Basiliximab in pediatric liver transplantation: a pharmacokinetic-derived dosing algorithm

A Simple Method for the Prediction of Therapeutic Proteins (Monoclonal and Polyclonal Antibodies and Non-Antibody Proteins) for First-in-Pediatric Dose Selection: Application of Salisbury Rule

In order to conduct a pediatric clinical trial, it is important to optimize pediatric dose as accurately as possible. In this study, a simple weight-based method known as ‘Salisbury Rule’ was used to predict pediatric dose for therapeutic proteins and was then compared with the observed pediatric dose. The observed dose was obtained mainly from the FDA package insert and if dosing information was not available from the FDA package insert then the observed dose was based on the dose given to an age group in a particular study. It was noted that the recommended doses of most of the therapeutic proteins were extrapolated to pediatrics from adult dose based on per kilogram (kg) body weight basis. Since it is widely believed that pediatric dose should be selected based on the pediatric clearance (CL), a CL based pediatric dose was projected from the following equation: Dose in children = Adult dose × (Observed CL in children/Observed adult CL). In this study, this dose was also considered observed pediatric dose for comparison. A ±30% prediction error (predicted vs. observed) was considered acceptable. There were 21 monoclonal antibodies, 5 polyclonal antibodies in children ≥ 2 years of age, 4 polyclonal antibodies in preterm and term neonates, and 11 therapeutic proteins (non-antibodies) in the study. In children < 30 kg body weight, the predicted doses were within 0.5−1.5-fold prediction error for 87% (monoclonal antibody), 100% (polyclonal antibody), and 92% (non-antibodies) observations. In children > 30 kg body weight, the predicted doses were within 0.5−1.5-fold prediction error for 96% (monoclonal antibody), 100% (polyclonal antibody), and 100% (non-antibodies) observations. The Salisbury Rule mimics more to CL-based dose rather than per kg body weight-based extrapolated dose from adults. The Salisbury Rule for the pediatric dose prediction can be used to select first-in-children dose in pediatric clinical trials and may be in clinical settings.

Prediction of Clearance of Monoclonal and Polyclonal Antibodies and Non-Antibody Proteins in Children: Application of Allometric Scaling

Allometric scaling can be used for the extrapolation of pharmacokinetic parameters from adults to children. The objective of this study was to predict clearance of therapeutic proteins (monoclonal and polyclonal antibodies and non-antibody proteins) allometrically in preterm neonates to adolescents. There were 13 monoclonal antibodies, seven polyclonal antibodies, and nine therapeutic proteins (non-antibodies) in the study. The clearance of therapeutic proteins was predicted using the age dependent exponents (ADE) model and then compared with the observed clearance values. There were in total 29 therapeutic proteins in this study with 75 observations. The number of observations with ≤30%, ≤50%, and >50% prediction error was 60 (80%), 72 (96%), and 3 (4%), respectively. Overall, the predicted clearance values of therapeutic proteins in children was good. The allometric method proposed in this manuscript can be used to select first-in-pediatric dose of therapeutic proteins in pediatric clinical trials.

Analysis of rabbit anti-thymocyte globulin vs basiliximab induction in pediatric liver transplant recipients

Literature is limited comparing induction immunosuppression in pediatric liver transplant (LTx) recipients. This is a single-center, retrospective cohort study of primary pediatric liver transplants at our center between 2005 and 2016 who received either basiliximab (BSX) or rabbit anti-thymocyte globulin (rATG) induction. Maintenance immunosuppression consisted of tacrolimus ± a corticosteroid taper. Exclusions included receipt of an ABO-incompatible graft, retransplantation, and multi-organ transplantation. Primary outcomes were incidence of treated biopsy-proven acute rejection (tBPAR) and PTLD within the first year and infections within 90 days of LTx. Secondary outcomes included graft and patient survival, time to first tBPAR, and incidence of steroid-resistant rejection (SRR) within the first year post-LTx. A total of 136 patients were included in the final analysis of which 57 patients (42%) received BSX induction. Patients who received rATG induction with or without a 2-week corticosteroid taper experienced significantly more tBPAR compared to those who received BSX induction with a 6-month corticosteroid taper (55.7% vs 33.3%, P = .01). There were no differences in the incidence of PTLD, infections, SRR, graft or patient survival, or time to first tBPAR between the two groups. Induction with rATG either with or without a short corticosteroid taper was associated with significantly more tBPAR in primary pediatric LTx recipients when compared to BSX induction with a prolonged corticosteroid taper in the setting of maintenance immunosuppression with tacrolimus.

Effects of the FcRn developmental pharmacology on the pharmacokinetics of therapeutic monoclonal IgG antibody in pediatric subjects using minimal physiologically-based pharmacokinetic modelling

The aim of this study was to investigate neonatal Fc receptor (FcRn) concentration developmental pharmacology in adult and pediatric subjects using minimal physiologically-based pharmacokinetic (mPBPK) modelling. Three types of pharmacokinetic (PK) data for three agents (endogenous/exogenous native IgG, bevacizumab and palivizumab) were used. The adult group contained six subjects with weights from 50 to 100 kg. For pediatric subjects, seven age groups were assumed, with five subjects each having the weight of 95%, 75%, 50%, 25% and 5% percentile of the population. A first evidence-based rating system to evaluate the quality of the source data used to derive pediatric-specific mPBPK model parameter was proposed. A stepwise approach was used to examine the best combination of age/weight effect on the parameters of the mPBPK model in adult and pediatric subjects. IgG synthesis rate (K_syn), extravasation rate (ER) and FcRn were fitted simultaneously to the PK of bevacizumab and native-IgG in both adult and pediatric. All fitting showed good fits based on the graphs and the coefficient of variation of the fitted parameters (< 50%). Estimated weight-normalized K_syn increased while weight-normalized FcRn and ER decreased with increasing age. The age and weight effect on FcRn were successfully estimated from the data. The final mPBPK model developed with native IgG and bevacizumab was able to predict the PK of palivizumab in pediatric subjects. Implementation of the mPBPK model enables us to analyze the relationships of age, weight, FcRn, ER and K_syn in both adult and pediatric subject. This information may benefit the understanding of complex interaction between the FcRn developmental pharmacology and PK parameters, and improve the prediction of the antibody disposition in pediatric subjects.

Pediatric physiology in relation to the pharmacokinetics of monoclonal antibodies

INTRODUCTION

Dose design for pediatric trials with monoclonal antibodies (mAbs) is often extrapolated from the adult dose according to weight, age, or body surface area. While these methods account for the size differences between adults and children, they do not account for the maturation of processes that may play a key role in the pharmacokinetics and/or pharmacodynamics of mAbs. With the same weight-based dose, infants and young children typically receive lower plasma exposures when compared to adults. Areas covered: The mechanistic features of mAb distribution, elimination, and absorption are explored in detail and literature-based hypotheses are generated to describe their age-dependence. This knowledge can be incorporated into a physiologically based pharmacokinetic (PBPK) modeling approach to pediatric dose determination. Expert opinion: As data from pediatric clinical trials become increasingly available, we have the opportunity to reflect on the physiologic drivers of pharmacokinetics, safety, and efficacy in children with mathematical models. A modeling approach that accounts for the age-related features of mAb disposition can be used to derive first-in-pediatric doses, design optimal sampling schemes for children in clinical trials and even explore new pharmacokinetic end-points as predictors of safety and efficacy in children.

A New Enzyme-Linked Immunosorbent Assay for a Total Anti-T Lymphocyte Globulin Determination: Development, Analytical Validation, and Clinical Applications

BACKGROUND

Anti-T lymphocyte globulin (ATLG) modulates the alloreactivity of T lymphocytes, reducing the risk of immunological posttransplant complications, in particular rejection and graft-versus-host disease, after allogeneic hematopoietic stem cell transplantation (HSCT). We developed and validated a new enzyme-linked immunosorbent assay (ELISA) method to measure serum levels of total ATLG and evaluate the pharmacokinetics (PK) of the drug in children with β-Thalassemia, receiving allogeneic HSCT.

METHODS

Diluted serum samples were incubated with Goat-anti-Rabbit IgG antibody coated on a microtiter plate and then, with Goat-anti-Human IgG labeled with horseradish peroxidase. After incubation and washings, substrate solution was added and absorbance was read at 492 nm. ATLG concentrations in samples were determined by interpolation from a standard curve (range: 200-0.095 ng/mL), prepared by diluting a known amount of ATLG in phosphate-buffered saline (PBS). Low, medium, and high-quality control concentrations were 1.56, 6.25, and 25 ng/mL, respectively. This method was developed and validated within the acceptance criteria in compliance with the Guidelines for a biological method validation: the sensitivity of the method was 0.095 ng/mL. We analyzed serum samples from 14 children with β-Thalassemia who received ATLG (Grafalon) at a dose of 10 mg/kg administered as intravenous (IV) infusion on days -5, -4, and -3 before HSCT (day 0). Blood sampling for PK evaluation was performed on days -5, -4, and -3 before and after drug infusion; and then from day -2 to +56.

RESULTS

The median total ATLG levels pre-IVand post-IV were 0 and 118 mcg/mL on day -5; 85.9 and 199.2 mcg/mL on day -4; 153 and 270.9 mcg/mL on day -3, respectively. The median PK values of CL was 0.0029 (range: 0.0028-0.0057) L·kg·d, Vd was 0.088 (range: 0.025-0.448) L/kg and t1/2 was 20.2 (range: 5.8-50.2) days.

CONCLUSIONS

These data suggest that given the marked interindividual variability of total ATLG disposition, the development of a validated ELISA method and the possibility to measure PK parameters in paediatric populations are essential steps to optimize drug therapeutic regimens.

Challenges and considerations for development of therapeutic proteins in pediatric patients

Target specificity and generally good tolerability of therapeutic proteins (TPs) present desirable treatment opportunities for pediatric patients. However, little is known on the ontogeny of processes related to the pharmacokinetics (PK) and disposition of TPs. The science, regulatory requirements and strategy of developing TPs for children are evolving. Our current review of TPs, (with focus on monoclonal antibodies and fusion proteins) that were approved for pediatric use indicates that dose-selection for pediatric pivotal studies is often based on adult PK information alone. This approach might not be sufficient if more complex PK properties than simple linear PK are present. Body weight-based dosing for pediatric patients directly scaled down from adult dosing can lead to under-exposure in young pediatric patients who are usually in the lowest body-weight range. Tiered-fixed dosing can be reasonably effective for TPs in achieving comparable exposure in children over a wide age range. The uniqueness of the pediatric population, the practical challenges in conducting clinical studies in this population, as well as regulations from health authorities warrant including pharmacometrics as an integral component of pediatric drug development. We propose a framework distinct from previous proposals, to guide clinical pharmacology strategy for pediatric drug development specifically for TPs.

Basiliximab with delayed introduction of calcineurin inhibitors as a renal-sparing protocol following liver transplantation in children with renal impairment

Renal impairment is frequently compromised in patients with end-stage liver disease and is associated with increased long-term mortality post-LT. In contrast to CNI, basiliximab is an immunosuppressive agent with minimal nephrotoxic potential. This study reviews the experience of a single pediatric liver transplant center's renal-sparing approach with the use of basiliximab and MMF to compensate for delayed entry of CNI in children with renal impairment at the time of organ availability. There were no differences in renal function between pediatric patients with and without pre-LT renal impairment within the first year (cGFR: 135 mL/min/1.73 m2 vs. 144 mL/min/1.73 m2 ; p = 0.56) or at 5-8 yr following LT, (129 mL/min/1.73 m2 vs. 130 mL/min/1.73 m2 ; p = 0.97). In addition, there was no difference in ACR rates (50% vs. 43%, p = 0.62) between patients in the basiliximab group and those patients receiving standard CNI and steroid strategies. The utilization of a renal-sparing approach with basiliximab alongside delayed entry and lower early target trough levels of CNI in children with renal impairment at the time of LT is safe and maintains excellent long-term kidney function.

Management of acute rejection in paediatric liver transplantation

The success of paediatric liver transplantation is attributed to improved surgical techniques and the advent of calcineurin inhibitor-based immunosuppression. Acute rejection (AR) rarely results in graft loss with calcineurin inhibitor immunosuppressive regimens, and the advent of newer agents like interleukin (IL)-2 receptor antibodies. The latter have the benefit of reducing the incidence of AR further and may be of use in patients who are susceptible to recurrent AR, were retransplanted for graft rejection or are in a steroid-sparing regimen. A total of 60 % of all paediatric liver transplants result in AR; however, there is a 75 % response rate to initial steroid therapy. Steroid therapy remains the mainstay of initial AR management, coupled with an increase in baseline immunosuppression. Steroid-resistant rejection (SRR), previously an immediate indication for potent anti-lymphocyte preparations, is now effectively treated with chimeric or humanised IL-2 receptor monoclonal antibodies. Recurrent AR can be treated by adding adjuvant immunosuppressive agents such as mycophenolate mofetil (MMF) or sirolimus. Studies have also demonstrated the efficacy of MMF as rescue therapy for SRR. Anti-lymphocyte preparations such as anti-thymocyte globulin (ATG) and OKT3 are rarely used in SRR but may be of use as rescue therapy for severe SRR. The challenges of the management of AR remain in the management of recurrent AR and SRR. We discuss the pathogenesis, diagnosis and management of AR, including prevention, and specific management of AR and SRR based on current evidence and our own experience at the King's College Paediatric Liver, Gastroenterology and Nutrition Centre in London.

Pharmakologische Aspekte

Kortikosteroide waren die ersten Therapeutika zur Kontrolle von Abstoßungsreaktionen nach Transplantation. Sie sind seit Langem und immer noch wichtiger Bestandteil vieler immunsuppressiver Therapiekonzepte. Kortikosteroide besitzen zahlreiche antiinflammatorische und immunsuppressive Effekte. Sie beeinflussen über die Bindung spezifischer zytoplasmatischer Rezeptoren die Gentranskriptionsrate für zentrale, immunregulatorische Proteine wie Interleukin 1β (IL-1β), IL-6, Tumor-Nekrose-Faktor α (TNF-α) mit resultierender Suppression der Makrophagenfunktion und konsekutiver T-Zell-Aktivierung. Sie inhibieren auch die IL-2-Synthese, hemmen damit die T-Zell-Proliferation und reduzieren die IL- 2-Rezeptorbindungsfähigkeit. Andererseits stimulieren sie die Synthese des inhibierenden Zytokins „transforming growth factor β“ (TGF-β), was in einem „antiinflammatorisch“ geprägten T-Helfer-Zell-2-artigen Zytokinprofil resultiert. Über die Inhibition der Expression von interferonabhängigen Adhäsionsmolekülen (einschließlich MHC-Klasse-II-Moleküle) bewirken Kortikosteroide darüber hinaus die Alteration von Leukozytenverkehr und -transmigration sowie eine Induktion der Lymphozytenapoptose.

Current status of immunosuppressive agents for solid organ transplantation in children

Immunosuppression after organ transplantation is complex and ever evolving. Over the past two decades, newer immunosuppressive agents have been introduced with an aim to provide better patient and graft survival. Improved therapeutic strategies have been developed offering the option to use combinations of drugs with non-overlapping toxicities. There are, however, only a few clinical studies with robust data to rationalize the use of these agents in children. This review will discuss the newer immunosuppressive agents used for solid organ transplant, their current status in post-transplant management and prevention of allograft rejection.

Pediatric Dosing and Body Size in Biotherapeutics

Although pediatric doses for biotherapeutics are often based on patients' body weight (mg/kg) or body surface area (mg/m²), linear body size dose adjustment is highly empirical. Growth and maturity are also important factors that affect the absorption, distribution, metabolism and excretion (ADME) of biologics in pediatrics. The complexity of the factors involved in pediatric pharmacokinetics lends to the reconsideration of body size based dose adjustment. A proper dosing adjustment for pediatrics should also provide less intersubject variability in the pharmacokinetics and/or pharmacodynamics of the product compared with no dose adjustment. Biological proteins and peptides generally share the same pharmacokinetic principle with small molecules, but the underlying mechanism can be very different. Here, pediatric and adult pharmacokinetic parameters are compared and summarized for selected biotherapeutics. The effect of body size on the pediatric pharmacokinetics for these biological products is discussed in the current review.

Pediatric liver transplantation

In previous decades, pediatric liver transplantation has become a state-of-the-art operation with excellent success and limited mortality. Graft and patient survival have continued to improve as a result of improvements in medical, surgical and anesthetic management, organ availability, immunosuppression, and identification and treatment of postoperative complications. The utilization of split-liver grafts and living-related donors has provided more organs for pediatric patients. Newer immunosuppression regimens, including induction therapy, have had a significant impact on graft and patient survival. Future developments of pediatric liver transplantation will deal with long-term follow-up, with prevention of immunosuppression-related complications and promotion of as normal growth as possible. This review describes the state-of-the-art in pediatric liver transplantation.

Steroid-free, tacrolimus-basiliximab immunosuppression in pediatric liver transplantation: clinical and pharmacoeconomic study in 50 children

Corticosteroid-free immunosuppression (IS) may be potentially beneficial for transplanted patients, particularly children. The purpose of this study was to evaluate the efficacy and cost of such strategy in primary pediatric liver transplantation (LT). Fifty pediatric LT recipients were prospectively treated with a steroid-free, tacrolimus-basiliximab-based IS (group TB). A group of 34 children transplanted under a conventional tacrolimus-steroids regimen served as control series (group TS). Groups TB and TS were compared regarding patient and graft survival, rejection incidence, infectious complications, and growth, as well as cost of the transplant procedure. Patient and graft survivals at 3 years were 96% and 94% in group TB, versus 91% and 88% in group TS (P = 0.380 and P = 0.370, respectively). Rejection-free graft survival at 3 years was 72% in group TB, versus 41% in group TS (P = 0.007). Patients in group TB had significantly less viral infections than patients in group TS (P = 0.045). Height standard deviation score was significantly enhanced in children from group TB, when compared to group TS. Medical care costs were similar in both groups. Steroid avoidance together with basiliximab immunoprophylaxis was not harmful in terms of allograft acceptance, and even seemed to be beneficial in the long term.

Pharmacologic approaches to composite tissue allograft

This article discusses the pharmacologic approaches and the most promising new compounds for composite tissue allograft tolerance. Although some approaches rely on a combination of immunosuppressive agents that act synergistically against rejection, other strategies use immunologic manipulation, including major histocompatibility complex matching, induction of chimerism, and use of monoclonal antibodies to abrogate the immune response. There is still a need, however, to reproduce these findings in species phylogenetically closer to humans. This may be the target of future research efforts, which may overcome the challenge of limb and face transplant rejection.

Randomized trial of basiliximab induction versus steroid therapy in pediatric liver allograft recipients under tacrolimus immunosuppression

Avoidance of corticosteroids could be beneficial after pediatric liver transplantation (LTx). To test this hypothesis, we performed a randomized prospective study to compare immunosuppression with tacrolimus (TAC) and steroids versus TAC and basiliximab (BAS) after pediatric LTx. Seventy-two patients were recruited, 36 receiving TAC and steroids and 36 TAC and BAS. The primary endpoint was the occurrence of the first rejection episode. Secondary endpoints were the cumulative incidence and severity of rejection, patient and graft survival, and incidence of adverse events. Overall 1-year patient and graft survival rates were 91.4% and 85.5% in the steroid group, and 88.6% and 80% in the BAS group (p = NS). Patients free from rejection were 87.7% in the BAS group and 67.7% in the steroid group (p = 0.036). The use of BAS was associated with a 63.6% reduction in incidence of acute rejection episodes. Overall incidence of infection was 72.3% in the steroid group and 50% in the BAS group (p = 0.035). We conclude that the combination of TAC with BAS is an alternative to TAC and steroid immunosuppression in pediatric LTx, which allows for a significant reduction in the incidence of acute rejection and infectious complications.

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.

Efficacy and Safety of Basiliximab with a Tacrolimus-Based Regimen in Liver Transplant Recipients

BACKGROUND

Induction with monoclonal antibodies for prevention of acute cellular rejection (ACR) may avoid many of the adverse events associated with polyclonal antibodies. Basiliximab, a chimeric monoclonal antibody directed against the alpha-chain of the interleukin 2 receptor (CD25), has been extensively evaluated as an induction therapy for kidney transplant recipients, more frequently in combination with a cyclosporine-based regimen. In this study, we assessed the efficacy and safety of basiliximab in combination with a tacrolimus-based regimen after liver transplantation.

METHODS

Fifty consecutive liver transplants (47 cadaveric donors; 3 living donors) were analyzed. All patients received two 20-mg doses of basiliximab (days 0 and 4 after transplantation) followed by tacrolimus (0.15 mg/kg/day; 10-15 ng/mL target trough levels) and a tapered dose regimen of steroids. Follow-up ranged from 404 to 1,364 days after transplantation (mean 799.89 days, SD+/-257.37; median 796 days).

RESULTS

A total of 88% of patients remained rejection-free during follow-up with an actuarial rejection-free probability of 75% within 3 months. The actuarial patient survival rate at 3 years was 88%, and the graft survival rate was 75%. Twelve (24%) patients experienced one episode of sepsis, requiring temporary reduction of immunosuppressive therapy. There were no immediate side effects associated with basiliximab and no evidence of cytomegalovirus infection or posttransplant lymphoproliferative disorder.

CONCLUSIONS

Basiliximab in combination with a tacrolimus-based immunosuppressive regimen is effective in reducing episodes of ACR and increasing ACR-free survival after liver transplantation. In addition, basiliximab does not increase the incidence of adverse effects or infections.

Current status of liver transplantation in children

There are two critical issues on opposite ends of the timeline for patients who are eligible for liver transplantation. On the one hand, the crisis in the cadaveric organ supply makes surviving to transplant ever more risky. On the other hand, patients who receive successful transplants face the consequences of long-term immunosuppression and its potentially life-threatening complications. The donor shortage is forcing difficult decisions that affect all patients who await liver transplantation. It is important to scrutinize carefully the results of all policies that govern allocation and the ethics of the solutions we advocate to ensure that no patient subgroup is being at a disadvantage. Current immunosuppression practices are being challenged by an increasing understanding of the immunologic events triggered by the allograft and the goal to free patients from consequences of a lifetime of immunosuppression. Clinicians can expect, and perhaps require, that new immunosuppressive protocols will address how the planned intervention might be expected to advance the understanding of tolerance mechanisms. As knowledge increases, clinicians can anticipate innovative new immunosuppressive proposals. Calcineurin and steroid-free induction, the use of donor-derived bone marrow infusion, recipient pretreatment, costimulatory blockade, and new antibody induction approaches are all being proposed--often in combination--for clinical trials. Researchers face additional challenges in defining endpoints if the goal is not just the short-term reduction in rejection but the minimization, and eventual discontinuation, of immunosuppressive drugs while maintaining excellent long-term graft function. How much "failure" will be accepted and how will it be defined? How will clinicians interpret liver biopsies if they begin to accept that some lymphocytic infiltrates may be beneficial mediators of the ongoing immune activation necessary for the maintenance of tolerance? How will they adjust immunosuppression practices to the dynamic processes in the immune response that maintain tolerance? Remarkable short-term successes in providing transplants for thousands of children with liver failure have brought these challenges into sharp focus. Clinicians must seek to move the life-giving science of transplantation toward a new goal: providing long lifetimes of excellent graft function with minimal toxicity from immunosuppressive drugs and the hope of freedom from immunosuppression altogether. Pediatric liver recipients, whose grafts have inherent tolerogenic potential and for whom we can anticipate decades of life after transplant, may prove to be an ideal study population to further these goals.

Use of basiliximab in pediatric liver transplantation for Langerhans cell histiocytosis

This report describes a 16-month-old girl with multi-system Langerhans cell histiocytosis (LCH), who developed end-stage liver disease despite intensive chemotherapy. She underwent a liver transplant at 28 months of age while receiving maintenance chemotherapy for bony lesions. In view of previous reports of a high incidence of acute cellular rejection and post-transplant lymphoproliferative disease (PTLD) in children transplanted for LCH, basiliximab was added to the post-transplant immunosuppression regime of tacrolimus and prednisolone. Sixteen months post-transplant, she has had no episodes of acute rejection or PTLD and her LCH has remained in remission. Current literature regarding liver transplantation (LTx) for LCH and the use of basiliximab in pediatric LTx is reviewed.

A rational dosing algorithm for basiliximab (Simulect) in pediatric renal transplantation based on pharmacokinetic-dynamic evaluations

BACKGROUND

The pharmacokinetics and immunodynamics of basiliximab were assessed in 39 pediatric de novo kidney allograft recipients to rationally chose a dose regimen for this age group.

METHODS

In study part 1, patients were given 12 mg/m(2) of basiliximab by bolus intravenous injection before surgery and on day 4. An interim pharmacokinetic evaluation supported a fixed-dose approach for study part 2 in which infants and children received two 10-mg doses and adolescents received two 20-mg doses. Blood samples were collected over a 12-week period for analysis of basiliximab and soluble interleukin-2 receptor concentrations, flow cytometry, and screening for anti-idiotype antibodies.

RESULTS

Basiliximab clearance in infants and children (n=25) was reduced by approximately half compared with adults from a previous study and was independent of age (1-11 years), weight (9-37 kg), and body surface area (0.44-1.20 m(2) ). Clearance in adolescents (12-16 years, n=14) approached or reached adult values. CD25-saturating basiliximab concentrations were maintained for 31+/-12 days in study part 1 with mg/m(2) dosing and for 36+/-14 days in study part 2 based on the fixed-dose regimen ( P=0.31). A single patient experienced a rejection episode during CD25 saturation. The duration of CD25 saturation in patients who experienced a rejection episode after desaturation did not differ from those who remained rejection-free for the full 6-month period: 34+/-6 days (n=6) vs. 35+/-14 days (n=33 patients); P=0.74. Anti-idiotype antibodies were detected in two patients; however, this did not influence the clearance of basiliximab or the duration of CD25 saturation.

CONCLUSIONS

To achieve similar basiliximab exposure as is efficacious in adults, pediatric patients <35 kg should receive two 10-mg doses and those > or =35 kg should receive two 20-mg doses of basiliximab by intravenous infusion or bolus injection. The first dose is given before surgery and the second on day 4 after transplantation.