Ron A. A. Mathôt

Cyclosporine interacts with mycophenolic acid by inhibiting the multidrug resistance-associated protein 2

In mycophenolate mofetil (MMF)‐treated organ transplant recipients, lower mycophenolic acid (MPA) plasma concentrations have been found in cyclosporine (CsA) compared with tacrolimus (Tac)‐based immunosuppressive regimens. We previously demonstrated that CsA decreases exposure to MPA and increases exposure to its metabolite MPA‐glucuronide (MPAG), possibly by interfering with the biliary excretion of MPAG. To elucidate the role of the multidrug resistance‐associated protein (Mrp)‐2 in the interaction between MMF and CsA, we treated three groups of 10 Mrp2‐deficient rats (TR− rat) for 6 days with either vehicle, CsA (8 mg/kg) or Tac (4 mg/kg) by oral gavage. Hereafter, co‐administration with MMF (20 mg/kg) was started in all groups and continued through day 14. The 24‐h MPA/MPAG area under the concentration‐time curve (AUC) was determined after single (day 7) and multiple MMF doses (day 14). On both study days, there were no significant differences in the mean MPA and MPAG AUC between CsA and Tac‐treated animals. We conclude that the pharmacokinetics of MMF are comparable in Mrp2‐deficient rats receiving either CsA or Tac as co‐medication. This finding suggests that CsA‐mediated inhibition of the biliary excretion of MPAG by the Mrp2 transporter is the mechanism responsible for the interaction between CsA and MMF.

Explaining Variability in Mycophenolic Acid Exposure to Optimize Mycophenolate Mofetil Dosing: A Population Pharmacokinetic Meta-Analysis of Mycophenolic Acid in Renal Transplant Recipients

Large between- and within-patient variability has been observed in the pharmacokinetics of mycophenolic acid (MPA). However, conflicting results exist about the influence of patient characteristics that explain the variability in MPA exposure. This population pharmacokinetic meta-analysis of MPA in renal transplant recipients was performed to explore whether race, renal function, albumin level, delayed graft function, diabetes, and co-medication are determinants of total MPA exposure. A total of 13,346 MPA concentration-time data points from 468 renal transplant patients who participated in six clinical studies were combined and analyzed retrospectively. Sampling occasions ranged from day 1 after transplantation to 10 yr after transplantation. Concentration-time data were analyzed with nonlinear mixed-effect modeling. Exposure to total MPA, as determined by MPA clearance, significantly increased with increasing renal function, albumin level, and hemoglobin as well as decreasing cyclosporine predose level (P<0.001). These variables could explain 18% of the between-patient and 38% of the within-patient variability in MPA exposure. Differences in MPA exposure between patients with or without delayed graft function or between patients of different races are likely to be caused by the effect of renal function on MPA exposure. Diabetes did not have an effect on MPA exposure. The clinical implication is that a change in renal function or albumin level provides an indication for therapeutic drug monitoring as MPA exposure may be altered. Patients in whom cyclosporine and mycophenolate mofetil are combined may need higher mycophenolate mofetil doses, especially during the early phase after transplantation than currently recommended for optimal MPA exposure.

Impact of goal-oriented and model-based clinical pharmacokinetic dosing of aminoglycosides on clinical outcome: a cost-effectiveness analysis.

The benefits of a pharmacy-based, active therapeutic drug monitoring (TDM) service (ATM) on outcomes were examined in a prospective study at four hospitals. ATM involved pharmacokinetic dosage optimization at the start of treatment, subsequent Bayesian adaptive control, and frequent patient evaluation. Cost-effectiveness was calculated based on real costs. The ATM group comprised 105 patients and 127 patients with nonguided TDM who were followed up as controls. Forty-eight of the ATM and 62 of the nonguided TDM patients had an infection on admission. Peak concentrations in ATM patients were significantly higher (10.6+/-2.9 mg/L; nonguided TDM, 7.6+/-2.2 mg/L; p < 0.01). Trough levels in the ATM group were significantly lower (p < 0.01). There was a trend toward lower mortality in the ATM group (nine of 105 versus 18 of 127; p = 0.26) that was significant for patients with an infection on admission (one of the 48 ATM patients died versus nine of the 62 nonguided TDM patients; p = 0.023). ATM reduced the length of hospital stay for all patients in the study (20.0+/-1.4 days; nonguided TDM, 26.3+/-2.9 days; p = 0.045) and for patients admitted with an infection (12.6+/-0.8 days; nonguided TDM, 18.0+/-1.4; p < 0.001). The incidence of nephrotoxicity was reduced from 13.4% (nonguided TDM) to 2.9% (p < 0.01). With ATM, total costs were lower for all patients (Dutch guilders [DFL], 13,125+/-9,267; nonguided TDM, DFL 16,862+/-17,721; p < 0.05) and for patients admitted with an infection (DFL 8,883+/-3,778; nonguided TDM, DFL 11,743+/-7,437; p < 0.01). Goal-oriented, model-based dosing of aminoglycosides resulted in higher antibiotic efficacy, shorter hospitalization, and reduced incidence of nephrotoxicity. By combining efficacy with savings, ATM offered a significant alternative to usual care.

Metformin in patients with advanced pancreatic cancer: a double-blind, randomised, placebo-controlled phase 2 trial

BACKGROUND In preclinical work and retrospective population studies, the anti-diabetic drug metformin has been associated with antineoplastic activity and decreased burden of many cancers, including pancreatic cancer. There is therefore interest in the hypothesis that this drug might be repurposed for indications in oncology. We aimed to assess the efficacy of the addition of metformin to a standard systemic therapy in patients with advanced pancreatic cancer, and provide the first report of a clinical trial with a survival endpoint of metformin for an oncological indication. METHODS We did this double-blind, randomised, placebo-controlled phase 2 trial at four centres in the Netherlands. Patients aged 18 years or older with advanced pancreatic cancer were randomly assigned (1:1), via a permutated computer-generated block allocation scheme (block size of six) to receive intravenous gemcitabine (1000 mg/m(2)) on days 1, 8, and 15 every 4 weeks and oral erlotinib (100mg) once daily in combination with either oral metformin or placebo twice daily. Metformin dose was escalated from 500 mg (in the first week) to 1000 mg twice daily in the second week. Randomisation was stratified by hospital, diabetes status, and tumour stage. The primary endpoint was overall survival at 6 months in the intention-to-treat population. This trial is complete and is registered with ClinicalTrials.gov, number NCT01210911. FINDINGS Between May 31, 2010, and Jan 3, 2014, we randomly assigned 121 patients to receive gemcitabine and erlotinib with either placebo (n=61) or metformin (n=60). Overall survival at 6 months was 63·9% (95% CI 51·9-75·9) in the placebo group and 56·7% (44·1-69·2) in the metformin group (p=0·41). There was no difference in overall survival between groups (median 7·6 months [95% CI 6·1-9·1] vs 6·8 months [95% CI 5·1-8·5] in the metformin group; hazard ratio [HR] 1·056 [95% CI 0·72-1·55]; log-rank p=0·78). The most frequent grade 3-4 toxic effects were neutropenia (15 [25%] patients in placebo group vs 15 [25%] in metformin group), skin rash (six [10%] vs four [7%]), diarrhoea (three [5%] vs six [10%]), and fatigue (two [3%] vs six [10%]). INTERPRETATION Addition of a conventional anti-diabetic dose of metformin does not improve outcome in patients with advanced pancreatic cancer treated with gemcitabine and erlotinib. Future research should include studies of more potent biguanides, and should focus on patients with hyperinsulinaemia and patients with tumours showing markers of sensitivity to energetic stress, such as loss of function of AMP kinase, a key regulator of cellular energy homoeostasis. FUNDING Academic Medical Centre, Amsterdam, and The Terry Fox Foundation, Vancouver, Canada.

Effect of intravenous paracetamol on postoperative morphine requirements in neonates and infants undergoing major noncardiac surgery: A randomized controlled trial

IMPORTANCE Continuous morphine infusion as standard postoperative analgesic therapy in young infants is associated with unwanted adverse effects such as respiratory depression. OBJECTIVE To determine whether intravenous paracetamol (acetaminophen) would significantly (>30%) reduce morphine requirements in neonates and infants after major surgery. DESIGN, SETTING, AND PATIENTS Single-center, randomized, double-blind study conducted in a level 3 pediatric intensive care unit in Rotterdam, The Netherlands. Patients were 71 neonates or infants younger than 1 year undergoing major thoracic (noncardiac) or abdominal surgery between March 2008 and July 2010, with follow-up of 48 hours. INTERVENTIONS All patients received a loading dose of morphine 30 minutes before the end of surgery, followed by continuous morphine or intermittent intravenous paracetamol up to 48 hours postsurgery. Infants in both study groups received morphine (boluses and/or continuous infusion) as rescue medication on the guidance of the validated pain assessment instruments. MAIN OUTCOME MEASURES Primary outcome was cumulative morphine dose (study and rescue dose). Secondary outcomes were pain scores and morphine-related adverse effects. RESULTS The cumulative median morphine dose in the first 48 hours postoperatively was 121 (interquartile range, 99-264) μg/kg in the paracetamol group (n = 33) and 357 (interquartile range, 220-605) μg/kg in the morphine group (n = 38), P < .001, with a between-group difference that was 66% (95% CI, 34%-109%) lower in the paracetamol group. Pain scores and adverse effects were not significantly different between groups. CONCLUSION AND RELEVANCE Among infants undergoing major surgery, postoperative use of intermittent intravenous paracetamol compared with continuous morphine resulted in a lower cumulative morphine dose over 48 hours. TRIAL REGISTRATION trialregister.nl Identifier: NTR1438.

Interpatient variability in IMPDH activity in MMF-treated renal transplant patients is correlated with IMPDH type II 3757T > C polymorphism.

Objectives The active metabolite of mycophenolate mofetil (MMF), mycophenolic acid, inhibits the activity of the target enzyme inosine monophosphate dehydrogenase (IMPDH). The aim of this study was to correlate eight different single nucleotide polymorphisms of the IMPDH type II gene to the activity of the IMPDH enzyme to explain between-patient differences in IMPDH activity. Methods and results In a prospective study, we measured IMPDH activity, mycophenolic acid plasma concentrations, and eight polymorphisms of IMPDH type II in de novo kidney transplant recipients, 6 days posttransplantation while on MMF treatment. Polymorphisms in the IMPDH type II gene were only observed for the IMPDH type II 3757T>C (rs11706052) single nucleotide polymorphism. Ten of 101 patients (10%) were heterozygous and two of 101 patients (2%) homozygous for IMPDH type II 3757T>C. The allele frequency was 6.9%. The IMPDH activity over 12 h (AUCact) was 49% higher for patients with an IMPDH type II 3757C variant [n = 12 vs. n = 68; 336 (95% confidence interval: 216–521) vs. 227 (95% confidence interval: 198–260) hμmol/s/mol adenosine monophosphate; P = 0.04]. The IMPDH activity measured before transplantation (Actpre-Tx) was not significantly different between IMPDH type II 3757TT wild-type and variant carrier patients (P = 0.99). Conclusion We report that the IMPDH type II 3757T>C polymorphism is associated with an increased IMPDH activity in MMF-treated renal transplant patients. This polymorphism explains 8.0% of the interpatient variability in IMPDH activity.

Clinical pharmacology of the novel marine-derived anticancer agent Ecteinascidin 743 administered as a 1- and 3-h infusion in a phase I study

Ecteinascidin 743 (ET-743) is an anticancer agent derived from the Caribbean tunicate Ecteinascidia turbinata. In the present article, the pharmacokinetics and pharmacodynamics of ET-743 are described within a phase I study. Forty patients with solid tumors initially received ET-743 as a 1-h i.v. infusion every 21 days at nine dose levels (50–1100 μ g/m2). The maximal tolerated dose (MTD) was 1100 μ g/m2, with thrombocytopenia and fatigue as dose-limiting toxicities (DLTs). As this MTD was substantially lower than in parallel phase I studies, dose escalation continued using a prolonged, 3-h infusion. Thirty-two patients were entered at five dose levels (1000–1800 μ g/m2). The MTD was 1800 μ g/m2 with pancytopenia and fatigue as DLTs. The recommended phase II dose was 1650 μ g/m2 given over 3 h at which 12 patients were treated. Pharmacokinetic monitoring was performed for both treatment schedules. Non-compartmental pharmacokinetic parameters at the recommended dose with the 3-h infusion were (mean value±SD): clearance 87±30 l/h and mean elimination half-life 26±7 h. Pharmacokinetics were linear at the dose range tested with this schedule. The percentage decrease in platelets, white blood cells and neutrophils correlated with the area under the plasma concentration versus time curve (AUC), dose and maximal plasma concentration (Cmax). Hepatic toxicity increased with dose, AUC and Cmax. Administration of 1650 μ g/m2 ET-743 over 3 h seemed clinically feasible; pharmacokinetics were linear with this schedule. Hepatic and hematological toxicities correlated with exposure to ET-743.

Methotrexate-induced side effects are not due to differences in pharmacokinetics in children with Down syndrome and acute lymphoblastic leukemia

Background Children with Down syndrome have an increased risk of developing acute lymphoblastic leukemia and a poor tolerance of methotrexate. This latter problem is assumed to be caused by a higher cellular sensitivity of tissues in children with Down syndrome. However, whether differences in pharmacokinetics play a role is unknown. Design and Methods We compared methotrexate-induced toxicity and pharmacokinetics in a retrospective case-control study between patients with acute lymphoblastic leukemia who did or did not have Down syndrome. Population pharmacokinetic models were fitted to data from all individuals simultaneously, using non-linear mixed effect modeling. Results Overall, 468 courses of methotrexate (1–5 g/m2) were given to 44 acute lymphoblastic leukemia patients with Down syndrome and to 87 acute lymphoblastic leukemia patients without Down syndrome. Grade 3–4 gastrointestinal toxicity was significantly more frequent in the children with Down syndrome than in those without (25.5% versus 3.9%; P=0.001). The occurrence of grade 3–4 gastrointestinal toxicity was not related to plasma methotrexate area under the curve. Methotrexate clearance was 5% lower in the acute lymphoblastic leukemia patients with Down syndrome (P=0.001); however, this small difference is probably clinically not relevant, because no significant differences in methotrexate plasma levels were detected at 24 and 48 hours. Conclusions We did not find evidence of differences in the pharmacokinetics of methotrexate between patients with and without Down syndrome which could explain the higher frequency of gastrointestinal toxicity and the greater need for methotrexate dose reductions in patients with Down syndrome. Hence, these problems are most likely explained by differential pharmaco-dynamic effects in the tissues between children with and without Down syndrome. Although the number of patients was limited to draw conclusions, we feel that it may be safe in children with Down syndrome to start with intermediate dosages of methotrexate (1–3 g/m2) and monitor the patients carefully.

Combination therapy of advanced invasive pulmonary aspergillosis in transiently neutropenic rats using human pharmacokinetic equivalent doses of voriconazole and anidulafungin

ABSTRACT At present, voriconazole (VOR) is the drug of first choice for treating invasive pulmonary aspergillosis (IPA). However, particularly in advanced stages of disease and in the severely immunocompromised host, the mortality remains substantial. The combination of VOR with an echinocandin may improve the therapeutic outcome. We investigate here whether combining VOR and anidulafungin (ANI) in advanced IPA in transiently neutropenic rats results in a higher therapeutic efficacy. Since VOR is metabolized more rapidly in rodents than in humans, dosage adjustment for VOR is necessary to obtain an area under the plasma concentration-time curve (AUC) in rodents that is equivalent to that of humans. In this study, the pharmacokinetics of VOR and ANI in rats were elucidated, and dosage schedules were applied that produced AUCs similar to those of humans. The developed dose schedules were well tolerated by the rats, without effects on renal and hepatic functions. VOR showed excellent efficacy in early IPA (100% rat survival). In advanced IPA, VOR was less efficacious (50% rat survival), whereas a significant decrease in galactomannan concentrations in lungs and sera was found in surviving rats. ANI administered in advanced IPA resulted in 22% rat survival, and the serum concentrations of fungal galactomannan were slightly but not significantly decreased. The addition of ANI to VOR did not result in significantly increased therapeutic efficacy in advanced IPA, resulting in 67% rat survival and a significant decrease in galactomannan concentration in serum. In conclusion, VOR monotherapy is therapeutically effective in the treatment of advanced-stage IPA and superior to the use of ANI. Combining both agents does not significantly improve the therapeutic outcome.

Bayesian pharmacokinetically guided dosing of paclitaxel in patients with non-small cell lung cancer

Purpose: Paclitaxel is a taxane derivative with a profound antitumor activity against a variety of solid tumors. In a previous clinical study in patients with non-small cell lung cancer (NSCLC) treated with paclitaxel, it was shown that paclitaxel plasma concentrations of 0.1 μmol/liter for ≥15 h were associated with prolonged survival. The purpose of this study was to evaluate the feasibility of Bayesian dose individualization to attain paclitaxel plasma concentrations >0.1 μmol/liter for ≥15 h. Experimental Design: Patients with stage IIIb-IV NSCLC were treated with paclitaxel and carboplatin once every 3 weeks for a maximum of six courses. During the first course, a standard paclitaxel dose of 175 mg/m2 was administered i.v. in 3 h. In subsequent courses, the paclitaxel dose was individualized based on observed paclitaxel concentrations in plasma during the previous course(s) using a Bayesian algorithm. The paclitaxel dose of a subsequent course was increased to the lowest dose for which the predicted time period during which the paclitaxel plasma concentration exceeds 0.1 μmol/liter was >15 h. Results: A total of 25 patients have been included in the study (92 evaluable courses). During the first course, the median time period above the threshold concentration was 16.3 h (range, 7.6–31.6 h), and was <15 h for 9 patients (36%). During subsequent individualized courses, the time period above the threshold concentration was <15 h in 23% (5 of 22), 14% (2 of 14), 23% (3 of 13), 11% (1 of 9), and 11% (1 of 9) of the patients in the second, third, fourth, fifth, and sixth course, respectively. Dose increments, ranging from 5 to 65 mg/m2, were performed in 29 of the 67 individualized courses. Patients with increased individualized doses had similar regimen related toxicities compared with those remaining at a dose of 175 mg/m2. Toxicity was reversible and manageable, and was mainly hematological (granulocytopenia CTC grade 3/4 in 80% of the patients). The objective response rate was 20%. Conclusions: The results indicate that the applied pharmacokinetically guided dosing strategy for paclitaxel is safe and technically feasible. A randomized study is necessary to demonstrate whether dose individualization may result in improved activity and efficacy in patients with NSCLC.