlates CYP3A5 genetic polymorphisms and tacrolimus efficacy, including the ethnical specifications and the general limittions of the studies. The CYP3A5 polymorphisms have pointed to alterations in the metabolism of tacrolimus according to the ethnic and populational genotype, specially the *1 and *3*3 alleles, reflecting in the need for dose adjustment and also in post liver transplant rejection.

Predictive engines based on pharmacokinetics modelling for tacrolimus personalized dosage in paediatric renal transplant patients

The development of predictive engines based on pharmacokinetic-physiological mathematical models for personalised dosage recommendations is an immature field. Nevertheless, these models are extensively applied during the design of new drugs. This study presents new advances in this subject, through a stable population of patients who underwent kidney transplantation and were prescribed tacrolimus. We developed 2 new population pharmacokinetic models based on a compartmental approach, with one following the physiologically based pharmacokinetic approach and both including circadian modulation of absorption and clearance variables. One of the major findings was an improved predictive capability for both models thanks to the consideration of circadian rhythms, both in estimating the population and in Bayesian individual customisation. This outcome confirms a plausible mechanism suggested by other authors to explain circadian patterns of tacrolimus concentrations. We also discovered significant intrapatient variability in tacrolimus levels a week after the conversion from a fast-release (Prograf) to a sustained-release formulation (Advagraf) using adaptive optimisation techniques, despite high adherence and controlled conditions. We calculated the intrapatient variability through parametric intrapatient variations, which provides a method for quantifying the mechanisms involved. We present a first application for the analysis of bioavailability changes in formulation conversion. The 2 pharmacokinetic models have demonstrated their capability as predictive engines for personalised dosage recommendations, although the physiologically based pharmacokinetic model showed better predictive behaviour.

Once-Daily versus Twice-Daily Tacrolimus in Kidney Transplantation: A Systematic Review and Meta-analysis of Observational Studies

BACKGROUND

Tacrolimus is the most commonly prescribed medication in initial immunosuppressive regimens to prevent acute rejection in kidney transplant recipients (KTRs). Tacrolimus was originally available as an immediate-release formulation (IR-Tac) given twice daily. Extended-release tacrolimus (ER-Tac) given once daily was later developed with the expectation of improved medication adherence. Data from observational studies, which compared outcomes between ER-Tac and IR-Tac in different populations of KTRs including those who are unlikely to be enrolled in randomized clinical trials, have been reported.

PURPOSE

To evaluate the incidence of biopsy-proven acute rejection (BPAR) at 12 months together with other outcomes reported in observational studies among adult KTRs who received ER-Tac compared to IR-Tac.

METHODS

In accordance with the recommendations of the Cochrane Collaboration and the Meta-analysis of Observational Studies in Epidemiology, we systematically reviewed all observational studies that compared clinical outcomes between ER-Tac and IR-Tac in KTRs. The systematic searches were conducted on PubMed, EMBASE, Scopus, and Web of Science without language restriction. Reference lists were also searched and reviewed. Data were extracted for BPAR, graft survival, patient survival, estimated glomerular filtration rate (eGFR), serum creatinine (Scr), creatinine clearance (CrCl), at different times after kidney transplantation (KT). A meta-analysis was performed to integrate the results from the eligible studies. This study is registered with PROSPERO, number CRD42019135705.

RESULTS

From the 1401 articles screened, 10 observational studies in KTRs who received tacrolimus were included. The pooled results showed significantly lower BPAR with ER-Tac than with IR-Tac at 12 months post-KT (5 studies, n = 659; RR, 0.69; 95% CI 0.51-0.95; p = 0.02; I² = 0%). No significant differences in BPAR at other time points after KT were found. Graft survival, patient survival, Scr, and eGFR were comparable between groups at different times over approximately 1 year after transplantation.

CONCLUSIONS

Based upon currently available evidence in observational studies, 30% lower risk of BPAR was observed in ER-Tac group compared with IR-Tac group at 12 months post-KT, while there was no significant difference in BPAR risk at any other studied time points. No differences in graft- and patient-survival rates and kidney function were found. Given the limitations of observational studies to make causal inference, as well as quality limitations among the included studies, caution should be exercised in interpreting these findings.

Estimation of Blood Sirolimus Concentration Based on Tacrolimus Concentration/Dose Normalized by Body Weight Ratio in Lung Transplant Patients

BACKGROUND

Sirolimus and tacrolimus require accurate drug dosing based on their target blood levels to produce better clinical outcomes, specifically, the avoidance of drug-induced adverse effects and the maintenance of efficacy. However, because the ideal dose of sirolimus and the schedule for measuring its blood levels are unclear in lung transplant patients, an index is required for estimating sirolimus blood concentrations. The aim of this work is to study the correlation between the trough concentration/dose normalized by body weight (C0/D) ratios of sirolimus and tacrolimus in lung transplant patients.

METHODS

Thirteen lymphangiomyomatosis patients who underwent lung transplantation and were treated with sirolimus and tacrolimus from February 2015 to July 2018 were divided into 2 groups, one receiving twice-daily (TD, n = 6) and the other once-daily (OD, n = 7) tacrolimus formulations. The correlation between the C0/D ratio of sirolimus and patient background was evaluated using Spearman's rank correlation coefficient. Correlations between sirolimus and tacrolimus C0/D ratios or doses were analyzed by single regression analysis.

RESULTS

Significant correlations were found between the C0/D ratios of sirolimus and tacrolimus. The regression equations from the initial data of TD and OD groups at steady state were y = 1.880x + 32.636 (adjusted R = 0.743, P = 0.017) and y = 1.684x + 38.816 (adjusted R = 0.919, P < 0.001), respectively. In addition, the regression equations from all data of TD and OD groups were y = 1.883x + 4.170 (adjusted R = 0.546, P < 0.001) and y = 1.950x + 43.188 (adjusted R = 0.898, P < 0.001), respectively. A significant correlation between the dosage of sirolimus and tacrolimus was observed only in the OD group, with relatively low accuracy.

CONCLUSIONS

Blood sirolimus concentrations can be estimated using the C0/D ratio of tacrolimus, suggesting that the C0/D ratio of tacrolimus is an index of required sirolimus dosage and the frequency of blood sirolimus concentration measurements.

Dosing Requirements of Extended-Release Tacrolimus (Astagraf XL) in African American Kidney Transplant Recipients Converted from Immediate-Release Tacrolimus (AAAKTRS)

BACKGROUND

The formal recommendation for converting twice-daily tacrolimus immediate release (IR) to once-daily tacrolimus extended release (ER) is a 1:1 dose conversion. However, more recent clinical analysis has shown that this may not be true; some patients may require a higher dose. In addition, de novo dosing tacrolimus ER has revealed that African Americans require approximately 20%-30% higher doses than Caucasians to achieve similar levels. As a result, this study sought to identify the appropriate dose conversion in the African American kidney transplant population, a population at high risk of rejection.

METHODS

This was a single-center, prospective, open-label study comparing the difference in dose-normalized trough and total daily dose necessary to reach steady-state therapeutic goal, after conversion from tacrolimus IR to tacrolimus ER, in 25 African American kidney transplant recipients.

RESULTS

After conversion to tacrolimus ER, there was a significant decrease in dose-normalized trough (C0) (0.44 versus 0.59, P = 0.03). Statistically significant differences were seen in both total daily and weight-based doses, when reported as actual values (15 versus 10 mg and 0.16 versus 0.11 mg/kg, respectively), as well as when standardized to achieve a target tacrolimus C0 of 8 ng/mL (18.1 versus 13.6 mg and 0.17 versus 0.15 mg/kg, respectively). The median standardized dose conversion required was 1.3 [1.0, 1.4], for the overall population. There were no instances of biopsy-proven acute rejection, allograft loss, or study drug discontinuation.

CONCLUSIONS

This single-center, open-label conversion study demonstrated that there was a statistically and clinically significant decrease in dose-normalized trough after conversion from tacrolimus IR to tacrolimus ER in an African American kidney transplant population and that a 1:1 dose conversion is unlikely to meet therapeutic goals.

Effectiveness and safety of the conversion to MeltDose® extended-release tacrolimus from other formulations of tacrolimus in stable kidney transplant patients: A retrospective study

Tacrolimus is the cornerstone of immunosuppressive therapy after kidney transplantation. Its narrow therapeutic window mandates serum level strict monitoring and dose adjustments to ensure the optimal risk‐benefit balance. This observational retrospective study analyzed the effectiveness and safety of conversion from twice‐daily immediate‐release tacrolimus (IR‐Tac) or once‐daily prolonged‐release tacrolimus (PR‐Tac) to the recent formulation once‐daily MeltDose^® extended‐release tacrolimus (LCP‐Tac) in 365 stable kidney transplant recipients. We compared kidney function three months before and three months after the conversion. Three months after conversion, the total daily dose was reduced ~35% (P < .0001), and improved bioavailability and stable serum LCP‐Tac concentrations were observed. There was no increase in the number of patients requiring tacrolimus dose adjustments after conversion. Renal function was unaltered, and no cases of BPAR were reported. Reports of tremors, as collected in the clinical histories for each patient, decreased from pre‐conversion (20.8%) to post‐conversion (11.8%, P < .0001). LCP‐Tac generated a cost reduction of 63% compared with PR‐Tac. In conclusion, the conversion strategy to LCP‐Tac from other tacrolimus formulations in stable kidney transplant patients showed safety and effectiveness in a real‐world setting, confirming the data from RCTs. The specific pharmacokinetic properties of LCP‐Tac could be potentially advantageous in patients with tacrolimus‐related adverse events.

Toward a robust tool for pharmacokinetic-based personalization of treatment with tacrolimus in solid organ transplantation: A model-based meta-analysis approach

AIMS

The objective of this study is to develop a generic model for tacrolimus pharmacokinetics modelling using a meta-analysis approach, that could serve as a first step towards a prediction tool to inform pharmacokinetics-based optimal dosing of tacrolimus in different populations and indications.

METHODS

A systematic literature review was performed and a meta-model developed with NONMEM software using a top-down approach. Historical (previously published) data were used for model development and qualification. In-house individual rich and sparse tacrolimus blood concentration profiles from adult and paediatric kidney, liver, lung and heart transplant patients were used for model validation. Model validation was based on successful numerical convergence, adequate precision in parameter estimation, acceptable goodness of fit with respect to measured blood concentrations with no indication of bias, and acceptable performance of visual predictive checks. External validation was performed by fitting the model to independent data from 3 external cohorts and remaining previously published studies.

RESULTS

A total of 76 models were found relevant for meta-model building from the literature and the related parameters recorded. The meta-model developed using patient level data was structurally a 2-compartment model with first-order absorption, absorption lag time and first-time varying elimination. Population values for clearance, intercompartmental clearance, central and peripheral volume were 22.5 L/h, 24.2 L/h, 246.2 L and 109.9 L, respectively. The absorption first-order rate and the lag time were fixed to 3.37/h and 0.33 hours, respectively. Transplanted organ and time after transplantation were found to influence drug apparent clearance whereas body weight influenced both the apparent volume of distribution and the apparent clearance. The model displayed good results as regards the internal and external validation.

CONCLUSION

A meta-model was successfully developed for tacrolimus in solid organ transplantation that can be used as a basis for the prediction of concentrations in different groups of patients, and eventually for effective dose individualization in different subgroups of the population.

Mass-producible microporous silicon membranes for specific leukocyte subset isolation, immunophenotyping, and personalized immunomodulatory drug screening in vitro

Widespread commercial and clinical adaptation of biomedical microfluidic technology has been limited in large part due to the lack of mass producibility of polydimethylsiloxane (PDMS) and glass-based devices commonly as reported in the literature. Here, we present a batch-fabricated, robust, and mass-producible immunophenotyping microfluidic device using silicon micromachining processes. Our Si and glass-based microfluidic device, named the silicon microfluidic immunophenotyping assay (SiMIPA), consists of a highly porous (∼40%) silicon membrane that can selectively separate microparticles below a certain size threshold. The device is capable of isolating and stimulating specific leukocyte populations, and allows for measuring their secretion of cell signaling proteins by means of a no-wash homogeneous chemiluminescence-based immunoassay. The high manufacturing throughput (∼170 devices per wafer) makes a large quantity of SiMIPA chips readily available for clinically relevant applications, which normally require large dataset acquisitions for statistical accuracy. With 30 SiMIPA chips, we performed in vitro immunomodulatory drug screening on isolated leukocyte subsets, yielding 5 data points at 6 drug concentrations. Furthermore, the excellent structural integrity of the device allowed for samples and reagents to be loaded using a micropipette, greatly simplifying the experimental protocol.

Envarsus, a novelty for transplant nephrologists: Observational retrospective study

The aim of this study was to evaluate the trough concentrations (Cp_trough) and the tacrolimus dosage regimen after the conversion of Prograf or Advagraf to Envarsus (new pharmaceutical form with MeltDose technology that improves the absorption of fat-soluble drugs) in patients with stable renal transplantation, and their renal function. We selected stable renal transplant patients who were converted to Envarsus. Two periods were defined: Baseline and Conversion (Envarsus) and they were stratified according to the pharmaceutical form used in the Baseline period. Sixty-one patients were included (24 with Advagraf and 37 with Prograf), with an average age of 52years. The mean post-transplant time at the time of conversion to Envarsus was 76.3months and the mean follow-up in the Baseline and Conversion period was 10.1months and 11.6months, respectively. In the Prograf and Envarsus group, the Cp_trough medians were 6.6 vs 6.4 ng/mL (P=.636), with a mean daily dose that decreased significantly from 3mg to 2mg (P<.001), respectively, maintaining the filtration rate. The median Cp_trough values in the Advagraf and Envarsus groups were 5.7ng/mL and 6.3ng/mL (P=.07), with a median daily dose of 7mg and 4mg (P<.001), respectively, and the same renal function. In stable renal transplant patients, the conversion from Advagraf to Envarsus has allowed the dose of tacrolimus to be reduced by 42.9% and, in the case of Prograf, by 33.3%, maintaining similar Cp_trough values, without renal function being altered.

Pharmacokinetics of Prolonged-Release Once-Daily Formulations of Tacrolimus in De Novo Kidney Transplant Recipients: A Randomized, Parallel-Group, Open-Label, Multicenter Study

INTRODUCTION

Different prolonged-release formulations of tacrolimus are available. To date, the pharmacokinetic (PK) profile of LCP-tacrolimus (LCPT; Envarsus^®) has not been compared with PR-Tac (Advagraf^®) in de novo kidney transplant recipients. These profiles will guide clinical recommendations for the initiation and dose titration strategies of once-daily tacrolimus formulations.

METHODS

This randomized, parallel-group, open-label, multicenter PK study randomized 75 de novo, adult, white kidney transplant recipients to LCPT 0.17 mg/kg/day (n = 37) or PR-Tac 0.20 mg/kg/day (n = 38) for 4 weeks. Dose adjustments were permitted to target a pre-defined therapeutic range based on measured trough blood concentrations.

RESULTS

PK analysis (days 1, 3, 7 and 14) included 68 patients (LCPT, n = 33; PR-Tac, n = 35). Similar proportions of patients were within the pre-defined therapeutic tacrolimus trough blood concentration range, with < 12% in each group having below-target trough levels over the study period. LCPT demonstrated ~ 30% greater relative bioavailability [LCPT/PR-Tac adjusted geometric mean ratio: day 3, 1.32 (p = 0.007); day 7, 1.25 (p = 0.051); day 14, 1.43 (p = 0.002)] and ~ 30% lower peak-to-trough percentage fluctuation of blood concentration [LCPT/PR-Tac adjusted geometric mean ratio: day 3, 0.70 (p < 0.001); day 7, 0.68 (p < 0.001); day 14, 0.73 (p = 0.004)] in addition to longer time to maximum blood concentration (t_max), lower maximum concentration (C_max) and a consistently lower daily dose (~ 40% dose reduction with LCPT vs. PR-Tac by day 28). Safety profiles were similar.

CONCLUSION

In de novo kidney transplant recipients, prolonged-release formulations of tacrolimus can reach therapeutic concentrations in the immediate post-transplant period. LCPT has greater relative bioavailability and lower peak-to-trough fluctuation compared with PR-Tac.

TRIAL REGISTRATION

Registered at ClinicalTrials.gov; study number NCT02500212.

FUNDING

Chiesi Farmaceutici S.p.A.

The potential impact of hematocrit correction on evaluation of tacrolimus target exposure in pediatric kidney transplant patients

BACKGROUND

Tacrolimus is an important immunosuppressive agent with high intra- and inter-individual pharmacokinetic variability and a narrow therapeutic index. As tacrolimus extensively accumulates in erythrocytes, hematocrit is a key factor in the interpretation of tacrolimus whole blood concentrations. However, as hematocrit values in pediatric kidney transplant patients are highly variable after kidney transplantation, translating whole blood concentration targets without taking hematocrit into consideration is theoretically incorrect. The aim of this study is to evaluate the potential impact of hematocrit correction on tacrolimus target exposure in pediatric kidney transplant patients.

METHODS

Data were obtained from 36 pediatric kidney transplant patients. Two hundred fifty-five tacrolimus whole blood samples were available, together responsible for 36 area under the concentration-time curves (AUCs) and trough concentrations. First, hematocrit corrected concentrations were derived using a formula describing the relationship between whole blood concentrations, hematocrit, and plasma concentrations. Subsequently, target exposure was evaluated using the converted plasma target concentrations. Ultimately, differences in interpretation of target exposure were identified and evaluated.

RESULTS

In total, 92% of our patients had lower hematocrit (median 0.29) than the reference value of adult kidney transplant patients. A different evaluation of target exposure for either trough level, AUC, or both was defined in 42% of our patients, when applying hematocrit corrected concentrations.

CONCLUSION

A critical role for hematocrit in therapeutic drug monitoring of tacrolimus in pediatric kidney transplant patients is suggested in this study. Therefore, we believe that hematocrit correction could be a step towards improvement of tacrolimus dose individualization.

Conversion from Twice-Daily Prograf® to Once-Daily Advagraf® in Multi-ethnic Asian Adult Renal Transplant Recipients With or Without Concomitant Use of Diltiazem: Impact of CYP3A5 and MDR1 Genetic Polymorphisms on Tacrolimus Exposure

BACKGROUND AND OBJECTIVES

Tacrolimus is the mainstay of immunosuppression in renal transplantation. Given that once-daily administration improves patient compliance, 1:1 dose conversion from twice-daily Prograf^® to once-daily Advagraf^® is recommended. Although cytochrome P450 (CYP) 3A5 and multi-drug resistance 1 (MDR1) polymorphisms influence tacrolimus concentrations, it is unknown if these impact on conversion. This study investigated the change in the pharmacokinetics of tacrolimus after conversion from Prograf^® to Advagraf^® and examined the impact of CYP3A5 and MDR1 C3435T polymorphisms on those pharmacokinetics.

METHODS

A prospective open-label pharmacokinetic study of 1:1 conversion from Prograf^® to Advagraf^® with or without diltiazem was conducted on 26 stable renal transplant recipients. Blood samples were collected over 24 h during each phase, tacrolimus concentrations were assayed, and noncompartmental pharmacokinetic analysis was performed. All participants were genotyped for CYP3A5*3 and MDR1 C3435T.

RESULTS

After conversion, without diltiazem, the area under the concentration-time curve at steady state from 0 to 24 h after dose administration (AUC_{ss, 0-24}) was significantly reduced [median 224 (range 172-366) vs. 184 (104-347) ng·h/mL, p = 0.006, n = 26]. A decrease in tacrolimus exposure (median 21%) was only evident among CYP3A5 expressors [227 (172-366) vs. 180 (104-347) ng·h/mL, p = 0.014, n = 18], not among non-expressors [215 (197-290) vs. 217 (129-281) ng·h/mL, p = 0.263, n = 8]. In contrast, among CYP3A5 expressors receiving diltiazem, AUC_{ss, 0-24} did not change significantly upon conversion [229 (170-296) vs. 221 (123-342) ng·h/mL, p = 0.575, n = 10]. An independent effect was not evident for MDR1 C3435T polymorphism.

CONCLUSION

The high prevalence of CYP3A5 polymorphism among Asians may lead to a significant reduction in tacrolimus exposure with 1:1 dose conversion of Prograf^® to Advagraf^®. These results advocate for CYP3A5 determination prior to conversion, and suggest that 1:1.25 conversion should be used for CYP3A5 expressors and 1:1 conversion for other patients.

Once-daily vs twice-daily tacrolimus for de novo living kidney transplantation patients including ABO/HLA compatible and incompatible: A randomized trial

Tacrolimus (TAC) is available as a twice-daily capsule (TAC-BID), once-daily capsule (TAC-QD), and once-daily tablet. Recipients with ABO-incompatible/anti-human leukocyte antigen (HLA)-incompatible transplantation were excluded in previous trials and have thus not been evaluated. We conducted a 5-year trial to determine whether TAC-QD is noninferior to TAC-BID for transplant outcomes. Adults who underwent de novo living kidney transplantation were randomly assigned (62 TAC-QD; 63 TAC-BID). We did not exclude ABO-/HLA- incompatible transplantation. TAC was initiated 7 days preoperatively (0.10 mg/kg/d). Mycophenolate mofetil, methylprednisolone, and basiliximab were administered. The primary endpoint was graft failure (non-censored for death). We performed a noninferiority test. The noninferiority margin was 10% in risk difference. Five-year graft failure rates were 6.5% and 9.5% for TAC-QD and TAC-BID, respectively (noninferiority, P = 0.009). The estimated glomerular filtration rates were similar between the groups (noninferiority, P < 0.001). TAC-QD did not have point estimates of risk difference above the inferiority margin in any assessed endpoints. However, a tendency of interaction was observed between biopsy-proven acute rejection and the follow-up period. In a living kidney transplant population with 40% of patients with ABO/HLA incompatibility, the effect of TAC-QD was not appreciably worse on various clinical transplant outcomes than that of TAC-BID over 5 years.

Extended release versus immediate release tacrolimus in kidney transplant recipients: a systematic review and meta-analysis

PURPOSE

To compare the estimated glomerular filtration rate (eGFR) at 12 months together with other outcomes among adult kidney transplant recipients (KTRs) who received extended release, once daily tacrolimus (ER-Tac) compared to those who received the immediate release, twice daily tacrolimus (IR-Tac) administration.

METHODS

In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement, we systematically reviewed all randomized controlled trials (RCTs) that compared clinical outcomes between ER-Tac versus IR-Tac in KTRs. The systematic searches were conducted on PubMed, EMBASE, Cochrane Register of Controlled Trials, Scopus, Web of Science, and CINAHL without language restriction. The trials registered and reference lists were also searched and reviewed. Data were extracted for eGFR, serum creatinine (Scr), creatinine clearance (CrCl), biopsy-proven acute rejection rate (BPAR), graft survival, and overall patient survival at different times over 24 months after kidney transplant (KT). A meta-analysis was performed to integrate the results from eligible studies.

RESULTS

From 1145 articles screened, 11 RCTs were included. The pooled results of included RCTs showed no significant difference of eGFR at 12 months between ER-Tac and IR-Tac groups (four trials, n = 1738; mean difference - 0.77 mL/min/1.73 m2, 95% CI: - 2.41 to 0.87; p = 0.56; I2 = 0%). Comparing between the two tacrolimus formulations, there were no significant differences of eGFR, CrCl, Scr, BPAR, graft survival, and patient survival at different times over 4 years after transplantation.

CONCLUSIONS

Based upon currently available evidences in KTRs, the impact on kidney allograft function appears to be comparable between ER-Tac and IR-Tac.

High tacrolimus intra-patient variability is associated with graft rejection, and de novo donor-specific antibodies occurrence after liver transplantation

AIM

To investigate the role of tacrolimus intra-patient variability (IPV) in adult liver-transplant recipients.

METHODS

We retrospectively assessed tacrolimus variability in a cohort of liver-transplant recipients and analyzed its effect on the occurrence of graft rejection and de novo donor-specific antibodies (dnDSAs), as well as graft survival during the first 2 years posttransplantation. Between 02/08 and 06/2015, 116 patients that received tacrolimus plus mycophenolate mofetil (with or without steroids) were included.

RESULTS

Twenty-two patients (18.5%) experienced at least one acute-rejection episode (BPAR). Predictive factors for a BPAR were a tacrolimus IPV of > 35% [OR = 3.07 95%CI (1.14-8.24), P = 0.03] or > 40% [OR = 4.16 (1.38-12.50), P = 0.01), and a tacrolimus trough level of < 5 ng/mL [OR=3.68 (1.3-10.4), P =0.014]. Thirteen patients (11.2%) developed at least one dnDSA during the follow-up. Tacrolimus IPV [coded as a continuous variable: OR = 1.1, 95%CI (1.0-1.12), P = 0.006] of > 35% [OR = 4.83, 95%CI (1.39-16.72), P = 0.01] and > 40% [OR = 9.73, 95%CI (2.65-35.76), P = 0.001] were identified as predictors to detect dnDSAs. IPV did not impact on patient- or graft-survival rates during the follow-up.

CONCLUSION

Tacrolimus-IPV could be a useful tool to identify patients with a greater risk of graft rejection and of developing a de novo DSA after liver transplantation

Prediction of Tacrolimus Exposure by CYP3A5 Genotype and Exposure of Co-Administered Everolimus in Japanese Renal Transplant Recipients

While tacrolimus and everolimus have common metabolic pathways through CYP3A4/5, tacrolimus is metabolized solely by CYP3A4 in recipients with the CYP3A5*3/*3. The purpose of this study was to evaluate how the area under the blood concentration-time curves (AUC) of tacrolimus could be predicted based on CYP3A5 genotype and the AUC of everolimus in renal transplant patients taking both drugs. The dose-adjusted AUC (AUC/D) of tacrolimus and everolimus were calculated at one month and one year after transplantation. Significant correlations between the AUC/D of tacrolimus and everolimus were found for patients with the CYP3A5*1 allele or CYP3A5*3/*3 at both one month and one year. At both stages, the determination coefficients were higher and the slopes of regression equations were larger for patients with CYP3A5*3/*3 compared to the CYP3A5*1 allele. A good correlation between single doses of tacrolimus and everolimus was found for CYP3A5*3/*3 patients at 1 year after transplantation (r = 0.794, p < 0.001). The variability of the AUC_0–24/D of tacrolimus for each CYP3A5 genotype could be predicted based on the AUC_0–12/D of everolimus. Clinicians may be able to comprehensively carry out the dose adjustments of tacrolimus and everolimus based on relationship with AUCs of both drugs in each CYP3A5 genotype.