Population pharmacokinetics of prednisolone in children with acute lymphoblastic leukemia

The Assessment of the Hypothalamic-Pituitary-Adrenal Axis After Oncological Treatment in Pediatric Patients with Acute Lymphoblastic Leukemia

OBJECTIVE

Oncologic treatment can affect the adrenal glands, which in stressful situations may lead to life threatening adrenal crisis. The aim of the study was to assess adrenal function in pediatric acute lymphoblastic leukemia (ALL) survivors and to identify the best markers for this assessment.

METHODS

Forty-three ALL survivors, mean age 8.5±3.6 years and 45 age and sex-matched healthy controls were recruited to the study. ALL patients were assessed once within five years following oncological treatment completion. Fasting blood samples were collected from all participants to measure: fasting blood glucose (FBG); cortisol; aldosterone; plasma renin activity (PRA); dehydroepiandrostendione-sulfate (DHEA-S); and adrenocorticotropic hormone (ACTH). Moreover, diurnal profile of cortisol levels and 24-hour urinary free cortisol (UFC) were assessed. ALL survivors underwent a test with 1 ug of synthetic ACTH.

RESULTS

The study revealed lower level of PRA (1.94±0.98 ng/mL/h vs 3.61±4.85 ng/mL/h, p=0.029) and higher FBG (4.6±0.38 mmol/L vs 4.41±0.39 mmol/L, p=0.018) in the ALL group compared to controls. UFC correlated with evening cortisol (p=0.015, r=0.26), midnight cortisol (p=0.002, r=0.33), and DHEA-S (p=0.004, r=0.32). UFC also correlated with systolic and diastolic blood pressure (p=0.033, r=0.23 and p=0.005, r=0.31, respectively). The ACTH test confirmed impaired adrenal function in 4/43 ALL survivors (9%). Two of the patients who needed permanent hydrocortisone replacement had low UFC, midnight cortisol and DHEA-S levels.

CONCLUSION

These results highlight the importance of reviewing adrenal gland functionality after chemo/radiotherapy in ALL survivors. DHEA-S proved to be a good marker to assess the adrenal glands after oncological therapy. Post-treatment disturbances of the adrenal axis could be associated with metabolic complications.

Evaluation of the pharmacokinetics of prednisolone in paediatric patients with acute lymphoblastic leukaemia treated according to Dutch Childhood Oncology Group protocols and its relation to treatment response

Glucocorticoids form the backbone of paediatric acute lymphoblastic leukaemia (ALL) treatment. Many studies have been performed on steroid resistance; however, few studies have addressed the relationship between dose, concentration and clinical response. The aim of the present study was to evaluate the pharmacokinetics of prednisolone in the treatment of paediatric ALL and the correlation with clinical parameters. A total of 1028 bound and unbound prednisolone plasma concentrations were available from 124 children (aged 0–18 years) with newly diagnosed ALL enrolled in the Dutch Childhood Oncology Group studies. A population pharmacokinetic model was developed and post hoc area under the curve (AUC) was tested against treatment outcome parameters. The pharmacokinetics of unbound prednisolone in plasma was best described with allometric scaling and saturable binding to proteins. Plasma protein binding decreased with age. The AUC of unbound prednisolone was not associated with any of the disease parameters or treatment outcomes. Unbound prednisolone plasma concentrations correlated with age. No effect of exposure on clinical treatment outcome parameters was observed and does not substantiate individualised dosing. Poor responders, high‐risk and relapsed patients showed a trend towards lower exposure compared to good responders. However, the group of poor responders was small and requires further research.

Inherited genetic variants associated with glucocorticoid sensitivity in leukaemia cells

Identification of genetic variants associated with glucocorticoids (GC) sensitivity of leukaemia cells may provide insight into potential drug targets and tailored therapy. In the present study, within 72 leukaemic cell lines derived from Japanese patients with B-cell precursor acute lymphoblastic leukaemia (ALL), we conducted genome-wide genotyping of single nucleotide polymorphisms (SNP) and attempted to identify genetic variants associated with GC sensitivity and NR3C1 (GC receptor) gene expression. IC50 measures for prednisolone (Pred) and dexamethasone (Dex) were available using an alamarBlue cell viability assay. IC50 values of Pred showed the strongest association with rs904419 (P = 4.34 × 10^-8 ), located between the FRMD4B and MITF genes. The median IC50 values of prednisolone for cell lines with rs904419 AA (n = 13), AG (n = 31) and GG (n = 28) genotypes were 0.089, 0.139 and 297 µmol/L, respectively. For dexamethasone sensitivity, suggestive association was observed for SNP rs2306888 (P = 1.43 × 10^-6 ), a synonymous SNP of the TGFBR3 gene. For NR3C1 gene expression, suggestive association was observed for SNP rs11982167 (P = 6.44 × 10^-8 ), located in the PLEKHA8 gene. These genetic variants may affect GC sensitivity of ALL cells and may give rise to opportunities in personalized medicine for effective and safe chemotherapy in ALL patients.

Pharmacokinetics and population pharmacokinetics in pediatric oncology

Pharmacokinetic research has become increasingly important in pediatric oncology as it can have direct clinical implications and is a crucial component in individualized medicine. Population pharmacokinetics has become a popular method especially in children, due to the potential for sparse sampling, flexible sampling times, computing of heterogeneous data, and identification of variability sources. However, population pharmacokinetic reports can be complex and difficult to interpret. The aim of this article is to provide a basic explanation of population pharmacokinetics, using clinical examples from the field of pediatric oncology, to facilitate the translation of pharmacokinetic research into the daily clinic.

Population Pharmacokinetics of Prednisolone in Relation to Clinical Outcome in Children With Nephrotic Syndrome

BACKGROUND

The relapse frequency in children with nephrotic syndrome (NS) is highly variable despite standardized prednisolone treatment regimens. Existing evidence on the relationship between prednisolone pharmacokinetics (PK) and clinical response in children with NS is scarce and limited. The aim of this study was to develop a pediatric popPK model for prednisolone based on our previous model based on healthy adults using salivary measurements in children with NS and to correlate clinical outcome with between-subject variability in prednisolone exposure.

METHODS

The pharmacokinetics of prednisolone in a well-defined, prospective cohort consisting of 104 children with NS while in remission was determined. Pharmacokinetic parameters were analyzed in relation to relapse patterns and side effects. Noninvasive salivary prednisolone measurements were performed using a sparse sampling strategy. A population pharmacokinetic approach was used to derive individual estimates of apparent clearance (CL/F) and apparent volume of distribution (V/F) from the salivary concentration-time curve, followed by calculation of the area under the curve (AUC) of free prednisolone. The individual free serum prednisolone exposure from prednisolone in saliva was derived from the salivary concentration-time curves. Genetic polymorphisms of CYP3A4, CYP3A5, ABCB1, NR1L2, and POR were explored in relation to between-subject variability of CL/F.

RESULTS

Moderate interindividual variability was found for CL/F (CV, 44.7%). Unexplained random between-subject variability (eta) of CL/F was lower in patients carrying 1 or 2 ABCB1 3435C>T alleles compared to wild type: median -0.04 (interquartile range, -0.17 to 0.21) and 0.00 (-0.11 to 0.16) versus 0.17 (-0.08 to 0.47), P = 0.046. Exposure to free prednisolone was not associated with frequent relapses or adverse effects.

CONCLUSIONS

This study provides evidence for the possibility of prednisolone drug monitoring through salivary measurements and this may be of particular usefulness in pediatric patients. However, the observed variability in prednisolone exposure, in the therapeutic dose range studied, is not considered to be a major determinant of clinical outcome in children with NS.

Dexamethasone and High-Dose Methotrexate Improve Outcome for Children and Young Adults With High-Risk B-Acute Lymphoblastic Leukemia: A Report From Children's Oncology Group Study AALL0232

PURPOSE

Survival for children and young adults with high-risk B-acute lymphoblastic leukemia has improved significantly, but 20% to 25% of patients are not cured. Children's Oncology Group study AALL0232 tested two interventions to improve survival.

PATIENTS AND METHODS

Between January 2004 and January 2011, AALL0232 enrolled 3,154 participants 1 to 30 years old with newly diagnosed high-risk B-acute lymphoblastic leukemia. By using a 2 × 2 factorial design, 2,914 participants were randomly assigned to receive dexamethasone (14 days) versus prednisone (28 days) during induction and high-dose methotrexate versus Capizzi escalating-dose methotrexate plus pegaspargase during interim maintenance 1.

RESULTS

Planned interim monitoring showed the superiority of the high-dose methotrexate regimens, which exceeded the predefined boundary and led to cessation of enrollment in January 2011. At that time, participants randomly assigned to high-dose methotrexate during interim maintenance 1 versus those randomly assigned to Capizzi methotrexate had a 5-year event-free survival (EFS) of 82% versus 75.4% (P = .006). Mature final data showed 5-year EFS rates of 79.6% for high-dose methotrexate and 75.2% for Capizzi methotrexate (P = .008). High-dose methotrexate decreased both marrow and CNS recurrences. Patients 1 to 9 years old who received dexamethasone and high-dose methotrexate had a superior outcome compared with those who received the other three regimens (5-year EFS, 91.2% v 83.2%, 80.8%, and 82.1%; P = .015). Older participants derived no benefit from dexamethasone during induction and experienced excess rates of osteonecrosis.

CONCLUSION

High-dose methotrexate is superior to Capizzi methotrexate for the treatment of high-risk B-acute lymphoblastic leukemia, with no increase in acute toxicity. Dexamethasone given during induction benefited younger children but provided no benefit and was associated with a higher risk of osteonecrosis among participants 10 years and older.

Avoiding perioperative dexamethasone may improve the outcome of patients with rectal cancer

BACKGROUND

Perioperative administration of dexamethasone may augment recurrence and mortality after tumor resection possibly by immunosuppression, which, unfortunately, has never been noted. We therefore carried out a retrospective study in rectal cancer to validate the hypothesis.

METHODS

Five hundreds and fifteen patients with stage I to III rectal cancers who underwent a curative resection from June 2007 and June 2011 were enrolled in the current study. Patients who had been given intravenous (IV) dexamethasone (4-10 mg) postoperatively and/or intraoperatively were assigned to dexamethasone group. The outcome of dexamethasone group and non-dexamethasone group were compared. The primary outcome was disease-free survival (DFS) and overall survival (OS).

RESULTS

dexamethasone group had significant lower three-year DFS (62.3% vs 71.8%, P = 0.026) and OS (74.1% vs 82.9%, P = 0.031) rate in comparison to non-dexamethasone group, the hazard ratios (HRs) of which were 1.59 (95% CI 1.05-2.39, P = 0.028) and 1.77 (95% CI 1.05-3.01, P = 0.034), respectively. Multivariate analysis revealed that administration of systemic dexamethasone were independently associated with DFS [adjusted HR 1.60 (95% CI 1.03-2.49, p = 0.039)], but for OS, dexamethasone didn't remain significant in this model. In the analyses of a subgroup of 428 patients (55/428 in dexamethasone group) without perioperative blood transfusion, dexamethasone had independently impact on both DFS and OS.

CONCLUSION

Patients not given dexamethasone had better three-year survival outcomes compared with patients given dexamethasone perioperatively. Our results indicate that rectal cancer patients treated with curative surgery may get survival benefit from avoiding low-dose perioperative dexamethasone.

A prospective study of the hypothalamic-pituitary-adrenal axis in children with acute lymphoblastic leukemia receiving chemotherapy

BACKGROUND

Glucocorticoids are essential in protocols of therapy of acute lymphoblastic leukemia (ALL).

OBJECTIVES

To assess the incidence, severity, morbidity, and risk factors of hypothalamic-pituitary-adrenal axis (HPA) suppression in children with ALL, and the time course of recovery.

DESIGN

Forty standard risk ALL children treated in the Pediatric Hematology/Oncology Unit, Ain-Shams University, Egypt, were classified into dexamethasone (DXM) group: 20 patients on children cancer group protocol and prednisone (PDN) group: 20 patients on modified Berlin-Frankfurt-Muenster (BFM) study group 90 protocol. Patients were followed clinically and by laboratory assessment of morning s.ACTH, basal and after low-dose adrenocorticotrophic hormone stimulation test of cortisol and DHEAS, at diagnosis and every 2 weeks till adrenal recovery.

RESULTS

HPA recovery was earlier in PDN than DXM group (P < 0.05). In induction phases 1 and 2: 65 and 75% of PDN group recovered on week 2, while 45 and 50% of DXM group recovered in week 4. Adrenal recovery was predicted 2 weeks earlier by normalized s.DHEAS. Children below 5 years of age had earlier recovery in PDN group (P = 0.04), no age effect in DXM group.

CONCLUSION

Adrenal suppression is an inevitable consequence of ALL therapy. Monitoring of cortisol levels and steroid coverage during stress is recommended, and gradual steroid tapering is suggested.

Monitoring prednisolone and prednisone in saliva: a population pharmacokinetic approach in healthy volunteers

BACKGROUND

Prednisolone (PLN) is a widely used corticosteroid in a variety of immune-mediated diseases. Treatment regimes generally consist of empirically derived treatment doses, whereas therapeutic response among patients is highly variable. Drug monitoring of serum PLN levels might support a more rational approach to dose selection, yet is invasive and laborious. In analogy to cortisol, salivary PLN may offer a good alternative for serum PLN, being a representative approximation of free serum PLN. The aims of this study were to evaluate the correlation between free serum and salivary PLN levels and to quantify this relationship within a population pharmacokinetic model.

METHODS

PLN and prednisone (PN) concentrations were measured in 396 samples from 19 healthy volunteers after oral ingestion of 80 mg PLN. Measurements in serum, ultrafiltrate, and saliva were performed with a recently validated liquid chromatography tandem mass spectrometry method. Population pharmacokinetic analysis was performed with nonlinear mixed effect modeling using NONMEM.

RESULTS

Salivary PLN levels correlated well with free serum PLN levels (r = 0.931, P < 0.01). A weaker correlation was found for PN (r = 0.318, P < 0.01), which may be explained by the finding that salivary PN levels mainly seemed to consist of PLN enzymatically converted to PN. Total and free serum PLN concentrations decreased over time after drug administration and showed a nonlinear mutual relationship, consistent with concentration-dependent protein binding. Modeled PLN pharmacokinetics corresponded with previous reports. Low to moderate interindividual variability was found for V/F and CL/F (coefficients of variation were 13.8% and 14.6%, respectively). Free and salivary PLN showed a nonlinear relationship with total PLN. An equation predicting free serum levels from salivary levels was successfully derived from the data.

CONCLUSIONS

This study is the first to describe the relationship between salivary and (free) serum PLN using a population pharmacokinetic model. Salivary PLN was found to be a reliable predictor of free and total serum PLN in healthy volunteers. The results of this study encourage further exploration of the use of saliva as a noninvasive and feasible method for drug monitoring of PLN.

Optimizing drug development of anti-cancer drugs in children using modelling and simulation

Modelling and simulation (M&S)-based approaches have been proposed to support paediatric drug development in order to design and analyze clinical studies efficiently. Development of anti-cancer drugs in the paediatric population is particularly challenging due to ethical and practical constraints. We aimed to review the application of M&S in the development of anti-cancer drugs in the paediatric population, and to identify where M&S-based approaches could provide additional support in paediatric drug development of anti-cancer drugs. A structured literature search on PubMed was performed. The majority of identified M&S-based studies aimed to use population PK modelling approaches to identify determinants of inter-individual variability, in order to optimize dosing regimens and to develop therapeutic drug monitoring strategies. Prospective applications of M&S approaches for PK-bridging studies have scarcely been reported for paediatric oncology. Based on recent developments of M&S in drug development there are several opportunities where M&S could support more informative bridging between children and adults, and increase efficiency of the design and analysis of paediatric clinical trials, which should ultimately lead to further optimization of drug treatment strategies in this population.

CD2-positive B-cell precursor acute lymphoblastic leukemia with an early switch to the monocytic lineage

Switches from the lymphoid to myeloid lineage during B-cell precursor acute lymphoblastic leukemia (BCP-ALL) treatment are considered rare and thus far have been detected in MLL-rearranged leukemia. Here, we describe a novel BCP-ALL subset, switching BCP-ALL or swALL, which demonstrated monocytosis early during treatment. Despite their monocytic phenotype, 'monocytoids' share immunoreceptor gene rearrangements with leukemic B lymphoblasts. All swALLs demonstrated BCP-ALL with CD2 positivity and no MLL alterations, and the proportion of swALLs cases among BCP-ALLs was unexpectedly high (4%). The upregulation of CEBPα and demethylation of the CEBPA gene were significant in blasts at diagnosis, prior to the time when most of the switching occurs. Intermediate stages between CD14(neg)CD19(pos)CD34(pos) B lymphoblasts and CD14(pos)CD19(neg)CD34(neg) 'monocytoids' were detected, and changes in the expression of PAX5, PU1, M-CSFR, GM-CSFR and other genes accompanied the switch. Alterations in the Ikaros and ERG genes were more frequent in swALL patients; however, both were altered in only a minority of swALLs. Moreover, switching could be recapitulated in vitro and in mouse xenografts. Although children with swALL respond slowly to initial therapy, risk-based ALL therapy appears the treatment of choice for swALL. SwALL shows that transdifferentiating into monocytic lineage is specifically associated with CEBPα changes and CD2 expression.

Pharmacokinetics of prednisolone at steady state in young patients with systemic lupus erythematosus on prednisone therapy: an open-label, single-dose study

BACKGROUND

Current prednisone dosing in the treatment of young patients with childhood-onset systemic lupus erythematosus (cSLE) is largely based on achieving balance between therapeutic efficacy and toxicity, with weight-based dosing a common clinical practice. Despite the widespread use of prednisone, few attempts have been made to improve its clinical dosing regimen, and response to prednisone therapy remains variable.

OBJECTIVE

The purpose of this study was to characterize the pharmacokinetic (PK) properties of prednisolone, the metabolite of the prodrug prednisone, in cSLE patients and explore the relationship between PK properties and cSLE disease activity.

METHODS

Blood samples were taken 1 hour before the morning prednisone dose and at 20, 40, 60, and 90 minutes, and 2, 3, 4, 6, and 9 hours from 8 patients (ages 12-28 years) after an 8-hour fast. The mean weight-adjusted daily prednisone dose, stable for at least 30 days pre-study, was 0.29 mg/kg/d. PK analysis of prednisolone was performed using noncompartmental analysis with WinNonlin. cSLE disease activity was measured using the British Isles Lupus Assessment Group index and Systemic Lupus Erythematosus Disease Activity Index.

RESULTS

Mean total prednisolone AUC(0-9), prednisone CL/F at steady state, and half-life were 1094 (range, 467-2404) ng/h/mL, 11 (range, 6.7-13.7) L/hr, and 2.6 (range, 1.3-3.9) hours. Mean total prednisolone AUC(0-9) normalized to prednisone dose by weight was 4361 (range, 1136-9580) ng/h/mL/mg/kg. Mean total prednisolone C(max) normalized to prednisone dose by weight was 1097 (range, 301-2211) ng/mL/mg/kg at 1.84 (range, 0.48-4) hours (T(max)). Patients on prednisone had interindividual variability in prednisolone AUC(0-9) (61% CV) and dose-adjusted AUC(0-9) (58% CV).

CONCLUSIONS

Interindividual variability in systemic exposure to prednisolone in cSLE patients was observed.

A population approach to eplerenone pharmacokinetics and saturable protein binding

Eplerenone deviates from linear pharmacokinetics at doses above the therapeutic dose range. In addition, saturable protein binding of eplerenone is observed in in vitro plasma protein binding studies. The purpose of the present study was to clarify the factors contributing to the nonlinear pharmacokinetics of eplerenone. Plasma concentration data for eplerenone and its metabolite SC-70303, to which eplerenone is reversibly converted, obtained from four phase I studies were analyzed using NONMEM. A population pharmacokinetic model incorporating protein binding and the reversible relationship between eplerenone and SC-70303 was developed. Models with linear and nonlinear protein binding were fitted to the observed concentration data. The observed concentration data of eplerenone and SC-70303 were best described by a model with nonlinear protein binding. The area under the plasma concentration-time curve of eplerenone simulated by the model increased less than proportionally with increasing dose, whereas that of SC-70303 increased proportionally with increasing dose, consistent with observations from the non-compartmental analysis. In conclusion, the nonlinear pharmacokinetics of eplerenone and the apparently linear pharmacokinetics of SC-70303 were described by applying a model with nonlinear protein binding to observed plasma eplerenone and SC-70303 concentrations, suggesting that nonlinear protein binding plays a role in the nonlinear kinetics.

Pharmacokinetics and anti-inflammatory pharmacodynamics of prednisolone in cynomolgus monkey

The purpose was to investigate whether the pharmacokinetics and pharmacodynamics of prednisolone in the non-human primate was an appropriate surrogate for man. After single intravenous doses of 0.03, 0.3, and 3 mg kg(-1), prednisolone demonstrated a dose-dependent clearance and volume of distribution. When corrected for concentration-dependent protein binding, the free clearance was linear at the tested dose levels. The protein binding-corrected volume of distribution was similar across doses. The serum half-life was estimated as being between 2 and 4 h. Prednisolone exhibits near complete inhibition of the cytokines TNF-alpha, IL-1beta, IL-6 and IL-8 with very similar IC50 estimates from 0.09 to 0.16 microg ml(-1) (from 0.24 to 0.44 microM). The monkey demonstrated a similar pharmacokinetics-pharmacodynamics profile of prednisolone when compared with man (from the literature).

Prednisolone exerts late mitogenic and biphasic effects on resistant acute lymphoblastic leukemia cells: Relation to early gene expression

Resistance or sensitivity to glucocorticoids is considered to be of crucial importance for disease prognosis in childhood acute lymphoblastic leukemia. Prednisolone exerted a delayed biphasic effect on the resistant CCRF-CEM leukemic cell line, necrotic at low doses and apoptotic at higher doses. At low doses, prednisolone exerted a pre-dominant mitogenic effect despite its induction on total cell death, while at higher doses, prednisolone's mitogenic and cell death effects were counterbalanced. Early gene microarray analysis revealed notable differences in 40 genes. The mitogenic/biphasic effects of prednisolone are of clinical importance in the case of resistant leukemic cells. This approach might lead to the identification of gene candidates for future molecular drug targets in combination therapy with glucocorticoids, along with early markers for glucocorticoid resistance.

Pharmacogenetics influence treatment efficacy in childhood acute lymphoblastic leukemia

Pharmacogenetics covers the genetic variation affecting pharmacokinetics and pharmacodynamics, and their influence on drug-response phenotypes. The genetic variation includes an estimated 15 million single nucleotide polymorphisms (SNPs) and is a key determinator for the interindividual differences in treatment resistance and toxic side effects. As most childhood acute lymphoblastic leukemia treatment protocols include up to 13 different chemotherapeutic agents, the impact of individual SNPs has been difficult to evaluate. So far focus has mainly been on the widely used glucocorticosteroids, methotrexate, and thiopurines, or on metabolic pathways and transport mechanisms that are common to several drugs, such as the glutathione S-transferases. However, beyond the thiopurine methyltransferase polymorphisms, the candidate-gene approach has not established clear associations between polymorphisms and treatment response. In the future, high-throughput, low-cost, genetic platforms will allow screening of hundreds or thousands of targeted SNPs to give a combined gene-dosage effect (=individual SNP risk profile), which may allow pharmacogenetic-based individualization of treatment.

Circulating glucocorticoid bioactivity during peroral glucocorticoid treatment in children and adolescents with inflammatory bowel disease

GOALS

Our objective was to investigate the changes in circulating glucocorticoid bioactivity (GBA) at the onset of systemic glucocorticoid therapy in pediatric patients with inflammatory bowel disease.

STUDY

Prednisolone (1 mg/kg/d) or budesonide (9 mg/d) was introduced as a single daily dose, and the patients (n=22) were subsequently followed up at 2 to 4 week intervals. The limit for a raised value of serum GBA was defined in pediatric patients (mean+2 SD; 118 nM cortisol equivalents; n=142).

RESULTS

Two weeks of prednisolone brought about an increase in serum GBA from 84+/-14 to 336+/-38 nM cortisol equivalents (mean+/-SE; P<0.001). Young patients (<10 y) had similar GBA values to older patients, even though their prednisolone dose was higher (1.3 vs. 0.79 mg/kg; P<0.05). Patients treated with budesonide displayed a minor increase in GBA (151+/-20 vs. 267+/-21 nM cortisol equivalents after 4 wk of treatment; P<0.05; n=3), and when switched to prednisolone (n=2), their GBA level increased 3-fold. GBA levels did not predict the development of glucocorticoid-related side effects.

CONCLUSIONS

Prednisolone doses used in the treatment of pediatric inflammatory bowel disease patients elicit a 4-fold increase in serum GBA that is significantly higher than the increase induced by budesonide. The GBA measurement is an additional tool for assessing steroid therapy at an individual level during systemic glucocorticoid treatment.

Etiology of common childhood acute lymphoblastic leukemia: the adrenal hypothesis

The pattern of infections in the first years of life modulates our immune system, and a low incidence of infections has been linked to an increased risk of common childhood acute lymphoblastic leukemia (ALL). We here present a new interpretation of these observations--the adrenal hypothesis--that proposes that the risk of childhood ALL is reduced when early childhood infections induce qualitative and quantitative changes in the hypothalamus-pituitary-adrenal axis that increase plasma cortisol levels. This may directly eliminate leukemic cells as well as preleukemic cells for the ALL subsets that dominate in the first 5-7 years of life and may furthermore suppress the Th1-dominated proinflammatory response to infections, and thus lower the proliferative stress on pre-existing preleukemic cells.

Cellular pharmacodynamics of immunosuppressive drugs for individualized medicine

The therapeutic effects of immunosuppressive drugs are known to deviate largely between patients, but efficient strategies for the differentiation of patients who show clinical resistance to immunosuppressive therapies have not been established. Accordingly, a considerable number of patients receive treatment with immunosuppressive drugs despite the onset of serious side effects and poor responses. Cellular pharmacodynamics of immunosuppressive drugs in vitro using peripheral lymphocytes derived from each patient, an attractive way to distinguish resistant patients, is respected and has been applied to the carrying out of individualized immunosuppressive therapy. In this article, I summarize experimental procedures for assaying immune cell responses to immunosuppressive drugs in vitro, and highlight the relationship between cellular sensitivity to immunosuppressive drugs and the therapeutic efficacy of drugs in organ transplantation and several immunological disorders. I will also overview the molecular mechanisms and genetic bases for cellular and clinical resistance to immunosuppressive drugs. Lastly, the future clinical prospects for the application of in vitro drug sensitivity tests for "patient-tailored" immunosuppressive therapies are discussed.

Methylprednisolone exposure in pediatric renal transplant patients

Glucocorticoid (GC) dosing is commonly based on body mass or surface area in children, although the drug effects appear to correlate with steroid exposure, rather than dose. We compared the area under the serum concentration-time curve (AUC) of methylprednisolone (MP) with a recombinant cell bioassay measuring serum glucocorticoid bioactivity (GBA), in prediction of side effects in 16 pediatric patients (5.4-18.4 years of age) 2.0-14.9 years after renal transplantation (TX). They received 0.3 mg/kg of MP orally and timed blood samples were drawn up to 8 h postdose. Serum MP concentrations correlated moderately with GBA (r= 0.65, p < 0.0001) with best linear fit at 6 and 8 h (r= 0.72, 0.79, respectively, p < 0.001). MP-AUC(t = 0-8) and GBA(t = 6) were significantly greater in patients who gained excessive weight soon after TX. Change in growth after TX was inversely correlated with MP-AUC (r= 0.73, p < 0.05) and GBA(t = 6) (r= 0.62, p < 0.05). No correlation of MP-AUC or GBA was found with blood glucose or serum lipid concentrations, glomerular filtration rate, bone mineral density or graft histology. In conclusion, GC exposure varies individually and dosing should be adjusted accordingly to control the adverse effects. GBA might provide a complementary tool for monitoring GC exposure but further studies are needed.

Pharmacokinetics and pharmacodynamics of systemically administered glucocorticoids

Glucocorticoids have pleiotropic effects that are used to treat diverse diseases such as asthma, rheumatoid arthritis, systemic lupus erythematosus and acute kidney transplant rejection. The most commonly used systemic glucocorticoids are hydrocortisone, prednisolone, methylprednisolone and dexamethasone. These glucocorticoids have good oral bioavailability and are eliminated mainly by hepatic metabolism and renal excretion of the metabolites. Plasma concentrations follow a biexponential pattern. Two-compartment models are used after intravenous administration, but one-compartment models are sufficient after oral administration.The effects of glucocorticoids are mediated by genomic and possibly nongenomic mechanisms. Genomic mechanisms include activation of the cytosolic glucocorticoid receptor that leads to activation or repression of protein synthesis, including cytokines, chemokines, inflammatory enzymes and adhesion molecules. Thus, inflammation and immune response mechanisms may be modified. Nongenomic mechanisms might play an additional role in glucocorticoid pulse therapy. Clinical efficacy depends on glucocorticoid pharmacokinetics and pharmacodynamics. Pharmacokinetic parameters such as the elimination half-life, and pharmacodynamic parameters such as the concentration producing the half-maximal effect, determine the duration and intensity of glucocorticoid effects. The special contribution of either of these can be distinguished with pharmacokinetic/pharmacodynamic analysis. We performed simulations with a pharmacokinetic/pharmacodynamic model using T helper cell counts and endogenous cortisol as biomarkers for the effects of methylprednisolone. These simulations suggest that the clinical efficacy of low-dose glucocorticoid regimens might be increased with twice-daily glucocorticoid administration.