Advances in pharmacokinetic-pharmacodynamic modelling for pediatric drug development: extrapolations and exposure-response analyses.

INTRODUCTION: Pharmacokinetic (PK)-Pharmacodynamic (PD) and exposure-response (E-R) modeling are critical parts of pediatric drug development. By integrating available knowledge and supportive data to support the design of future studies and pediatric dose selection, these techniques increase the efficiency of pediatric drug development and lowers the risk of exposing pediatric study participants to suboptimal or unsafe dose regimens. AREAS COVERED: The role of PK, PK-PD and E-R modeling within pediatric drug development and pediatric dose selection is discussed. These models allow investigation of the impact of age and bodyweight on PK and PD in children, despite the often sparse data on the pediatric population. Also discussed is how E-R analyses strengthen the evidence basis to support (full or partial) extrapolation of drug efficacy from adults to children, and between different pediatric age groups. EXPERT OPINION: Accelerated pediatric drug development and optimized pediatric dosing guidelines are expected from three future developments: (1) Increased focus on E-R modeling of currently approved drugs in children resulting in (novel) E-R modeling techniques and best practices, (2) increased use of real-world data for E-R (3) increased implementation of available population PK and E-R information in pediatric drug dosing guidelines.

A Phase IIa Clinical Trial of 2-Iminobiotin for the Treatment of Birth Asphyxia in DR Congo, a Low-Income Country.

AIM: The main burden of hypoxic-ischemic encephalopathy falls in low-income countries. 2-Iminobiotin, a selective inhibitor of neuronal and inducible nitric oxide synthase, has been shown to be safe and effective in preclinical studies of birth asphyxia. Recently, safety and pharmacokinetics of 2-iminobiotin treatment on top of hypothermia has been described. Since logistics and the standard of medical care are very different in low-resource settings, the aim of this study was to investigate safety and pharmacokinetics of Two-IminoBiotin in the Democratic Republic of Congo (TIBC). METHODS: Near-term neonates, born in Kinshasa, Democratic Republic of Congo, with a Thompson score ≥ 7 were eligible for inclusion. Excluded were patients with (1) inability to insert an umbilical venous catheter for administration of the study drug; (2) major congenital or chromosomal abnormalities; (3) birth weight < 1800 g; (4) clear signs of infection; and (5) moribund patients. Neonates received six infusions of 2-iminobiotin 0.16 mg/kg started within 6 h after birth, with 4-h intervals, targeting an AUC0-4h of 365 ng*h/mL. Safety, defined as vital signs, the need for clinical intervention after administration of study drug, occurrence of (serious) adverse events, and pharmacokinetics were assessed. RESULTS: After parental consent, seven patients were included with a median Thompson score of 10 (range 8-16). No relevant changes in vital signs were observed over time. There was no need for clinical intervention due to administration of study drug. Three patients died, two after completing the study protocol, one was moribund at inclusion and should not have been included. Pharmacokinetic data of 2-iminobiotin were best described using a two-compartment model. Median AUC0-4h was 664 ng*h/mL (range 414-917). No safety issues attributed to the administration of 2-iminobiotin were found. CONCLUSION: The present dosing regimen resulted in higher AUCs than targeted, necessitating a change in the dose regimen in future efficacy trials. No adverse effects that could be attributed to the use of 2-iminobiotin were observed. EudraCT number 2015-003063-12.

Favorable Pharmacokinetic Characteristics of Extended-Half-Life Recombinant Factor VIII BAY 94-9027 Enable Robust Individual Profiling Using a Population Pharmacokinetic Approach.

BACKGROUND: Prophylaxis with factor VIII (FVIII) should be individualized based on patient characteristics, including FVIII pharmacokinetics. Population pharmacokinetic (popPK) modeling simplifies pharmacokinetic studies by obviating the need for multiple samples. OBJECTIVE: The objective of this study was to characterize the pharmacokinetics and inter-individual variability (IIV) of BAY 94-9027 in relation to patient characteristics in support of a popPK-tailored approach, including identifying the optimal number and timing of pharmacokinetic samples. METHODS: Pharmacokinetic samples from 198 males (aged 2‒62 years) with severe hemophilia A, enrolled in BAY 94-9027 clinical trials, were analyzed. Baseline age, height, weight, body mass index, lean body weight (LBW), von Willebrand factor (VWF) level, and race were evaluated. A popPK model was developed and used to simulate pharmacokinetic endpoints difficult to observe from measured FVIII levels, including time to maintain FVIII levels above 1, 3, and 5 IU/dL after different BAY 94-9027 doses. RESULTS: A one-compartment model adequately described BAY 94-9027 pharmacokinetics. Clearance and central volume of distribution were significantly associated with LBW; clearance was inversely correlated with VWF. Due to the monophasic pharmacokinetics and well-understood IIV sources, identification of patient pharmacokinetics was achievable with sparse blood sampling. Median predicted time to maintain FVIII levels > 1 IU/dL in patients aged ≥ 12 years ranged from 120.1 to 127.2 h after single BAY 94-9027 doses of 45‒60 IU/kg. CONCLUSIONS: This analysis evaluated the pharmacokinetics of BAY 94-9027 and its sources of IIV. Using the model, determination of individual patient pharmacokinetics was possible with few FVIII samples, and a sparse sampling design to support pharmacokinetic-guided dosing was identified.

Pharmacokinetics and short-term safety of the selective NOS inhibitor 2-iminobiotin in asphyxiated neonates treated with therapeutic hypothermia.

BACKGROUND: Neonatal encephalopathy following perinatal asphyxia is a leading cause for neonatal death and disability, despite treatment with therapeutic hypothermia. 2-Iminobiotin is a promising neuroprotective agent additional to therapeutic hypothermia to improve the outcome of these neonates. METHODS: In an open-label study, pharmacokinetics and short-term safety of 2-iminobiotin were investigated in neonates treated with therapeutic hypothermia. Group A (n = 6) received four doses of 0.16 mg/kg intravenously q6h. Blood sampling for pharmacokinetic analysis and monitoring of vital signs for short-term safety analysis were performed. Data from group A was used to determine the dose for group B, aiming at an AUC0-48 h of 4800 ng*h/mL. RESULTS: Exposure in group A was higher than targeted (median AUC0-48 h 9522 ng*h/mL); subsequently, group B (n = 6) received eight doses of 0.08 mg/kg q6h (median AUC0-48 h 4465 ng*h/mL). No changes in vital signs were observed and no adverse events related to 2-iminobiotin occurred. CONCLUSION: This study indicates that 2-iminobiotin is well tolerated and not associated with any adverse events in neonates treated with therapeutic hypothermia after perinatal asphyxia. Target exposure was achieved with eight doses of 0.08 mg/kg q6h. Optimal duration of therapy for clinical efficacy needs to be determined in future clinical trials.

A 769 µW Battery-Powered Single-Chip SoC With BLE for Multi-Modal Vital Sign Monitoring Health Patches.

An all-in-one battery powered low-power SoC for measuring multiple vital signs with wearables is proposed. All functionality needed in a typical wearable use case scenario, including dedicated readouts, power management circuitry, digital signal processing and wireless communication (BLE) is integrated in a single die. This high level of integration allows an unprecedented level of miniaturization leading to smaller component count which reduces cost and improves comfort and signal integrity. The SoC includes an ECG, Bio-Impedance and a fully differential PPG readout and can interface with external sensors (like an IMU). In a typical application scenario where all sensor readouts are enabled and key features (like heart rate) are calculated on the chip and streamed over the radio, the SoC consumes only 769 µW from the regulated 1.2 V supply.

Pharmacokinetics and Pharmacokinetic/Pharmacodynamic Relationships of Etravirine in HIV-1-Infected, Treatment-Experienced Children and Adolescents in PIANO.

PIANO (NCT00665847) investigated etravirine pharmacokinetics, efficacy, and safety in children and adolescents. Treatment-experienced, HIV-1-infected patients (≥6 to <18 years) received etravirine 5.2 mg/kg twice daily (maximum 200 mg twice daily) plus background antiretrovirals. A population pharmacokinetic model was developed, and etravirine C0h and AUC0-12h were estimated. Relationships among intrinsic/extrinsic factors and etravirine pharmacokinetics and pharmacokinetics with pharmacodynamics were assessed. The best model describing etravirine pharmacokinetics consisted of a single compartment with sequential zero- and first-order absorption following a lag time. Interindividual variability terms were included on clearance (CL/F) and the first-order input rate constant (KA). The final model estimates (coefficient of variation, %) for CL/F and KA were 46.3 (11) L/h and 1.07 (34) h-1 , respectively. Overall, median (range) estimated etravirine C0h and AUC0-12h were 287 (2-2276) ng/mL and 4560 (62-28,865) ng · h/mL, respectively. Exposure was slightly lower in adolescents vs children. Sex and adherence did not affect etravirine pharmacokinetics. Factors significantly affecting etravirine exposure were body weight (higher with lower weight), race (lower in Asians than in white or black patients), and the use of certain HIV protease inhibitors. Virologic response (<50 copies/mL at week 48) was lower in the lowest etravirine AUC0-12h quartile vs the upper 3 quartiles (41% vs 67% to 76%). Rash occurred more frequently in the highest quartile than in the lower 3 quartiles (52% versus 8% to 20%). Etravirine 5.2 mg/kg twice daily in treatment-experienced, HIV-1-infected children and adolescents provides comparable exposure to that in adults receiving etravirine 200 mg twice daily and is the recommended dose for children and adolescents.

Population pharmacokinetic drug-drug interaction pooled analysis of existing data for rifabutin and HIV PIs.

OBJECTIVES: Extensive but fragmented data from existing studies were used to describe the drug-drug interaction between rifabutin and HIV PIs and predict doses achieving recommended therapeutic exposure for rifabutin in patients with HIV-associated TB, with concurrently administered PIs. METHODS: Individual-level data from 13 published studies were pooled and a population analysis approach was used to develop a pharmacokinetic model for rifabutin, its main active metabolite 25-O-desacetyl rifabutin (des-rifabutin) and drug-drug interaction with PIs in healthy volunteers and patients who had HIV and TB (TB/HIV). RESULTS: Key parameters of rifabutin affected by drug-drug interaction in TB/HIV were clearance to routes other than des-rifabutin (reduced by 76%-100%), formation of the metabolite (increased by 224% in patients), volume of distribution (increased by 606%) and distribution to the peripheral compartment (reduced by 47%). For des-rifabutin, clearance was reduced by 35%-76% and volume of distribution increased by 67%-240% in TB/HIV. These changes resulted in overall increased exposure to rifabutin in TB/HIV patients by 210% because of the effects of PIs and 280% with ritonavir-boosted PIs. CONCLUSIONS: Given together with non-boosted or ritonavir-boosted PIs, rifabutin at 150 mg once daily results in similar or higher exposure compared with rifabutin at 300 mg once daily without concomitant PIs and may achieve peak concentrations within an acceptable therapeutic range. Although 300 mg of rifabutin every 3 days with boosted PI achieves an average equivalent exposure, intermittent doses of rifamycins are not supported by current guidelines.

Modeling and simulation for medical product development and evaluation: highlights from the FDA-C-Path-ISOP 2013 workshop.

Medical-product development has become increasingly challenging and resource-intensive. In 2004, the Food and Drug Administration (FDA) described critical challenges facing medical-product development by establishing the critical path initiative [1]. Priorities identified included the need for improved modeling and simulation tools, further emphasized in FDA's 2011 Strategic Plan for Regulatory Science [Appendix]. In an effort to support and advance model-informed medical-product development (MIMPD), the Critical Path Institute (C-Path) [www.c-path.org], FDA, and International Society of Pharmacometrics [www.go-isop.org] co-sponsored a workshop in Washington, D.C. on September 26, 2013, to examine integrated approaches to developing and applying model- MIMPD. The workshop brought together an international group of scientists from industry, academia, FDA, and the European Medicines Agency to discuss MIMPD strategies and their applications. A commentary on the proceedings of that workshop is presented here.

Population pharmacokinetics of bedaquiline (TMC207), a novel antituberculosis drug.

Bedaquiline is a novel agent for the treatment of pulmonary multidrug-resistant Mycobacterium tuberculosis infections, in combination with other agents. The objective of this study was to develop a population pharmacokinetic (PK) model for bedaquiline to describe the concentration-time data from phase I and II studies in healthy subjects and patients with drug-susceptible or multidrug-resistant tuberculosis (TB). A total of 5,222 PK observations from 480 subjects were used in a nonlinear mixed-effects modeling approach. The PK was described with a 4-compartment disposition model with dual zero-order input (to capture dual peaks observed during absorption) and long terminal half-life (t1/2). The model included between-subject variability on apparent clearance (CL/F), apparent central volume of distribution (Vc/F), the fraction of dose via the first input, and bioavailability (F). Bedaquiline was widely distributed, with apparent volume at steady state of >10,000 liters and low clearance. The long terminal t1/2 was likely due to redistribution from the tissue compartments. The final covariate model adequately described the data and had good simulation characteristics. The CL/F was found to be 52.0% higher for subjects of black race than that for subjects of other races, and Vc/F was 15.7% lower for females than that for males, although their effects on bedaquiline exposure were not considered to be clinically relevant. Small differences in F and CL/F were observed between the studies. The residual unexplained variability was 20.6% and was higher (27.7%) for long-term phase II studies.

Pharmacokinetics and Pharmacodynamics of Darunavir and Etravirine in HIV-1-Infected, Treatment-Experienced Patients in the Gender, Race, and Clinical Experience (GRACE) Trial.

Objectives. Evaluation of pharmacokinetics and pharmacodynamics of darunavir and etravirine among HIV-1-infected, treatment-experienced adults from GRACE, by sex and race. Methods. Patients received darunavir/ritonavir 600/100mg twice daily plus other antiretrovirals, which could include etravirine 200mg twice daily. Population pharmacokinetics for darunavir and etravirine were determined over 48 weeks and relationships assessed with virologic response and safety. Rich sampling for darunavir, etravirine, and ritonavir was collected in a substudy at weeks 4, 24, and 48. Results. Pharmacokinetics were estimated in 376 patients for darunavir and 190 patients for etravirine. Median darunavir AUC(12h) and C(0h) were 60,642ng·h/mL and 3624ng/mL, respectively; and for etravirine were 4183ng · h/mL and 280ng/mL, respectively. There were no differences in darunavir or etravirine AUC(12h) or C(0h) by sex or race. Age, body weight, or use of etravirine did not affect darunavir exposure. No relationships were seen between darunavir pharmacokinetics and efficacy or safety. Patients with etravirine exposure in the lowest quartile generally had lower response rates. Rich sampling showed no time-dependent relationship for darunavir, etravirine, or ritonavir exposure over 48 weeks. Conclusions. Population pharmacokinetics showed no relevant differences in darunavir or etravirine exposure by assessed covariates. Lower etravirine exposures were associated with lower response rates.

Pharmacokinetics, safety and efficacy of darunavir/ritonavir in treatment-experienced children and adolescents.

OBJECTIVE: To assess pharmacokinetics, safety and efficacy of darunavir/ritonavir (DRV/r) and optimized background regimen in treatment-experienced patients (6-17 years). DESIGN: Forty-eight-week, open-label, two-part, phase II study. METHODS: In part I, 44 patients were randomized (1: 1 ratio) to receive a body weight-adjusted, adult-equivalent dose (group A) or a 20-33% higher DRV/r twice daily (b.i.d.) dose (group B). Pharmacokinetics, safety and efficacy were assessed following 2-week dosing (part I), which determined dosing for part II (evaluated 48-week safety and efficacy). RESULTS: In part I, both groups met the protocol-specified criteria for pharmacokinetics and showed favorable tolerability and efficacy. The following body-weight doses were selected: DRV/r 375/50 mg b.i.d. (20-<30 kg), 450/60 mg b.i.d. (30-<40 kg) and 600/100 mg b.i.d. (> or =40 kg); these gave an AUC24h, C0h and Cmax of 102, 114 and 112%, respectively, versus the corresponding mean adult pharmacokinetic parameter. In part II, 80 patients received DRV/r (median age: 14 years, mean baseline HIV-1 RNA: 4.64 log(10)copies/ml). One patient (1%) discontinued (treatment-unrelated grade 3 anxiety). An abnormal mean baseline triglyceride level was normalized at 48 weeks (P < 0.01). At week 48, 65% had at least 1.0 log(10)HIV-1 RNA reduction; 59 and 48% achieved HIV-1 RNA less than 400 and less than 50 copies/ml, respectively (time-to-loss-of-virologic response). Mean age-adjusted weight z-score increased by 0.2 (P = 0.003). CONCLUSION: In treatment-experienced children and adolescents, DRV/r showed comparable exposure to adults with appropriate dose selection, favorable safety and tolerability, improved body weight and significant virologic response. DRV/r is a valuable therapeutic option for this population.

Minutes from the round table held in Paris on July 6, 2007: 'Contribution of modelling in the paediatric drug development'.

A symposium called "Contribution of modelling in the paediatric drug development" was organized at Paris on July 5-6, 2007 under the auspices of INSERM. The following issues were highlighted and discussed by the participants at the end of the meeting during a round table: *What is the place of modelling at a preclinical stage in the paediatric development? *What is the place of modelling at a clinical stage in the paediatric development? *What are the requirements for an evaluation based on modelling? *What are the recommendations and guidelines need to be established to facilitate the use of modelling techniques in paediatrics? This paper summarizes the discussion around these four questions.

Duloxetine and venlafaxine-XR in the treatment of major depressive disorder: a meta-analysis of randomized clinical trials.

BACKGROUND: Duloxetine has joined venlafaxine on the antidepressant market as a second serotonin-norepinephrine reuptake inhibitor. No previous studies have directly compared these drugs. OBJECTIVE: To compare indirectly the efficacy and safety of extended-release (XR) venlafaxine and duloxetine, the 2 currently available serotonin-norepinephrine reuptake inhibitors (SNRIs) in treating major depressive disorder. METHODS: Outcomes from published, randomized, placebo-controlled trials reporting on moderately to severely depressed patients (Hamilton Rating Scale for Depression [HAM-D] > or =15 or Montgomery-Asberg Depression Rating Scale [MADRS] > or =18). A systematic literature search of Cochrane, EMBASE, and MEDLINE (1996-January 2005) was performed. Two independent reviewers judged the trials for acceptance, and last observation carried forward data were extracted. Differences in remission (8-week HAM-D score < or =7 or MADRS < or =10), response (50% decrease on either scale), and dropout rates from lack of efficacy and adverse events were meta-analyzed using a random effects model. Each rate was contrasted with placebo. Sensitivity analyses were performed to examine the robustness of the results. RESULTS: Data were obtained from 8 trials evaluating 1754 patients for efficacy and 1791 patients for discontinuation/safety. Venlafaxine-XR rates were 17.8% (95% CI 9.0 to 26.5) and 24.4% (95% CI 15.0 to 37.7) greater than those with placebo for remission and response compared with 14.2% (95% CI 8.9 to 26.5) and 18.6% (95% CI 13.0 to 24.2) for duloxetine. Although numerically higher for venlafaxine-XR, no statistically significant differences were found between the drugs; however, both demonstrated overall remission and response rates significantly higher than the rates achieved with placebo (p < 0.001). Reported adverse events were comparable between drugs. CONCLUSIONS: Venlafaxine-XR tends to have a favorable trend in remission and response rates compared with duloxetine. However, dropout rates and adverse events did not differ. A direct comparison is warranted to confirm this tendency.