Prenatal Developmental Toxicity Study Research Articles

Prenatal developmental toxicity studies of allyl alcohol in rats and rabbits

Allyl alcohol (C3H6O; prop-2-en-1-ol; CAS RN 107-18-6; EINECS 203-470-7) is used as an intermediate/monomer in polymerization reactions producing chemicals/optical resins or as a coupling/cross-linking agent for unsaturated polyester and alkyd resins. Human exposure to allyl alcohol (AA) is restricted to workplace manufacturing facilities where it is used in enclosed systems, which limits release and impact on environmental receptors. To address regulatory questions about possible developmental toxicity, two OECD Guideline studies were conducted. A rat developmental toxicity study found fetal and maternal toxicity, in the form of resorptions and decreased body weight and food consumption, but no teratogenic effects. A rabbit developmental toxicity study was subsequently conducted upon request by the European Chemical Agency in 2011 under the REACH program and likewise reported maternal toxicity in the form of reductions in body weight gain and food consumption, but neither fetal toxicity or teratogenic effects. The results of both studies are presented and compared in this paper. Based on our review of the collective results of these studies, AA is considered non-teratogenic, yet does elicit increased post-implantation loss and reduced fetal body weight, possibly resulting from concomitant maternal toxicity. Based on the results of these studies, a maternal and developmental toxicity No Observed Adverse Effect Level of 10 mg/kg/day was apparent for both species.

Genetic and prenatal developmental evaluation of anthraquinone

Anthraquinone is a recently identified contaminant present in teas globally, and its potential teratogenic and genotoxic impacts have yet to be fully comprehended. Hence, this study's objective was to determine anthraquinone's genotoxicity using various studies such as the Ames test, Mammalian erythrocyte micronucleus test, and in-vitro mammalian chromosome aberration study. Additionally, the study assessed its effects on maternal gestational toxicity and the fetus's teratogenicity through prenatal developmental toxicity research in rats. Results indicated that anthraquinone did not manifest mutagenic effects on Salmonella typhimurium histidine-deficient, did not cause chromosomal aberrations in Chinese hamster ovary cell subclone CHO-K1, and did not exhibit a genotoxic effect on mouse bone marrow erythrocytes. However, in the prenatal developmental toxicity study, administering anthraquinone orally to pregnant rats from day 5 to day 19 of gestation resulted in decreased body weight and food consumption of pregnant rats, along with a higher number of visceral malformations in the fetuses in the highest dose group (217.6 mg/kg BW). Additionally, two pregnant rats died in this group. The study has established the no observed adverse effect level (NOAEL) as 21.76 mg/kg BW, while the lowest observed adverse effect level (LOAEL) was 217.6 mg/kg BW.

OECD 414 supplementary prenatal developmental toxicity study of sodium molybdate dihydrate in the rat and benchmark dose evaluation

In a continuing investigation of the potential for reproductive and developmental toxicity of molybdenum (Mo), consequent to the previous published OECD studies [1,2] and as directed by the European Chemicals Agency [3], a supplemental rat GLP-compliant Prenatal Developmental Toxicity (PNDT) study was conducted to investigate higher dose levels of sodium molybdate dihydrate (SMD) in an identical study design (OECD 414)[4] to Murray et al. 2014a [1], at dietary concentrations calculated to provide target Mo levels of 80 and 120 mg/kg bw/day (the maximum-tolerated dose). There was no effect on post-implantation loss, litter size, sex ratio or the incidence of external, visceral or skeletal fetal malformations or variations. Fetal weight was reduced proportionate to maternal dose. Minimal differences observed in the ossification status of some extremities of fetuses from females receiving 120 mg Mo/kg bw/day were confirmed as transient by skeletal examination of PND 21 pups from a further group of females receiving the same dose regime. There was no evidence of copper depletion in serum, placenta or liver. A benchmark dose evaluation using continuous and dichotomous approaches by combining the fetal body weight data from this study and the previous study determined that the BMD05 ranged from 47 to 57 mg Mo/kg bw/day, depending on the modelling approach and the BMDL05 estimates ranged from 37 to 47 mg Mo/kg bw/day. These levels are considered a more statistically robust point of departure for risk assessment for reproductive effects than the established NOAEL of 40 mg Mo/kg bw/day.

Computational model for fetal skeletal defects potentially linked to disruption of retinoic acid signaling.

All-trans retinoic acid (ATRA) gradients determine skeletal patterning morphogenesis and can be disrupted by diverse genetic or environmental factors during pregnancy, leading to fetal skeleton defects. Adverse Outcome Pathway (AOP) frameworks for ATRA metabolism, signaling, and homeostasis allow for the development of new approach methods (NAMs) for predictive toxicology with less reliance on animal testing. Here, a data-driven model was constructed to identify chemicals associated with both ATRA pathway bioactivity and prenatal skeletal defects. The phenotype data was culled from ToxRefDB prenatal developmental toxicity studies and produced a list of 363 ToxRefDB chemicals with altered skeletal observations. Defects were classified regionally as cranial, post-cranial axial, appendicular, and other (unspecified) features based on ToxRefDB descriptors. To build a multivariate statistical model, high-throughput screening bioactivity data from >8,070 chemicals in ToxCast/Tox21 across 10 in vitro assays relevant to the retinoid signaling system were evaluated and compared to literature-based candidate reference chemicals in the dataset. There were 48 chemicals identified for effects on both in vivo skeletal defects and in vitro ATRA pathway targets for computational modeling. The list included 28 chemicals with prior evidence of skeletal defects linked to retinoid toxicity and 20 chemicals without prior evidence. The combination of thoracic cage defects and DR5 (direct repeats of 5 nucleotides for RAR/RXR transactivation) disruption was the most frequently occurring phenotypic and target disturbance, respectively. This data model provides valuable AOP elucidation and validates current mechanistic understanding. These findings also shed light on potential avenues for new mechanistic discoveries related to ATRA pathway disruption and associated skeletal dysmorphogenesis due to environmental exposures.

Safety of freeze-dried mycelia of Antrodia camphorata as a novel food pursuant to regulation (EU) 2015/2283.

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on freeze‐dried mycelia of Antrodia camphorata as a novel food (NF) pursuant to Regulation (EU) 2015/2283. The NF is produced by solid‐state cultivation from tissue cultures derived from the fungus Antrodia camphorata. The applicant intends to market the NF in food supplements at a maximum dose of 990 mg per day. The target population is the general population. The NF mainly consists of carbohydrates, proteins and fats, and it contains numerous constituents, such as β‐glucans, antroquinonol and triterpenoids. Taking into account the composition of the NF and the proposed conditions of use, the consumption of the NF is not nutritionally disadvantageous. There are no concerns regarding genotoxicity of the NF. Based on a 90‐day repeated dose toxicity study and a prenatal developmental toxicity study performed with the NF, the Panel derives a safe level of 16.5 mg/kg body weight per day. The Panel concludes that the NF, freeze‐dried mycelia of Antrodia camphorata, is safe at the proposed use level for individuals aged 14 years and above.

Prenatal developmental toxicity study of 2,4-dichlorobenzyl alcohol in rats

Sore throat lozenges, which are over-the-counter drugs, contain 2,4-dichlorobenzyl alcohol (DCBA) as the primary ingredient. However, comprehensive data on the prenatal developmental toxicity of DCBA is limited. Therefore, this study was conducted to determine the effects of DCBA on pregnant rats and prenatal development. Sprague-Dawley rats were administered different doses of DCBA (0, 25, 100, 400, and 800 mg/kg/day) daily via an oral gavage from gestation day (GD) 6–19. Thereafter, all the live dams were sacrificed on GD 20, and caesarean sections were conducted. Live fetuses and their placenta were weighed and then examined for external, visceral, and skeletal malformations and variations. Based on the results obtained, dams at 800 mg/kg/day showed systemic toxicities, including a decrease in body weight and food consumption, and liver changes. Additionally, this treatment induced decreases in fetal and placental weights, as well as the increased incidence of retarded ossifications and full supernumery rib, and the decreased number of ossification centers. Therefore, based on these findings, the no-observed-adverse-effect level of DCBA was determined to be 400 mg/kg/day for dams and prenatal development.

Teratogenicity of D-allulose

The objective of this study was to evaluate whether D-allulose has teratogenic effects on rats. A prenatal developmental toxicity test was conducted in SD rats in compliance with modified OECD guidelines test number 414, prenatal developmental toxicity study. Pregnant female rats received repeated doses of 1250, 2500, or 5000 mg/kg body weight D-allulose, or a vehicle control by gavage on GD 6–15. On GD 20, one day prior to the expected day of delivery, pregnant rats were weighed and anesthetized, and laparotomized to remove the uterine and its content were weighed. Fetuses were examined macroscopically for any soft tissue and skeletal changes. The evaluation indicators included general sign observation, body weight, food consumption, animal death, corpora lutea, numbers of embryonic or fetal deaths, and viable fetuses including live birth rate, fetal resorption rate, and stillbirth rate, as well as sex, body weights, and skeletal and soft tissue alterations of fetuses. No treatment-related abnormalities were observed in prenatal developmental toxicity and fetal malformation parameters, indicating that D-allulose had no teratogenic effects on pregnant rats and fetuses. From the findings of this prenatal developmental toxicity study, the NOAEL of D-allulose was estimated to be 5000 mg/kg/day in pregnant SD rats.

Prenatal developmental toxicity study of herbal tea of Moringa stenopetala and Mentha spicata leaves formulation in Wistar rats

BackgroundMoringa stenopetala and Mentha spicata have long been used to treat diabetes, hypertension, asthma, and other ailments. Herbal tea of M. stenopetala and Mentha spicata leaves formulation showed better antidiabetic and antihypertensive activities. This study investigated the prenatal developmental toxicity potential of the herbal tea of M. stenopetala and M. spicata leaves blend in rats. MethodsWistar pregnant rats were randomly distributed into four groups (n = 8). Group I (control) dams received distilled water. Group II-IV dams were treated with 559.36, 1118.72, and 2237.44 mg/kg of herbal tea of M. stenopetala and Mentha spicata leaves formulations, respectively, during days 5–19 of gestation. Maternal mortality, clinical signs, body weight changes, and food consumption were recorded. On gestation day 20, cesarean sections were performed, and maternal parameters of systemic toxicity (e.g., body weight, serum biochemistry, organ weight, and macro-pathology) as well as reproductive toxicity (e.g., number of corpora lutea, implantations, resorptions (early/late), pre/postimplantation losses, number of fetuses (live/dead), and fetal body weights, length, and their sex ratio) were evaluated. Fetuses were further examined for external, soft tissue, and skeletal alterations. ResultsNo herbal tea-related maternal deaths or overt toxic symptoms were observed. The measured maternal systemic and reproductive toxicity parameters showed no herbal tea-associated significant alterations at any dosage levels. Moreover, there were no overt toxic effects of the herbal tea on the fetal external, visceral, or skeletal prenatal growth and development. ConclusionThe study findings demonstrated that the herbal tea of M. stenopetala and M. spicata leaves blend could be relatively safe/low toxic to pregnant rats and developing fetuses. The no-observed-adverse-effect level (NOAEL) of herbal tea for maternal toxicity, fetotoxicity, and teratogenicity in rats is estimated to be > 2237.44 mg/kg/day.

Re-evaluation of thaumatin (E 957) as food additive.

The present opinion deals with the re‐evaluation of thaumatin (E 957) when used as a food additive. Thaumatin is a natural plant protein, consisting of thaumatin I and thaumatin II proteins together with minor amounts of plant constituents, obtained by acidic aqueous extraction of the arils of the fruit of Thaumatococcus daniellii plant. The Panel followed the conceptual framework for the risk assessment of certain food additives and considered that thaumatin is a digestible protein; adequate exposure estimates were available; there was no concern with respect to the genotoxicity; no conclusion on oral allergenicity could be drawn from the available human data; no adverse effects were observed in sub‐chronic toxicity studies in rats and dogs at the highest dose tested of up 5,200 and 1,476 mg/kg bodyweight (bw) per day, respectively, and in a prenatal developmental toxicity study up to 2,000 mg/kg bw per day; moderate confidence in the body of evidence supported the absence of association between exposure to thaumatin and adverse health outcomes. Therefore, the Panel concluded that there is no need for a numerical acceptable daily intake (ADI) for thaumatin (E 957) and, based on a margin of safety (MOS) of 5,417, considered to be an underestimate and derived using the highest 95th percentile (P95) exposure of 0.48 mg/kg bw per day in consumers only, there is no safety concern for thaumatin (E 957) at the regulatory maximum level exposure assessment scenario, which was considered the most appropriate. The Panel recommended that European Commission considers introducing in the EU specifications for thaumatin (E 957) a new specification limit for the minimum combined content of thaumatin I and II proteins in E 957, a specification limit for yeast, mould counts and Salmonella spp and lowering the existing maximum limit for arsenic along with the inclusion of maximum limits for mercury and cadmium.

Safety evaluation of long-chain glycolipids from Dacryopinax spathularia.

The EFSA Panel on Food Additives and Flavourings (FAF) provides a scientific opinion on the safety of long‐chain glycolipids from Dacryopinax spathularia (also called AM‐1) as a food additive. AM‐1 is a purified mixture of long‐chain glycolipid congeners obtained by fermentation of the edible non‐genetically modified fungus Dacryopinax spathularia. AM‐1 glycolipids have very low oral bioavailability and overall available toxicology data do not demonstrate any adverse effects of the proposed food additive. Considering the available data set the Panel established an ADI of 10 mg/kg bw per day based on a range of NOAELs between 1,000 and 1,423 mg/kg bw per day (the highest doses tested), from the reproductive and a prenatal developmental toxicity studies in rats and 90‐day studies in rat and dog. At the proposed maximum use levels, the exposure estimates ranged at the mean from 0.01 to 1.07 mg/kg bw per day and at the p95 from 0 to 3.1 mg/kg mg/kg bw per day. At the proposed typical use levels, the exposure estimates ranged at the mean from < 0.01 mg/kg bw per day to 0.23 mg/kg bw per day and at the p95 from 0 to 0.64 mg/kg bw per day. The Panel noted that the highest estimate of exposure of 3.1 mg/kg bw per day (in toddlers) is within the established ADI of 10 mg/kg bw per day and concluded that the exposure to long‐chain glycolipids from Dacryopinax spathularia does not raise a safety concern at the uses and use levels proposed by the applicant.

An automated technique for double staining of bone and cartilage in fetal mouse skeletal specimens using alizarin red S and Alcian blue

ABSTRACT Automated methods exist for double staining bone and cartilage in fetal rat, rabbit and mice using alizarin red S and Alcian blue. None of the published methods produce consistently stained bone and cartilage in mouse fetuses. Consequently, we modified an automated staining method for use with mouse fetuses. Methanol replaced 95% industrial denatured alcohol, and 5% glacial acetic acid was used instead of 20%. We describe here our new protocol, which has been used successfully to stain specimens for regulatory prenatal developmental toxicity studies.

Developmental toxicity testing of the fume condensate extracts of bitumen and oxidized asphalt in a series of in vitro alternative assays

The potential developmental toxicity and mode-of-action of fume condensate extracts of bitumen and oxidized asphalt were evaluated in the aryl hydrocarbon receptor (AhR) CALUX assay, the zebrafish embryotoxicity test (ZET), and the mouse embryonic stem cell test (mEST). In the AhR CALUX assay, both fume condensate extracts showed a concentration-dependent AhR induction following 6-h of exposure, but this activity was substantially reduced after 24-h, indicating a transient AhR activation. The main effect observed in the ZET was early embryonic lethality that occurred mostly in the 24 h-post-fertilization (hpf). This typically reflects non-specific toxicity rather than in vitro developmental toxicity of the fume condensate extracts tested since this effect was not seen as a result of the whole cumulative exposure period in the ZET (up to 96 hpf). No malformations were seen in any zebrafish embryo exposed to these fume condensate extracts, although some developed pericardial and/or yolk-sac edemas. Furthermore, both fume condensate extracts tested negative in the mEST. In conclusion, the results show that fume condensate extracts of bitumen and oxidized asphalt do not induce any in vitro developmental toxicity, which is in line with the results observed in the in vivo prenatal developmental toxicity studies performed with the same materials.

Prenatal developmental toxicity studies on fumes from oxidised asphalt (OA) in the rat

The prenatal developmental toxicity of the fumes of oxidised asphalt (OA) was tested by nose-only inhalation in the rat. The test material was generated by collecting fumes from the headspace of storage tanks filled with OA. The composition of these fumes was matched to fumes sampled at a workplace where the same OA was applied in a pour-and-roll operation, representing occupational exposure with high concentrations of fumes to not underestimate the possible hazard. In the main study, dams were exposed to 0, 53, 158 and 536 mg/m3 of fume (as total organic mass), for 6 h/day for 19 days p.c. The maternal NOAEC was 53 mg/m³ (lowest dose tested). In the high-dose group treatment-related effects on body weight gain were seen. In the mid- and high-dose groups treatment-related effects on food consumption, lung weights, and histopathological changes in lungs and the upper respiratory tract were observed. The NOAEC for prenatal developmental toxicity was 536 mg/m³ since no exposure-related effects were found in any of the exposure groups for any of the investigated reproductive endpoints. Furthermore, nose-only exposure to OA fumes in concentrations up to 536 mg/m³ from days 1–19 p.c. did not induce any significant fetal abnormalities.

Palmitoylethanolamide: Prenatal Developmental Toxicity Study in Rats.

Palmitoylethanolamide (PEA) is an endogenous ethanolamine playing a protective and homeodynamic role in animals and plants. Prenatal developmental toxicity of PEA was tested following oral administration to pregnant female Wistar rats, from days 0 to 19 of gestation, at dosage of 250, 500, or 1,000 mg/kg body weight, according to Organisation for Economic Co-operation and Development Test Guideline No. 414. On gestation day 20, cesarean sections were performed on the dams, followed by examination of their ovaries and uterine contents. The fetuses were further examined for external, visceral, and skeletal abnormalities. Palmitoylethanolamide did not cause any alterations at any of the given dosages in the measured maternal parameters of systemic toxicity (body weight, food consumption, survival, thyroid functions, organ weight, histopathology), reproductive toxicity (preimplantation and postimplantation losses, uterus weight, number of live/dead implants and early/late resorptions, litter size and weights, number of fetuses, their sex ratio), and fetal external, visceral, or skeletal observations. Any alterations that were recorded were “normal variations” or “minor anomalies,” which were unrelated to treatment with PEA. Under the condition of this prenatal study, the no-observed-adverse-effect level of PEA for maternal toxicity, embryotoxicity, fetotoxicity, and teratogenicity in rats was found to be >1,000 mg/kg body weight/d. It indicates that PEA is well tolerated by and is safe to pregnant rats even at a high dose of 1,000 mg/kg body weight/d, equivalent to a human dose of greater than 9.7 g/d. This prenatal developmental toxicity study contributes greatly in building a robust safety profile for PEA.

Developing a screening test for toxicity studies of prenatal development with the use of Hydra attenuata and embryos of zebrafish.

11 active substances used in pesticides were selected. Substances were divided into three groups depending the effect on embryos or fetuses of laboratory animals: 1 - damaging effect on embryos or fetuses (embryotoxic, fetotoxic or teratogenic), 2 - damaging effect on embryos or fetuses, but only at dose toxic for mother (maternal toxicity), 3 - no damaging effect. Changes for hydra in acute toxicity tests and recovery tests were assessed on an change scale from 0 to 10. The index of the effect on development (TI) for hydras was calculated for every compound. Changes in zebrafish embryos were assessed using a descriptive method. Pearson correlation coefficient showed the correlation between the concentration and the toxic effect in the zebrafish embryos for the substances of the first group. The study showed that substances having a strong damaging effect on fetuses cause changes that are apparent and easy to evaluate both in hydras and zebrafish embryos. A scoring system was introduced to evaluate the changes of hydras and zebrafish embryos. The point system of evaluation of changes allows quick classification of a substance as potentially embryotoxic, fetotoxic or teratogenic. It allows developing a cheap and fast method alternative to prenatal developmental toxicity studies, a screening method that enables substances of great teratogenic potential to be excluded from studies on laboratory animals.

A study of the genetic and prenatal developmental toxicity potential of lithothamnion sp

Due to its calcium-rich and diverse multimineral profile, Aquamin (derived from the red seaweed Lithothamnion sp.) is used globally as a dietary food supplement. Published reports on the genetic and prenatal developmental toxicity of Lithothamnion sp. do not exist. In accordance with the standardized protocols set by the Ministry of Health of the People’s Republic of China (GB-15193), the following studies were performed: the Ames test, the mammalian erythrocyte micronucleus test, the mammalian spermatocyte chromosome test, and prenatal developmental toxicity testing. The results showed that Lithothamnion sp. did not induce a significant increase in the following: revertant colony numbers for Salmonella typhimurium strains TA 97, 98, 100, 102 and 1535; frequency of micronucleated polychromatic erythrocytes (MNPCE); spermatocyte chromosomal aberration rate. In the prenatal developmental toxicity study, no mortality, no abnormal changes in behavior and activities, and the absence of toxic symptoms and abnormalities in macroscopic autopsy were observed in each dam/all pups. Compared to the negative control group, Lithothamnion sp. at all tested doses had no effects on body weight gain, number of corpora lutea and implantations, fetal body weight and length, external, visceral and skeletal malformations. In conclusion, Lithothamnion sp. did not cause genetic toxicity. Furthermore, the prenatal developmental toxicity no observed adverse effect level (NOAEL) was determined to be greater than 2000 mg/kg.bw.

Prenatal developmental toxicity studies on fumes from bitumen in the rat

The prenatal developmental toxicity of bitumen fume was tested by nose-only inhalation in the rat. The fumes for exposure were collected from the headspace of a storage tank filled with a bitumen corresponding in composition to an anticipated worst-case occupational exposure. The composition of these fumes was compared to actual paving site fumes to ensure its representativeness for workplace exposures. In a dose-range-finding study male and female rats were exposed to 0, 103, 480 or 1043 mg/m3 of fume (as total organic mass), for 6 h/day during 20 days post conception (p.c.). Dose-related effects on body weight and lungs were observed in the mid- and high-dose groups. In the main study, dams were exposed to 0, 52, 151 and 482 mg/m3 of fume, for 6 h/day during 19 days p.c. The maternal NOAEL was 52 mg/m³. In the high-dose group treatment-related effects on body weight (gain), food consumption, lung weights, and histopathological changes in lungs and larynx were observed. In the mid-dose group only histopathological changes in the larynx and lungs were found. The NOAEL for prenatal developmental toxicity was 151 mg/m³ based on reduced fetal weight in the high-dose group (482 mg/m³). However, these changes are most likely a consequence of the maternal toxicity, in particular the reduction of maternal body weight gain by 26 % as compared to control. Nose-only exposure to bitumen fumes in concentrations up to 482 mg/m³ from days 1–19 p.c. did not induce any significant fetal anomalies.

Prenatal developmental toxicity study of an alkaloid-free Ageratum conyzoides extract powder in rats by oral administration

A prenatal developmental toxicological study was conducted to evaluate the safety of an alkaloid-free Ageratum conyzoides extract powder administration on pregnant female Wistar rats and on the development of the conceptus in accordance with OECD test guideline (no. 414). Pyrrolizidine alkaloids (PAs) naturally present in A. conyzoides have been shown to induce toxicity in past studies, particularly towards hepatic cells. Therefore our test item preparation of A.conyzoides extract (aerial part of the plant) consisted of the removal of PAs. There were no treatment related adverse effects found during maternal examinations (body weights, food consumption, numbers of pregnant and non-pregnant female rats, endocrine evaluation, gravid uterine weights, and number of corpora lutea), maternal/fetal examinations (numbers of implantation sites, pre-and post-implantation loss (%), dead and live fetuses (%), resorption sites), or fetal examinations (litter size and weights, number of fetuses, sex ratio, or external, visceral, and skeletal variations and malformations) in the Ageratum conyzoides extract powder groups at doses of 500, 1000 and 2000 mg/kw bw/day compared to vehicle control group. The no observed adverse effect level (NOAEL) determined for both maternal and developmental toxicity was 2000 mg/kg bw/day, which was the highest dose tested.

Use of toxicokinetic data for afidopyropen to determine the dose levels in developmental toxicity studies

Afidopyropen is an insecticide that acts as a TRPV channel modulator in chordotonal organs of target insects and has been assessed for a wide range of toxicity endpoints including developmental toxicity in rats and rabbits. The GLP developmental toxicity study in rabbits did not produce evidence of maternal or fetal toxicity at the highest dose tested (32 mg/kg/day) but pharmacokinetics (PK) in pregnant rabbits in this study exhibited onset of PK nonlinearity from 5 mg/kg/day on, as measured by plasma Cmax and AUC. The NOAEL (32 mg/kg/day) is 9000X higher than maximum expected human dietary exposures to afidopyropen; the dose range where nonlinear PK were observed (5–15 mg/kg/day) is 1400–4200X higher. As nonlinearity occurred between 5 and 15 mg/kg/day, 32 mg/kg/day is concluded to be a sufficiently high dose (kinetically derived maximum dose) for a prenatal developmental toxicity study. As recognized by regulatory dose-selection guidance, onset of saturated PK is evidence of excessive biological stress to test animals rendering any effects at such doses of questionable relevance for human risk assessment. These data demonstrate that consideration of PK is critical for improving the dose-selection in developmental toxicity studies to enhance human relevance of animal toxicity studies.

Innovative selection approach for a new antifungal agent mefentrifluconazole (Revysol®) and the impact upon its toxicity profile

Mefentrifluconazole (trade name: Revysol®) is an agrochemical active ingredient from the new sub-class of isopropanol-triazole fungicides, with high selective fungicide activity. A full program of toxicity testing conducted according to OECD guidelines has shown mefentrifluconazole (MFZ) to be non-genotoxic and non-carcinogenic. Repeated dose studies in rats, mice and dogs identified the liver as the main target organ. Prenatal developmental toxicity studies in rats and rabbits did not indicate treatment-related embryofetal toxicity or teratogenicity up to the highest dose levels tested. In a two-generation dietary study in rats, the high dose level resulted in reduced food consumption and body weight gain throughout the dosing-period. Mating performance and fertility, estrous cycles, gestation length and pre-and post-natal survival of offspring were essentially unaffected and there was no evidence of masculinization of female pups or feminization of male pups. The screening strategy that led to the selection of MFZ was aimed to identify candidates with both high fungicidal activity and minimal likelihood of adverse side effects thought to arise from aromatase inhibition. The success of the selection strategy has been illustrated for MFZ by the absence in toxicity studies of effects that would indicate an endocrine disrupting potential.