Clinical Pharmacokinetics and Pharmacodynamics of Prednisolone and Prednisone in Solid Organ Transplantation

Food effects and pharmacokinetic evaluation of oral single-dose prednisone acetate and prednisolone in healthy Chinese subjects

BACKGROUND

To assess the food effects and pharmacokinetic profile of oral prednisone (test preparation,5 mg) and prednisolone tablets (reference preparation,5 mg) using a randomized, two-period, two crossover, single-dose, fast and fed trial in 48 (24 in fast, 24 in fed) healthy Chinese adult subjects.

MATERIALS AND METHODS

In the trial, the plasma concentrations were determined at different time points up to 24 h and the pharmacokinetic parameters were analyzed according to the concentration data by non-compartmental analysis using WinNonlin software. All laboratory parameters, vital signs and adverse events (AEs) were monitored and recorded under the supervision of the clinicians throughout the whole process of the study.

RESULTS

Prednisone and prednisolone undergo interconversion in liver. On average, the bioavailability of prednisolone after oral prednisone is approximately 80% of that after prednisolone. And about 20% of prednisolone is converted to prednisone after administration of equivalent oral of prednisolone tablet. Food taken with prednisone or prednisolone tablets delays the time reach the peak prednisone or prednisolone concentration (Tmax) by approximately 0.5 h but does not affect systemic exposure. Prednisone and prednisolone tablets were well tolerated, and there were no serious adverse events reported in the study.

CONCLUSIONS

For there was no information about the pharmacokinetic profile and food effects of oral prednisone and prednisolone tablets, the result of this research would be a clinical medication for doctors especially dealing patients with varying degrees of liver diseases.

CLINICAL TRIAL REGISTRATION

CTR20200093; registered in http://www.chinadrugtrials.org.cn/ at 11 March 2020.

Hypothalamic-Pituitary-Adrenal Axis Activity and Metabolic Disorders in Kidney Transplant Recipients on Long-Term Glucocorticoid Therapy

Background/Objectives: Glucocorticoids are commonly used for maintenance immunosuppressive therapy in kidney transplant recipients (KTRs). We aimed to investigate the prevalence of hypothalamic-pituitary-adrenal (HPA) axis suppression and its association with metabolic disorders in stable KTRs on low-dose glucocorticoids. Methods: This cross-sectional study included adult KTRs on low-dose glucocorticoids. HPA axis suppression was defined as baseline morning cortisol < 5 μg/dL. Adrenocorticotropic hormone (ACTH), dehydroepiandrosterone-sulphate (DHEAS) and 24 h urinary free cortisol (UFC) levels were also assessed. Examined metabolic disorders included hypertension, dyslipidemia, central obesity and post-transplant diabetes mellitus (PTDM). Results: Eighty adult KTRs with a median 57 months (IQR 24-102) since transplantation were included in the study. The mean prednisolone dose was 5.0 ± 1.3 mg/day. Baseline cortisol < 5.0 μg/dL was observed in 27.5% of the KTRs. Participants with baseline cortisol < 5.0 μg/dL were older (55.1 vs. 47.4 years, p = 0.023) and had had a transplant for a longer time (101.4 vs. 67.0 months, p = 0.043), compared with the rest of the cohort. Baseline cortisol correlated positively with ACTH (rho = 0.544, p < 0.001), DHEAS (rho:0.459, p < 0.001) and UFC (rho: 0.377, p = 0.002). The area under the receiver-operating characteristic curve for ACTH as a predictor of baseline cortisol > 5.0 μg/dL was 0.79 [95% confidence interval (CI): 0.68-0.89]. After adjustment for covariates, HPA axis suppression was not associated with the examined metabolic disorders. Conclusions: Our study showed that stable KTRs on chronic low-dose glucocorticoids exhibited an increased prevalence of HPA axis suppression. ACTH may serve as a surrogate biomarker for HPA axis activity in this population. Further research could evaluate the association of glucocorticoid-induced HPA axis inhibition with metabolic disorders.

Does Age Influence Immunosuppressant Drug Pharmacokinetics in Kidney Transplant Recipients?

BACKGROUND

The pharmacokinetics of immunosuppressant drugs may change with advancing age, potentially affecting patient outcomes.

OBJECTIVE

To characterise the effects of age on the pharmacokinetic and exposure parameters of tacrolimus, mycophenolate, and prednisolone.

METHODS

Pharmacokinetic profiling, involving whole blood tacrolimus, total and free plasma mycophenolic acid (MPA), total plasma mycophenolic acid glucuronide (MPAG), and total and free plasma prednisolone, was performed in an older and younger adult cohort. Thirteen samples were drawn on a single occasion, pre-oral dose and then at 0.25, 0.5, 0.75, 1, 1.25, 1.5, 2, 3, 4, 6, 9, and 12 h post-dose. Non-compartmental analysis was conducted using the PKNCA package, and pharmacokinetic and exposure parameters were compared between age groups using a Mann-Whitney test. A regression analysis was conducted for free MPA and MPAG using significant variables of interest.

RESULTS

This exploratory study included 21 older and 18 younger adults. Dose-adjusted tacrolimus, total MPA and free prednisolone pharmacokinetic parameters were not different between age groups; however, for free MPA and MPAG, older recipients had significantly greater minimum and maximum concentrations, trough concentrations, and half-life. There was a two-fold increase in free MPA exposure in older adults (median dose-adjusted AUC0-12: 1284 vs. 684 μg h/L, p < 0.0001); MPAG exposure similarly increased. Age was significantly associated with free MPA and MPAG exposure, and free MPA exposure was associated with haematocrit (p < 0.05).

CONCLUSION

Differences in MPA were found with advancing age and may be due to altered kidney function, haematocrit, plasma protein binding and/or drug absorption. Future research should explore specific covariate contributions to this further.

Systemic immunostimulation induces glucocorticoid-mediated thymic involution succeeded by rebound hyperplasia which is impaired in aged recipients

The thymus is the central organ involved with T-cell development and the production of naïve T cells. During normal aging, the thymus undergoes marked involution, reducing naïve T-cell output and resulting in a predominance of long-lived memory T cells in the periphery. Outside of aging, systemic stress responses that induce corticosteroids (CS), or other insults such as radiation exposure, induce thymocyte apoptosis, resulting in a transient acute thymic involution with subsequent recovery occurring after cessation of the stimulus. Despite the increasing utilization of immunostimulatory regimens in cancer, effects on the thymus and naïve T cell output have not been well characterized. Using both mouse and human systems, the thymic effects of systemic immunostimulatory regimens, such as high dose IL-2 (HD IL-2) with or without agonistic anti-CD40 mAbs and acute primary viral infection, were investigated. These regimens produced a marked acute thymic involution in mice, which correlated with elevated serum glucocorticoid levels and a diminishment of naïve T cells in the periphery. This effect was transient and followed with a rapid thymic "rebound" effect, in which an even greater quantity of thymocytes was observed compared to controls. Similar results were observed in humans, as patients receiving HD IL-2 treatment for cancer demonstrated significantly increased cortisol levels, accompanied by decreased peripheral blood naïve T cells and reduced T-cell receptor excision circles (TRECs), a marker indicative of recent thymic emigrants. Mice adrenalectomized prior to receiving immunotherapy or viral infection demonstrated protection from this glucocorticoid-mediated thymic involution, despite experiencing a substantially higher inflammatory cytokine response and increased immunopathology. Investigation into the effects of immunostimulation on middle aged (7-12 months) and advance aged (22-24 months) mice, which had already undergone significant thymic involution and had a diminished naïve T cell population in the periphery at baseline, revealed that even further involution was incurred. Thymic rebound hyperplasia, however, only occurred in young and middle-aged recipients, while advance aged not only lacked this rebound hyperplasia, but were entirely absent of any indication of thymic restoration. This coincided with prolonged deficits in naïve T cell numbers in advanced aged recipients, further skewing the already memory dominant T cell pool. These results demonstrate that, in both mice and humans, systemic immunostimulatory cancer therapies, as well as immune challenges like subacute viral infections, have the potential to induce profound, but transient, glucocorticoid-mediated thymic involution and substantially reduced thymic output, resulting in the reduction of peripheral naive T cells. This can then be followed by a marked rebound effect with naïve T cell restoration, events that were shown not to occur in advanced-aged mice.

Genetic variability in the glucocorticoid pathway and treatment outcomes in hospitalized patients with COVID-19: a pilot study

Introduction: Corticosteroids are widely used for the treatment of coronavirus disease (COVID)-19. Genetic polymorphisms of the glucocorticoid receptor, metabolizing enzymes, or transporters may affect treatment response to dexamethasone. This study aimed to evaluate the association of the glucocorticoid pathway polymorphisms with the treatment response and short-term outcomes in patients with severe COVID-19. Methods: Our pilot study included 107 hospitalized patients with COVID-19 treated with dexamethasone and/or methylprednisolone, genotyped for 14 polymorphisms in the glucocorticoid pathway. Results: In total, 83% of patients had severe disease, 15.1% had critical disease and only 1.9% had moderate disease. CYP3A4 rs35599367 was the major genetic determinant of COVID-19 severity as carriers of this polymorphism had higher risk of critical disease (OR = 6.538; 95% confidence interval = 1.19-35.914: p = 0.031) and needed intensive care unit treatment more frequently (OR = 10; 95% CI = 1.754-57.021: p = 0.01). This polymorphism was also associated with worse disease outcomes, as those patients had to switch from dexamethasone to methylprednisolone more often (OR = 6.609; 95% CI = 1.137-38.424: p = 0.036), had longer hospitalization (p = 0.022) and needed longer oxygen supplementation (p = 0.040). Carriers of NR3C1 rs6198 polymorphic allele required shorter dexamethasone treatment (p = 0.043), but had higher odds for switching therapy with methylprednisolone (OR = 2.711; 95% CI = 1.018-7.22: p = 0.046). Furthermore, rs6198 was also associated with longer duration of hospitalization (p = 0.001) and longer oxygen supplementation (p = 0.001). NR3C1 rs33388 polymorphic allele was associated with shorter hospitalization (p = 0.025) and lower odds for ICU treatment (OR = 0.144; 95% CI = 0.027-0.769: p = 0.023). GSTP1 rs1695 was associated with duration of hospitalization (p = 0.015), oxygen supplementation and (p = 0.047) dexamethasone treatment (p = 0.022). Conclusion: Our pathway-based approach enabled us to identify novel candidate polymorphisms that can be used as predictive biomarkers associated with response to glucocorticoid treatment in COVID-19. This could contribute to the patient's stratification and personalized treatment approach.

Budesonide in Liver Immunology: A Therapeutic Opportunity in Liver Transplantation

Purpose of Review

A major remaining challenge in liver transplantation is achieving the balance between adequate immunosuppression to prevent allograft rejection and minimising immunosuppression-related side effects. Systemic corticosteroids contribute to the development of multi-system adverse effects that increase recipient morbidity and mortality. Oral budesonide undergoes significant first-pass hepatic metabolism, thereby minimising systemic availability, but maintains a similar immunosuppressive impact on the liver and gastrointestinal tract as systemic corticosteroids. This review aims to explore the rationale for oral budesonide as an alternative immunosuppressant to conventional corticosteroids following liver transplantation.

Recent findings

Despite increasing evidence of efficacy and safety in other gastrointestinal conditions, research on the role of budesonide as an alternative immunosuppressant to conventional corticosteroids in the liver transplant setting remains scarce. However, existing literature suggests efficacy in the treatment and prevention of acute rejection after liver transplantation, with minimal toxicity.

Summary

The unique pharmacokinetic profile of oral budesonide may address the unmet need for a medical therapy that has efficacy but with a better safety profile compared to conventional corticosteroids in the liver transplant setting.

The effect of genetic variants in the transcription factor TSPYL family on the CYP3A4 mediated cyclosporine metabolism in kidney transplant patients

CYP3A4 activity shows considerable interindividual variability. Although studies indicate 60%-80% is heritable, common single nucleotide variants (SNVs) in CYP3A4 together only explain ~10%. Transcriptional factors, such as the testis-specific Y-encoded-like proteins (TSPYLs) family, have been reported to regulate the expression of CYP enzymes including CYP3A4 in vitro. Here, we investigated the effect of genetic variants in TSPYL on CYP3A4 activity using data from a clinical study and a human liver bank. Five SNVs (rs3828743, rs10223646, rs6909133, rs1204807, and rs1204811) in TSPYL were selected because of a reported effect on CYP3A4 expression in vitro or suggested clinical effect. For the clinical study, whole blood concentrations, clinical data, and DNA were available from 295 kidney transplant recipients participating in the prospective MECANO study. A multivariate pharmacokinetic model adjusted for body weight, steroid treatment, and CYP3A4 genotype was used to assess the effect of the genetic variants on cyclosporine clearance. In multivariate analysis, homozygous carriers of rs3828743 had a 18% lower cyclosporin clearance compared to the wild-type and heterozygous patients (28.72 vs. 35.03 L/h, p = 0.018) indicating a lower CYP3A4 activity and an opposite direction of effect compared to the previously reported increased CYP3A4 expression. To validate, we tested associations between rs3828743 and CYP3A4 mRNA and protein expression as well as enzyme activity with data from a liver bank (n = 150). No association with any of these end points was observed. In conclusion, the totality of evidence is not in support of a significant role for TSPYL SNV rs3828743 in explaining variability in CYP3A4 activity.

Feasibility of steroid-free tacrolimus-basiliximab immunosuppression in pediatric liver transplantation and predictors for steroid requirement

Avoidance of steroids in pediatric liver transplantation may reduce toxicity and morbidity. The aim of this study was to analyze the feasibility of a steroid-free tacrolimus-basiliximab immunosuppression scheme, the risk factors associated with steroid requirement, and safety parameters. Patients who underwent liver transplantation for biliary atresia between 2011 and 2019 were included and followed for 6 months after transplantation. Immunosuppression consisted of tacrolimus-based treatment with basiliximab induction. Steroid-free survival was estimated, and risk factors for steroid requirement were evaluated using multivariate Cox regression analysis. A total of 76 patients were included, of whom 42 (55.3%) required steroids (>14 d) due to biopsy-proven acute rejection (47.6%, n = 20), instability in liver function tests (35.7%, n = 15), tacrolimus-related adverse drug reactions (14.3%, n = 6), or other reasons (bronchospasm episode, n = 1). Steroid-free survival was 45.9% (95% CI, 35.9-58.8). Independent factors associated with steroid requirement included tortuosity in tacrolimus trough levels (≥1.76 vs. <1.76: HR 5.8, 95% CI, 2.6-12.7; p < 0.001) and mean tacrolimus trough levels (≥ 6.4 ng/mL vs. < 6.4 ng/mL: HR 0.4, 95% CI, 0.2-0.7; p = 0.002). The rate of bacterial and viral infections was comparable between patients with and without steroids, although in the former group, cytomegalovirus infection developed earlier ( p = 0.03). Patients receiving steroids had higher total cholesterol, LDL, and HDL levels ( p < 0.05) during follow-up, but no changes in the height Z-score were observed 1 year after transplantation. Basiliximab induction in combination with tacrolimus-based treatment avoided steroid requirements in 45% of the patients. Tacrolimus variability and trough levels below 6.4 ng/mL independently increased the risk of steroid requirement. Further efforts should be focused on personalizing immunosuppressive treatment.

Incidence and Risk Factors of Systemic Adverse Effects and Complications of Ultrasound- and Fluoroscopy-Guided Glucocorticoid Injections: A Retrospective Cohort Study

OBJECTIVES

The aims of the study are to assess the incidence of systemic adverse effects and complications of ultrasound-guided and fluoroscopy-guided glucocorticoid injections and to identify associated risk factors.

DESIGN

This retrospective cohort study compared participants who received a glucocorticoid injection at the outpatient clinic and participants who had an appointment but did not receive a glucocorticoid injection. Participants were called to verify whether they had experienced any of the predetermined systemic adverse effects and complications. Multiple binary logistic regression was used to identify systemic adverse effect and complication risk factors.

RESULTS

There were 1010 participants in the glucocorticoid injection group and 328 in the nonglucocorticoid injection group. There was no statistically significant difference in the occurrence of systemic infection and decompensated heart failure between the two groups. More participants in the glucocorticoid injection group developed abnormal uterine bleeding and erectile dysfunction, but the differences did not reach statistical significance. Female participants were 1.9 times more likely to develop systemic adverse effects ( P < 0.001). Younger age ( P < 0.001), diabetes ( P = 0.012), and higher glucocorticoid injection doses ( P = 0.024) were also associated with an increased risk of developing systemic adverse effects.

CONCLUSIONS

Identified risk factors for developing glucocorticoid injection systemic adverse effects were younger age, female sex, diabetes, tobacco use, and high glucocorticoid injection doses.

Immunosuppression for older liver transplant recipients

Older liver transplant recipients have a lower risk of acute rejection than younger patients (9% for patients aged ≥65 years versus 23% for those aged 18-34 years) and are more vulnerable to immunosuppression-related complications. The number of liver transplant recipients ≥65 years has risen to 22% in Europe and the US, but limited information is available on the optimal immunosuppressive regimen for these patients. In this review, we discuss the appropriate management of immunosuppressive agents in older adults to minimize adverse events while avoiding acute rejection. The way the body processes drugs greatly depends on age. In the case of calcineurin inhibitor drugs, aging reduces hepatic metabolism, leading to changes in their pharmacokinetics. Corticosteroids also show decreased clearance as the patient ages. In severe cases of hypoalbuminemia, dose adjustment of mycophenolate acid derivatives may be necessary. However, the pharmacokinetic profiles of the mammalian target of rapamycin inhibitors, basiliximab, and rabbit anti-thymocyte globulin remain unaffected by age. Furthermore, age-related frailty may impact drug metabolism and require tailored interventions and closer follow-up. Although there is limited research, elderly liver transplant recipients require less immunosuppression with double or triple-agent regimens, lower exposure to calcineurin inhibitors, and a shorter course of corticosteroids. The usage of mammalian target of rapamycin inhibitors in older transplant populations has not been specifically investigated, and thus their usage should align with indications for younger patient groups.

Simultaneous Determination of Prednisone and Prednisolone in Serum by Turbulent Flow Liquid Chromatography-Tandem Mass Spectrometry

Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative therapeutic treatment for patients with high-risk hematologic malignancies and bone marrow failure syndromes. While allo-HCT can be highly effective, it is met with significant regimen-related toxicities and complications such as graft-versus-host disease (GVHD), poor immune reconstitution, and infections. Prednisone is the preferred treatment for patients with both acute and chronic GVHD. While effective, high-dose prednisone can cause many complications, including weight gain, skin fragility, muscle weakness, bone demineralization, hyperglycemia, insomnia, and psychosis. Optimizing prednisone (and prednisolone) dosing by measuring their concentrations and calculating their pharmacokinetic parameters will allow for personalized treatments for patients, producing more effective and safer treatments for GVHD. This chapter describes a method to measure both compounds simultaneously. Prednisone and prednisolone are extracted from serum by the addition of methanol containing deuterated internal standards. Chromatographic separation is achieved using a reversed-phase HPLC column followed by tandem mass spectrometry performed in the positive ion mode. This assay is fast, accurate, sensitive and allows for rapid drug measurements and timely dose modifications.

Dosage optimization of tacrolimus based on the glucocorticoid dose and pharmacogenetics in adult patients with systemic lupus erythematosus

BACKGROUND

The purpose of the study was to develop a genotype-incorporated population pharmacokinetic (PPK) model of tacrolimus (TAC) in adults with systemic lupus erythematosus (SLE) to investigate the factors influencing TAC pharmacokinetics and to develop an individualized dosing regimen based on the model. In addition, a non-genotype-incorporated model was also established to assess its predictive performance compared to the genotype-incorporated model.

METHODS

A total of 365 trough concentrations from 133 adult SLE patients treated with TAC were collected to develop a genotype-incorporated PPK model and a non-genotype-incorporated PPK model of TAC using a nonlinear mixed-effects model (NONMEM). External validation of the two models was performed using data from an additional 29 patients. Goodness-of-fit diagnostic plots, bootstrap method, and normalized predictive distribution error test were used to validate the predictive performance and stability of the final models. The goodness-of-fit of the two final models was compared using the Akaike information criterion (AIC). The dosing regimen was optimized using Monte Carlo simulations based on the developed optimal model.

RESULTS

The typical value of the apparent clearance (CL/F) of TAC estimated in the final genotype-incorporated model was 14.3 L h-1 with inter-individual variability of 27.6%. CYP3A5 polymorphism and coadministered medication were significant factors affecting TAC-CL/F. CYP3A5 rs776746 GG genotype carriers had only 77.3% of the TAC-CL/F of AA or AG genotype carriers. Omeprazole reduced TAC-CL/F by 3.7 L h-1 when combined with TAC, while TAC-CL/F increased nonlinearly as glucocorticoid dose increased. Similar findings were demonstrated in the non-genotype-incorporated PPK model. Comparing these two models, the genotype-incorporated PPK model was superior to the non-genotype-incorporated PPK model (AIC = 643.19 vs. 657.425). Monte Carlo simulation based on the genotype-incorporated PPK model indicated that CYP3A5 rs776746 AA or AG genotype carriers required a 1/2-1 fold higher dose of TAC than GG genotype carriers to achieve the target concentration. And as the daily dose of prednisone increases, the dose of TAC required to reach the target concentration increases appropriately.

CONCLUSIONS

We developed the first pharmacogenetic-based PPK model of TAC in adult patients with SLE and proposed a dosing regimen based on glucocorticoid dose and CYP3A5 genotype according to the model, which could facilitate individualized dosing for TAC.

Staging and clinical characteristics of pregnant women with chronic hepatitis B virus infection: A retrospective cohort study from Nanjing, China

AIM

To investigate the immune status of Chinese chronic hepatitis B (CHB) pregnant women and their clinical characteristics.

METHODS

About 1544 CHB pregnant women without antiviral therapy from 2013 to 2018 were selected from the hospital records. The definition of immune status is based on American Association for the Study of Liver Diseases (AASLD) 2018 Hepatitis B Guidance, and those who did not meet any criteria of the immune status were referred to in the gray zones (GZ).

RESULTS

There were 284 patients in the immune-tolerance phase, 72 patients in the HBeAg-positive immune active phase, 553 patients in the inactive phase, 61 patients in the HBeAg-negative immune active phase. Of note, 574 (37.18%) patients did not fit into any of the above phases were defined as the GZ. Patients with elevated ALT had a higher rate of intrahepatic cholestasis of pregnancy (ICP). Mother to child HBV transmission was rare (only two cases) and occurred in mothers in the immune-tolerant phase.

CONCLUSIONS

Our data showed that more than one-third of CHB pregnant women were classified into the GZ. In standard stages, advanced age is associated with HBeAg-negative and a higher cesarean rate in the inactive phase. The incidence of ICP was higher in immune active phases, including GB and GD. The probability of mother-to-child transmission in gray zones is low.

Therapeutic Drug Monitoring and Dosage Adjustments of Immunosuppressive Drugs When Combined With Nirmatrelvir/Ritonavir in Patients With COVID-19

ABSTRACT

Nirmatrelvir/ritonavir (Paxlovid) consists of a peptidomimetic inhibitor (nirmatrelvir) of the SARS-CoV-2 main protease and a pharmacokinetic enhancer (ritonavir). It is approved for the treatment of mild-to-moderate COVID-19. This combination of nirmatrelvir and ritonavir can mediate significant and complex drug-drug interactions (DDIs), primarily due to the ritonavir component. Indeed, ritonavir inhibits the metabolism of nirmatrelvir through cytochrome P450 3A (CYP3A) leading to higher plasma concentrations and a longer half-life of nirmatrelvir. Coadministration of nirmatrelvir/ritonavir with immunosuppressive drugs (ISDs) is particularly challenging given the major involvement of CYP3A in the metabolism of most of these drugs and their narrow therapeutic ranges. Exposure of ISDs will be drastically increased through the potent ritonavir-mediated inhibition of CYP3A, resulting in an increased risk of adverse drug reactions. Although a decrease in the dosage of ISDs can prevent toxicity, an inappropriate dosage regimen may also result in insufficient exposure and a risk of rejection. Here, we provide some general recommendations for therapeutic drug monitoring of ISDs and dosing recommendations when coadministered with nirmatrelvir/ritonavir. Particularly, tacrolimus should be discontinued, or patients should be given a microdose on day 1, whereas cyclosporine dosage should be reduced to 20% of the initial dosage during the antiviral treatment. Dosages of mammalian target of rapamycin inhibitors (m-TORis) should also be adjusted while dosages of mycophenolic acid and corticosteroids are expected to be less impacted.

Conventional and Novel Approaches to Immunosuppression in Lung Transplantation

Most therapeutic advances in immunosuppression have occurred over the past few decades. Although modern strategies have been effective in reducing acute cellular rejection, excess immunosuppression comes at the price of toxicity, opportunistic infection, and malignancy. As our understanding of the immune system and allograft rejection becomes more nuanced, there is an opportunity to evolve immunosuppression protocols to optimize longer term outcomes while mitigating the deleterious effects of traditional protocols.

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

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

Fingerprick Microsampling Methods Can Replace Venepuncture for Simultaneous Therapeutic Drug Monitoring of Tacrolimus, Mycophenolic Acid, and Prednisolone Concentrations in Adult Kidney Transplant Patients

BACKGROUND

Kidney transplant patients undergo repeated and frequent venepunctures during allograft management. Microsampling methods that use a fingerprick draw of capillary blood, such as dried blood spots (DBS) and volumetric absorptive microsamplers (VAMS), have the potential to reduce the burden and volume of blood loss with venepuncture.

METHODS

This study aimed to examine microsampling approaches for the simultaneous measurement of tacrolimus, mycophenolic acid, mycophenolic acid glucuronide (MPAG), and prednisolone drug concentrations compared with standard venepuncture in adult kidney transplant patients. DBS and VAMS were simultaneously collected with venepuncture samples from 40 adult kidney transplant patients immediately before and 2 hours after immunosuppressant dosing. Method comparison was performed using Passing-Bablok regression, and bias was assessed using Bland-Altman analysis. Drug concentrations measured through microsampling and venepuncture were also compared by estimating the median prediction error (MPE) and median absolute percentage prediction error (MAPE).

RESULTS

Passing-Bablok regression showed a systematic difference between tacrolimus DBS and venepuncture [slope of 1.06 (1.01-1.13)] and between tacrolimus VAMS and venepuncture [slope of 1.08 (1.03-1.13)]. Tacrolimus values were adjusted for this difference, and the corrected values showed no systematic differences. Moreover, no systematic differences were observed when comparing DBS or VAMS with venepuncture for mycophenolic acid and prednisolone. Tacrolimus (corrected), mycophenolic acid, and prednisolone microsampling values met the MPE and MAPE predefined acceptability limits of <15% when compared with the corresponding venepuncture values. DBS and VAMS, collected in a controlled environment, simultaneously measured multiple immunosuppressants.

CONCLUSIONS

This study demonstrates that accurate results of multiple immunosuppressant concentrations can be generated through the microsampling approach, with a preference for VAMS over DBS.

Mania after long-term treatment with daily 10 mg prednisolone

Background

High-dose corticosteroids may be accompanied by central nervous system side-effects, including psychiatric disorders. These psychiatric disorders tend to appear relatively early in treatment. We report an unusual case of mania after long-term administration of a small dose of prednisolone.

Case Presentation

A patient was treated for relapsed Crohn's disease with a small dose of prednisolone (10 mg/day). After 6 months, she became severely manic. There was no family history of psychiatric disorders. The mania was resistant to olanzapine and sodium valproate, but improved with the reduction of the prednisolone dose. Prednisolone was tapered off while confirming with the gastroenterologist that there was no flare-up of Crohn's disease. She is now off prednisolone and is doing well, with no outbreaks of Crohn's disease or manic episodes.

Conclusion

This case of severe mania after 6 months of low-dose prednisolone is unusual. Physicians should be aware that even small doses of long-term prednisolone may cause the emergence of severe mania.

Tacrolimus Population Pharmacokinetic Model in Adult Chinese Patients with Nephrotic Syndrome and Dosing Regimen Identification Using Monte Carlo Simulations

BACKGROUND

The study aimed to establish a population pharmacokinetic (PPK) model of tacrolimus for Chinese patients with nephrotic syndrome using the patient's genotype and Wuzhi capsule dosage as the main test factors.

METHODS

Ninety-six adult patients with nephrotic syndrome, who were receiving tacrolimus treatment, were enrolled. A nonlinear mixed-effects model was used to determine the influencing factors of interindividual tacrolimus metabolism variation and establish a PPK model. To optimize the tacrolimus dosage, 10,000 Monte Carlo simulations were performed.

RESULTS

The 1-chamber model of first-order absorption and elimination was the most suitable model for the data in this study. The typical population tacrolimus clearance (CL/F) value was 16.9 L/h. The percent relative standard error (RSE%) of CL/F was 12%. Increased Wuzhi capsule and albumin doses both decreased the tacrolimus CL/F. In CYP3A5 homozygous mutation carriers, the CL/F was 39% lower than that of carriers of the wild-type and heterozygous mutation. The tacrolimus CL/F in patients who were coadministered glucocorticoids was 1.23-fold higher than that of the control. According to the patient genotype and combined use of glucocorticoids, 26 combinations of Wuzhi capsule and tacrolimus doses were matched. The Monte Carlo simulation identified the most suitable combination scheme.

CONCLUSIONS

An improved tacrolimus PPK model for patients with nephrotic syndrome was established, and the most suitable combination of Wuzhi capsule and tacrolimus doses was identified, thus, facilitating the selection of a more economical and safe administration regimen.

The impact of sepsis on hepatic drug metabolism in critically ill patients: a narrative review

INTRODUCTION

Hepatic drug metabolism is important in improving drug dosing strategies in sepsis. Pharmacokinetics in the critically ill population are severely altered due to changes in absorption, distribution, excretion and metabolization. Hepatic drug metabolism might be altered due to changes in hepatic blood flow, drug metabolizing protein availability, and protein binding. The purpose of this review is to examine evidence on whether hepatic drug metabolism is significantly affected in septic patients, and to provide insights in the need for future research.

AREAS COVERED

This review describes the effect of sepsis on hepatic drug metabolism in humans. Clinical trials, pathophysiological background information and example drug groups are further discussed. The literature search has been conducted in Embase, Medline ALL Ovid, and Cochrane CENTRAL register of trials.

EXPERT OPINION

Limited research has been conducted on drug metabolism in the sepsis population, with some trials having researched healthy individuals using endotoxin injections. Notwithstanding this limitation, hepatic drug metabolism seems to be decreased for certain drugs in sepsis. More research on the pharmacokinetic behavior of hepatic metabolized drugs in sepsis is warranted, using inflammatory biomarkers, hemodynamic changes, mechanical ventilation, organ support, and catecholamine infusion as possible confounders.

Adrenal insufficiency is common amongst kidney transplant recipients receiving maintenance prednisolone and can be predicted using morning cortisol

BACKGROUND

Long-term glucocorticoid therapy is a key component of immunosuppression for kidney transplant recipients (KTRs), leading to significant cumulative glucocorticoid exposure. The aims of this study are to investigate the prevalence of adrenal insufficiency (AI) in KTRs taking prednisolone and to develop a screening algorithm to identify patients at the highest risk of AI.

METHODS

In this cross-sectional cohort study, 67 KTRs receiving prednisolone underwent a short synacthen test (SST) and measurement of cumulative glucocorticoid exposure.

RESULTS

A total of 72% (n = 48) of participants failed the SST. Participants with AI had a higher daily prednisolone dose (4.9 versus 4.2 mg/day; P = .002) and greater cumulative glucocorticoid exposure (289 versus 111 mg/kg; P = .03) than those with intact adrenal function. Participants with AI had lower baseline cortisol than participants with intact adrenal function (143 versus 303 nmol/L; P < .001). Morning cortisol of >288 nmol/L predicted a normal SST with 100% specificity [95% confidence interval (CI) 92-100] and 70% sensitivity (95% CI 56-78%), therefore excluding AI.

CONCLUSIONS

Our results suggest KTRs are at a higher risk for AI than previously reported. A morning serum cortisol measurement is a useful screening tool in this cohort, reducing the need for stimulatory testing by 44%. KTRs with AI need education regarding glucocorticoid sick rules, similar to patients with other forms of AI.

Impact of Combined Antiretroviral Therapy on Metabolic Syndrome Components in Adult People Living with HIV: A Literature Review

The development of metabolic derangements as a result of HIV treatment has been an important area of research since the introduction of zidovudine in the 1980's. Antiretroviral therapy has intensely evolved in the last three decades, with new drugs gradually incorporated into everyday clinical practice. With the life expectancy of people living with HIV rapidly approaching that of their HIV-negative counterparts, the influence of these antiretrovirals on the development of the components of the metabolic syndrome remains of major interest to clinicians and their patients. In this review, we aimed to discuss the impact of cART on components of the metabolic syndrome, i.e., weight, plasma lipid levels, plasma glucose levels, and blood pressure, describing the influence of cART classes and of individual antiretrovirals. We also aimed to outline the limitations of the research conducted to date and the remaining knowledge gaps in this area.

Management of Chronic Graft-vs.-Host Disease in Children and Adolescents With ALL: Present Status and Model for a Personalised Management Plan

Herein we review current practice regarding the management of chronic graft-vs.-host disease (cGvHD) in paediatric patients after allogeneic haematopoietic stem cell transplantation (HSCT) for acute lymphoblastic leukaemia (ALL). Topics covered include: (i) the epidemiology of cGvHD; (ii) an overview of advances in our understanding cGvHD pathogenesis; (iii) current knowledge regarding risk factors for cGvHD and prevention strategies complemented by biomarkers; (iii) the paediatric aspects of the 2014 National Institutes for Health-defined diagnosis and grading of cGvHD; and (iv) current options for cGvHD treatment. We cover topical therapy and newly approved tyrosine kinase inhibitors, emphasising the use of immunomodulatory approaches in the context of the delicate counterbalance between immunosuppression and immune reconstitution as well as risks of relapse and infectious complications. We examine real-world approaches of response assessment and tapering schedules of treatment. Furthermore, we report on the optimal timepoints for therapeutic interventions and changes in relation to immune reconstitution and risk of relapse/infection. Additionally, we review the different options for anti-infectious prophylaxis. Finally, we put forth a theory of a holistic view of paediatric cGvHD and its associated manifestations and propose a checklist for individualised risk evaluation with aggregated considerations including site-specific cGvHD evaluation with attention to each individual's GvHD history, previous medical history, comorbidities, and personal tolerance and psychosocial circumstances. To complement this checklist, we present a treatment algorithm using representative patients to inform the personalised management plans for patients with cGvHD after HSCT for ALL who are at high risk of relapse.

The Impact of SARS-CoV-2 Infection, and Application of Immunosuppressive Agents in Kidney Transplant Recipients Suffering from COVID-19

In December 2019, the COVID-19 pandemic began to ravage the world quickly, causing unprecedented losses in human life and the economy. A statistical study revealed that the proportion of solid organ transplant (SOT) recipients with severe symptoms and deaths after being infected by SARS-CoV-2 is considerably higher than that of non-SOT recipients, and the prognosis is relatively poor. In addition, the clinical manifestation of SOT recipients suffering from COVID-19 is different from that of general COVID-19 patients. Acute kidney injury (AKI) is a common complication in COVID-19 patients, and it is likely more common among SOT recipients infected with SARS-CoV-2. Clinical experts consider that SOT recipients have long-term treatment with immunosuppressants, and the comorbidities are driven by a high rate of severe symptoms and mortality. Orthotopic kidney allograft transplantation is an effective treatment for patients suffering from end-stage kidney disease/kidney failure through which they can easily extend their life. Indeed, kidney transplant recipients have suffered significant damage during this pandemic. To effectively reduce the severity of symptoms and mortality of kidney transplant recipients suffering from COVID-19, precise application of various drugs, particularly immunosuppressants, is necessary. Therefore, herein, we will collate the current clinical experience of treating COVID-19 infection in kidney transplant recipients and discuss the adjustment of patients using immunosuppressive agents in the face of COVID-19.

Immunosuppressant Management in Renal Transplant Patients with COVID-19

The coronavirus disease 2019 (COVID-19) pandemic poses a special risk for both immunosuppressed patients, especially transplant recipients. Although the knowledge about this infection is growing, many uncertainties remain, particularly regarding the kidney. Kidney transplant recipients (KDRs) should be considered immunocompromised hosts since a potential risk for infection, comorbidity, and immunosuppression exposure exists. Additionally, the management of immunosuppressive agents in KDRs remains challenging. Potential drug interactions with immunosuppressive treatment escalated the risk of unwanted side effects. In this review, we aimed to attain an augmented awareness and improved management immunosuppressant for COVID-19 KDRs.

In vitro assessments predict that CYP3A4 contributes to a greater extent than CYP3A5 to prednisolone clearance

Because several steroid hormones are metabolized to their respective 6β-hydroxy forms by CYP3A4 and CYP3A5, these isoenzymes have been assumed to metabolize the immunosuppressive drug prednisolone, with conflicting results in the literature with respect to their relative importance. A direct study of the metabolism of prednisolone by microsomal CYP3A4 and CYP3A5 is missing. The aim of this in vitro study was to investigate the relative importance of recombinant CYP3A4 and recombinant CYP3A5 in the metabolism of prednisolone and to compare the extent of formation of 6β-OH-prednisolone by the two enzymes. Through in vitro incubations using rCYP3A4 and rCYP3A5 enzymes, intrinsic clearance (CL_int ) of prednisolone was determined by the substrate depletion approach. Formation of the metabolite 6β-OH-prednisolone by rCYP3A4 and rCYP3A5, respectively, were compared. Prednisolone concentrations were measured and its metabolite 6β-OH-prednisolone was identified using a HPLC-MS/MS in-house method. CL_int for prednisolone by rCYP3A5 was less than 26% relative to rCYP3A4. Formation of 6β -OH-prednisolone by rCYP3A5 was less than 11% relative to rCYP3A4. The study indicates that 6β-hydroxylation of prednisolone assessed in vitro in recombinant CYP enzymes depends on rCYP3A4 rather than rCYP3A5, and that CYP3A5 may be responsible for the formation of other prednisolone metabolite(s) in addition to 6β-OH-prednisolone.

A randomised controlled unblinded multicentre non-inferiority trial with activated vitamin D and prednisolone treatment in patients with minimal change nephropathy (ADAPTinMCN)

BACKGROUND

Minimal change nephropathy (MCN) is a common cause of nephrotic syndrome in both adults and children. International guidelines recommend treatment with prednisolone 1 mg/kg/day to adults. This dose is derived from an empirically established dose in children, although children generally attain remission faster and relapse more rapidly than adults. Prednisolone is associated with multiple and serious adverse events. Activated vitamin D has been shown to reduce albuminuria in other glomerular renal diseases with a minimum of adverse events. This study tests the hypothesis that a new treatment regimen in MCN combining reduced dose prednisolone and active vitamin D is as efficient in inducing remission and has fewer and less severe adverse events than standard prednisolone. Furthermore, we aim to establish models allowing for more personalized medicine based on assessment of the individual's prednisolone metabolism.

METHODS

A randomised controlled multicentre non-inferior unblinded trial including 96 adult, incident patients with biopsy-proven MCN, albuminuria > 3 g/day, and an estimated glomerular filtration rate (eGFR) > 30 ml/min from renal departments in Denmark. Patients are randomised to standard prednisolone (1 mg/kg/day) or reduced prednisolone (0.5 mg/kg/day) and alfacalcidol (0.5 μg/day). The primary outcome is the rate of remissions after 16 weeks and the time from diagnosis to remission. The study will include a saliva test to characterise prednisolone pharmacokinetics and compare them to genetic variations in specific liver enzymes responsible for prednisolone metabolism.

DISCUSSION

Reducing the prednisolone dose is expected to reduce the number of severe adverse events. This study will examine if reduced prednisolone dose with active vitamin D but without additional immunosuppression is feasible in the treatment of MCN and will reduce the number of adverse events. The findings can potentially change current guidelines for treatment of MCN in adults. Additional outcomes on inter-individual pharmacokinetic and metabolic variations may allow for a more personalised treatment strategy.

TRIAL REGISTRATION

EudraCT 2017-001206-16, ClinicalTrials.gov NCT03210688 . Registered on June 3, 2017.

Immunosuppression Considerations for Older Kidney Transplant Recipients

PURPOSE OF REVIEW

While kidney transplantation improves the long-term survival of the majority of patients with end-stage kidney disease (ESKD), age-related immune dysfunction and associated comorbidities make older transplant recipients more susceptible to complications related to immunosuppression. In this review, we discuss appropriate management of immunosuppressive agents in older adults to minimize adverse events, avoid acute rejection, and maximize patient and graft survival.

RECENT FINDINGS

Physiological changes associated with senescence can impact drug metabolism and increase the risk of posttransplant infection and malignancy. Clinical trials assessing the safety and efficacy of immunosuppressive agents in older adults are lacking. Recent findings from U.S. transplant registry-based studies suggest that risk-adjusted death-censored graft failure is higher among older patients who received antimetabolite avoidance, mammalian target of rapamycin inhibitor (mTORi)-based, and cyclosporine-based regimens. Observational data suggest that risk-adjusted mortality may be increased in older patients who receive mTORi-based and cyclosporine-based regimens but lower in those managed with T-cell induction and maintenance steroid avoidance/withdrawal.

SUMMARY

Tailored immunosuppression management to improve patient and graft survival in older transplant recipients is an important goal of personalized medicine. Lower intensity immunosuppression, such as steroid-sparing regimens, appear beneficial whereas mTORi- and cyclosporine-based maintenance are associated with greater potential for adverse effects. Prospective clinical trials to assess the safety and efficacy of immunosuppression agents in older recipients are urgently needed.

Prednisolone and Prednisone Pharmacokinetics in Adult Renal Transplant Recipients

BACKGROUND

Prednisolone (PL) is a standard component of most immunosuppressive protocols after solid organ transplantation (Tx). Adverse effects are frequent and well known. The aim of this study was to characterize the pharmacokinetics (PKs) of PL and prednisone (PN), including cortisol (CL) and cortisone (CN) profiles, after PL treatment in renal Tx recipients in the early post-Tx phase.

METHODS

This single-center, prospective, observational study included stable renal Tx recipients, >18 years of age, and in the early postengraftment phase. Blood samples were obtained predose and during a 24-hour dose interval [n = 26 samples per area under the curve (AUC0-24)], within the first 8 weeks post-Tx. PL, PN, CL, and CN concentrations were measured using high-performance liquid chromatography-tandem mass spectrometry.

RESULTS

In renal Tx recipients (n = 28), our results indicated a relatively high PL exposure [median, range AUC0-24 = 3821 (2232-5382) mcg h/L], paralleled by strong suppression of endogenous CL profile, demonstrated by a low CL evening-to-morning ratio [median, range 11 (3-47)%]. A negative correlation (r = -0.83) between PL AUC0-24 and morning CL levels was observed. The best single PK variable to predict PL AUC0-24 was PL C6 (r2 = 0.82). An algorithm based on 3 PK sampling time points: trough, 2, and 4 hours after PL dosing, predicted PL AUC0-24 with a low percentage prediction error (PPE = 5.2 ± 1.5%) and a good correlation of determination (r2 = 0.91). PL AUC0-24 varied 3-fold among study participants, whereas CL AUC0-24 varied by 18-fold.

CONCLUSIONS

The large interindividual variability in both PL exposure and suppression of endogenous CL implies a possible role for therapeutic drug monitoring. An abbreviated profile within the first 4 hours after PL dosing provides a good prediction of PL exposure in renal Tx recipients. The strong negative correlation between PL AUC0-24 and morning CL levels suggests a possible surrogate marker for drug exposure for further evaluation.

Prednisone is genotoxic in mice and Drosophila melanogaster

Prednisone (PD) is one of the most commonly used corticosteroids in immunosuppressive therapy for patients with autoimmune diseases and transplants. Chronic use of corticosteroids is associated with several side effects and an increase in neoplasia. Since genotoxic effects are associated with an increased risk of cancer development, this study evaluated the genotoxic and cytotoxic activities of PD using the SMART/wing assay in Drosophila melanogaster and the micronucleus test and comet assay in mouse bone marrow cells. Further, the toxic effects of PD on mouse organ tissues were assessed using histopathological analyses. In the SMART/wing assay, PD showed a significant genotoxic activity at all concentrations tested (0.375, 0.75, 1.5, and 2.0 mg/mL) compared to the negative control (p < 0.05). The micronucleus test and comet assay also showed an elevated genotoxicity of PD at all treatment conditions (24, 48, and 120 h with doses ranging from 0.5 to 1.5 mg/kg) compared to the negative control (p < 0.05). The histopathological analyses did not show toxicity of PD in mouse cells and tissues. Therefore, our results demonstrate that PD is a potent genotoxic immunosuppressant in mice and D. melanogaster cells. Somatic recombination was the primary contributor (46%-82%) to the induced genotoxicity observed in the SMART test.

The Immunobiogram, a Novel In Vitro Assay to Evaluate Treatment Resistance in Patients Receiving Immunosuppressive Therapy

Immunosuppressive drugs are widely used to treat several autoimmune disorders and prevent rejection after organ transplantation. However, intra-individual variations in the pharmacological response to immunosuppressive therapy critically influence its efficacy, often resulting in poor treatment responses and serious side effects. Effective diagnostic tools that help clinicians to tailor immunosuppressive therapy to the needs and immunological profile of the individual patient thus constitute a major unmet clinical need. In vitro assays that measure immune cell responses to immunosuppressive drugs constitute a promising approach to individualized immunosuppressive therapy. Here, we present the Immunobiogram, a functional pharmacodynamic immune cell-based assay for simultaneous quantitative measurement of a patient's immune response to a battery of immunosuppressive drugs. Peripheral blood mononuclear cells collected from patients are immunologically stimulated to induce activation and proliferation and embedded in a hydrogel mixture in which they are exposed to a concentration gradient of the immunosuppressants of interest. Analysis of samples from kidney transplant patients using this procedure revealed an association between the sensitivity of individual patients to the immunosuppressive regimen and their immunological risk of transplant rejection. Incorporation of the Immunobiogram assay into clinical settings could greatly facilitate personalized optimization and monitoring of immunosuppressive therapy, and study of the mechanisms underlying resistance to immunosuppressants.

Glucocorticoid agonists enhance retinal stem cell self-renewal and proliferation

BACKGROUND

Adult mammalian retinal stem cells (RSCs) readily proliferate, self-renew, and generate progeny that differentiate into all retinal cell types in vitro. RSC-derived progeny can be induced to differentiate into photoreceptors, making them a potential source for retinal cell transplant therapies. Despite their proliferative propensity in vitro, RSCs in the adult mammalian eye do not proliferate and do not have a regenerative response to injury. Thus, identifying and modulating the mechanisms that regulate RSC proliferation may enhance the capacity to produce RSC-derived progeny in vitro and enable RSC activation in vivo.

METHODS

Here, we used medium-throughput screening to identify small molecules that can expand the number of RSCs and their progeny in culture. In vitro differentiation assays were used to assess the effects of synthetic glucocorticoid agonist dexamethasone on RSC-derived progenitor cell fate. Intravitreal injections of dexamethasone into adult mouse eyes were used to investigate the effects on endogenous RSCs.

RESULTS

We discovered that high-affinity synthetic glucocorticoid agonists increase RSC self-renewal and increase retinal progenitor proliferation up to 6-fold without influencing their differentiation in vitro. Intravitreal injection of synthetic glucocorticoid agonist dexamethasone induced in vivo proliferation in the ciliary epithelium-the niche in which adult RSCs reside.

CONCLUSIONS

Together, our results identify glucocorticoids as novel regulators of retinal stem and progenitor cell proliferation in culture and provide evidence that GCs may activate endogenous RSCs.

Physiologically Based Pharmacokinetic Modeling Involving Nonlinear Plasma and Tissue Binding: Application to Prednisolone and Prednisone in Rats

The pharmacokinetics (PK) of prednisolone (PNL) exhibit nonlinearity related to plasma protein binding, tissue binding, metabolic interconversion with prednisone (PN), and renal elimination. Blood and 11 tissues were collected from male Wistar rats after steady-state (SS) infusion and after subcutaneous boluses of 50 mg/kg of PNL. Concentrations of PNL and PN were measured by liquid chromatography-tandem mass spectrometry. Plasma and tissue profiles were described using a complex physiologically based pharmacokinetics (PBPK) model. Concentrations of PN and PNL were in rapid equilibrium in plasma and tissues. The tissue partition coefficients (K p ) of PNL calculated from most subcutaneously dosed tissue and plasma areas were similar to SS infusion and in silico values. The blood-to-plasma ratio of PNL was 0.71 with similar red blood cell and unbound-plasma concentrations. Plasma protein binding (60%-90%) was related to corticosteroid-binding globulin (CBG) saturation. Tissue distribution was nonlinear. The equilibrium dissociation constant (K d ) of PNL shared by all tissues was 3.01 ng/ml, with the highest binding in muscle, followed by liver, heart, intestine, and bone and the lowest binding in skin, spleen, fat, kidney, lung, and brain. Fat and bone distribution assumed access only to interstitial space. Brain PNL concentrations (K p = 0.05) were low owing to presumed P-glycoprotein-mediated efflux. Clearances of CBG-free PNL were 1789 from liver and 191.2 ml/h from kidney. The PN/PNL ratio was nonlinear for plasma, spleen, heart, intestine, bone, fat, and linear for the remaining tissues. Our PBPK model with multiple complexities well described the PK profiles of PNL and PN in blood, plasma, and diverse tissues. SIGNIFICANCE STATEMENT: Because steroids, such as prednisolone and prednisone, have similar and complex pharmacokinetics properties in various species, receptors in most tissues, and multiple therapeutic and adverse actions, this physiologically based pharmacokinetics (PBPK) model may provide greater insights into the pharmacodynamic complexities of corticosteroids. The complex properties of these compounds require innovative PBPK modeling approaches that may be instructive for other therapeutic agents.

Hepatopatia esteroidal em gatas após terapia com prednisolona: aspectos laboratoriais, tomográficos e histopatológicos

RESUMO Glicocorticoides são amplamente utilizados na clínica de pequenos animais, entretanto seu uso contínuo pode causar efeitos colaterais. Os gatos são considerados menos susceptíveis a esses efeitos do que outras espécies, mas existem poucos trabalhos abordando os efeitos adversos em felinos. O objetivo deste estudo foi avaliar possíveis alterações laboratoriais, histopatológicas e do grau de atenuação radiográfica do parênquima hepático de gatas submetidas à terapia com prednisolona. Um ensaio clínico foi realizado em quatro gatas hígidas, as quais receberam prednisolona, por via oral, na dose de 3mg/kg, durante 60 dias consecutivos. Nos achados histopatológicos após 60 dias de tratamento, observou-se desorganização dos cordões de hepatócitos e degeneração vacuolar, além de necrose de hepatócitos, porém não foram observados sinais de fibrose no parênquima hepático. Os dados da tomografia computadorizada demonstram aumento do grau de atenuação do parênquima hepático a partir do 30º dia da administração de prednisolona, que persistiu até o final do experimento. No presente estudo, foi possível caracterizar a existência de hepatopatia esteroidal em gatos em estágios precoces da terapia com prednisolona.

Severe COVID-19 in a renal transplant recipient: A focus on pharmacokinetics

The current coronavirus disease 2019 (COVID-19) pandemic requires extra attention for immunocompromised patients, including solid organ transplant recipients. We report on a case of a 35-year-old renal transplant recipient who suffered from a severe COVID-19 pneumonia. The clinical course was complicated by extreme overexposure to the mammalian target of rapamycin inhibitor everolimus, following coadministration of chloroquine and lopinavir/ritonavir therapy. The case is illustrative for dilemmas that transplant professionals may face in the absence of evidence-based COVID-19 therapy and concurrent pressure for exploration of experimental pharmacological treatment options. However, the risk-benefit balance of experimental or off-label therapy may be weighed differently in organ transplant recipients than in otherwise healthy COVID-19 patients, owing to their immunocompromised status and potential drug interactions with immunosuppressive therapy. With this case report, we aimed to achieve increased awareness and improved management of drug-drug interactions associated with the various treatment options for COVID-19 in renal transplant patients.

Body mass index, weight-adjusted immunosuppression and the risk of acute rejection and infection after kidney transplantation: a cohort study

BACKGROUND

Body mass index (BMI) is associated with patient outcomes after kidney transplantation. We hypothesized that immunosuppression (IS) dosing is a contributing factor.

METHODS

Using Australia and New Zealand Dialysis and Transplant registry data, we included all adult kidney-only transplant recipients over 2000-14 treated with prednisolone, mycophenolate and tacrolimus/cyclosporin (n = 7919). The exposure was BMI and the outcomes were time to: (i) acute rejection, (ii) fatal infection, (iii) cancer and (iv) graft; and (v) patient survival. We modelled BMI and IS dosing (in quartiles) as time-varying covariates in extended Cox models.

RESULTS

Compared with a BMI of 25 kg/m2, a BMI of 35 was associated with acute rejection after adjusting for demographics and comorbidities [adjusted hazard ratio (aHR) = 1.29, 95% confidence interval (CI) 1.12-1.49]. This association virtually disappeared after correcting for IS (aHR = 1.09, 95% CI 0.93-1.29). A BMI of 35 was non-significantly associated with fewer fatal infections (aHR = 0.91, 95% CI 0.66-1.25), but this reversed after adjusting for IS (aHR = 1.54, 95% CI 1.03-2.28). Results for cancer were not significantly altered after adjusting for IS. Results for lower BMI were similarly not significantly altered though generally associated with worse outcomes.

CONCLUSIONS

Our findings show that the associations between high BMI, acute rejection and fatal infection after kidney transplantation were significantly altered after correcting for IS suggesting that relative under-dosing of obese patients may partially explain these associations.

Transitioning from Basic toward Systems Pharmacodynamic Models: Lessons from Corticosteroids

Technology in bioanalysis, -omics, and computation have evolved over the past half century to allow for comprehensive assessments of the molecular to whole body pharmacology of diverse corticosteroids. Such studies have advanced pharmacokinetic and pharmacodynamic (PK/PD) concepts and models that often generalize across various classes of drugs. These models encompass the "pillars" of pharmacology, namely PK and target drug exposure, the mass-law interactions of drugs with receptors/targets, and the consequent turnover and homeostatic control of genes, biomarkers, physiologic responses, and disease symptoms. Pharmacokinetic methodology utilizes noncompartmental, compartmental, reversible, physiologic [full physiologically based pharmacokinetic (PBPK) and minimal PBPK], and target-mediated drug disposition models using a growing array of pharmacometric considerations and software. Basic PK/PD models have emerged (simple direct, biophase, slow receptor binding, indirect response, irreversible, turnover with inactivation, and transduction models) that place emphasis on parsimony, are mechanistic in nature, and serve as highly useful "top-down" methods of quantitating the actions of diverse drugs. These are often components of more complex quantitative systems pharmacology (QSP) models that explain the array of responses to various drugs, including corticosteroids. Progressively deeper mechanistic appreciation of PBPK, drug-target interactions, and systems physiology from the molecular (genomic, proteomic, metabolomic) to cellular to whole body levels provides the foundation for enhanced PK/PD to comprehensive QSP models. Our research based on cell, animal, clinical, and theoretical studies with corticosteroids have provided ideas and quantitative methods that have broadly advanced the fields of PK/PD and QSP modeling and illustrates the transition toward a global, systems understanding of actions of diverse drugs. SIGNIFICANCE STATEMENT: Over the past half century, pharmacokinetics (PK) and pharmacokinetics/pharmacodynamics (PK/PD) have evolved to provide an array of mechanism-based models that help quantitate the disposition and actions of most drugs. We describe how many basic PK and PK/PD model components were identified and often applied to the diverse properties of corticosteroids (CS). The CS have complications in disposition and a wide array of simple receptor-to complex gene-mediated actions in multiple organs. Continued assessments of such complexities have offered opportunities to develop models ranging from simple PK to enhanced PK/PD to quantitative systems pharmacology (QSP) that help explain therapeutic and adverse CS effects. Concurrent development of state-of-the-art PK, PK/PD, and QSP models are described alongside experimental studies that revealed diverse CS actions.

Endogenous urinary glucocorticoid metabolites and mortality in prednisolone-treated renal transplant recipients

BACKGROUND

Chronic corticosteroid treatment suppresses HPA-axis activity and might alter activity of 11β hydroxysteroid dehydrogenases (11β-HSD). We aimed to investigate whether the endogenous glucocorticoid production and 11β-HSD activities are altered in prednisolone-treated renal transplant recipients (RTR) compared with healthy controls and whether this has implications for long-term survival in RTR.

METHODS

In a longitudinal cohort of 693 stable RTR and 275 healthy controls, 24-hour urinary cortisol, cortisone, tetrahydrocorisol (THF), allotetrahydrocortisol (alloTHF), and tetrahydrocortisone (THE) were measured using liquid chromatography tandem-mass spectrometry. Twenty-four-hour urinary excretion of cortisol and metabolites were used as measures of endogenous glucocorticoid production; (THF + alloTHF)/THE and cortisol/cortisone ratios were used as measures of 11β-HSD activity.

RESULTS

Urinary cortisol and metabolite excretion were significantly lower in RTR compared with healthy controls (P < .001), whereas (THF + alloTHF)/THE and cortisol/cortisone ratios were significantly higher (P < .001 and P = .002). Lower total urinary metabolite excretion and higher urinary (THF + alloTHF)/THE ratios were associated with increased risk of mortality, independent of age, sex, estimated glomerular filtration rate, C-reactive protein, body surface area, and daily prednisolone dose, respectively.

CONCLUSIONS

Endogenous glucocorticoid production and 11β-HSD activities are altered in prednisolone-treated RTR. Decreased total urinary endogenous glucocorticoid metabolite excretion and increased urinary (THF + alloTHF)/THE ratios are associated with increased risk of mortality.

Ocular Considerations in Face Transplantation: Report of 2 Cases and Review of the Literature

PURPOSE

Periorbital injuries are common in face transplantation (FT) candidates. It is therefore essential that the ophthalmologist play a central role in the multidisciplinary treatment of these patients. In this study, the authors perform a comprehensive review of all procedures involving periorbital components, provide an update for the ophthalmology community regarding the current state of the field, and present 2 cases.

METHODS

A comprehensive review of the literature for all FT procedures including periorbital components was performed. The authors also present 2 patients who received FT including periorbital components for extensive facial disfigurement. One patient sustained high-energy avulsive ballistic injury and underwent a total face, double jaw, and tongue transplant in 2012. The second patient received a total face, eyelids, ears, and skeletal subunits transplant for extensive facial burns in 2015.

RESULTS

Literature review demonstrated that 22 (54%) of the 41 patients undergoing FT received allografts containing periorbital components. Only 14 cases (64%) reported on the presence of ocular and periocular complications. The most common complications consisted of lower eyelid ectropion and lagophthalmos, and nearly all required revisional procedures. Both patients presented with significant periorbital scarring and demonstrated good visual acuity and aesthetic outcomes at postoperative follow up between 6 and 28 months.

CONCLUSIONS

Face transplantation can address extensive facial and periorbital disfigurement with satisfactory functional and aesthetic outcomes. The majority of FT performed to date have included periorbital components, and postoperative ocular and periocular complications are common. It is critical for ophthalmologists to play a central role in the care of these patients.

Use of Herbal Medicine by Pregnant Women: What Physicians Need to Know

About 80% of the consumers worldwide use herbal medicine (HMs) or other natural products. The percentage may vary significantly (7%-55%) among pregnant women, depending upon social status, ethnicity, and cultural traditions. This manuscript discusses the most common HMs used by pregnant women, and the potential interactions of HMs with conventional drugs in some medical conditions that occur during pregnancy (e.g., hypertension, asthma, epilepsy). It also includes an examination of the characteristics of pregnant HM consumers, the primary conditions for which HMs are taken, and a discussion related to the potential toxicity of HMs taken during pregnancy. Many cultures have used HMs in pregnancy to improve wellbeing of the mother and/or baby, or to help decrease nausea and vomiting, treat infection, ease gastrointestinal problems, prepare for labor, induce labor, or ease labor pains. One of the reasons why pregnant women use HMs is an assumption that HMs are safer than conventional medicine. However, for pregnant women with pre-existing conditions like epilepsy and asthma, supplementation of conventional treatment with HMs may further complicate their care. The use of HMs is frequently not reported to healthcare professionals. Providers are often not questioning HM use, despite little being known about the HM safety and HM-drug interactions during pregnancy. This lack of knowledge on potential toxicity and the ability to interact with conventional treatments may impact both mother and fetus. There is a need for education of women and their healthcare professionals to move away from the idea of HMs not being harmful. Healthcare professionals need to question women on whether they use any HMs or natural products during pregnancy, especially when conventional treatment is less efficient and/or adverse events have occurred as herbal-drug interactions could be the reason for these observations. Additionally, more preclinical and clinical studies are needed to evaluate HM efficacy and toxicity.

Free prednisolone pharmacokinetics predicted from total concentrations in patients with inflammatory - immunonologic conditions

Prednisone is an anti-inflammatory drug widely used in internal medicine and rheumatology, but dosing remains empirical. The active metabolite of prednisone is free prednisolone. The aim of this work was to build a population pharmacokinetic (PK) model that can predict free prednisolone concentrations in patients with inflammatory/immunologic conditions.A total of 107 patients from the department of internal medicine of Cochin hospital provided 343 observations. Blood samples drawn for biological analyses were used for drug determination. Total plasma prednisolone concentrations were measured by liquid chromatography-mass spectrometry, and the data were modelled using Monolix. The pharmacokinetics was ascribed a one-compartment open model with three transit compartments standing for the absorption and metabolism process. The model used predicts free concentrations that served to derive total concentrations given published binding constants. Only size parameters influenced the pharmacokinetics. Free prednisolone CL_U /F and V_U /F, scaled allometrically on lean body weight, were, respectively, 26.7 L/h and 94.3 L for 50 kg LBW. CL_U /F interindividual variability was 0.20. The additive and proportional residual variabilities were, respectively, 4.3 µg/L and 0.20. The results point out some dosing issues, that is the possibility of under- or over-dosage in thin or overweight patients respectively.

Total Eyelid Transplantation in a Face Transplant: Analysis of Postoperative Periorbital Function

BACKGROUND

Prolonged impairment of protective ocular functions can compromise vision and lead to blindness if uncorrected. Several facial transplants have incorporated periorbital structures with variable eyelid preservation, but objective assessment of post-transplant periorbital function has been limited.

MATERIALS AND METHODS

Kinematic data were collected from a full-face recipient that included the fist total eyelid transplantation at 5 separate pre-transplant (PRE) and post-transplant time points (T1-T4). Using optical facial tracking, eyelid movements were tracked during involuntary blinking and compared with controls.

RESULTS

There was significant improvement in right eye aperture from PRE to T1 (β = 5.54, P < 0.001), with no change between T1 and T4. Aperture fluctuated in the left eye, with a temporary decrease between T2 and T3 corresponding with revision brow lift (β = -4.57, P < 0.001). Although improved from the pre-transplantation, right and left eye apertures remained significantly smaller than controls at T1 and T4 (P < 0.001). Similarly, spatial coupling increased from PRE to T1 (β = 0.63, P < 0.001) and remained high at T4, albeit significantly less than controls (P < 0.001). Temporal coupling improved from PRE to T2 (β = 2.29, P < 0.02) and was sustained at subsequent time points, with no difference relative to controls at T4. Considerable improvement was observed on clinical examination, with full functional status.

CONCLUSIONS

Application of a novel method for assessing functional eyelid recovery using facial tracking technology to the first total eyelid transplantation in the setting of a full facial transplant shows clear functional improvement after transplantation and suggests revisions can be performed safely to optimize aesthetic outcomes without permanent negative functional impact.

Characterizing the pharmacokinetics and pharmacodynamics of immunosuppressant medicines and patient outcomes in elderly renal transplant patients

This review examines what is currently known about the pharmacokinetics and pharmacodynamics of commonly prescribed immunosuppressant medicines, tacrolimus, cyclosporine, mycophenolate and prednisolone, in elderly renal transplant recipients, and reported patient outcomes in this cohort. Renal transplantation is increasing rapidly in the elderly, however, currently, long-term patient outcomes are relatively poor compared to younger adults. Some studies have suggested that elderly recipients may have higher dose-adjusted exposure and/or lower clearance of the calcineurin inhibitors tacrolimus and cyclosporine; with one study reporting up to 50% reduction in tacrolimus exposure in the elderly. Elderly transplant recipients do not appear to have higher dosage-adjusted exposure to mycophenolic acid (MPA). The effects of ageing on the pharmacokinetics of prednisolone are unknown. Only one study has examined how aging effects drug target enzymes, reporting no difference in baseline inosine 5'-monophosphate dehydrogenase (IMPDH) activity and MPA-induced IMPDH activity in elderly compared to younger adult renal transplant recipients. In elderly transplant recipients, immunosenescence likely lowers the risk of acute rejection, but increases the risk of drug-related adverse effects. Currently, the three main causes of death in elderly renal transplant recipients are cardiovascular disease, infection and malignancy. One study has showed that renal transplant recipients aged over 65 years are seven times more likely to die with a functioning graft compared with young adults (aged 18-29 years). This suggests that an optimal balance between immunosuppressant medicine efficacy and toxicity is not achieved in elderly recipients, and further studies are needed to foster long-term graft and patient survival. Lower maintenance immunosuppressant targets in elderly recipients may decrease patient susceptibility to drug side effects, however, further studies are required and appropriate targets need to be established.

Pharmacology and pharmacogenetics of prednisone and prednisolone in patients with nephrotic syndrome

Nephrotic syndrome is one of the most common glomerular disorders in childhood. Glucocorticoids have been the cornerstone of the treatment of childhood nephrotic syndrome for several decades, as the majority of children achieves complete remission after prednisone or prednisolone treatment. Currently, treatment guidelines for the first manifestation and relapse of nephrotic syndrome are mostly standardized, while large inter-individual variation is present in the clinical course of disease and side effects of glucocorticoid treatment. This review describes the mechanisms of glucocorticoid action and clinical pharmacokinetics and pharmacodynamics of prednisone and prednisolone in nephrotic syndrome patients. However, these mechanisms do not account for the large inter-individual variability in the response to glucocorticoid treatment. Previous research has shown that genetic factors can have a major influence on the pharmacokinetic and dynamic profile of the individual patient. Therefore, pharmacogenetics may have a promising role in personalized medicine for patients with nephrotic syndrome. Currently, little is known about the impact of genetic polymorphisms on glucocorticoid response and steroid-related toxicities in children with nephrotic syndrome. Although the evidence is limited, the data summarized in this study do suggest a role for pharmacogenetics to improve individualization of glucocorticoid therapy. Therefore, studies in larger cohorts with nephrotic syndrome patients are necessary to draw final conclusions about the influence of genetic polymorphisms on the glucocorticoid response and steroid-related toxicities to ultimately implement pharmacogenetics in clinical practice.

IL-2 gene polymorphisms affect tacrolimus response in myasthenia gravis

PURPOSE

The IL-2 gene polymorphisms have been reported to be associated with the development of autoimmune disease. However, there are no published studies examining the influence of the IL-2 gene polymorphisms on the response of myasthenia gravis (MG) patients to tacrolimus (Tac). The goal of this study was to investigate the relationship between the polymorphisms of IL-2 and Tac response in MG patients.

METHODS

Ninety-two MG patients treated with Tac were studied, including 57 Tac-effective patients and 35 Tac-ineffective patients. Then, we selected four single-nucleotide polymorphisms (SNPs: rs2069776, rs2069772, rs2069762, rs2069763) in the IL-2 gene. Next, we analyzed the distribution of genotypes, allelic frequencies of SNPs, and haplotype frequencies among polymorphisms in the two groups of patients.

RESULTS

The distribution of the allelic frequency of the rs2069762 variant differed between the Tac-effective and Tac-ineffective patients (P = 0.02). Genotypes G/T and G/G of rs2069762 were differently distributed between the two groups when the wild genotype T/T was assigned as a reference (P < 0.001 for G/T; P = 0.003 for G/G). Patients with the TAGG haplotype tended to be Tac-ineffective (P < 0.001, OR: 0.15, 95% CI: 0.05-0.43).

CONCLUSION

Myasthenia gravis patients with the rs2069762 variant, rs2069762 G/T and G/G genotype, and TAGG haplotype for IL-2 tended to respond poorly to Tac treatment.

Survival Time to Biopsy-Proven Acute Rejection and Tacrolimus Adverse Drug Reactions in Pediatric Liver Transplantation

BACKGROUND

Despite advances in surgical procedures and the optimization of immunosuppressive therapies in pediatric liver transplantation, acute rejection (AR) and serious adverse drug reaction (ADR) to tacrolimus still contribute to morbidity and mortality. Identifying risk factors of safety and efficacy parameters may help in optimizing individual immunosuppressive therapies. This study aimed to identify peritransplant predictors of AR and factors related to the risk of ADR to tacrolimus in a large Latin American cohort of pediatric liver transplant patients.

METHODS

We performed a retrospective cohort study in a pediatric liver transplant population (n = 72). Peritransplant variables were collected retrospectively including demographic, clinical, laboratory parameters, genomic (CYP3A5 donor and recipients polymorphism), and tacrolimus trough concentrations (C0) over a 2-year follow-up period. Variability in tacrolimus C0 was calculated using percent coefficient of variation and tortuosity. ADR- and AR-free survival rates were calculated using the Kaplan-Meier method, and risk factors were identified by multivariate Cox regression models.

RESULTS

Cox-proportional hazard models identified that high tortuosity in tacrolimus C0 was associated with an 80% increased risk of AR [hazard ratio (HR), 1.80; 95% confidence interval (CI), 1.01-3.22; P < 0.05], whereas steroid in maintenance doses decreased this risk (HR, 0.56; 95% CI, 0.31-0.99; P < 0.05). Forty-six patients experienced at least one ADR including hypomagnesemia, nephrotoxicity, hypertension, malignancies, and tremor as a first event. Multivariate analysis showed that C0 values 10 days before the event (HR, 1.25; 95% CI, 1.21-1.39; P < 0.0001) and CYP3A5 expresser recipients (HR, 2.05; 95% CI, 1.03-4.06; P < 0.05) were independent predictors of ADR.

CONCLUSIONS

Tacrolimus C0 values, its variability, and CYP3A5 polymorphisms were identified as risk factors of AR and tacrolimus ADR. This knowledge may help to control and reduce their incidence in pediatric liver transplant patients. Prospective studies are important to validate these results.

Autologous Reconstruction of a Face Transplant Candidate

Since 2005, facial transplantation has emerged as a viable reconstructive option for the most severe defects not amenable to conventional reconstructive techniques, with promising aesthetic and functional outcomes to date. Key facial subunits and midface structures such as the eyelids, lips, and nose are now able to be successfully replaced rather than reconstructed, enabling adequate functional outcomes in even the most extensive defects. However, even in cases of severe facial disfigurement, the decision to proceed with transplantation versus autologous reconstruction remains a source of debate, with no current consensus regarding precise indications and inclusion/exclusion criteria. This report details the case of a candidate referred for face transplantation who ultimately underwent autologous facial reconstruction. Through this representative case, our objective is to clarify the criteria that make a patient a suitable face transplant candidate, as well as to demonstrate the outcomes achievable with a conventional autologous reconstruction, using a methodically planned, multistaged approach.

The availability of drug by liposomal drug delivery : Individual kinetics and tissue distribution of encapsulated and released drug in mice after administration of PEGylated liposomal prednisolone phosphate

Lately, the usefulness of liposomal drug delivery systems has been debated. To better understand the underlying pharmacokinetics of the targeted drug delivery by liposomes, individual encapsulated and non-encapsulated drug concentrations in blood, tumor, liver, spleen and kidneys were quantified after i.v. administration of liposomal prednisolone phosphate in mice. Kinetic analysis shows that the tumor influx of encapsulated drug is not dominant compared to the uptake by the other tissues. Further, from a quantitative point of view, the availability of non-encapsulated drug in the tumor tissue after liposomal delivery is not pronounced as compared to the other tissues studied. However, drug release in the tumor seems more extended than in the other tissues and the non-encapsulated drug concentration decreases more slowly in the tumor than in the liver and spleen. The spleen shows a high affinity for the uptake of encapsulated drug as well as the release of drug from the liposomes. Subsequently, released drug in the spleen, and possibly also in other tissues, is probably quickly redistributed towards the blood and other tissues. This also impairs the drug delivery effect of the liposomes. In contrast to the released drug in the central circulation, liver and spleen, the released drug concentration in the tumor remains at a fairly constant level likely due to the extended release kinetics from the liposomes. These extended release characteristics in the tumor most probably contribute to the beneficial effect. Nevertheless, it should be noted that larger released drug concentrations are formed in healthy tissues.