NT-proBNP for Predicting All-Cause Death and Heart Transplant in Children and Adults with Heart Failure.

Plasma N-terminal prohormone B-type natriuretic peptide (NT-proBNP) concentration is a heart failure (HF) biomarker in adults and children. Its prognostic value for HF-related events has been established only in adults. Therefore, we aimed to test the hypothesis that plasma NT-proBNP concentrations predicted the risk of heart transplantation or death in children with HF. We studied the medical records of 109 children with HF enrolled in the IBM Watson Explorys database and from 150 children enrolled in the Pediatric Cardiomyopathy Registry (PCMR). Nonlinear regression was used to assess the relationship between plasma NT-proBNP concentrations and the risk of events in the two cohorts. All children in the PCMR cohort had dilated cardiomyopathy. The Explorys cohort also included children with congenital cardiovascular malformations. Median plasma NT-proBNP concentrations were 1250 pg/mL and 184 pg/mL in the Explorys and PCMR cohorts, respectively. The percentage of deaths/heart transplantations was 7%/22%, over 2 years in the Explorys cohort and 3%/16% over 5 years in the PCMR cohort. Mean estimates of plasma NT-proBNP concentration indicative of half-maximum relative risk for events (EC50 values) at 2 and 5 years were 3730 pg/mL and 4199 pg/mL, respectively, values both close to the mean of 3880 pg/mL established for adults with HF. The plasma NT-proBNP concentration is suitable for estimating relative risk of mortality and heart transplantation in children with HF, independent of etiology and shows similar relations to clinical outcomes as in adults, indicating its likely value as a surrogate marker both for adult and pediatric HF.ClinicalTrials.gov Identifiers: NCT00005391 (May 26, 2000), NCT01873976 (June 10, 2013).

Electronic health record characterization and outcomes of heart failure with preserved ejection fraction.

BACKGROUND: Electronic health record (EHR)-based identification of heart failure with preserved ejection fraction (HFpEF) in the clinical setting may facilitate screening for clinical trials by improving the understanding of its epidemiology and outcomes; yet, previous data have yielded variable results. We sought to characterize groups identified with HFpEF by different EHR screening strategies and their associated long-term outcomes across a large and diverse population. METHODS: We retrospectively analyzed 116,499 consecutive patients from an academic referral center who underwent echocardiography, and 9,263 patients who underwent echocardiography within 6 months of right heart catheterization (RHC), between 2008 and 2018. EHR-based screening strategies identified patients with HFpEF using 1) International Classification of Diseases (ICD)-9/10 codes, 2) H2FpEF score ≥6 and ejection fraction (EF) ≥50%, or 3) RHC wedge pressure ≥15 mmHg and EF ≥50%, when available. Primary outcomes were 1) cumulative incident heart failure hospitalization (HFH), and 2) death, over 10 years. RESULTS: There were 33,461 (29%) patients who met either ICD or H2FpEF-HFpEF definition, of whom 5,310 (16%) met both criteria. Compared to ICD-HFpEF, patients with H2FpEF-HFpEF were more likely older (median age 72 vs 67), White (78% vs 64%), and had atrial fibrillation (97% vs 41%). Among those also with RHC, 6,353 (69%) patients met any HFpEF criteria, of whom only 783 (12%) satisfied all three criteria. Female sex was more common among RHC-HFpEF (55%) compared to other methods (H2FpEF-HFpEF, 47%; ICD-HFpEF, 43%). Atrial fibrillation was substantially higher among HFpEF identified by the H2FpEF score (97%) compared to other methods (49% for ICD and 47% for RHC). Across HFpEF screening methods, 10-year cumulative incidence rates for HFH was 32% to 45% for echocardiography only and 43% to 52% for echocardiography and RHC populations; 10-year risk of death was 54% to 56% for echocardiography only and 52% to 57% for echocardiography and RHC populations. CONCLUSIONS: Different EHR-based HFpEF definitions identified cohorts with modest overlap and varying baseline characteristics. Yet, long-term risk for HFH and death were similarly high for cohorts identified among both populations undergoing echocardiography only or echocardiography and RHC. These data aid in identifying relevant subgroups in clinical trials of HFpEF.

Evaluation of changes in oral drug absorption in preterm and term neonates for Biopharmaceutics Classification System (BCS) class I and II compounds.

AIMS: Evidence suggests that the rate of oral drug absorption changes during early childhood. Yet, respective clinical implications are currently unclear, particularly for preterm neonates. The objective of this study was to evaluate changes in oral drug absorption after birth for different Biopharmaceutics Classification System (BCS) class I and II compounds to better understand respective implications for paediatric pharmacotherapy. METHODS: Two paradigm compounds were selected for BCS class I (paracetamol (acetaminophen) and theophylline) and II (indomethacin and ibuprofen), respectively, based on the availability of clinical literature data following intravenous and oral dosing. A comparative population pharmacokinetic analysis was performed in a step-wise manner in NONMEM® 7.2 to characterize and predict changes in oral drug absorption after birth for paracetamol, theophylline and indomethacin. RESULTS: A one compartment model with an age-dependent maturation function for oral drug absorption was found appropriate to characterize the pharmacokinetics of paracetamol. Our findings indicate that the rate at which a drug is absorbed from the GI tract reaches adult levels within about 1 week after birth. The maturation function for paracetamol was found applicable to theophylline and indomethacin once solubility limitations were overcome via drug formulation. The influence of excipients on solubility and, hence, oral bioavailability was confirmed for ibuprofen, a second BCS class II compound. CONCLUSIONS: The findings of our study suggest that the processes underlying changes in oral drug absorption after birth are drug-independent and that the maturation function identified for paracetamol may be generally applicable to other BCS class I and II compounds for characterizing drug absorption in preterm as well as term neonates.

The Paradox of Time Post-Pregnancy Loss: Three Things Not to Say When Communicating Social Support.

In this essay, I interrogate the role time plays in the three most common social support messages I received post-pregnancy loss. In doing so, I illustrate how our most common "social support" responses to pregnancy loss, while uttered from caring, intentional places of support, can actually serve to marginalize and invalidate experiences of pregnancy loss.

Characterization of a caprine model for the subclinical initial phase of Mycobacterium avium subsp. paratuberculosis infection.

BACKGROUND: Paratuberculosis caused by Mycobacterium avium subsp. paratuberculosis (MAP) is difficult to control due to a long phase of clinically non-apparent (latent) infection for which sensitive diagnostics are lacking. A defined animal model for this phase of the infection can help to investigate host-MAP interactions in apparently healthy animals and identify surrogate markers for disease progress and might also serve as challenge model for vaccines. To establish such a model in goats, different age at inoculation and doses of oral inoculum of MAP were compared. Clinical signs, faecal shedding as well as MAP-specific antibody, IFN-γ and IL-10 responses were used for in vivo monitoring. At necropsy, about one year after inoculation (pi), pathomorphological findings and bacterial organ burden (BOB) were scored. RESULTS: MAP infection manifested in 26/27 inoculated animals irrespective of age at inoculation and dose. Clinical signs developed in three goats. Faecal shedding, IFN-γ and antibody responses emerged 6, 10-14 and 14 wpi, respectively, and continued with large inter-individual variation. One year pi, lesions were detected in 26 and MAP was cultured from tissues of 23 goats. Positive animals subdivided in those with high and low overall BOB. Intestinal findings resembled paucibacillary lesions in 23 and multibacillary in 4 goats. Caseous and calcified granulomas predominated in intestinal LNN. BOB and lesion score corresponded well in intestinal mucosa and oGALT but not in intestinal LNN. CONCLUSIONS: A defined experimental infection model for the clinically non-apparent phase of paratuberculosis was established in goats as suitable basis for future studies.

Applied physiologically-based pharmacokinetic modeling to assess uridine diphosphate-glucuronosyltransferase-mediated drug-drug interactions for Vericiguat.

Vericiguat (Verquvo; US: Merck, other countries: Bayer) is a novel drug for the treatment of chronic heart failure. Preclinical studies have demonstrated that the primary route of metabolism for vericiguat is glucuronidation, mainly catalyzed by uridine diphosphate-glucuronosyltransferase (UGT)1A9 and to a lesser extent UGT1A1. Whereas a drug-drug interaction (DDI) study of the UGT1A9 inhibitor mefenamic acid showed a 20% exposure increase, the effect of UGT1A1 inhibitors has not been assessed clinically. This modeling study describes a physiologically-based pharmacokinetic (PBPK) approach to complement the clinical DDI liability assessment and support prescription labeling. A PBPK model of vericiguat was developed based on in vitro and clinical data, verified against data from the mefenamic acid DDI study, and applied to assess the UGT1A1 DDI liability by running an in silico DDI study with the UGT1A1 inhibitor atazanavir. A minor effect with an area under the plasma concentration-time curve (AUC) ratio of 1.12 and a peak plasma concentration ratio of 1.04 was predicted, which indicates that there is no clinically relevant DDI interaction anticipated. Additionally, the effect of potential genetic polymorphisms of UGT1A1 and UGT1A9 was evaluated, which showed that an average modest increase of up to 1.7-fold in AUC may be expected in the case of concomitantly reduced UGT1A1 and UGT1A9 activity for subpopulations expressing non-wild-type variants for both isoforms. This study is a first cornerstone to qualify the PK-Sim platform for use of UGT-mediated DDI predictions, including PBPK models of perpetrators, such as mefenamic acid and atazanavir, and sensitive UGT substrates, such as dapagliflozin and raltegravir.

Clinical Pharmacokinetic and Pharmacodynamic Profile of Vericiguat.

Vericiguat is an oral soluble guanylate cyclase stimulator and enhances the cyclic guanosine monophosphate pathway independently of nitric oxide as well as synergistically in normal- and low-nitric oxide conditions. This review describes the pharmacokinetic and pharmacodynamic profile of vericiguat and summarizes the effect of vericiguat on cardiac electrophysiology and population pharmacokinetic/pharmacodynamic relationships. Vericiguat demonstrates virtually complete absorption and increased exposure with food. Vericiguat has high oral bioavailability when taken with food (93.0%) with dose-proportional pharmacokinetics in healthy volunteers. Vericiguat has slightly less than dose-proportional pharmacokinetics with a slight decrease in bioavailability at higher doses in patients with heart failure (HF) with reduced ejection fraction (HFrEF). Vericiguat is a low-clearance drug, with a half-life of approximately 20 h in healthy volunteers and 30 h in patients with HFrEF. Most drug metabolism is achieved by glucuronidation. Vericiguat has pharmacodynamic effects as expected from its pharmacological mechanism of action (i.e., relaxation of the smooth muscles in the vasculature leading to changes in hemodynamics). In the VICTORIA trial (NCT02861534), which enrolled patients with HFrEF, no meaningful exposure-response relationships for the incidence of symptomatic hypotension or syncope were evident. There were no significant imbalances in the incidence of undesirable hemodynamic-related effects (symptomatic hypotension and syncope) in subgroups with HFrEF defined by sex, age, race, and renal impairment. In addition, most patients achieved the 10-mg target dose per the blood pressure-guided titration regimen. No dose adjustments due to body weight, age, sex, race, or hepatic/renal impairment are necessary in adult patients with HFrEF. Observed and predicted changes in vericiguat exposure when co-administered with perpetrator drugs were small and not clinically meaningful. In addition, vericiguat has low potential as a perpetrator to affect exposure and/or pharmacodynamic effects of drugs commonly prescribed in patients with heart failure; therefore, no dose adjustment of these drugs is required in patients taking vericiguat. There is limited experience on the combined use of vericiguat with long-acting nitrates in patients with HFrEF. The ongoing VICTOR trial (NCT05093933), which is investigating vericiguat in patients with HFrEF, permits the co-administration of long-acting nitrates. Combined use of vericiguat and phosphodiesterase type-5 inhibitors has not been studied in patients with HFrEF and is therefore not recommended because of the potential increased risk for symptomatic hypotension. Vericiguat was not associated with electrophysiological abnormalities in preclinical and clinical studies up to the approved dose of 10 mg at steady state. Vericiguat is approved for the treatment of recently decompensated patients with worsening HFrEF. Vericiguat's safety and efficacy profile in patients with HFrEF will be further characterized by the VICTOR trial (NCT05093933) in adults without recent decompensation and in a pediatric population with HF due to left ventricular systolic dysfunction (VALOR trial, NCT05714085).

Assessing QTc Effects of Vericiguat Using Two Different Concentration-QTc Modeling Approaches.

BACKGROUND AND OBJECTIVES: Vericiguat is a soluble guanylate cyclase stimulator indicated to reduce the risk of cardiovascular death and hospitalization due to heart failure. A dedicated QTc study in patients with chronic coronary syndromes demonstrated no clinically relevant QTc effect of vericiguat for exposures across the therapeutic dose range (2.5-10 mg). Interval prolongation concentration-QTc (C-QTc) modeling was performed to complement the statistical evaluations of QTc in the dedicated QTc study. METHODS: Individual time-matched, baseline- and placebo-corrected Fridericia-corrected QT interval values (ΔΔQTcF) were derived. Two approaches for ΔΔQTcF calculation were investigated: (1) ΔΔQTcF correction with data from a single baseline (as in the primary statistical analysis); and (2) ΔΔQTcF correction with a modeled baseline (considering all available individual non-treatment baselines). The ΔΔQTcF values were related to observed vericiguat concentrations with linear mixed-effects modeling. RESULTS: For both modeling approaches, a positive relationship was found between ΔΔQTcF and vericiguat concentration; however, the slope for the single-baseline approach was not statistically significant, whereas the slope from the modeled-baseline approach was statistically significant. The upper bound of the two-sided 90% confidence interval for model-derived QTc was < 10 ms at the highest observed exposure (745 µg/L; investigated dose range 2.5-10 mg). CONCLUSION: By applying a single-baseline approach and a modeled-baseline approach that integrated all available QTc data across doses to characterize the QTc prolongation potential, this study showed that vericiguat 2.5-10 mg is not associated with clinically relevant QTc effects, in line with the conclusion from the primary statistical analysis. CLINICAL TRIALS REGISTRATION NUMBER: ClinicalTrials.gov NCT03504982.

Population pharmacokinetics of riociguat in a pediatric population (aged ≥ 6 years) with pulmonary arterial hypertension.

BACKGROUND: The PATENT-CHILD study investigated riociguat in children aged ≥ 6 to <18 years with pulmonary arterial hypertension (PAH) treated with tablets or an oral pediatric suspension based on bodyweight-adjusted dosing of up to 2.5 mg three times daily. PATENT-CHILD demonstrated an acceptable riociguat safety profile and individual plasma concentrations in pediatric patients were consistent with those in adult patients. METHODS: Using the data set from PATENT-CHILD and building on existing population pharmacokinetic (PK) models for riociguat and its major metabolite (M1) in adults with PAH, a coupled riociguat-M1 PK model was developed. The final model developed incorporated a one-compartment model for riociguat, coupled to a one-compartment model for M1, allowing for presystemic formation of M1. It included allometric scaling exponents for bodyweight. RESULTS: Apparent clearance of riociguat was similar in children and adult patients with PAH (median [interquartile range] 2.20 [1.75-3.44] and 2.08 L/h [1.55-2.97]). Factors contributing to lower PK exposure were lower riociguat maintenance dose in PATENT-CHILD, and a higher riociguat clearance in some adolescent patients, compared with adult patients. No effects of formulation, sex, or age on riociguat PK were observed. An exploratory PK/pharmacodynamics analysis found the increase in 6-min walking distance in pediatric patients treated with riociguat was not related to riociguat PK. CONCLUSIONS: Body size is the main determinant of PK in growing children, and the model supports clinical data that, for children weighing < 50 kg, a bodyweight-adjusted dose of riociguat should be used to achieve a similar exposure to that observed in adults with PAH.

Coding of sound direction in the auditory periphery of the lake sturgeon, Acipenser fulvescens.

The lake sturgeon, Acipenser fulvescens, belongs to one of the few extant nonteleost ray-finned fishes and diverged from the main vertebrate lineage about 250 million years ago. The aim of this study was to use this species to explore the peripheral neural coding strategies for sound direction and compare these results to modern bony fishes (teleosts). Extracellular recordings were made from afferent neurons innervating the saccule and lagena of the inner ear while the fish was stimulated using a shaker system. Afferents were highly directional and strongly phase locked to the stimulus. Directional response profiles resembled cosine functions, and directional preferences occurred at a wide range of stimulus intensities (spanning at least 60 dB re 1 nm displacement). Seventy-six percent of afferents were directionally selective for stimuli in the vertical plane near 90° (up down) and did not respond to horizontal stimulation. Sixty-two percent of afferents responsive to horizontal stimulation had their best axis in azimuths near 0° (front back). These findings suggest that in the lake sturgeon, in contrast to teleosts, the saccule and lagena may convey more limited information about the direction of a sound source, raising the possibility that this species uses a different mechanism for localizing sound. For azimuth, a mechanism could involve the utricle or perhaps the computation of arrival time differences. For elevation, behavioral strategies such as directing the head to maximize input to the area of best sensitivity may be used. Alternatively, the lake sturgeon may have a more limited ability for sound source localization compared with teleosts.

Using expression data for quantification of active processes in physiologically based pharmacokinetic modeling.

Active processes involved in drug metabolization and distribution mediated by enzymes, transporters, or binding partners mostly occur simultaneously in various organs. However, a quantitative description of active processes is difficult because of limited experimental accessibility of tissue-specific protein activity in vivo. In this work, we present a novel approach to estimate in vivo activity of such enzymes or transporters that have an influence on drug pharmacokinetics. Tissue-specific mRNA expression is used as a surrogate for protein abundance and activity and is integrated into physiologically based pharmacokinetic (PBPK) models that already represent detailed anatomical and physiological information. The new approach was evaluated using three publicly available databases: whole-genome expression microarrays from ArrayExpress, reverse transcription-polymerase chain reaction-derived gene expression estimates collected from the literature, and expressed sequence tags from UniGene. Expression data were preprocessed and stored in a customized database that was then used to build PBPK models for pravastatin in humans. These models represented drug uptake by organic anion-transporting polypeptide 1B1 and organic anion transporter 3, active efflux by multidrug resistance protein 2, and metabolization by sulfotransferases in liver, kidney, and/or intestine. Benchmarking of PBPK models based on gene expression data against alternative models with either a less complex model structure or randomly assigned gene expression values clearly demonstrated the superior model performance of the former. Besides accurate prediction of drug pharmacokinetics, integration of relative gene expression data in PBPK models offers the unique possibility to simultaneously investigate drug-drug interactions in all relevant organs because of the physiological representation of protein-mediated processes.

Population Pharmacokinetics of Vericiguat in Patients With Heart Failure With Reduced Ejection Fraction: An Integrated Analysis.

Vericiguat, a novel stimulator of soluble guanylate cyclase (sGC), is indicated for the treatment of patients following a hospitalization for heart failure or need for outpatient intravenous diuretics, with symptomatic chronic heart failure and ejection fraction less than 45%. Pharmacokinetic (PK) data from the phase II trial SOCRATES-REDUCED (Soluble Guanylate Cyclase Stimulator in Heart Failure Study) and the phase III trial VICTORIA (Vericiguat Global Study in Patients With Heart Failure With Reduced Ejection Fraction) were used to characterize vericiguat PK. A total of 8,092 concentration records from 2,321 participants (362 from SOCRATES-REDUCED and 1,959 from VICTORIA) were utilized for the development of the population PK model. The final PK model was a one-compartment model with first-order absorption and linear elimination. Baseline body weight and time-varying body weight were identified as statistically significant covariates affecting apparent clearance (CL/F) and volume of distribution, respectively. Age, sex, race, bilirubin, estimated glomerular filtration rate, and albumin did not affect vericiguat PK. Baseline disease-related factors, such as left ventricular ejection fraction, New York Heart Association (NYHA) class, and N-terminal pro B-type natriuretic peptide, also did not influence vericiguat PK. Since vericiguat is a titrated drug, the impact of vericiguat PK on the titration to and maintenance of the target dose in VICTORIA was assessed. The distribution of steady-state doses in VICTORIA was similar across CL/F quartiles, suggesting that the ability to reach and maintain dosing at the target 10-mg dose was not related to vericiguat exposure.

Diisopropyl-ammonium methane-sulfonate.

The title molecular salt, C(6)H(16)N(+)·CH(3)SO(3) (-), has been determined at 150 K. Two diisopropyl-ammonium cations (dipH) and two anions form N-H⋯O hydrogen-bonded cyclic dimers lying around centers of symmetry. Only two of the three O atoms of the methane-sulfonate anion are involved in hydrogen bonding, resulting in slightly longer S-O bond lengths. The title structure represents an example of a sulfonate anion that is part of a hydrogen-bonding R(4) (4)(12) graph-set motif, which is well known for related dipH acetates. Additionally, the Raman and the IR spectroscopic data for the title compound are presented.

NT-proBNP Qualifies as a Surrogate for Clinical End Points in Heart Failure.

N-terminal pro-B-type natriuretic peptide (NT-proBNP) is a well-established biomarker in heart failure (HF) but controversially discussed as a potential surrogate marker in HF trials. We analyzed the NT-proBNP/mortality relationship in real-world data (RWD) of 108,330 HF patients from the IBM Watson Health Explorys database and compared it with the NT-proBNP / clinical event end-point relationship in 20 clinical HF studies. With a hierarchical statistical model, we quantified the functional relationship and interstudy variability. To independently qualify the model, we predicted outcome hazard ratios in five phase III HF studies solely based on NT-proBNP measured early in the respective study. In RWD and clinical studies, the relationship between NT-proBNP and clinical outcome is well described by an Emax model. The NT-proBNP independent baseline risk (R0 , RWD/studies median (interstudy interquartile range): 5.5%/3.0% (1.7-4.9%)) is very low compared with the potential NT-proBNP-associated maximum risk (Rmax : 55.2%/79.4% (61.5-89.0%)). The NT-proBNP concentration associated with the half-maximal risk is comparable in RWD and across clinical studies (EC50 : 3,880/2,414 pg/mL (1,460-4,355 pg/mL)). Model-based predictions of phase III outcomes, relying on short-term NT-proBNP data only, match final trial results with comparable confidence intervals. Our analysis qualifies NT-proBNP as a surrogate for clinical outcome in HF trials. NT-proBNP levels after short treatment durations of less than 10 weeks quantitatively predict hazard ratios with confidence levels comparable to final trial readout. Early NT-proBNP measurement can therefore enable shorter and smaller but still reliable HF trials.

Population Pharmacokinetics and Pharmacodynamics of Vericiguat in Patients with Heart Failure and Reduced Ejection Fraction.

BACKGROUND: Vericiguat, a stimulator of soluble guanylate cyclase, has been developed as a first-in-class therapy for worsening chronic heart failure in adults with left ventricular ejection fraction < 45%. OBJECTIVE: The objective of this article was to characterize the pharmacokinetics and pharmacokinetic variability of vericiguat combined with guideline-directed medical therapy (standard of care), and identify exposure-response relationships for safety (hemodynamics) and pharmacodynamic markers of efficacy (N-terminal pro-B-type natriuretic peptide concentration [NT-proBNP]) in patients with heart failure and left ventricular ejection fraction < 45% in the SOCRATES-REDUCED study (NCT01951625). METHODS: Vericiguat and NT-proBNP plasma concentrations in 454 and 432 patients in SOCRATES-REDUCED, respectively, were analyzed using nonlinear mixed-effects modeling. RESULTS: Vericiguat pharmacokinetics were well described by a one-compartment model with apparent clearance, apparent volume of distribution, and absorption rate constant. Age, bodyweight, plasma bilirubin, and creatinine clearance were identified as significant covariates on apparent clearance; sex and bodyweight on apparent volume of distribution; and bodyweight and plasma albumin level on absorption rate constant. Pharmacokinetic/pharmacodynamic analysis showed initial minor and transient effects of vericiguat on blood pressure with low clinical impact. There were no changes in heart rate following initial or repeated vericiguat administration. An exposure-dependent and time-dependent turnover pharmacokinetic/pharmacodynamic model for NT-proBNP described production and elimination rates and an demonstrated exposure-dependent reduction in [NT-proBNP] by vericiguat plus standard of care compared with placebo plus standard of care. This effect was dependent on baseline [NT-proBNP]. CONCLUSIONS: Vericiguat has predictable pharmacokinetics, with no long-term effects on blood pressure in patients with heart failure and left ventricular ejection fraction < 45%. A pharmacokinetic/pharmacodynamic model described a vericiguat exposure-dependent reduction of NT-proBNP. CLINICAL TRIAL IDENTIFIER: NCT01951625.

Predictive Performance of Physiology-Based Pharmacokinetic Dose Estimates for Pediatric Trials: Evaluation With 10 Bayer Small-Molecule Compounds in Children.

Development and guidance of dosing schemes in children have been supported by physiology-based pharmacokinetic (PBPK) modeling for many years. PBPK models are built on a generic basis, where compound- and system-specific parameters are separated and can be exchanged, allowing the translation of these models from adults to children by accounting for physiological differences. Owing to these features, PBPK modeling is a valuable approach to support clinical decision making for dosing in children. In this analysis, we evaluate pediatric PBPK models for 10 small-molecule compounds that were applied to support clinical decision processes at Bayer for their predictive power in different age groups. Ratios of PBPK-predicted to observed PK parameters for the evaluated drugs in different pediatric age groups were estimated. Predictive performance was analyzed on the basis of a 2-fold error range and the bioequivalence range (ie, 0.8 ≤ predicted/observed ≤ 1.25). For all 10 compounds, all predicted-to-observed PK ratios were within a 2-fold error range (n = 27), with two-thirds of the ratios within the bioequivalence range (n = 18). The findings demonstrate that the pharmacokinetics of these compounds was successfully and adequately predicted in different pediatric age groups. This illustrates the applicability of PBPK for guiding dosing schemes in the pediatric population.

Frequency tuning and intensity coding of sound in the auditory periphery of the lake sturgeon, Acipenser fulvescens.

Acipenser fulvescens, the lake sturgeon, belongs to one of the few extant non-teleost ray-finned (bony) fishes. The sturgeons (family Acipenseridae) have a phylogenetic history that dates back about 250 million years. The study reported here is the first investigation of peripheral coding strategies for spectral analysis in the auditory system in a non-teleost bony fish. We used a shaker system to simulate the particle motion component of sound during electrophysiological recordings of isolated single units from the eighth nerve innervating the saccule and lagena. Background activity and response characteristics of saccular and lagenar afferents (such as thresholds, response-level functions and temporal firing) resembled the ones found in teleosts. The distribution of best frequencies also resembled data in teleosts (except for Carassius auratus, goldfish) tested with the same stimulation method. The saccule and lagena in A. fulvescens contain otoconia, in contrast to the solid otoliths found in teleosts, however, this difference in otolith structure did not appear to affect threshold, frequency tuning, intensity- or temporal responses of auditory afferents. In general, the physiological characteristics common to A. fulvescens, teleosts and land vertebrates reflect important functions of the auditory system that may have been conserved throughout the evolution of vertebrates.

Calcium ions as "miscibility switch": colocalization of surfactant protein B with anionic lipids under absolute calcium free conditions.

One of the main determinants of lung surfactant function is the complex interplay between its protein and lipid components. The lipid specificity of surfactant protein B (SP-B), however, and the protein's ability to selectively squeeze out lipids, has remained contradictory. In this work we present, for the first time to our knowledge, by means of time-of-flight secondary ion mass spectrometry chemical imaging, a direct evidence for colocalization of SP-B as well as its model peptide KL(4) with negatively charged dipalmitoylphosphatidylglycerol under absolute calcium free conditions. Our results prove that protein/lipid localization depends on the miscibility of all surfactant components, which itself is influenced by subphase ionic conditions. In contrast to our earlier studies reporting SP-B/KL(4) colocalization with zwitterionic dipalmitoylphosphatidylcholine, in the presence of even the smallest traces of calcium, we finally evidence an apparent reversal of protein/lipid mixing behavior upon calcium removal with ethylene diamine tetraacetic acid. In addition, scanning force microscopy measurements reveal that by depleting the subphase from calcium ions the protrusion formation ability of SP-B or KL(4) is not hampered. However, in the case of KL(4), distinct differences in protrusion morphology and height are visible. Our results support the idea that calcium ions act as a "miscibility switch" in surfactant model systems and probably are one of the major factors steering lipid/protein mixing behavior as well as influencing the protein's protrusion formation ability.

Gestation-Specific Changes in the Anatomy and Physiology of Healthy Pregnant Women: An Extended Repository of Model Parameters for Physiologically Based Pharmacokinetic Modeling in Pregnancy.

BACKGROUND: In the past years, several repositories for anatomical and physiological parameters required for physiologically based pharmacokinetic modeling in pregnant women have been published. While providing a good basis, some important aspects can be further detailed. For example, they did not account for the variability associated with parameters or were lacking key parameters necessary for developing more detailed mechanistic pregnancy physiologically based pharmacokinetic models, such as the composition of pregnancy-specific tissues. OBJECTIVES: The aim of this meta-analysis was to provide an updated and extended database of anatomical and physiological parameters in healthy pregnant women that also accounts for changes in the variability of a parameter throughout gestation and for the composition of pregnancy-specific tissues. METHODS: A systematic literature search was carried out to collect study data on pregnancy-related changes of anatomical and physiological parameters. For each parameter, a set of mathematical functions was fitted to the data and to the standard deviation observed among the data. The best performing functions were selected based on numerical and visual diagnostics as well as based on physiological plausibility. RESULTS: The literature search yielded 473 studies, 302 of which met the criteria to be further analyzed and compiled in a database. In total, the database encompassed 7729 data. Although the availability of quantitative data for some parameters remained limited, mathematical functions could be generated for many important parameters. Gaps were filled based on qualitative knowledge and based on physiologically plausible assumptions. CONCLUSION: The presented results facilitate the integration of pregnancy-dependent changes in anatomy and physiology into mechanistic population physiologically based pharmacokinetic models. Such models can ultimately provide a valuable tool to investigate the pharmacokinetics during pregnancy in silico and support informed decision making regarding optimal dosing regimens in this vulnerable special population.

Development of a Physiologically Based Pharmacokinetic Modelling Approach to Predict the Pharmacokinetics of Vancomycin in Critically Ill Septic Patients.

BACKGROUND AND OBJECTIVES: Sepsis is characterised by an excessive release of inflammatory mediators substantially affecting body composition and physiology, which can be further affected by intensive care management. Consequently, drug pharmacokinetics can be substantially altered. This study aimed to extend a whole-body physiologically based pharmacokinetic (PBPK) model for healthy adults based on disease-related physiological changes of critically ill septic patients and to evaluate the accuracy of this PBPK model using vancomycin as a clinically relevant drug. METHODS: The literature was searched for relevant information on physiological changes in critically ill patients with sepsis, severe sepsis and septic shock. Consolidated information was incorporated into a validated PBPK vancomycin model for healthy adults. In addition, the model was further individualised based on patient data from a study including ten septic patients treated with intravenous vancomycin. Models were evaluated comparing predicted concentrations with observed patient concentration-time data. RESULTS: The literature-based PBPK model correctly predicted pharmacokinetic changes and observed plasma concentrations especially for the distribution phase as a result of a consideration of interstitial water accumulation. Incorporation of disease-related changes improved the model prediction from 55 to 88% within a threshold of 30% variability of predicted vs. observed concentrations. In particular, the consideration of individualised creatinine clearance data, which were highly variable in this patient population, had an influence on model performance. CONCLUSION: PBPK modelling incorporating literature data and individual patient data is able to correctly predict vancomycin pharmacokinetics in septic patients. This study therefore provides essential key parameters for further development of PBPK models and dose optimisation strategies in critically ill patients with sepsis.