Dose-response Model Research Articles

Quantitative Assessment of Human Health Risks Associated with Heavy Metal and Bacterial Pollution in Groundwater from Mankweng in Limpopo Province, South Africa

Heavy metal and microbial pollution in groundwater raises health concerns due to its adverse effects. This study aimed to assess the health risks associated with heavy metal and bacterial pollution in groundwater in Mankweng. Heavy metals and Escherichia coli were detected using inductively coupled plasma mass spectrophotometry and a Colilert system, respectively. The heavy metal pollution index (HPI) and non-carcinogenic and carcinogenic risks were computed. The β-Poisson dose–response model was employed to predict the probability of E. coli infection. The metals’ concentrations were all within the permissible limits of the South African National Standard (SANS). However, Pb levels at sites E and G exceeded the World Health Organization (WHO) guideline (≤0.01 mg/L). HPI values were all less than 100, indicative of low contamination. The hazard quotient values were all less than 1, except for vanadium. The cumulative cancer risk ranged between 3.06 × 10−5 and 1.81 × 10−4 and between 3.55 × 10−5 and 2.20 × 10−4 for adults and children, respectively. E. coli was only detected at site L. The annual risk of E. coli infection exceeded the WHO risk limit of 10−4. The results underscore the need for the regular monitoring of groundwater.

Pharmacokinetic/pharmacodynamic analysis of geographic atrophy lesion area in patients receiving pegcetacoplan treatment or sham.

Pegcetacoplan is a complement C3/C3b inhibitor indicated for the treatment of geographic atrophy (GA). A population pharmacokinetic (PK)/pharmacodynamic (PD) analysis of pegcetacoplan used GA lesion area measurements from three clinical studies to determine the effect of pegcetacoplan exposure on GA progression. A base disease progression model was developed using data from sham-treated eyes and untreated fellow eyes, followed by treatment effect assessment in dose-response and PK/PD models. In total, 1501 patients from FILLY (NCT02503332), OAKS (NCT03525613), and DERBY (NCT03525600) received intravitreal pegcetacoplan 15 mg monthly or every other month (EOM) or sham treatment monthly or EOM and were included in the population analysis of lesion area. Disease progression over time was adequately described as linear-with-time over the 24-month maximal study duration. Disease-specific covariates associated with slower lesion growth were unilateral, unifocal, and subfoveal GA lesions and >20 intermediate or large drusen groups (≥63 μm) at baseline. The dose-response model estimated 0.80-fold (95% CI: 0.75, 0.84) and 0.83-fold (95% CI: 0.78, 0.87) reductions in GA lesion growth rate with pegcetacoplan monthly and EOM, respectively, versus sham. A relationship between vitreous humor concentration and GA lesion growth rate was quantified as 2.6% per unit of log-transformed vitreous pegcetacoplan concentration in the PK/PD model. PK/PD predictions of treatment effect based on exposure (pegcetacoplan monthly: 0.80 [90% CI: 0.77, 0.84]; pegcetacoplan EOM: 0.83 [90% CI: 0.80, 0.86]) were consistent with predictions based on dose response. These results support the benefit of pegcetacoplan administered monthly or EOM in slowing GA lesion growth.

Benchmark dose modeling for epidemiological dose-response assessment using case-control studies.

Following a previous article that focused on integrating epidemiological data from prospective cohort studies into toxicological risk assessment, this paper shifts the focus to case-control studies. Specifically, it utilizes the odds ratio (OR) as the main epidemiological measure, aligning it with the benchmark dose (BMD) methodology as the standard dose-response modeling approach to determine chemical toxicity values for regulatory risk assessment. A standardized BMD analysis framework has been established for toxicological data, including input data requirements, dose-response models, definitions of benchmark response, and consideration of model uncertainty. This framework has been enhanced by recent methods capable of handling both cohort and case-control studies using summary data that have been adjusted for confounders. The present study aims to investigate and compare the "effective count" based BMD modeling approach, merged with an algorithm used for converting odds ratio to relative risk in cohort studies with partial data information (i.e., the Wang algorithm), with the adjusted OR-based BMD analysis approach. The goal is to develop an adequate BMD modeling framework that can be generalized for analyzing published case-control study data. As in the previous study, these methods were applied to a database examining the association between bladder and lung cancer and inorganic arsenic exposure. The results indicate that estimated BMDs and BMDLs are relatively consistent across both methods. However, modeling adjusted OR values as continuous data for BMD estimation aligns better with established practices in toxicological BMD analysis, making it a more generalizable approach.

Modeling the health impact of wastewater contamination events in drinking water networks

Pathogen intrusion in drinking water systems can pose severe health risks. To better prepare in planning and responding to such events, computational models that capture the intrusion and health impact dynamics are needed. This study presents a novel benchmark testbed that integrates current knowledge on pathogen transport and fate in chlorinated systems and can assess infection risk from contamination events. The model considers organic matter degradation, chlorine decay mechanisms, pathogen inactivation kinetics, as well as stochastic water demands.We studied modeling of wastewater intrusion events that can occur anywhere within a chlorinated and non-chlorinated network. We applied the Quantitative Microbial Risk Assessment framework focusing on three pathogens: enterovirus, Campylobacter, and Cryptosporidium, and their respective dose-response models. Synthetic household-level water demand time series were used to model the individual water consumption timing and calculate the infection risk (exposure via ingestion).Model outcomes indicate that while chlorination aids mitigation, larger contaminations can still lead to infections due to chlorine resistance (for Cryptosporidium) and chlorine depletion at the contamination point. In our example scenarios, chlorine-susceptible pathogens infected of the downstream population, while chlorine-resistant ones infected the entire downstream population. Enterovirus infection risk is higher, despite the concentrations in the contamination source being lower, due to the lower susceptibility to chlorine than Campylobacter. In non-chlorinated networks, the modeled wastewater contamination events led to infection risk in the total population, depending on the contamination location. Hydraulic uncertainty had a limited influence on infection risk. Furthermore, Campylobacter’s infection risk is more sensitive to the initial concentration in the contamination source whereas enterovirus infection risk to the inactivation rate. The model further indicates that the time window for effective mitigation of the magnitude of a waterborne outbreak is short (within hours).

Fluoride exposure and risk of fractures: a systematic review and dose-response meta-analysis

Abstract Introduction Fluoride (F) is a widespread natural element, whose exposure occurs mostly through drinking water, fluoridated foods and use of toothpastes. At high levels, it may adversely affect human health by altering thyroid and cognitive function in children, and inducing dental and skeletal fluorosis. Since bone health significantly impacts quality of life, we performed a systematic review and meta-analysis to evaluate the effect of F exposure on risk of bone fractures. Methods We conducted a literature search in online databases and selected studies that were carried out in humans and reported risk estimates with 95% confidence intervals for bone fractures according to F exposure. We eventually performed a meta-analysis using a random effects model, comparing the highest versus the lowest exposure, and one-stage dose-response model, to explore the shape of the association. Results Of the 1052 potentially eligible articles, 28 were included in the quantitative analyses. Most studies were conducted in adults (n = 26) and in Western countries (North America=16, Europe=11) and assessed fluoride exposure in drinking water, urine, serum, toenail or diet. The preliminary dose-response curve showed a positive non-linear relation between F exposure through drinking water and bone fracture risk, regardless of site, starting at 1.5 mg/L. Sex-stratified analyses, based on a lower number of studies, showed similar trends, with an indication of higher susceptibility in males compared with females. Conclusions Overall, risk of bone fractures appears to non-linearly increase along with exposure to fluoride in drinking water, regardless of bone site and sex, at levels of exposure above the WHO standard and similar to those that have associated to altered thyroid and cognitive function. Under a public health perspective, fluoride in drinking water should be kept below 1.5 mg/L to prevent bone fractures. Key messages • Our analysis revealed a positive non-linear association between fluoride in drinking water and bone fracture risk. • Public Health actions should be oriented in keeping fluoride in drinking water below 1.5 mg/L to prevent bone fractures.

Levofloxacin activity at increasing doses in a murine model of fluoroquinolone-susceptible and -resistant tuberculosis.

High-dose levofloxacin was explored in a clinical trial against multidrug-resistant tuberculosis and failed to show increased efficacy. In this study, we used a murine model to explore the efficacy of a dose increase in levofloxacin monotherapy beyond the maximum dose evaluated in humans. A total of 120 4-week-old female BALB/c mice were intravenously infected with 106 CFU of Mycobacterium tuberculosis H37Rv wild-type (WT) or isogenic H37Rv mutants harboring GyrA A90V or D94G substitutions; the MICs were 0.25, 4, and 6 µg/mL, respectively. Levofloxacin 250 and 500 mg/kg were given every 12 h (q12h) orally for 4 weeks. Pharmacokinetic parameters were determined after five doses. These two regimens decreased lung bacillary load in mice infected with H37Rv WT but not in mice infected with the A90V and D94G mutants. Levofloxacin 250 mg/kg q12h in mice generated pharmacokinetic parameters equivalent to 1,000 mg/d in humans, whereas 500 mg/kg q12h generated a twofold greater exposure than the highest equivalent dose tested in humans (1,500 mg/d). In our dose-response model, the effective concentration at 50% (EC50) produced an AUC/MIC (AUC0-24h/MIC) ratio of 167.9 ± 27.5, and at EC80 it was 281.2 ± 97.3. Based on this model, high-dose levofloxacin regimens above 1,000 mg/d are not expected to cause a significant increase in bactericidal activity. This study suggests no benefit of high-dose levofloxacin above 1,000 mg/d in the treatment of fluoroquinolone-susceptible or -resistant tuberculosis.

Updated Risk Assessment of Cannabidiol in Foods Based on Benchmark Dose–Response Modeling

Cannabidiol (CBD), a non-psychotropic main component of the Cannabis plant, has been approved as a drug in the European Union (EU) under the name “Epidyolex”. However, its approval process as a food ingredient under the Novel Food Regulation was paused by the European Food Safety Authority (EFSA) due to a lack of safety data. Nevertheless, there is a growing, unregulated market in which CBD is advertised with various health claims and dosage instructions. Of particular concern is its toxic effect on the liver and possible reproductive toxicity in humans. Studies suitable for calculating the benchmark dose were identified from the available data. Animal studies yielded a benchmark dose lower confidence limit (BMDL) of 43 mg/kg bw/day, which translates into a safe human dose of approximately 15 mg/day. Only the Lowest-Observed-Adverse-Effect Level (LOAEL) of 4.3 mg/kg bw/day could be identified from the human data. This updated risk assessment confirmed a health-based guidance value (HBGV) of 10 mg/day based on human LOAEL. Despite the existing data gaps, preliminary regulation appears advisable because the current form of the gray CBD market is unacceptable from the standpoint of consumer safety and protection.

Decay hazard of wood exposed in-ground in changing climates in Germany

ABSTRACT The ability to identify locations that have a high risk of fungal decay is important for service life planning and analysing changes in risk can help inform scenarios where climate change may shift some areas into states that are more suitable for decay. The ERA5-Land database was used to obtain soil moisture and temperature data, which was applied in a dose–response model for in-ground wood decay. Dose was used as an indicator of decay risk and to produce hazard maps over Germany for the past two climate normals (1963–1992 and 1993–2022). There was an increase of 3.16 dose days over Germany. Brandenburg and Mecklenburg-Vorpommern, had the highest decay risk in both climate normals and southern states experienced the lowest decay risk. In Germany, larger dose increases were seen in central to southern latitude regions and mid to high altitudes. With further climate change, conditions that are most suitable for in-ground wood decay may shift to locations that previously did not experience such risk. It is important to be informed of the durability requirements of wood products in areas where increased resistance may be required.

Comparing robust proton versus online adaptive photon radiotherapy for short-course treatment of rectal cancer

Background and purposeImage-guided proton beam therapy (IG-PBT) and cone-beam CT (CBCT)-based online adaptive photon radiotherapy (oART) have potentials to restrict radiation toxicity. They are both hypothesised to reduce therapy limiting bowel toxicity in the multimodality treatment of locally advanced rectal cancer (LARC). This study aimed to quantify the difference in relevant dose-volume metrics for these modalities. Material and MethodsSix-degrees-of-freedom IG-PBT and oART short-course radiotherapy (SCRT) were simulated for 18 LARC patients. Relative biological effectiveness (RBE) was 1.1 for IG-PBT. Delivered dose was evaluated using post-CBCTs. Target coverage was considered robust if average dose to 99 % of the clinical target volume was ≥ 95 % of the prescription. Organ at risk (OAR) doses were compared using dose-volume histograms and severe bowel toxicity estimated using dose–response modelling. ResultsTarget coverage was robust in all patients for oART and all but one patient for IG-PBT. For the main OARs, IG-PBT increased the volume exposed to ≥ 15 Gy (RBE), but reduced volumes exposed to lower doses. Both low- and high-dose exposure to bowel loops were significantly different between the modalities (median (interquartile range) IG-PBT-V8.9Gy(RBE) = 92 cm3 (51–156), oART-V8.9Gy(RBE) = 166 cm3 (107–234), p < 0.001; IG-PBT-V23Gy(RBE) = 62 cm3 (25–106), oART-V23Gy(RBE) = 38 cm3 (18–75), p < 0.001), translating into similar total grade ≥ 3 bowel toxicity risk. ConclusionIG-PBT and oART delivered comparable and satisfying target coverage in SCRT for LARC with similar estimated risk of severe bowel toxicity. Volumes of OAR exposed to 15 Gy (RBE) or more were reduced by oART, while IG-PBT reduced the volumes receiving doses below this level.

Temperature-mortality associations by age and cause: a multi-country multi-city study.

Heterogeneity in temperature-mortality relationships across locations may partly result from differences in the demographic structure of populations and their cause-specific vulnerabilities. Here we conduct the largest epidemiological study to date on the association between ambient temperature and mortality by age and cause using data from 532 cities in 33 countries. We collected daily temperature and mortality data from each country. Mortality data was provided as daily death counts within age groups from all, cardiovascular, respiratory, or noncardiorespiratory causes. We first fit quasi-Poisson regression models to estimate location-specific associations for each age-by-cause group. For each cause, we then pooled location-specific results in a dose-response multivariate meta-regression model that enabled us to estimate overall temperature-mortality curves at any age. The age analysis was limited to adults. We observed high temperature effects on mortality from both cardiovascular and respiratory causes compared to noncardiorespiratory causes, with the highest cold-related risks from cardiovascular causes and the highest heat-related risks from respiratory causes. Risks generally increased with age, a pattern most consistent for cold and for nonrespiratory causes. For every cause group, risks at both temperature extremes were strongest at the oldest age (age 85 years). Excess mortality fractions were highest for cold at the oldest ages. There is a differential pattern of risk associated with heat and cold by cause and age; cardiorespiratory causes show stronger effects than noncardiorespiratory causes, and older adults have higher risks than younger adults.

Long-chain perfluoroalkylether carboxylic acids PFO5DoA and PFO4DA alter glucose, bile acid, and thyroid hormone homeostasis in fetal rats from 5-day maternal oral exposure

Chemical monitoring studies in North Carolina, USA and Shandong, China have reported detections of perfluoroalkylether carboxylic acids of increasing chain length with ether bonds between each fluorinated carbon. Despite detection there is limited hazard data available to inform risk assessment. Here, we exposed pregnant Sprague-Dawley rats to two of these compounds, perfluoro-3,5,7,9-butaoxadecanoic acid (PFO4DA) and perfluoro-3,5,7,9,11-pentaoxadodecanoic acid (PFO5DoA), from gestation days 18-22 across a series of doses (0.3 - 62.5 mg/kg/d) via oral gavage. PFO5DoA was acutely toxic to rat dams and fetuses at the top two doses (30 and 62.5 mg/kg), while PFO4DA did not cause acute toxicity at any doses tested. PFO5DoA significantly increased maternal liver weight (≥3 mg/kg; 28% increase at 10 mg/kg) while PFO4DA did not affect maternal liver weight up to 62.5 mg/kg. PFO4DA and PFO5DoA both significantly reduced serum total thyroxine in maternal (≥10 mg/kg for both) and fetal (≥1 mg/kg) rats. Both compounds significantly reduced fetal liver glycogen concentrations, increased fetal serum total bile acids, and altered expression levels of multiple genes associated with glucose metabolism in the fetal liver. Serum concentrations of PFO5DoA were higher than PFO4DA in both rat dams and fetuses at equivalent maternal oral doses indicating greater accumulation. Dose response modelling of several fetal endpoints as a function of serum molar concentration indicates PFO5DoA was ∼3-4-fold more potent than PFO4DA. PFO5DoA and PFO4DA produced maternal and fetal toxicity from short-term oral maternal exposure indicating need for additional toxicity data to evaluate potential human health risks.

Population pharmacokinetic and dose-response models of nepadutant, a selective antagonist of the NK2 receptors, in infants with colic.

The aim of the current analyses was to develop a population pharmacokinetic model for nepadutant in infants with colic, and a pharmacokinetic-pharmacodynamic model based on observations of duration of crying and fussing following oral nepadutant administration in infants (3-25 weeks) with colic. The models were developed based on data obtained at baseline and following treatment with placebo, nepadutant 0.1mg/kg or nepadutant 0.5mg/kg administered for 7days. A continuous response variable, duration of crying and fussing in minutes within 2h interval, was assembled based on records from "baby's day" diary. The pharmacokinetics of nepadutant was described by a one-compartment model with first-order absorption and elimination with body weight as a structural covariate incorporated allometrically. For an infant weighing 5.3kg, the estimated apparent clearance was 68.6L/h (12% relative standard error) and exhibited large variability (78% coefficient of variation). The pharmacokinetic-pharmacodynamic model described (i) a circadian rhythm in the response with lowest and highest observations at 4a.m. and 9p.m., respectively, (ii) a placebo effect increasing and flattening out with time in an exponential manner, and (iii) a statistically significant (P < .01) linearly increasing response with dose. The observed and model predicted relative change in response from baseline was -35% and -28% (95% prediction interval -36%; -19%) following placebo, and -44% and -36% (-46%; -27%) after 0.5mg/kg. Population pharmacokinetic and dose-response models were successfully developed characterizing the available nepadutant pharmacokinetics and duration of crying and fussing data in infants.

Risk Assessment of Pulegone in Foods Based on Benchmark Dose-Response Modeling.

This study presents a new risk assessment of pulegone, a substance classified as possibly carcinogenic to humans (Group 2B) by the WHO International Agency for Research on Cancer (IARC). The analysis used data from a two-year carcinogenicity studies in rats and mice conducted by the National Toxicology Program (NTP) in 2011. Because of the absence of a no-observed adverse effect level (NOAEL) in these studies, the benchmark dose (BMD) approach was employed as an alternative risk assessment method. The lowest BMD lower confidence level (BMDL) of 4.8 mg/kg b.w./day among the eight endpoints served as the point of departure for calculating an acceptable daily intake (ADI) of 48 μg/kg b.w./day. This new ADI is significantly lower than the previously established tolerable daily intake of 0.1 mg/kg b.w./day set in 1997. The analysis also considered various genotoxicity studies, which indicate that pulegone's effects follow a nongenotoxic, thresholded mechanism. The estimated intake levels of pulegone in the European Union and USA were below the newly calculated ADI, suggesting a low health risk based on current consumption patterns.

A Dose-Response Study on the Relationship between White Meat Intake and Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) in Southern Italy: Results from the Nutrihep Study.

(1) Background: Metabolic dysfunction-associated liver disease (MASLD) is one of the most important causes of liver disease worldwide. Meat consumption is a growing trend and white meat has been shown to have beneficial effects on cardiometabolic risk factors. The aim of this study was to investigate the dose-response relationship between white meat intake and MASLD at survey level in a Southern Italy setting. (2) Methods: This cross-sectional study encompassed 1192 subjects (509 males, 42.7%) without missing data from the second wave of the NUTRIHEP cohort (2014-2016). Adjusted dose-response modeling was employed for statistical analysis; (3) Results: There were 587 subjects with MASLD (49.2%), i.e., 278 males (54.6%) and 309 females (45.2%). By increasing the intake, an unfavorable influence of white meat on MASLD was significantly revealed in females, whereas a protective effect of white meat was detectable in males. Male sex was shown to be involved in other associations in this study, such as influencing the preference for specific foods such as poultry and chicken skin. (4) Conclusions: Our data suggest that white meat does not have a clear-cut independent dose-response effect on MASLD, but sex may be a trigger moderator for age and BMI, with an increasing unfavorable effect of white meat in women, and a favorable effect in men.

Modeling the Toxicokinetics of Suspensions of Soluble Metallic Nanomaterials.

Proper risk assessment of the many new nanoforms (NFs) that are currently being developed and marketed is hindered by constraints in time and resources for testing their fate and (eco) toxicity profile. This problem has also been encountered in conventional chemical risk assessments, where the definition of related chemical groups can facilitate risk assessment for all class members. Whereas grouping and read-across methods are well established, such approaches are in the early stages of development for NFs. In this study, a modeling framework was developed for grouping NFs into distinct classes regarding the contribution of released ions to suspension-induced toxicity. The framework is based on combining dissolution rate constants of NFs with information about the toxicokinetics of the NFs and the dissolution products formed. The framework is exemplified for the specific case of suspension toxicity of metallic NFs (silver and copper). To this end, principles of mixture toxicity and dose-response modeling are integrated to derive threshold values for the key NF properties determining suspension toxicity: size, shape, and chemical composition. The threshold values thus derived offer a possible solution for the high-throughput screening of NFs according to their morphological and compositional properties in a regulatory context.

Partial Residual Plots as an Integrated Model Diagnostic Tool in Model-Based Meta-Analysis.

The use of partial residual plots (PRPs) was explored as a model diagnostic tool in Model-based Meta-Analysis (MBMA). Mathematical derivations illustrating the concepts were followed by an MBMA example using publicly available literature data of anti-depressive treatments with fluoxetine and venlafaxine. An Emax dose-response model was identified for venlafaxine while a constant drug effect combining all dose levels vs. placebo was identified for fluoxetine. The larger the mean baseline Hamilton Depression Rating (HAMD) score, the larger the expected drug effect (P = 0.0122), based on the likelihood ratio test. Mean baseline HAMD score (range) was 25.4 (23.5, 29.4) and 20.8 (15, 26) while mean placebo change from baseline (range) was -9.02 (-12.2, -4.8) and - 6.22 (-10.9, -1.3) for venlafaxine and fluoxetine, respectively. Average baseline HAMD score appeared larger for venlafaxine compared to fluoxetine, albeit a wider range for fluoxetine. Placebo response seemed lower but also more variable in fluoxetine compared to venlafaxine studies. Observed data points tended to deviate from model predictions when the mean baseline HAMD and placebo response values associated with those data points differed substantially from the corresponding values used for the model prediction. Normalizing observed data addressed this, providing a "like-to-like" comparison with model predictions in PRP when assessing the effect of one covariate (dose) after normalizing for other covariates/effects (placebo response and mean baseline). PRPs provide a robust integrated diagnostic tool in MBMA that uses all data to show the correlation between response and any covariate while controlling for other covariates included in the model.

Progress in toxicogenomics to protect human health.

Toxicogenomics measures molecular features, such as transcripts, proteins, metabolites and epigenomic modifications, to understand and predict the toxicological effects of environmental and pharmaceutical exposures. Transcriptomics has become an integral tool in contemporary toxicology research owing to innovations in gene expression profiling that can provide mechanistic and quantitative information at scale. These data can be used to predict toxicological hazards through the use of transcriptomic biomarkers, network inference analyses, pattern-matching approaches and artificial intelligence. Furthermore, emerging approaches, such as high-throughput dose-response modelling, can leverage toxicogenomic data for human health protection even in the absence of predicting specific hazards. Finally, single-cell transcriptomics and multi-omics provide detailed insights into toxicological mechanisms. Here, we review the progress since the inception of toxicogenomics in applying transcriptomics towards toxicology testing and highlight advances that are transforming risk assessment.

Risk of BSE transmission when fishmeal derived from fish fed bovine spray-dried red blood cells is included in calf milk replacers

The use of residual streams from agricultural production and food consumption containing animal proteins entails the risk of disease transmission as illustrated by the epidemics of bovine spongiform encephalopathy (BSE) and African swine fever. To combat this risk, the use of animal proteins in livestock feed was banned in the European Union, resulting in a drain of valuable proteins from the agricultural system. With an increasing call for a circular food system, the use of residual streams as a feed ingredient needs to be reconsidered with the associated disease risks being assessed and mitigated where needed. In this study, we assessed the BSE risk of bovine spray-dried red blood cells (SDRBC) as an ingredient of aquafeed. Fish fed with bovine SDRBC could indirectly result in exposure of ruminants to BSE infectivity because one of the exemptions of the feed ban is the use of fishmeal as an ingredient in calf milk replacers. A quantitative risk model was built to evaluate the BSE infectivity present in blood sourced from a slaughtered BSE-infected cow and the reduction of infectivity due to processing steps along the production chain. The end point of the model was the BSE infectivity, expressed in cattle oral ID50 (CoID50), reaching calves fed calf milk replacer containing fishmeal, and the corresponding probability that this will result in at least one new BSE infection.The expected BSE infectivity in blood from a BSE-infected cow at the clinical end state of infection is 0.75 CoID50 (median value). Infectivity in blood mainly results from cross-contamination with brain tissue during stunning at the slaughterhouse. The initial infectivity is reduced along the pathway from slaughtered cow to calf milk replacer, with the highest reduction achieved by clearance of infectivity by fish fed bovine SDRBC as an ingredient of aquafeed, although this parameter has high uncertainty. The final infectivity reaching calves via inclusion of fishmeal in calf milk replacer is estimated to be very low (median value: 1.1 × 10−5 CoID50). Assuming an exponential dose-response model, this corresponds with an expected probability that < 10 out of a million slaughtered BSE-infected cows will result in new BSE infections, which is far below the threshold value of 1 for the basic reproduction number (R0) to initiate a new epidemic. We thus conclude that it is very unlikely that the use of bovine SDRBC as ingredient of aquafeed will result in a new BSE epidemic in cattle. What-if analysis indicated that this conclusion is robust, despite high uncertainty for some input parameters.

From Plan to Pivot: How Model-Informed Drug Development Shaped the Dose Strategy of the Zibotentan/Dapagliflozin ZENITH Trials.

Getting the dose right is a key challenge in drug development; model-informed drug development (MIDD) provides powerful tools to shape dose strategies and inform decision making. In this tutorial, the case study of the ZENITH trials showcases how a set of clinical pharmacology and MIDD approaches informed an impactful dose strategy. The endothelin A receptor antagonist zibotentan, combined with the sodium-glucose co-transporter-2 inhibitor dapagliflozin, has yielded a robust and significant albuminuria reduction in the Phase IIb trial ZENITH-CKD and is being investigated for reduction of kidney function decline in a high-risk chronic kidney disease population in the Phase III trial ZENITH High Proteinuria. Endothelin antagonist treatment has, until now, been limited by the class effect fluid retention. ZENITH-CKD investigated a wide range of zibotentan doses based on pharmacokinetics in renal impairment, competitor-data exposure-response modeling, and clinical trial simulations. Recruitment delays reduced interim analysis data availability; here, supportive dose-response modeling recovered decision-making confidence. At trial completion, the low-dose arm enabled Phase III dose selection between Phase IIb doses. Dose-response modeling of efficacy and Kaplan-Meier analyses of tolerability identified a kidney-function-based low-dose strategy of 0.25 or 0.75 mg zibotentan (with 10 mg dapagliflozin) to balance benefit/risk in ZENITH High Proteinuria. The applied clinical pharmacology and MIDD principles enabled successful Phase IIb dose finding, rationalized and built confidence in the innovative Phase III dosing strategy and identified a potential therapeutic window for zibotentan/dapagliflozin, providing the opportunity for a significant improvement in the treatment of chronic kidney disease with high proteinuria.

Exploring maternal and developmental toxicity of perfluoroalkyl ether acids PFO4DA and PFO5DoA using hepatic transcriptomics and serum metabolomics

Production of per- and polyfluoroalkyl substances (PFAS) has shifted from long-chain perfluoroalkyl acids to short-chain compounds and those with ether bonds in the carbon chain. Next-generation perfluoroalkylether PFAS include HFPO-DA (“GenX chemicals”), Nafion Byproducts, and the PFOx homologous series that includes perfluoro-3,5,7,9-butaoxadecanoic acid (PFO4DA) and perfluoro-3,5,7,9,11-pentaoxadodecanoic acid (PFO5DoA). PFO4DA and PFO5DoA have been detected in serum and/or tissues from humans and wildlife proximal to contamination point sources. However, toxicity data are extremely limited, with no in vivo developmental toxicology data. To address these data gaps, pregnant Sprague-Dawley rats were exposed via oral gavage to vehicle, PFO4DA, or PFO5DoA across a series of doses (0.1 to 62.5 mg/kg/day) from gestation day (GD) 18–22. Hepatic transcriptomics were assayed in dams and fetuses, and serum metabolomics in dams. These data were overlaid with serum PFO4DA and PFO5DoA concentrations to perform dose-response modeling. Both dams and fetuses exhibited dose-responsive disruption of hepatic gene expression in response to PFO4DA or PFO5DoA, with fetal expression disrupted at lower doses than dams. Several differentially expressed genes were upregulated by every dose of PFO5DoA in both maternal and fetal samples, including genes encoding enzymes that hydrolyze acyl-coA to free fatty acids. Maternal serum metabolomics revealed PFO4DA exposure did not induce significant changes at any tested dose, whereas PFO5DoA exposure resulted in dose-dependent differential metabolite abundance for 149 unique metabolites. Multi-omics pathway analyses of integrated maternal liver transcriptomics and serum metabolomics revealed significant convergent changes as low as 3 mg/kg/d PFO4DA and 0.3 mg/kg/d PFO5DoA exposure. Overall, transcriptomic and metabolomic effects of PFO4DA and PFO5DoA appear consistent with other carboxylic acid PFAS, with primary changes related to lipid metabolism, bile acids, cholesterol, and cellular stress. Importantly, PFO5DoA exposure more potently induced changes in maternal and fetal hepatic gene expression and maternal circulating metabolites, despite high structural similarity. Further, we report in vitro PPARα and PPARγ receptor activation for both compounds as putative molecular mechanisms. This work demonstrates the potential developmental toxicity of alternative moiety perfluoroethers and highlights the developing liver as particularly vulnerable to transcriptomic disruption.Synopsis: Developmental exposure to fluoroether carboxylic acids PFO4DA and PFO5DoA result in differential impacts on hepatic transcriptome in dams and offspring and circulating metabolome in dams, with PFO5DoA exhibiting higher potency than PFO4DA.