The new paradigm of toxicity testing approaches involves rapid screening of thousands of chemicals across hundreds of biological targets through use of assays. Such assays may lead to false negatives when the complex metabolic processes that render a chemical bioactive in a living system are unable to be replicated in an environment. In the current study, a workflow is presented for complementing testing results with and techniques to identify inactive parents that may produce active metabolites. A case study applying this workflow involved investigating the influence of metabolism for over 1,400 chemicals considered inactive across18 assays related to the estrogen receptor (ER) pathway. Over 7,500 first-generation and second-generation metabolites were generated for these inactive chemicals using an software program. Next, a consensus model comprised of four individual quantitative structure activity relationship (QSAR) models was used to predict ER-binding activity for each of the metabolites. Binding activity was predicted for ~8-10% of metabolites in each generation, with these metabolites linked to 259 inactive parent chemicals. Metabolites were enriched in substructures consisting of alcohol, aromatic, and phenol bonds relative to their inactive parent chemicals, suggesting these features are potentially favorable for ER-binding. The workflow presented here can be used to identify parent chemicals that can be potentially bioactive, to aid confidence in high throughput risk screening.

A few different exposure prediction tools were evaluated for use in the new in vitro-based safety assessment paradigm using di-2-ethylhexyl phthalate (DEHP) and dibutyl phthalate (DnBP) as case compounds. Daily intake of each phthalate was estimated using both high-throughput (HT) prediction models such as the HT Stochastic Human Exposure and Dose Simulation model (SHEDS-HT) and the ExpoCast heuristic model and non-HT approaches based on chemical specific exposure estimations in the environment in conjunction with human exposure factors. Reverse dosimetry was performed using a published physiologically based pharmacokinetic (PBPK) model for phthalates and their metabolites to provide a comparison point. Daily intakes of DEHP and DnBP were estimated based on the urinary concentrations of their respective monoesters, mono-2-ethylhexyl phthalate (MEHP) and monobutyl phthalate (MnBP), reported in NHANES (2011e2012). The PBPK-reverse dosimetry estimated daily in-takes at the 50th and 95th percentiles were 0.68 and 9.58 μg/kg/d and 0.089 and 0.68 μg/kg/d for DEHP and DnBP, respectively. For DEHP, the estimated median from PBPK-reverse dosimetry was about 3.6-fold higher than the ExpoCast estimate (0.68 and 0.18 mg/kg/d, respectively). For DnBP, the estimated median was similar to that predicted by ExpoCast (0.089 and 0.094 mg/kg/d, respectively). The SHEDS-HT prediction of DnBP intake from consumer product pathways alone was higher at 0.67 mg/kg/d. The PBPK-reverse dosimetry-estimated median intake of DEHP and DnBP was comparable to values previously reported for US populations. These comparisons provide insights into establishing criteria for selecting appropriate exposure prediction tools for use in an integrated modeling platform to link exposure to health effects.

Background: Elexacaftor/tezacaftor/ivacaftor (E/T/I), has broadened access to life-changing pharmacotherapy for people living with cystic fibrosis (plwCF). However, case reports suggest CFTR modulators may induce psychiatric adverse symptoms. To systematically examine this, we studied depression and anxiety symptoms before and after initiation of E/T/I. Methods: Patient Health Questionnaire-9 (PHQ-9, depression symptoms) and Generalized Anxiety Disorder-7 (GAD-7, anxiety symptoms) scores recorded in a clinic database were studied. Patients who had scores collected pre- and post-E/T/I initiation were included. Mean total score changes were calculated for each questionnaire, and regression analyses described associations between score changes and age, race, ethnicity, sex, CFTR mutation, and prior depression and/or anxiety diagnoses. Secondary analyses examined the possible confounding effects of the SARS-CoV-2 (COVID-19) pandemic. Results: Eighty-six patients were included. Mean GAD-7 and PHQ-9 total scores did not change from pre-initiation (4.90 ± 5.31 and 4.98 ± 5.77, respectively) to post-initiation (5.27 ± 5.59 and 4.82 ± 5.55, respectively). Although patients (N = 40) evaluated prior to the COVID-19 pandemic showed a significant worsening of GAD-7 scores post-E/T/I initiation, this difference was not observed in the overall cohort (N=92). Pre-existent anxiety, depression, or other clinical factors did not predict an increased risk of mental health symptoms post-E/T/I initiation. Conclusions: Treatment with E/T/I does not lead to changes in depression or anxiety symptoms at the population level. No clinical predictors were identified to stratify potential risk. Overall, these findings are reassuring for clinicians and pwCF when deciding about initiating E/T/I treatment.

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