Current Assessment of the Effects of Environmental Chemicals on the Mammary Gland in Guideline Rodent Studies by the U.S. Environmental Protection Agency (U.S. EPA), Organisation for Economic Co-operation and Development (OECD), and National Toxicology Program (NTP)

Background: Evaluation of the structural and/or functional integrity of the mammary gland (MG) across life stages is integral to the assessment of developmental, reproductive, and carcinogenic risk for environmental chemicals

Unmasking silent neurotoxicity following developmental exposure to environmental toxicants

AbstractSilent neurotoxicity, a term introduced approximately 25years ago, is defined as a persistent change to the nervous system that does not manifest as overt evidence of toxicity (i.e. it remains clinically unapparent) unless unmasked by experimental or natural processes. Silent neurotoxicants can be challenging for risk assessors, as the multifactorial experiments needed to reveal their effects are seldom conducted, and they are not addressed by current study design guidelines. This topic was the focus of a symposium addressing the interpretation and use of silent neurotoxicity data in human health risk assessments of environmental toxicants at the annual meeting of the Developmental Neurotoxicology Society (previously the Neurobehavioral Teratology Society) on June 30th, 2014. Several factors important to the design and interpretation of studies assessing the potential for silent neurotoxicity were discussed by the panelists and audience members. Silent neurotoxicity was demonstrated to be highly specific to the characteristics of the animals being examined, the unmasking agent tested, and the behavioral endpoint(s) evaluated. Overall, the experimental examples presented highlighted a need to consider common adverse outcomes and common biological targets for chemical and non-chemical stressors, particularly when the exposure and stressors are known to co-occur. Risk assessors could improve the evaluation of silent neurotoxicants in assessments through specific steps from researchers, including experiments to reveal the molecular targets and mechanisms that may result in specific types of silent neurotoxicity, and experiments with complex challenges reminiscent of the human situation

Impact of Sex and Menopausal Status on Episodic Memory Circuitry in Early Midlife

Cognitive neuroscience of aging studies traditionally target participants age 65 and older. However, epidemiological surveys show that many women report increased forgetfulness earlier in the aging process, as they transition to menopause. In this population-based fMRI study, we stepped back by over a decade to characterize the changes in memory circuitry that occur in early midlife, as a function of sex and women's reproductive stage. Participants (N = 200; age range, 45–55) performed a verbal encoding task during fMRI scanning. Reproductive histories and serologic evaluations were used to determine menopausal status. Results revealed a pronounced impact of reproductive stage on task-evoked hippocampal responses, despite minimal difference in chronological age. Next, we examined the impact of sex and reproductive stage on functional connectivity across task-related brain regions. Postmenopausal women showed enhanced bilateral hippocampal connectivity relative to premenopausal and perimenopausal women. Across women, lower 17β-estradiol concentrations were related to more pronounced alterations in hippocampal connectivity and poorer performance on a subsequent memory retrieval task, strongly implicating sex steroids in the regulation of this circuitry. Finally, subgroup analyses revealed that high-performing postmenopausal women (relative to low and middle performers) exhibited a pattern of brain activity akin to premenopausal women. Together, these findings underscore the importance of considering reproductive stage, not simply chronological age, to identify neuronal and cognitive changes that unfold in the middle decades of life. In keeping with preclinical studies, these human findings suggest that the decline in ovarian estradiol production during menopause plays a significant role in shaping memory circuitry

A systematic approach for identifying and presenting mechanistic evidence in human health assessments

Clear documentation of literature search and presentation methodologies can improve transparency in chemical hazard assessments. We sought to improve clarity for the scientific support for cancer mechanisms of action using a systematic approach to literature retrieval, selection, and presentation of studies. The general question was “What are the mechanisms by which a chemical may cause carcinogenicity in the target tissue?” Di(2-ethylhexyl)phthalate was used as a case study chemical with a complex database of >3,000 publications. Relevant mechanistic events were identified from published reviews. The PubMed search strategy included relevant synonyms and wildcards for DEHP and its metabolites, mechanistic events, and species of interest. Tiered exclusion/inclusion criteria for study pertinence were defined, and applied to the retrieved literature. Manual curation was conducted for mechanistic events with large literature databases. Literature trees documented identification and selection of the literature evidence. The selected studies were summarized in evidence tables accompanied by succinct narratives. Primary publications were deposited into the Health and Environmental Research Online (http://hero.epa.gov/) database and identified by pertinence criteria and key terms to permit organized retrieval. This approach contributes to human health assessment by effectively managing a large volume of literature, improving transparency, and facilitating subsequent synthesis of information across studies

Factor IX Expression within the Normal Range Prevents Spontaneous Bleeds Requiring Treatment Following FLT180a Gene Therapy in Patients with Severe Hemophilia B: Long-Term Follow- up Study of the B-Amaze Program

Introduction: FLT180a (verbrinacogene setparvovec) is an investigational, liver-directed AAV gene therapy for the treatment of patients with hemophilia B (HB). FLT180a consists of a novel, potent, engineered capsid (AAVS3) containing an expression cassette encoding a Factor IX (FIX) gain-of-function protein variant ('Padua'; FIX-R338L). The B-AMAZE study was designed to identify a dose of FLT180a that maintains FIX activity within the normal range (50-150%) and thereby protect patients with severe HB from spontaneous and traumatic bleeds. Methods: B-AMAZE was a multicentre, open-label Phase 1/2 clinical trial (NCT03369444; sponsored by UCL) that evaluated FLT180a dose levels using an escalating/descending adaptive design in patients with severe (FIX activity <1%) or moderately severe (FIX activity 1-2%) HB who were negative for AAVS3 neutralizing antibodies. A novel regimen of prophylactic corticosteroids with/without tacrolimus was implemented to mitigate the impact of vector-related transaminitis on FIX expression. Patients who completed the 26-week B-AMAZE study were eligible for the ongoing long-term follow-up study (NCT03641703; sponsored by Freeline). Results: Ten HB patients received a single dose of FLT180a. Four FLT180a doses ranging from 3.84e11 vg/kg to 1.28e12 vg/kg were assessed. As of the data cut-off date, all patients have been followed for ≥16 months. FLT180a demonstrated a favorable safety profile, without evidence of inhibitors against FIX, infusion-related or allergic reactions. The most common treatment-related adverse event was transient elevation in alanine aminotransferase. An event of AV fistula thrombosis occurred in a 67-year-old patient who received the highest dose of 1.28e12 vg/kg (total dose of 1.15e14 vg) and had supranormal FIX levels; this patient was treated with anticoagulants. While these FIX levels demonstrate the potency of our proprietary AAVS3 capsid, this dose will not be used in future hemophilia studies. At Week 26 after FLT180a administration, a dose-response relationship was observed with mean FIX activity of 45.0%, 35.5%, 141.5%, and 175.5% for 3.84e11, 6.4e11, 8.32e11, and 1.28e12 vg/kg doses, respectively (Table); FIX activity levels ≥50% were achieved in 7 of 8 patients treated with the three highest doses. One patient (Patient 4) who received 6.4e11 vg/kg lost transgene expression early due to transaminitis and resumed routine factor prophylaxis. The 8.32e11 vg/kg cohort received an extended immune management regimen (9-18 weeks) with prophylactic tacrolimus in addition to prednisolone to prevent breakthrough vector-related transaminitis. However, after cessation of the immune management regimen, transaminitis with concomitant reductions in FIX activity was observed in all patients in the 8.32e11 vg/kg cohort. The combination of prophylactic tacrolimus and prednisolone appeared to have suppressed immune-mediated transaminitis while administered, but recurrence of transaminitis developed soon after cessation. This unique and previously unreported observation suggests that the longer-duration prophylactic immune management regimen may have prevented tolerization to the vector because this was not observed in earlier cohorts where a brief course of tacrolimus was given reactively for breakthrough transaminitis. All patients (including the 8.32e11 vg/kg cohort) have achieved steady state. Patients in the earliest cohort who received the lowest dose (3.84e11 vg/kg) have shown stable FIX activity for >3 years. There were no spontaneous bleeds that required FIX supplementation in patients who maintained FIX activity above 50%; Patient 4 in the 6.4e11 vg/kg cohort experienced two bleeds (cause unknown) after he lost transgene expression, which were treated with exogenous FIX. One patient received exogenous FIX for treatment of a traumatic bleed, but his FIX activity level was 57% at the time of the event. Additional efficacy and safety results with >3.5 years of follow-up will be presented. Conclusions: B-AMAZE is the first HB gene therapy study to achieve normal levels of FIX activity using relatively low vector doses. Results suggest that a dose of 7.7e11 vg/kg, coupled with a short course of prophylactic immune management, has the potential to achieve durable FIX activity in the normal range (50-150%) and thereby prevent spontaneous bleeds and normalize hemostasis in the event of traumatic bleeds

Considering sex as a biological variable in preclinical research

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154390/1/fsb2fj201600781r.pd

A proposal to facilitate weight-of-evidence assessments: Harmonization of Neurodevelopmental Environmental Epidemiology Studies (HONEES)

The ability to conduct weight-of-evidence assessments to inform the assessment of potential environmental neurotoxicants is limited by lack of comparability of study methods, data analysis, and reporting. There is a need to establish consensus guidelines for conducting, analyzing, and reporting neurodevelopmental environmental epidemiologic studies, while recognizing that consistency is likewise needed for epidemiology studies examining other health outcomes. This paper proposes a set of considerations to be used by the scientific community at-large as a tool for systematically evaluating the quality of proposed and/or published studies in terms of their value for weight-of-evidence assessments. Particular emphasis is placed on evaluating the sensitivity and specificity of neurodevelopmental function tests, as these characteristics directly affect the risk of false positive and false negative decisions at the level of the individual, thus influencing the risk of incorrect conclusions at the level of study findings. The proposed considerations are the first step in what must be a larger consensus-based process and can serve to catalyze such a discussion. Achieving consensus in these types of endeavors is difficult; however, opportunities exist for further interdisciplinary discussion, collaboration, and research that will help realize this goal. Broad acceptance and application of such an approach can facilitate the expanded use of environmental epidemiology studies of potential neurodevelopmental toxicants in the protection of public health, and specifically children's health

Continuing Education Course #3: Current Practices and Future Trends in Neuropathology Assessment for Developmental Neurotoxicity Testing

The continuing education course on Developmental Neurotoxicity Testing (DNT) was designed to communicate current practices for DNT neuropathology, describe promising innovations in quantitative analysis and noninvasive imaging, and facilitate a discussion among experienced neuropathologists and regulatory scientists regarding suitable DNT practices. Conventional DNT neuropathology endpoints are qualitative histopathology and morphometric endpoints of particularly vulnerable sites (e.g., cerebral, cerebellar, or hippocampal thickness). Novel imaging and stereology measurements hold promise for automated analysis of factors that cannot be effectively examined in routinely processed specimens (e.g., cell numbers, fiber tract integrity). The panel recommended that dedicated DNT neuropathology data sets be acquired on a minimum of 8 sections (for qualitative assessment) or 3 sections (for quantitative linear and stereological analyses) using a small battery of stains to examine neurons and myelin. Where guidelines permit discretion, immersion fixation is acceptable for younger animals (postnatal day 22 or earlier), and peripheral nerves may be embedded in paraffin. Frequent concerns regarding DNT data sets include false-negative outcomes due to processing difficulties (e.g., lack of concordance among sections from different animals) and insensitive analytical endpoints (e.g., qualitative evaluation) as well as false-positive results arising from overinterpretation or misreading by inexperienced pathologists