Interleukin-2 receptor antibody-induced alterations of ciclosporin dose requirements in paediatric transplant recipients

Evanescing renal allograft cortical necrosis from living donor renal transplantation: A lesson learned over two decades

BACKGROUND

Renal graft cortical necrosis (GCN) is a catastrophic cause of graft failure. We evaluated the incidence, causes, management, and outcome of GCN across two decades from our center.

METHODS

This is a retrospective analysis of transplant patients who had biopsy-proven GCN transplanted between 2000 and 2020. The clinical details, immunological workup, induction, maintenance regimen, causes of cortical necrosis, and the outcomes were compared between the first period 2000-2012, and the second period 2013-2020, when Flow cytometric and Luminex based crossmatch were included in the workup plan.

RESULTS

Among 2333 live ABO-compatible renal transplants, 37 (0.015%) patients (36 patients between 2000 and 2012 and 1 between 2013 and 2020) developed GCN (60% had diffuse and 40% patchy GCN) at a median of 8 days after transplantation.Twenty-six (60%) received ATG, 4 received plasmapheresis, and ATG (10.8%) as antirejection therapy. The cyclosporine-based regimen was associated with a higher risk of GCN (RR 2.54; 95% CI 1.26 to 5.12, p = 0.009), whereas tacrolimus-based therapy had a lower risk (RR 0.39; 95% CI 0.19 to 0.79, p = 0.009). The introduction of flow cytometry and DSA assay has significantly decreased the incidence of acute rejection and GCN. Only one patient had GCN during the 2013-2020 period because of graft's mucormycosis. Twenty-five (67.56%) patients had no recovery, and 12 (32.43%) had partial recovery of graft function.

CONCLUSION

GCN is mainly associated with rejection, and cyclosporin-based maintenance regimen had a higher incidence. The remarkable decrease in GCN after 2013 onwards could be attributed to the use of Flowcytometry, Luminex-based DSA assays, and tacrolimus-based regimens.

Not your usual drug-drug interactions: Monoclonal antibody-based therapeutics may interact with antiseizure medications

Therapeutic monoclonal antibodies (mAbs) have emerged as the fastest growing drug class. As such, mAbs are increasingly being co-prescribed with other drugs, including antiseizure medications (ASMs). Although mAbs do not share direct targets or mechanisms of disposition with small-molecule drugs (SMDs), combining therapeutics of both types can increase the risk of adverse effects and treatment failure. The primary goal of this literature review was identifying mAb-ASM combinations requiring the attention of professionals who are treating patients with epilepsy. Systematic PubMed and Embase searches (1980-2021) were performed for terms relating to mAbs, ASMs, drug interactions, and their combinations. Additional information was obtained from documents from the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA). Evidence was critically appraised - key issues calling for clinicians' consideration and important knowledge gaps were identified, and practice recommendations were developed by a group of pharmacists and epileptologists. The majority of interactions were attributed to the indirect effects of cytokine-modulating antibodies on drug metabolism. Conversely, strong inhibitors or inducers of drug-metabolizing enzymes or drug transporters could potentially interact with the cytotoxic payload of antibody-drug conjugates, and ASMs could alter mAb biodistribution. In addition, mAbs could potentiate adverse ASM effects. Unfortunately, few studies involved ASMs, requiring the formulation of class-based recommendations. Based on the current literature, most mAb-ASM interactions do not warrant special precautions. However, specific combinations should preferably be avoided, whereas others require monitoring and potentially adjustment of the ASM doses. Reduced drug efficacy or adverse effects could manifest days to weeks after mAb treatment onset or discontinuation, complicating the implication of drug interactions in potentially deleterious outcomes. Prescribers who treat patients with epilepsy should be familiar with mAb pharmacology to better anticipate potential mAb-ASM interactions and avoid toxicity, loss of seizure control, or impaired efficacy of mAb treatment.

Impact of Inflammation on Cytochromes P450 Activity in Pediatrics: A Systematic Review

Background and Objective

Cytochromes P450 (CYP) are the major enzymes involved in hepatic metabolism of drugs. Personalization of treatment in pediatrics is a major challenge, as it must not only take into account genetic, environmental, and physiological factors but also ontogeny. Published data in adults show that inflammation had an isoform-specific impact on CYP activities and we aimed to evaluate this impact in the pediatric population.

Methods

Articles listed in PubMed through 7 January, 2021 that studied the impact of inflammation on CYP activities in pediatrics were included in this systematic review. Sources of inflammation, victim drugs (CYP involved), effect of drug–disease interactions, number and age of subjects, and study design were extracted.

Results

Twenty-seven studies and case reports were included. The impact of inflammation on CYP activities appeared to be age dependent and isoform-specific, with some drug–disease interactions having significant pharmacokinetic and clinical impact. For example, midazolam clearance decreases by 70%, while immunosuppressant and theophylline concentrations increase three-fold and two-fold with intensive care unit admission and infection. Cytochrome P450 activity appears to return to baseline level when the disease is resolved.

Conclusions

Studies that have assessed the impact of inflammation on CYP activity are lacking in pediatrics, yet it is a major factor to consider to improve drug efficacy or safety. The scarce current data show that the impact of inflammation is isoform and age dependent. An effort must be made to improve the understanding of the impact of inflammation on CYP activities in children to better individualize treatment.

Impact of Interferons and Biological Drug Inhibitors of IL-2 and IL-6 on Small-Molecule Drug Metabolism Through the Cytochrome P450 System

OBJECTIVE

Assess the impact of interferons and interleukin (IL)-2 and IL-6 inhibitors on cytochrome P450 (CYP) drug metabolism in human subjects.

DATA SOURCES

PubMed search from 1980 to March 31, 2021, limited to human subjects and English language via search strategy: (biological drug names) [AND] (cytochrome [OR] CYP metabolism).

STUDY SELECTION AND DATA EXTRACTION

Narrative review of human studies assessing biological drugs in select classes that affect CYP drug metabolism.

DATA SYNTHESIS

Exogenous interferons suppress CYP1A2 (theophylline, caffeine, antipyrone) clearance by 20% to 49% in patients; have minimal impact on CYP3A4 (midazolam and dapsone), CYP2C9 (tolbutamide), or CYP2C19 (mephenytoin) metabolism; and increase CYP2D6 (debrisoquine, dextromethorphan) metabolism. Biological IL-2 inhibitors (basiliximab, daclizumab) have no effect on metabolism via CYP1A2 (caffeine), CYP2C9 (s-warfarin), CYP2C19 (omeprazole), CYP2D6 (dextromethorphan), and CYP3A4 (midazolam, tacrolimus) but may enhance CYP3A4 (cyclosporin) metabolism over time. IL-6 inhibitors (sirukumab, tocilizumab, sarilumab) significantly enhance metabolism via CYP2C9 (s-warfarin), CYP2C19 (omeprazole), and CYP3A4 (simvastatin, midazolam) and reduce metabolism via CYP1A2 (caffeine).

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

Patients using interferons, IL-2, or IL-6 blocking drugs at steady state with CYP substrates could have altered drug metabolism and experience adverse events. With interferons and biological anti-inflammatory drugs, some isoenzymes will be inhibited, whereas others will be enhanced, and the magnitude of the effect can sometimes be significant. In clinical practice, clinicians may consider these metabolic changes as an additive effect to a patient's entire disease and medication profile when determining risk/benefit of treatment.

CONCLUSIONS

Interferon therapy or inflammatory suppression via IL-2 or IL-6 can alter steady-state concentrations of CYP-metabolized small-molecule drugs.

Probable Drug Interaction Between Etanercept and Cyclosporine Resulting in Clinically Unexpected Low Trough Concentrations: First Case Report

Preclinical studies have shown that anti-cytokine therapies could alter drug dispositions through affecting cytochrome P450 synthesis; however, evidence and case reports evaluating clinical relevance of this interaction are scarce. This is the first reported case of interaction between cyclosporine (CsA) and etanercept in a 42-year-old male patient with ankylosing spondylitis and immunoglobulin A nephropathy in whom cytokine levels were monitored both before and after CsA initiation. The initiation of etanercept led to at least 2.5-folds increase in total clearance of CsA. After comprehensive assessment and stepwise exclusion of alternative causes, it was considered that inflammation resolution with etanercept administration has highly induced clearance of CsA, probably mediated by interleukin-2. The case has shown that co-administration of CsA and anti-cytokine therapies such as etanercept needs close monitoring of trough levels. Physicians and pharmacists should be aware of similar interactions especially when the biological therapy is initiated or discontinued and for patients undergoing acute inflammation phase. Monitoring cytokine levels should be considered when drug-cytokine interaction is suspected.

Interactions Between Therapeutic Proteins and Small Molecules: The Shared Role of Perpetrators and Victims

Therapeutic proteins (TPs) are becoming increasingly important as therapeutic agents. A consequence of expanding their clinical indications is coadministration with well-established small-molecule drugs (sMDs), which could lead to unpredictable effects. According to the existing regulatory guidance, the development of an sMD includes the evaluation of potential drug-drug interactions (DDIs). For TPs, only a few drug interaction studies have been published. Limited clinically relevant models, long half-lives, and complex elimination pathways are among the associated difficulties.

Regulation of drug-metabolizing enzymes in infectious and inflammatory disease: implications for biologics-small molecule drug interactions

INTRODUCTION

Drug-metabolizing enzymes (DMEs) are primarily down-regulated during infectious and inflammatory diseases, leading to disruption in the metabolism of small molecule drugs (smds), which are increasingly being prescribed therapeutically in combination with biologics for a number of chronic diseases. The biologics may exert pro- or anti-inflammatory effect, which may in turn affect the expression/activity of DMEs. Thus, patients with infectious/inflammatory diseases undergoing biologic/smd treatment can have complex changes in DMEs due to combined effects of the disease and treatment. Areas covered: We will discuss clinical biologics-SMD interaction and regulation of DMEs during infection and inflammatory diseases. Mechanistic studies will be discussed and consequences on biologic-small molecule combination therapy on disease outcome due to changes in drug metabolism will be highlighted. Expert opinion: The involvement of immunomodulatory mediators in biologic-SMDs is well known. Regulatory guidelines recommend appropriate in vitro or in vivo assessments for possible interactions. The role of cytokines in biologic-SMDs has been documented. However, the mechanisms of drug-drug interactions is much more complex, and is probably multi-factorial. Studies aimed at understanding the mechanism by which biologics effect the DMEs during inflammation/infection are clinically important.

Therapeutic protein-drug interaction assessment for daclizumab high-yield process in patients with multiple sclerosis using a cocktail approach

AIMS

To characterize the potential effect of daclizumab high-yield process (DAC HYP), a monoclonal antibody that blocks the high-affinity interleukin-2 receptors for treatment of multiple sclerosis, on activity of cytochrome P450 (CYP) enzymes.

METHODS

Twenty patients with multiple sclerosis received an oral cocktail of probe substrates of CYP1A2 (caffeine 200 mg), CYP2C9 (warfarin 10 mg/vitamin K 10 mg), CYP2C19 (omeprazole 40 mg), CYP2D6 (dextromethorphan 30 mg) and CYP3A (midazolam 5 mg) on two sequential occasions: 7 days before and 7 days after subcutaneous administration of DAC HYP 150 mg every 4 weeks for three doses. Serial pharmacokinetic blood samples up to 96 h post dose and 12-h urine samples were collected on both occasions. Area under the curve (AUC) for caffeine, S-warfarin, omeprazole and midazolam, and urine dextromethorphan to dextrorphan ratio were calculated. Statistical analyses were conducted on log-transformed parameters using a linear mixed-effects model.

RESULTS

The 90% confidence intervals (CIs) for the geometric mean ratio (probe substrate with DAC HYP/probe substrate alone) for caffeine AUC from 0-12 h (0.93-1.15), S-warfarin AUC from 0 to infinity (AUC[0-inf]) (0.95-1.06), omeprazole AUC(0-inf) (0.88-1.13) and midazolam AUC(0-inf) (0.89-1.15) were within the no-effect boundary of 0.80-1.25. The geometric mean ratio for urine dextromethorphan to dextrorphan ratio was 1.01, with the 90% CI (0.76-1.34) extending slightly outside the no-effect boundary, likely due to high variability with urine collections and CYP2D6 activity.

CONCLUSIONS

DAC HYP treatment in patients with multiple sclerosis had no effect on CYP 1A2, 2C9, 2C19, 2D6 and 3A activity.

Antibody induction versus corticosteroid induction for liver transplant recipients

BACKGROUND

Liver transplantation is an established treatment option for end-stage liver failure. To date, no consensus has been reached on the use of immunosuppressive T-cell specific antibody induction compared with corticosteroid induction of immunosuppression after liver transplantation.

OBJECTIVES

To assess the benefits and harms of T-cell specific antibody induction versus corticosteroid induction for prevention of acute rejection in liver transplant recipients.

SEARCH METHODS

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, Science Citation Index Expanded, and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) on 30 September 2013 together with reference checking, citation searching, contact with trial authors and pharmaceutical companies to identify additional trials.

SELECTION CRITERIA

We included all randomised clinical trials assessing immunosuppression with T-cell specific antibody induction versus corticosteroid induction in liver transplant recipients. Our inclusion criteria stated that participants within each included trial should have received the same maintenance immunosuppressive therapy.

DATA COLLECTION AND ANALYSIS

We used RevMan for statistical analysis of dichotomous data with risk ratio (RR) and of continuous data with mean difference (MD), both with 95% confidence intervals (CIs). We assessed risk of systematic errors (bias) using bias risk domains with definitions. We used trial sequential analysis to control for random errors (play of chance).

MAIN RESULTS

We included 10 randomised trials with a total of 1589 liver transplant recipients, which studied the use of T-cell specific antibody induction versus corticosteroid induction. All trials were with high risk of bias. We compared any kind of T-cell specific antibody induction versus corticosteroid induction in 10 trials with 1589 participants, including interleukin-2 receptor antagonist induction versus corticosteroid induction in nine trials with 1470 participants, and polyclonal T-cell specific antibody induction versus corticosteroid induction in one trial with 119 participants.Our analyses showed no significant differences regarding mortality (RR 1.01, 95% CI 0.72 to 1.43), graft loss (RR 1.12, 95% CI 0.82 to 1.53) and acute rejection (RR 0.84, 95% CI 0.70 to 1.00), infection (RR 0.96, 95% CI 0.85 to 1.09), hepatitis C virus recurrence (RR 0.89, 95% CI 0.79 to 1.00), malignancy (RR 0.59, 95% CI 0.13 to 2.73), and post-transplantation lymphoproliferative disorder (RR 1.00, 95% CI 0.07 to 15.38) when any kind of T-cell specific antibody induction was compared with corticosteroid induction (all low-quality evidence). Cytomegalovirus infection was less frequent in patients receiving any kind of T-cell specific antibody induction compared with corticosteroid induction (RR 0.50, 95% CI 0.33 to 0.75; low-quality evidence). This was also observed when interleukin-2 receptor antagonist induction was compared with corticosteroid induction (RR 0.55, 95% CI 0.37 to 0.83; low-quality evidence), and when polyclonal T-cell specific antibody induction was compared with corticosteroid induction (RR 0.21, 95% CI 0.06 to 0.70; low-quality evidence). However, when trial sequential analysis regarding cytomegalovirus infection was applied, the required information size was not reached. Furthermore, diabetes mellitus occurred less frequently when T-cell specific antibody induction was compared with corticosteroid induction (RR 0.45, 95% CI 0.34 to 0.60; low-quality evidence), when interleukin-2 receptor antagonist induction was compared with corticosteroid induction (RR 0.45, 95% CI 0.35 to 0.61; low-quality evidence), and when polyclonal T-cell specific antibody induction was compared with corticosteroid induction (RR 0.12, 95% CI 0.02 to 0.95; low-quality evidence). When trial sequential analysis was applied, the trial sequential monitoring boundary for benefit was crossed. We found no subgroup differences for type of interleukin-2 receptor antagonist (basiliximab versus daclizumab). Four trials reported on adverse events. However, no differences between trial groups were noted. Limited data were available for meta-analysis on drug-specific adverse events such as haematological adverse events for antithymocyte globulin. No data were available on quality of life.

AUTHORS' CONCLUSIONS

Because of the low quality of the evidence, the effects of T-cell antibody induction remain uncertain. T-cell specific antibody induction seems to reduce diabetes mellitus and may reduce cytomegalovirus infection when compared with corticosteroid induction. No other clear benefits or harms were associated with the use of T-cell specific antibody induction compared with corticosteroid induction. For some analyses, the number of trials investigating the use of T-cell specific antibody induction after liver transplantation is small, and the numbers of participants and outcomes in these randomised trials are limited. Furthermore, the included trials are heterogeneous in nature and have applied different types of T-cell specific antibody induction therapy. All trials were at high risk of bias. Hence, additional randomised clinical trials are needed to assess the benefits and harms of T-cell specific antibody induction compared with corticosteroid induction for liver transplant recipients. Such trials ought to be conducted with low risks of systematic error and of random error.

An evaluation of the potential for drug-drug interactions between bendamustine and rituximab in indolent non-Hodgkin lymphoma and mantle cell lymphoma

Purpose

Bendamustine plus rituximab has been reported to be effective in treating lymphoid malignancies. This analysis investigated the potential for drug–drug interactions between the drugs in patients with indolent non-Hodgkin lymphoma or mantle cell lymphoma.

Methods

Data were derived from a bendamustine–rituximab combination therapy study, a bendamustine monotherapy study, and published literature on rituximab monotherapy and combination therapy. Analysis of the potential for rituximab to affect bendamustine systemic exposure included comparing bendamustine concentration–time profile following monotherapy to that following combination therapy and comparing model-predicted Bayesian bendamustine clearance in the presence and absence of rituximab. Analysis of the potential for bendamustine to affect rituximab systemic exposure included plotting observed minimum, median, and maximum serum rituximab concentrations at the end of rituximab infusion (EOI) and 24 h and 7 days post-infusion in patients receiving combination therapy versus concentrations reported in literature following rituximab monotherapy.

Results

The established population pharmacokinetic model following bendamustine monotherapy was evaluated to determine its applicability to combination therapy for the purpose of confirming lack of pharmacokinetic interaction. The model adequately described the bendamustine concentration–time profile following monotherapy and combination therapy in adults. There was no statistically significant difference in estimated bendamustine clearance either alone or in combination. Also, rituximab concentrations from EOI to 24 h and 7 days demonstrated a pattern of decline similar to that seen in rituximab studies without bendamustine, suggesting that bendamustine does not affect the rituximab clearance rate.

Conclusions

Neither bendamustine nor rituximab appears to affect systemic exposure of the other drug when coadministered.

Utility of population pharmacokinetic modeling in the assessment of therapeutic protein-drug interactions

Assessment of pharmacokinetic (PK) based drug-drug interactions (DDI) is essential for ensuring patient safety and drug efficacy. With the substantial increase in therapeutic proteins (TP) entering the market and drug development, evaluation of TP-drug interaction (TPDI) has become increasingly important. Unlike for small molecule (e.g., chemical-based) drugs, conducting TPDI studies often presents logistical challenges, while the population PK (PPK) modeling may be a viable approach dealing with the issues. A working group was formed with members from the pharmaceutical industry and the FDA to assess the utility of PPK-based TPDI assessment including study designs, data analysis methods, and implementation strategy. This paper summarizes key issues for consideration as well as a proposed strategy with focuses on (1) PPK approach for exploratory assessment; (2) PPK approach for confirmatory assessment; (3) importance of data quality; (4) implementation strategy; and (5) potential regulatory implications. Advantages and limitations of the approach are also discussed.

Pharmacokinetics, pharmacodynamics and physiologically-based pharmacokinetic modelling of monoclonal antibodies

Development of monoclonal antibodies (mAbs) and their functional derivatives represents a growing segment of the development pipeline in the pharmaceutical industry. More than 25 mAbs and derivatives have been approved for a variety of therapeutic applications. In addition, around 500 mAbs and derivatives are currently in different stages of development. mAbs are considered to be large molecule therapeutics (in general, they are 2-3 orders of magnitude larger than small chemical molecule therapeutics), but they are not just big chemicals. These compounds demonstrate much more complex pharmacokinetic and pharmacodynamic behaviour than small molecules. Because of their large size and relatively poor membrane permeability and instability in the conditions of the gastrointestinal tract, parenteral administration is the most usual route of administration. The rate and extent of mAb distribution is very slow and depends on extravasation in tissue, distribution within the particular tissue, and degradation. Elimination primarily happens via catabolism to peptides and amino acids. Although not definitive, work has been published to define the human tissues mainly involved in the elimination of mAbs, and it seems that many cells throughout the body are involved. mAbs can be targeted against many soluble or membrane-bound targets, thus these compounds may act by a variety of mechanisms to achieve their pharmacological effect. mAbs targeting soluble antigen generally exhibit linear elimination, whereas those targeting membrane-bound antigen often exhibit non-linear elimination, mainly due to target-mediated drug disposition (TMDD). The high-affinity interaction of mAbs and their derivatives with the pharmacological target can often result in non-linear pharmacokinetics. Because of species differences (particularly due to differences in target affinity and abundance) in the pharmacokinetics and pharmacodynamics of mAbs, pharmacokinetic/pharmacodynamic modelling of mAbs has been used routinely to expedite the development of mAbs and their derivatives and has been utilized to help in the selection of appropriate dose regimens. Although modelling approaches have helped to explain variability in both pharmacokinetic and pharmacodynamic properties of these drugs, there is a clear need for more complex models to improve understanding of pharmacokinetic processes and pharmacodynamic interactions of mAbs with the immune system. There are different approaches applied to physiologically based pharmacokinetic (PBPK) modelling of mAbs and important differences between the models developed. Some key additional features that need to be accounted for in PBPK models of mAbs are neonatal Fc receptor (FcRn; an important salvage mechanism for antibodies) binding, TMDD and lymph flow. Several models have been described incorporating some or all of these features and the use of PBPK models are expected to expand over the next few years.

Significant increase in plasma 4β-hydroxycholesterol concentration in patients after kidney transplantation

Several previous studies have shown that renal failure decreases not only renal elimination but also metabolic clearance of drugs, particularly those metabolized by CYP3A. However, whether recovery of renal function results in recovery of hepatic CYP3A activity remains unknown. In this study, we evaluated the effect of renal function on CYP3A activity after kidney transplantation in patients with end-stage renal disease (ESRD) by measuring the change in CYP3A activity using plasma concentration of 4β-hydroxycholesterol as a biomarker. The study enrolled 13 patients with ESRD who underwent the first kidney allograft transplantation. Morning blood samples were collected before and 3, 7, 10, 14, 21, 30, 60, 90, 120, 150 and 180 days after kidney transplantation. Plasma concentration of 4β-hydroxycholesterol was measured using GC-MS. Compared with before kidney transplantation, creatinine clearance increased significantly from day 3 after kidney transplantation and stabilized thereafter. Plasma concentration of 4β-hydroxycholesterol was elevated significantly on days 90 and 180 after kidney transplantation. In conclusion, this study suggests the recovery of CYP3A activity with improvement in renal function after kidney transplantation in patients with ESRD.

Therapeutic protein drug-drug interactions: navigating the knowledge gaps-highlights from the 2012 AAPS NBC Roundtable and IQ Consortium/FDA workshop

The investigation of therapeutic protein drug-drug interactions has proven to be challenging. In May 2012, a roundtable was held at the American Association of Pharmaceutical Scientists National Biotechnology Conference to discuss the challenges of preclinical assessment and in vitro to in vivo extrapolation of these interactions. Several weeks later, a 2-day workshop co-sponsored by the U.S. Food and Drug Administration and the International Consortium for Innovation and Quality in Pharmaceutical Development was held to facilitate better understanding of the current science, investigative approaches and knowledge gaps in this field. Both meetings focused primarily on drug interactions involving therapeutic proteins that are pro-inflammatory cytokines or cytokine modulators. In this meeting synopsis, we provide highlights from both meetings and summarize observations and recommendations that were developed to reflect the current state of the art thinking, including a four-step risk assessment that could be used to determine the need (or not) for a dedicated clinical pharmacokinetic interaction study.

Immunological response as a source to variability in drug metabolism and transport

Through the last decades it has become increasingly evident that disease-states involving cytokines affect the pharmacokinetics of drugs through regulation of expression and activity of drug metabolizing enzymes, and more recently also drug transporters. The clinical implication is however difficult to predict, since these effects are dependent on the degree of inflammation and may be changed when the diseases are treated. This article will give an overview of the present understanding of the effects of cytokines on cytochrome P450 enzymes and drug transporters, and highlight the importance of considering these issues in regard to increasing use of the relatively new class of drugs, namely therapeutic proteins.

Acute cortical necrosis following renal transplantation in a case of sickle cell trait

Renal transplant recipients who have sickle cell disease are at risk of infection, recurrent graft disease, and sickling crisis that affects the long-term outcome. We report a patient of sickle cell trait who developed patchy cortical necrosis in the perioperative period but had a good long-term outcome. The renal cortical necrosis was presumed to be secondary to cyclosporine-basiliximab interaction in the backdrop of sickling trait. The patient additionally had spontaneous closure of vascular access and severe hypertension immediately following transplantation suggestive of vaso-occlusive crisis. Cyclosporine and basiliximab drug interaction needs to be recognized and steps need to be taken in patients to avoid perioperative graft dysfunction.

How current understanding of clearance mechanisms and pharmacodynamics of therapeutic proteins can be applied for evaluation of their drug-drug interaction potential

Increasing use of therapeutic proteins (TPs) in polypharmacy settings calls for more in-depth understanding of the biological interactions that can lead to increased toxicity or loss of pharmacological effect. Factors such as patient population, medications that are likely to be coadministered in that population, clearance mechanisms of a TP, and concomitant drugs have to be taken into account to determine the potential for drug-drug interactions (DDIs). The most well documented TP DDI mechanism involves cytokine-mediated changes in drug-metabolizing enzymes. Because of the limitations of the current preclinical models for addressing this type of DDI, clinical evaluation is currently the most reliable approach. Other DDI mechanisms need to be addressed on a case-by-case basis. These include altered clearance of TPs resulting from the changes in the target protein levels by the concomitant medication, displacement of TPs from binding proteins, modulation of Fcγ receptor expression, and others. The purpose of this review is to introduce the approach used by Pfizer scientists for evaluation of the DDI potential of novel TP products during drug discovery and development.

The role of basiliximab in the evolving renal transplantation immunosuppression protocol

Basiliximab is a chimeric mouse-human monoclonal antibody directed against the alpha chain of the interleukin-2 (IL-2) receptor on activated T lymphocytes. It was shown in phase III trials to reduce the number and severity of acute rejection episodes in the first year following renal transplantation in adults and children, with a reasonable cost-benefit ratio. The drug does not increase the incidence of opportunistic infections or malignancies above baseline in patients treated with conventional calcineurin inhibitor-based immunosuppression. In the field of renal transplantation, basiliximab does not increase kidney or patient survival, despite the reduction in the number of rejection episodes. Basiliximab may reduce the incidence of delayed graft function. In comparison with lymphocyte-depleting antibodies basiliximab appears to have equal efficacy in standard immunological risk patients. Recently, IL-2 receptor monoclonal antibodies have been used with the objective of reducing or eliminating the more toxic elements of the standard immunosuppression protocol. Several trials have incorporated basiliximab in protocols designed to avoid or withdraw rapidly corticosteroids, as well as protocols which substitute target-of-rapamycin (TOR) inhibitors for calcineurin inhibitors.

AAPS workshop report: strategies to address therapeutic protein-drug interactions during clinical development

Therapeutic proteins (TPs) are increasingly combined with small molecules and/or with other TPs. However preclinical tools and in vitro test systems for assessing drug interaction potential of TPs such as monoclonal antibodies, cytokines and cytokine modulators are limited. Published data suggests that clinically relevant TP-drug interactions (TP-DI) are likely from overlap in mechanisms of action, alteration in target and/or drug-disease interaction. Clinical drug interaction studies are not routinely conducted for TPs because of the logistical constraints in study design to address pharmacokinetic (PK)- and pharmacodynamic (PD)-based interactions. Different pharmaceutical companies have developed their respective question- and/or risk-based approaches for TP-DI based on the TP mechanism of action as well as patient population. During the workshop both company strategies and regulatory perspectives were discussed in depth using case studies; knowledge gaps and best practices were subsequently identified and discussed. Understanding the functional role of target, target expression and their downstream consequences were identified as important for assessing the potential for a TP-DI. Therefore, a question-and/or risk-based approach based upon the mechanism of action and patient population was proposed as a reasonable TP-DI strategy. This field continues to evolve as companies generate additional preclinical and clinical data to improve their understanding of possible mechanisms for drug interactions. Regulatory agencies are in the process of updating their recommendations to sponsors regarding the conduct of in vitro and in vivo interaction studies for new drug applications (NDAs) and biologics license applications (BLAs).

Clinical pharmacokinetics of therapeutic monoclonal antibodies

Monoclonal antibodies (mAbs) have been used in the treatment of various diseases for over 20 years and combine high specificity with generally low toxicity. Their pharmacokinetic properties differ markedly from those of non-antibody-type drugs, and these properties can have important clinical implications. mAbs are administered intravenously, intramuscularly or subcutaneously. Oral administration is precluded by the molecular size, hydrophilicity and gastric degradation of mAbs. Distribution into tissue is slow because of the molecular size of mAbs, and volumes of distribution are generally low. mAbs are metabolized to peptides and amino acids in several tissues, by circulating phagocytic cells or by their target antigen-containing cells. Antibodies and endogenous immunoglobulins are protected from degradation by binding to protective receptors (the neonatal Fc-receptor [FcRn]), which explains their long elimination half-lives (up to 4 weeks). Population pharmacokinetic analyses have been applied in assessing covariates in the disposition of mAbs. Both linear and nonlinear elimination have been reported for mAbs, which is probably caused by target-mediated disposition. Possible factors influencing elimination of mAbs include the amount of the target antigen, immune reactions to the antibody and patient demographics. Bodyweight and/or body surface area are generally related to clearance of mAbs, but clinical relevance is often low. Metabolic drug-drug interactions are rare for mAbs. Exposure-response relationships have been described for some mAbs. In conclusion, the parenteral administration, slow tissue distribution and long elimination half-life are the most pronounced clinical pharmacokinetic characteristics of mAbs.

Pharmacokinetics and pharmacodynamics of monoclonal antibodies: concepts and lessons for drug development

Monoclonal antibodies (mAbs) have complex pharmacology; pharmacokinetics and pharmacodynamics depend on mAb structure and target antigen. mAbs targeting soluble antigens often exhibit linear pharmacokinetic behavior, whereas mAbs targeting cell surface antigens frequently exhibit nonlinear behavior due to receptor-mediated clearance. Where nonlinear kinetics exist, clearance can change due to receptor loss following repeated dosing and/or disease severity. mAb pharmacodynamics are often indirect, with delayed clinically relevant outcomes. This behavior provides challenges during clinical development; studies must be carefully planned to account for complexities specific to each agent. Selection of a starting dose for human studies can be difficult. Species differences in pharmacology need to be considered. Various metrics are available for scaling from animals to humans. Optimal dose selection should ensure uniform mAb exposure across all individuals. Traditional approaches such as flat dosing and variable dosing based upon body surface area or weight should be supported by pharmacokinetic and pharmacodynamic behavior, including target antigen and concurrent disease states. The use of loading doses or dose adjustments to improve clinical response is also a consideration. The evaluation of drug interactions requires innovative designs. Due to the pharmacokinetic properties of mAbs, interacting drugs may need to be administered for protracted periods. Consequently, population pharmacokinetic and pharmacodynamic model-based approaches are often implemented to evaluate mAb drug interactions.

Anti-interleukin-2 receptor antibodies-basiliximab and daclizumab-for the prevention of acute rejection in renal transplantation

The use of antibody induction after kidney transplantation has increased from 25% to 63% in the past decade and roughly one half of the induction agent used is anti-interleukin-2 receptor antibody (IL-2RA, ie, basiliximab or daclizumab). When combined with calcineurin inhibitor (CNI)-based immunosuppression, IL-2RAs have been shown to reduce the incidence of acute rejection, one of the predictors of poor graft survival, without increasing risks of infections and malignancies in kidney transplantation. For low-immunological-risk patients, IL-2RAs, as compared with lymphocyte-depleting antibodies, are equally efficacious and have better safety profiles. For high-risk patients, however, IL-2RAs may be inferior to lymphocyte-depleting antibodies for the prophylaxis of acute rejection. In an effort to reduce toxicities of other immunosuppressive medications without increasing the risk of acute rejection and chronic graft loss, IL-2RAs have often been combined with steroid- and CNI-sparing immunosuppression protocols. More data support the benefits of early steroid withdrawal with IL-2RA in low-risk patients, but preferred induction therapy for high-risk patients has yet to be determined. Although CNI-sparing protocols with IL-2RA may preserve renal function and improve long-term survival in selected patients, further studies are needed to identify those who benefit most from this strategy.

Induction therapy in pediatric renal transplant recipients: an overview

Induction therapy to prevent the acute rejection of mismatched allografts with the ultimate aim of prolonging the life of the allograft has been the cornerstone of immunosuppression since the introduction of renal transplantation. Agents used for induction therapy have changed over time. Their role in transplantation is expanding to include corticosteroid avoidance and immunosuppression minimization. This review provides an overview of induction therapies for renal transplantation including historic therapies such as total lymphoid irradiation and Minnesota antilymphocyte globulin, and current therapies with polyclonal and monoclonal antibodies and chemical agents, with special emphasis on children. Data from adult studies, and pediatric studies whenever available, are summarized. A brief summary of experimental therapies with fingolimod and belatacept is provided. Historically, induction therapies were targeted at T cells. The role of induction therapies targeted at B cells is emerging in select groups of patients that include highly sensitized recipients and those receiving transplants from blood group incompatible donors. With the advent of newer maintenance immunosuppressive medications and with very low rates of acute rejection, induction protocols for renal transplantation need to be targeted so that excessive immunosuppression and infections are avoided. Several single-center and registry data analyses in children suggest that the addition of an interleukin (IL)-2 receptor antagonist may improve graft survival compared with no induction. The safety profile of IL-2 receptor antagonists is indistinguishable from that of placebo, with no apparent difference in the incidence of infection or post-transplant lymphoproliferative disease. IL-2 receptor antagonists and polyclonal lymphocyte-depleting antibodies offer equivalent efficacy in standard-risk populations. However, in high-risk patients, acute rejection rates and graft outcomes may be improved with the use of lymphocyte-depleting agents such as Thymoglobulin. However, cytomegalovirus infection and other infections may be more common with this therapy. Therefore, in patients at high risk of graft loss, Thymoglobulin may be the preferred choice for induction therapy, while for all other patients, IL-2 receptor antagonists should be considered the first-line choice for induction therapy. Newer lymphocyte-depleting agents such as alemtuzumab may be better utilized in minimization regimens involving one or two oral maintenance immunosuppressive agents.

Pharmacokinetic drug-drug interaction potentials for therapeutic monoclonal antibodies: reality check

A formal assessment of the drug-drug interaction potential of any investigational drug product often requires multiple metabolic and pharmacokinetic evaluations. In contrast to a small-molecule drug, investigating the drug-drug interaction potential of a monoclonal antibody is inherently complicated. High molecular weight monoclonal antibodies are often genetically engineered to demonstrate strong specificity for a particular human antigen target. Consequently, monoclonal antibodies usually have few clinically relevant animal models--other than nonhuman primates--in which to conduct appropriate nonclinical studies. Likewise, clinical drug-drug interaction studies of monoclonal antibodies with long elimination half-lives pose definite operational challenges as conventional crossover studies with adequate washout periods are difficult to conduct. Furthermore, the current regulatory guidance on the design and conduct of in vitro and in vivo drug-drug interaction studies applies more readily to small-molecule drugs than protein-based biologics. Nevertheless, a certain amount of clinically useful information has begun to emerge from the published literature on drug-drug interaction potentials of therapeutic monoclonal antibodies. This article provides a systematic review of the current literature and offers some practical considerations for the design and conduct of pharmacokinetic drug-drug interaction assessments involving novel monoclonal antibodies. Ideally, these evaluations should be performed throughout all stages of drug development. In particular, pharmacokinetic interaction studies with any marketed drugs that are likely to be coadministered with the monoclonal antibody will yield the most clinically useful information for practitioners and patients alike.

Immunosuppression in pediatric solid organ transplantation: opportunities, risks, and management

The pediatric transplant community stands at a time of unprecedented choice of immunosuppressive agents - and with a legacy of morbidity from those agents used in the previous two decades. This review considers the clinical utility and side-effect profiles of immunosuppressants used widely in current practice (e.g., glucocorticoids, azathioprine, ciclosporin, tacrolimus, mycophenolate, and sirolimus) and those agents which are in increasing use or in evaluation (e.g., IL-2 receptor antibodies, everolimus, FTY720, LEA29Y, and deoxyspergualin). Further consideration is given to the wider drug interactions likely during the use of new immunosuppressant regimens and to our growing awareness of the influences of genetic heterogeneity on drug efficacy and handling. Finally, we consider the new demands being placed on the use of drug monitoring to regulate dosage of this new repertoire of immunosuppressants.

Basiliximab combined with low-dose rabbit anti-human thymocyte globulin: a possible further step toward effective and minimally toxic T cell-targeted therapy in kidney transplantation

In high-risk kidney transplant recipients, induction therapy with rabbit anti-human thymocyte globulin (RATG) reduces the risk for acute rejection but is associated with significant toxicity, opportunistic infections, and cancer. Using reduced doses of RATG combined with anti-IL-2 antibodies may achieve the same antirejection activity of standard-dose RATG but with a better safety profile. This randomized, open-label study compared the efficacy, tolerability, and costs of low-dose RATG (0.5 mg/kg per d) plus basiliximab (20 mg 4 d apart) versus standard-dose RATG (2 mg/kg per d) in 33 consecutive high-risk renal transplant recipients (living-related transplant recipients, sensitized patients or patients who received another transplant, and patients with delayed graft function) over 6 mo of follow-up. All patients received concomitant therapy with steroids, cyclosporin A, and azathioprine or mycophenolate mofetil. Seventeen patients received low-dose RATG plus basiliximab, and 16 received standard-dose RATG. Patient (100 versus 100%) and graft (94 versus 100%) survival were comparable in the two groups, but the incidence of fever (17.6 versus 56.5%; P = 0.01), leukopenia (23.5 versus 56.3%; P < 0.05), anemia (29.4 versus 62.5%; P < 0.05), cytomegalovirus reactivations (17.6 versus 56.5%; P = 0.01), the number of transfused units (0.5 +/- 0.9 versus 2.0 +/- 2.4; P < 0.001), and treatment costs (3652 +/- 704 versus 5400 +/- 1960 euro; P = 0.001) were lower with low-dose RATG plus basiliximab than with standard-dose RATG. There was one episode of biopsy-proven acute rejection on low-dose RATG plus basiliximab, and there were two on standard-dose RATG. In renal transplantation, induction therapy with basiliximab plus low-dose RATG effectively prevents acute rejection and is safer and more cost-effective than induction with standard-dose RATG.

Disposition of paclitaxel (Taxol®) and its metabolites in patients with advanced breast cancer (ABC) when combined with trastuzumab (Hercpetin®)

Monoclonal antibodies are capable of modulating drug metabolising enzymes resulting in unexpected plasma concentrations of a drug when given concomitantly. Therefore plasma concentration of paclitaxel (PTX) and its metabolites has been monitored in 10 patients with advanced breast cancer during treatment with PTX alone or combined with trastuzumab (TMAB, paired cross over design). Compared to the MONO regimen PTX peak plasma concentrations were about 25% lower in the TMAB schedule: cmax = 3294 +/- 1174 ng/ml (MONO: 4368 +/- 1887 ng/ml). TMAB also caused lower peak plasma concentration of the main metabolite 6-hydroxy PTX (248 +/- 89 ng/ml) compared to the MONO schedule (194 +/- 82 ng/ml). Cmax of the minor metabolites was distinctly below 100 ng/ml and consequently differed negligible in both schedules. The similar apparent formation rate of the metabolites in both schedules (range from 30 to 50 min) as well as identical tmax values (range 170-190 min) suggested that TMAB had no influence on PTX metabolism. In accordance to plasma concentrations, AUClast of PTX was lower in the MONO schedule (733 +/- 197 microg/ml*min, AUClast = 669 +/- 248 microg/ml*min for TMAB) but without significance. In summary no indices for an altered plasma disposition of PTX and its metabolites could be found when TMAB was given concomitantly.

Pharmacokinetics of Gemcitabine Combined with Trastuzumab in Patients with Advanced Breast Cancer

BACKGROUND

Combining the monoclonal antibody trastuzumab (TMAB) with chemotherapy is a new strategy in treatment of advanced breast cancer in HER+++ overexpressing patients.

PATIENTS AND METHODS

The disposition of gemcitabine has been investigated in 8 breast cancer patients (prospective cross-over design). Gemcitabine was administered as a 30-min i.v. infusion (1,000 mg/m(2) in 250 ml) on day 1 weekly for 3 weeks. On day 2 TMAB was infused with a loading dose of 4 mg/kg (90-min infusion) followed by a weekly maintenance dose of 2 mg/kg (30-min infusion). Pharmacokinetic analysis was performed after the first (= MONO) and after the third gemcitabine infusion (= TMAB).

RESULTS

Cmax was 22.2 microg/ml (t(max) = 24 min) in the MONO and 24.6 microg/ml (t(max) = 23 min) in the TMAB schedule. Gemcitabine distributed rapidly from plasma within a few minutes and was eliminated with a t1/2el of about 80 min in both arms of the study. The metabolite difluorodeoxyuridine (dFdU) appeared in plasma with t1/2appin = 12.8 min (MONO) or t1/2appin = 10.2 min (TMAB) reaching a mean peak concentration of 35.9 microg/ml (MONO) or 30.4 microg/ml (TMAB), respectively.

CONCLUSION

The results gave evidence that TMAB does not affect the disposition of gemcitabine.

Anti-IL-2 receptor antibody vs. polyclonal anti-lymphocyte antibody as induction therapy in pediatric transplantation

Current concerns in pediatric transplantation focus on chronic rejection which commonly leads to graft loss, and on long-term maintenance immunosuppression toxicity. Acute rejection has been associated with the subsequent development of chronic rejection. Therefore, induction therapy may provide potential benefits by preventing early acute rejection episodes and allowing delayed administration of calcineurin inhibitors or steroid avoidance. This review of the literature showed that induction therapy can reduce early and recurrent acute rejection episodes after pediatric solid organ transplantation. Whether this might result in better long-term graft survival has still to be confirmed. However, induction therapy has beneficial effects in high-risk recipients and allows steroid avoidance or calcineurin inhibitor minimization. Because they are very well tolerated, anti-IL-2 receptor antibodies are increasingly preferred to rabbit-antithymocyte globulin, but the former have not yet been proven to be more effective or to have less late toxicity than polyclonal agents. Benefits in early outcome and no increase in adverse events lead to recommend the use of IL-2 receptor antagonists as induction therapy after pediatric organ transplantation.

Bayesian estimation of cyclosporin exposure for routine therapeutic drug monitoring in kidney transplant patients

AIMS

AUC-based monitoring of cyclosporin A (CsA) is useful to optimize dose adaptation in difficult cases. We developed a population pharmacokinetic model to describe dose-exposure relationships for CsA in renal transplant patients and applied it to the Bayesian estimation of AUCs using three blood concentrations.

METHODS

A total of 84 renal graft recipients treated with CsA microemulsion were included in this study. Population pharmacokinetic analysis was conducted using NONMEM. A two-compartment model with zero-order absorption and a lag time best described the data. Bayesian estimation was based on CsA blood concentrations measured before dosing and 1 h and 2 h post dose. Predictive performance was evaluated using a cross-validation approach. Estimated AUCs were compared with AUCs calculated by the trapezoidal method. The Bayesian approach was also applied to an independent group of eight patients exhibiting unusual pharmacokinetic profiles.

RESULTS

Mean population pharmacokinetic parameters were apparent clearance 30 l h(-1), apparent volume of distribution 79.8 l, duration of absorption 52 min, absorption lag time 7 min. No significant relationships were found between any of the pharmacokinetic parameters and individual characteristics. A good correlation was obtained between Bayesian-estimated and experimental AUCs, with a mean prediction error of 2.8% (95% CI [-0.6, 6.2]) and an accuracy of 13.1% (95% CI [7.5, 17.2]). A good correlation was also obtained in the eight patients with unusual pharmacokinetic profiles (r(2) = 0.96, P < 0.01).

CONCLUSIONS

Our Bayesian approach enabled a good estimation of CsA exposure in a population of patients with variable pharmacokinetic profiles, showing its usefulness for routine AUC-based therapeutic drug monitoring.

Efficacy and safety of basiliximab in kidney transplantation

The efficacy and safety of basiliximab, in combination with different maintenance regimens, are extensively addressed in the available literature. Basiliximab reduces the incidence of acute rejection, allows a safe reduction of steroid dosage, and is associated with economic savings, although there is substantially no proof that basiliximab prolongs either patient or graft survival. Initial basiliximab administration entails a low-risk and is associated with fewer adverse events than T cell depleting agents. However, life-threatening reactions were reported following re-exposure to basiliximab in recipients who lost graft function early after transplantation and, therefore, discontinued all immunosuppressive agents.

Basiliximab-chimeric anti-IL2-R monoclonal antibody in pediatric liver transplantation: comparative study

Basiliximab is a monoclonal antibody that binds to the alpha subunit (CD(25)) of the interleukin-2 receptor of activated T lymphocytes. The advantage of basiliximab in organ transplantation is the reduce possibility to calcineurin inhibitor dosages to avoid nephrotoxicity. Basiliximab has significantly reduced the incidence of acute rejection (AR) in renal transplant recipients; however, the results are uncertain in liver transplantation (LT). The objective of this investigation was to assess the effect of basiliximab to prevent AR in the first 6 months after pediatric LT. From March 2000 to October 2001, 32 recipients of a primary orthotopic cadaveric or living donor LT were given basiliximab by intravenous bolus injection on the day of transplantation (day 0) and on day 4. Four children who received one dose were excluded from the study. The rate and the intensity of AR episodes, the incidence of chronic rejection, serum creatinine level, incidence of infections, adverse side effects, and daily oral dosage of cyclosporine (Neoral) to maintain the target blood level of 850 to 1000 mg/dL at C2, 2 hours after the administration, were analyzed in the remaining 28 recipients. Results were compared to those obtained from a matched historical group (n = 28) of similar age, weight, and hepatic diseases distribution. None of the analyzed parameters was statistically significant (P >.05) except for the daily oral dose of cyclosporine (7 to 13 mg/kg/dose, P <.05). In our series, the addition of basiliximab to the immunosuppressive therapy did not reduce the incidence of AR in pediatric LT.

Immunosuppressants

Immunosuppressants are prescribed to prevent rejection of transplanted tissues and organs and are also used in the treatment of autoimmune disorders. Consultation-liaison psychiatrists increasingly encounter patients taking these agents as the number of transplant recipients increases and the indications for the use of immunosuppressants expands. These drugs have potentially deleterious physical, mental, and biochemical side effects. In addition, transplant recipients and patients with autoimmune disorders commonly have comorbid illnesses that require pharmacologic treatment. The management of these patients is challenging secondary to the severity of these illnesses, the number of medications prescribed, and the potential for adverse drug-drug interactions. Knowledge of the pharmacokinetic properties of these drugs and the potential for serious drug-drug interactions that cause alterations in serum levels of the immunosuppressant medications is essential. Increased serum levels may cause serious toxic effects and decreased serum levels may lead to rejection of the transplanted organ or worsening of the autoimmune disorder. Adverse events may also occur when serum levels of medications prescribed for comorbid illnesses are altered by administration of immunosuppressants. The pharmacokinetic drug-drug interaction profiles of the glucocorticoids, cyclosporine, tacrolimus, sirolimus, mycophenolate mofetil, azathioprine, and monoclonal antibodies are discussed in this review.

Anti-interleukin-2 receptor antibodies for the prevention of rejection in pediatric renal transplant patients: current status

The anti-interleukin-2 receptor (anti-IL-2R) antibody therapy is an exciting approach to the prevention of acute rejection after renal allograft transplantation whereby immunosuppression is exerted by a selective and competitive inhibition of IL-2-induced T cell proliferation, a critical pathway of allorecognition. The anti-IL-2R antibodies specifically block the alpha-subunit of the IL-2R on activated T cells, and prevent T cell proliferation and activation of the effector arms of the immune system. The anti-IL-2R antibodies are used as induction therapy, immediately after renal transplantation, for prevention of acute cellular rejection in children and adults. During acute rejection, the IL-2Ralpha chain is no longer expressed on T cells; thus, the antibodies cannot be used to treat an existing acute rejection. Two anti-IL-2R monoclonal antibodies are currently in clinical use: daclizumab and basiliximab. In placebo-controlled phase III clinical trials in adults, daclizumab and basiliximab in combination with calcineurin inhibitor-based immunosuppression, significantly reduced the incidence of acute rejection and corticosteroid-resistant acute rejection without increasing the risk of infectious or malignant complications, and neither antibody was associated with the cytokine-release syndrome. Children who receive calcineurin inhibitors and corticosteroids for maintenance immunosuppression, as well as children who receive augmented immunosuppression to treat acute rejection, are at increased risk of growth impairment, hypertension, hyperlipidemia, lymphoproliferative disorders, diabetes mellitus, and cosmetic changes. In older children, the cosmetic adverse effects frequently reduce compliance with the treatment, and subsequently increase the risk of allograft loss. Being effective and well tolerated in children, the anti-IL-2R antibodies reduce the need for calcineurin inhibitors while maintaining the overall efficacy of the regimen; thus, the anti-IL-2R antibodies increase the safety margin (less toxicity, fewer adverse effects) of the baseline immunosuppression. Secondly, the anti-IL-2R antibodies decrease the need for corticosteroids and muromonab CD3 (OKT3) in children as a result of decreased incidence of acute rejection. The recommended pediatric dose of daclizumab is 1 mg/kg intravenously every 14 days for five doses, with the first dose administered within 24 hours pre-transplantation. This administration regimen maintains daclizumab levels necessary to completely saturate the IL-2Ralpha (5-10 microg/mL) in children for at least 12 weeks.The recommended pediatric dose of basiliximab for recipients <35 kg is 10 mg, and 20 mg for recipients > or =35 kg, intravenously on days 0 and 4 post-transplantation. This administration regimen maintains basiliximab levels necessary to completely saturate the IL-2Ralpha (>0.2 microg/mL) in children for at least 3 weeks.

C2 blood concentrations of orally administered cyclosporine in pediatric liver graft recipients with a body weight below 10 kg

Pharmacokinetic studies in adult and pediatric liver transplant recipients have shown that the C(2) monitoring is superior to the traditional determination of CsA trough levels (C(0)) as an estimate of CsA exposure. However, target reference values for C(2) in very small infants have not been established yet. The objective of our study was to assess the distribution of C(2) levels in the first week following Ltx and to analyze enteral absorption of CsA for this group of patients. We documented CsA C(0) and C(2) levels in 25 infants with a body weight below 10 kg (median 6.8 kg; range 3.0-9.8 kg) in the first 7 days after Ltx. The infants had a median age at transplantation of 7 months (range 0.3-20.0 months). The underlying diagnoses were biliary atresia (n = 17), acute liver failure (n = 4), metabolic disease (n = 4). All children received CsA microemulsion (Neoral, initial 10 mg/kg/day), prednisolone, and two single doses of basiliximab as immunosuppressive drugs. The mean C(0) and C(2) levels were as follows: day 1: C(0) 77.0 +/- 39.6, C(2) 340.5 +/- 140.0 ng/mL; day 2: C(0) 135.5 +/- 53.2, C(2) 467.0 +/- 168.2 ng/mL; day 3: C(0) 146.5 +/- 70.8, C(2) 519.0 +/- 219.1 ng/mL; day 4: C(0) 168.5 +/- 55.1, C(2) 570.0 +/- 163.7 ng/mL; day 5: C(0) 156.5 +/- 38.0, C(2) 612.0 +/- 132.4 ng/mL; day 6: C(0) 177.0 +/- 41.1, C(2) 606.0 +/- 149.2 ng/mL; day 7: C(0) 174.0 +/- 27.2, C(2) 622.0 +/- 98.8 ng/mL (r = 0.82, p < 0.05). This analysis demonstrates that there is a good enteral absorption of CsA in very small children post-Ltx in the early post-operative period. Based on the C(2) levels achieved, we conclude that there is a good correlation between C(0) and C(2) levels even in very small infants.

Cyclosporine in pediatric kidney transplantation

Before the era of cyclosporine (CsA), immunosuppression with azathioprine and steroids resulted in high rejection rates and severe growth retardation in pediatric renal transplant recipients. In the early 1980s, immunosuppression with CsA was introduced for children. Because of differences in metabolism rates and relation of weight and body surface area, special pediatric dosing regimens and monitoring strategies had to be developed. Use of CsA led to a decreased number of acute rejections and, consequently, to a marked increase in graft survival rates. The growth rates of transplanted children were significantly higher under CsA-based immunosuppression than with classical regimens. This was due to a decreased need of steroid co-administration. Main side effects of CsA in children were nephrotoxicity and hirsutism. The introduction of CsA microemulsion in the 1990s led to more reliable absorption profiles and to a lower interindividual variability of CsA area-under-the-curve concentrations and thus to another improvement in rejection rates. New monitoring strategies, based on CsA levels taken 2 hours' postdose, seem promising. In pediatric transplantation, CsA is often successfully combined with an antibody-induction therapy in order to reduce the number of early acute rejections. Combination with mycophenolate mofetil reduces the appearance of chronic rejection. Additional therapy with ToR inhibitors might enforce a reduction of CsA doses and therefore lead to a reduction of CsA toxic effects.

Basiliximab

Basiliximab (Simulect), a chimeric (human/murine) monoclonal antibody, is indicated for the prevention of acute organ rejection in adult and paediatric renal transplant recipients in combination with other immunosuppressive agents. Basiliximab significantly reduced acute rejection compared with placebo in renal transplant recipients receiving dual- (cyclosporin microemulsion and corticosteroids) or triple-immunotherapy (azathioprine- or mycophenolate mofetil-based); graft and patient survival rates at 12 months were similar. Significantly more basiliximab than placebo recipients were free from the combined endpoint of death, graft loss or acute rejection 3 years, but not 5 years, after transplantation. The incidence of adverse events was similar in basiliximab and placebo recipients, with no increase in the incidence of infection, including cytomegalovirus (CMV) infection. Malignancies or post-transplant lymphoproliferative disorders after treatment with basiliximab were rare, with a similar incidence to that seen with placebo at 12 months or 5 years post-transplantation. Rare cases of hypersensitivity reactions to basiliximab have been reported. The efficacy of basiliximab was similar to that of equine antithymocyte globulin (ATG) and daclizumab, and similar to or greater than that of muromonab CD3. Basiliximab was as effective as rabbit antithymocyte globulin (RATG) in patients at relatively low risk of acute rejection, but less effective in high-risk patients. Numerically or significantly fewer patients receiving basiliximab experienced adverse events considered to be related to the study drug than ATG or RATG recipients. The incidence of infection, including CMV infection, was similar with basiliximab and ATG or RATG. Basiliximab plus baseline immunosuppression resulted in no significant differences in acute rejection rates compared with baseline immunosuppression with or without ATG or antilymphocyte globulin in retrospective analyses conducted for small numbers of paediatric patients. Limited data from paediatric renal transplant recipients suggest a similar tolerability profile to that in adults. Basiliximab appears to allow the withdrawal of corticosteroids or the use of corticosteroid-free or calcineurin inhibitor-sparing regimens in renal transplant recipients. Basiliximab did not increase the overall costs of therapy in pharmacoeconomic studies.

CONCLUSION

Basiliximab reduces acute rejection without increasing the incidence of adverse events, including infection and malignancy, in renal transplant recipients when combined with standard dual- or triple-immunotherapy. The overall incidence of death, graft loss or acute rejection was significantly reduced at 3 years; there was no significant difference for this endpoint 5 years after transplantation. Malignancy was not increased at 5 years. The overall efficacy, tolerability, ease of administration and cost effectiveness of basiliximab make it an attractive option for the prophylaxis of acute renal transplant rejection.

Concomitant basiliximab with low-dose calcineurin inhibitors in children post-liver transplantation

Orthotopic liver transplantation (OLT) is effective therapy for end-stage liver disease but immunosuppression with calcineurin inhibitors (CNI) leads to significant nephrotoxicity, resulting in either a reduction of dosage to below the therapeutic level or omission of the drug altogether. Basiliximab (Bx) is a human/mouse chimeric monoclonal antibody that inhibits binding of interleukin-2 (IL-2) to IL-2 receptors and thus prevents proliferation of T cells, which is the main step in the development of acute cellular rejection. The aim of this study was to identify the role of Bx in the prevention of acute cellular rejection and in the reduction of nephrotoxicity in children post-liver transplantation. We evaluated three children (19 months, 22 months, and 11 yr of age; one male, two female) who were treated with Bx post-OLT on compassionate grounds. The indications were: nephrotoxicity in two children, requiring re-transplantation for hepatic artery thrombosis and recurrent giant cell hepatitis, respectively; and nephrotoxicity secondary to chemotherapy for hepatoblastoma in the third child. All patients received 10 mg of Bx, at OLT and on Day 4. Tacrolimus (0.15 mg/kg/day) was started at 48 h (n = 2) and cyclosporin (5 mg/kg/day) at 2 weeks (n = 1). Trough levels of tacrolimus were maintained at 5-8 ng/mL and trough levels of cyclosporin at 100-150 mg/L for the first 3 months. All patients received methylprednisolone (2 mg/kg) with azathioprine (1.5 mg/kg) (n = 2) and/or mycophenolate mofetil (20 mg/kg) (n = 1). The glomerular filtration rate (cGFR) was calculated using the Schwartz formula before and 10 weeks after transplant. Bx was found to be easy to administer and no major side-effects were reported. One child had two episodes of mild acute rejection at 5 and 9 weeks post-OLT and one developed chronic rejection requiring re-transplantation at 9 weeks post-OLT. One child did not develop rejection. The mean pretransplant cGFR was 58.1 (54.6-64.1) mL/min/m2. Within 10 weeks of transplantation, the cGFR had improved by 69% to a mean of 116 (88-157.6) mL/min/m2. To conclude, Bx was well tolerated in all children and had a renal sparing effect. It was effective in preventing early acute rejection, but the combination of Bx and low-dose CNI drugs did not prevent late acute or chronic rejection. Further studies to evaluate the appropriate levels of CNI immunosuppression with Bx are required.

Single centre experience with basiliximab in paediatric renal transplantation

BACKGROUND

Introduction of IL-2-receptor antagonists has led to significantly decreasing numbers of acute rejection episodes in renal transplantation in adults. No data are available in paediatric recipients.

METHODS

Between 1997 and 2000, 78 renal transplantations were performed in 77 children aged 0.5-16 years. Basiliximab, cyclosporin A (CsA) and prednisolone were administered in 48 children (age 7.8 +/- 5.3 years) and compared with 29 children (age 7.3 +/- 5.2 years) receiving CsA and prednisolone only. The number of acute rejections, survival, glomerular filtration rate (GFR) and side effects were determined for 3 years after transplantation.

RESULTS

All 77 patients survived the observation period. One year graft survival in the basiliximab group was 95%, which is similar to the comparison group (93%). Children receiving basiliximab showed a lower incidence of acute rejection than the comparison group (14% vs 34%). The calculated GFR was lower in the basiliximab group when discharging from hospital, with 51 compared with 66 ml/min/1.73 m(2) in the non-basiliximab group. This was associated with higher CsA trough levels (214 vs 174 ng/ml) in the basiliximab patients. After 1 year the GFR was comparable in both groups (58 vs 52 ml/min/1.73 m(2)).

CONCLUSIONS

Basiliximab offers excellent allograft survival, a lower incidence of acute rejections and almost no side effects. Therefore it can be recommended for routine immunosuppressive therapy in paediatric renal transplantation.