Phenyl diamidophosphate

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2019-01-16 - 2019-12-03

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2019

Report date:

2019

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Phenyl diamidophosphate

EC Number:

231-218-6

EC Name:

Phenyl diamidophosphate

Cas Number:

7450-69-3

Molecular formula:

C6H9N2O2P

IUPAC Name:

[(diaminophosphoryl)oxy]benzene

Test material form:

solid: crystalline

Details on test material:

Name PPDA
Composition phosphoric acid phenylester diamide

CAS No. 7450-69-3
EINECS-No. 231-218-6
Molecular formula C6H9N2O2P
Molecular weight 172.1 g/mol
Purity 97.77% (HPLC)

Specific details on test material used for the study:

Chemical name Phenyl phosphorodiamidate
further referred as PPDA
CAS no. 7450-69-3
Batch no. P 107/97/S-8
Receipt no. 66988
Date of receipt 24 October 2018
Characteristics White powder
Molecular weight 172.12 g/mol

Test animals

Species:

rat

Strain:

other: CD/ Crl:CD (SD)

Details on test animals or test system and environmental conditions:

Breeder: Charles River Laboratories, Research Models and Services, Germany GmbH, Sandhofer Weg 7, 97633 Sulzfeld, Germany
Adaptation period: 5 days
Age: (on day 0 of pregnancy): 55 - 69 days
Body weight: (on day 0 of pregnancy): 178.8 g - 269.0 g
Selection of species: The rat is a commonly used rodent species for such embryotoxicity studies.
Diet:
Commercial diet ssniff® R/Z V1324 (ssniff Spezialdiäten GmbH, 59494 Soest, Germany served as food. This food was offered daily ad libitum.
Samples of the food are analysed for contaminants based on EPA/USA2 by LUFAITL3 at least twice a year .
Certificates of analysis of the composition and for contaminants were provided by the manufacturer and are included in the raw data. No contaminants above the limitations were noted.
Housing:
The animals were kept singly in MAKROLON cages (type III plus) with a basal surface of approx. 39 cm x 23 cm and a height of approx. 18 cm. The room temperature was 22°C ± 3°C (maximum range) and the relative humidity 55% ± 10% (maximum range).
The rooms were alternately lit (about 150 lux at approximately 1.5 m room height) and darkened in a 12 hours dark/12 hours light cycle. The ventilation rate of the animal room was between fifteen to twenty air changes per hour.
Drinking water:
Drinking water (in drinking bottles) was offered ad libitum.
Samples of drinking water are taken periodically by the Wasserwerk Wankendorf (24601 Wankendorf, Germany), and periodic analyses are performed by LUFA-ITL according to the 'Deutsche Trinkwasserverordnung 2001' [German Regulations on drinking water 2001].

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: tap water

Details on exposure:

Route of administration: Oral, via gavage
Frequency of administration: Once daily
Treatment period: Day 6 to 20 of gestation
Vehicle: Tap water
Administration volume: 2 mL/kg b.w./day
Selection of route of administration: According to OECD guideline 414
The test item formulations were freshly prepared every day. The test item was suspended in the vehicle to the appropriate concentrations and
was administered orally at a constant volume/kg b.w. once daily from the 6th to the 20th day of gestation. The administration formulations were continuously agitated by stirring throughout the entire administration procedure. The amount of the test item was adjusted to the animal's current body weight daily. The control animals received the vehicle at the same administration volume daily in the same way. In addition, the stability, homogeneity and concentration of the test item mixture was monitored.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

For the analysis of the test item-vehicle formulations, samples of approximately 10 mL were taken at the following times and stored at -20°C ± 10% until analysis at LPT: At start of dosing: Analysis of stability and concentration:
Immediately after preparation of the formulation as well as after 8 and 24 hours storage of the test item preparation at room temperature.
(3 samples/test item group).
Number of samples: 3 x 3 = 9
(Sampling date: 29 January 2019)
Homogeneity:
At the start of administration, during (middle) administration and before administration to the last animal of the test item group.
(3 samples/test item group)
Number of samples: 3 x 3 = 9
(Sampling date: 29 January 2019)
At the end of the dosing period, at a time when the majority of the animals was dosed
Analysis of concentration:
During treatment always before administration to the last animal of the group (1 sample/test item group).
Number of samples: 1 x 3 = 3
(Sampling date: 11 February 2019)
Sum of all samples: 21
The samples were labelled with the study number, species, type of sample,
concentration, sampling time, date and test day.

Details on mating procedure:

Sexually mature ('proven') male rats of the same breed served as partners. The female breeding partners were randomly chosen.
Mating was monogamous: 1 male and 1 female animal were placed together in one cage during the dark period. Each morning a vaginal smear was taken to check for the presence of sperm. If findings were negative, mating was repeated with the same partner. The day on which sperm was found was considered as the day of conception (day 0 of pregnancy). This procedure was repeated until 25 mated dams were available for each group. The non-pregnant rats were excluded from the analysis of the results and replaced by other animals. A post-mortem negative staining according to SALEWSKI was carried out in the replaced animals in order to confirm the non-pregnancy status.

Duration of treatment / exposure:

Day 6 to 20 of gestation.

Frequency of treatment:

Once daily

Duration of test:

Day 6 to 20 of gestation.

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day

Doses / concentrations 2

Dose / conc.:

20 mg/kg bw/day

Doses / concentrations 3

Dose / conc.:

60 mg/kg bw/day

Doses / concentrations 4

Dose / conc.:

200 mg/kg bw/day

No. of animals per sex per dose:

25 females per group

Control animals:

yes, concurrent vehicle

Details on study design:

The dose levels for this study have been selected in agreement with the Sponsor based on the results of a dose-range-finding study in rats
and an acute toxicity study.
In the dose-range-finding study, the test item PPDA was administered orally to female rats at dose levels of 15, 50 and 150 mg/kg b.w./day from 6th to 20th day of pregnancy. The following observations were made:
Possibly, a marginal decrease of a maximum 2.2% in body weight was observed in the high dose group of 150 mg/kg b.w. on gestation days 8, 9, 11 and 13.
No changes were noted for the behaviour, external appearance or the faeces. Furthermore, no test item-related differences were noted for the body weight, the food consumption and also the reproduction parameters (number of fetuses, number of resorptions).
In an acute toxicity study in the rat single doses of 2000, 500 and 300 mg PPDA/kg b.w. were given to 4 administration groups of three fasted female animals each, (2000 mg/kg in 3 females, 500 mg/kg in 3 females, 300 mg/kg in 6 females) by gavage in a sequential manner.
All animals of the 2000 mg/kg administration group and two animals of the 500 mg/kg administration group were found dead from hour 1 through hour 2 after administration.
No mortality occurred in the 300 mg/kg administration groups. Clinical observation in the administration groups revealed impaired and poor general
state, dyspnoea, apathy, excitation, abdominal position, staggering, tremor, twitching, fibrillary contractions, clonic convulsions, piloerection, smeared fur, diarrhea, exsiccosis, salivation, lacrimation, chromodacryorrhea and reduced faeces. Findings were observed from hour 1 through to study day 5 after administration. The mean body weights of the 300 mg/kg administration groups and the body weight of the surviving animal of the 500 mg/kg group increased throughout the study period. No macroscopic pathologic abnormalities were noted in the animals that died and in
animals examined at the end of the observation period.
Under the conditions of this study the median lethal dose of the test item after oral administration was found to be greater than 300 mg/kg and less than 500 mg/kg b.w. in rats.
Therefore, the suggested dose levels were 20, 60 and 200 mg PPDA/kg b.w. for the treatment groups of this study.

Examinations

Maternal examinations:

Clinical signs:
Individual animals were observed daily for behavioural changes, reaction to treatment, or illness. Immediately after administration, any signs of illness or reaction to treatment were recorded. In case of changes, the animals were observed until the symptoms disappeared. In addition, animals were checked regularly throughout the working day from 7.00 a.m. to 3.45 p.m. On Saturdays and Sundays, the animals were checked regularly starting from 7.00 a.m. to 11.00 a.m. with a final check performed at approximately 3.30 p.m. Dated and signed records of appearance, change and disappearance of clinical signs were maintained on clinical history sheets for individual animals. Special attention was paid to ascertain if there were any signs of irritation after oral dosing, such as increased salivation, redness of the oral cavity etc.
Viability:
Further checks were made early in the morning and again in the afternoon of each working day to look for dead or moribund animals. This allowed post mortem examinations to be carried out during the working period of that day. On Saturdays and Sundays, a similar procedure was followed except that the final check was carried out at approximately midday. Animals showing signs of abortion or premature delivery would have been sacrificed on the same day. Fetuses obtained this way were examined for abnormal development, whenever possible. No abortion or premature delivery occurred in the study. Cannibalism (i.e. after premature delivery) would have been recorded, if detectable.
Body weight:
The weight of each rat was recorded on day 0 of gestation (the day of detection of a positive mating sign), followed by daily weighing - always at the same time of the day. The body weight gain was calculated in intervals (i.e. gestation day 0-3, 3-6, 6-9, 9-12, 12-15, 15-18 and 18-21), for the whole study (gestation day 0 - 21) and for the period after the start of dosing (gestation day 6 to gestation day 21). Furthermore, the carcass weight and the net weight gain5 from day 6 is given.
Food and drinking water consumption:
The quantity of food consumed by each rat was recorded daily. Food intake per rat (g/rat/day) was calculated using the total amount of food given to and left by each rat in each group on completion of a treatment day. Daily monitoring by visual appraisal of the drinking water bottles was maintained
throughout the study. Dehydration of the dams was avoided.
Thyroid hormone (T3, T4, TSH) determination:
In order to obtain approximately 2 x 150 μL serum for each endocrine endpoint (T3, T4, TSH), a sufficient volume of blood was taken from the retrobulbar venous plexus under isoflurane anaesthesia from animals fasted overnight following a randomisation scheme. Blood samples were taken always at the same time of day (approximately from 7:00 a.m. to 10:00 a.m.).
Examination of the dams
Dissection technique and evaluation of the animals:
On gestation day 21, the rats were laparotomised under CO2 narcosis. The thyroids (including parathyroids) and the gravid uterus (in toto) of the dams were removed and weighed. In order to check for possible test item effects, a dissection with macroscopic examination of the internal organs and placentae of the dams was carried out on the day of sacrifice or on the day on which the animals were found dead. The
thyroids and any organs with macroscopic findings of all dams (including deceased or prematurely sacrificed animals) were fixed in 7% neutral buffered formalin.
Histopathology (thyroid only):
The thyroids of all evaluated dams were examined histopathological after preparation or hematoxylin-eosin stained paraffin sections.

Ovaries and uterine content:

Corpora lutea
- number per dam
- absolute number per group
- mean per group
Implantations
- number per dam
- distributions in the uterine horns
- absolute number per group
- mean per group
Resorptions
- number of early and late resorptions per dam
- distributions in the uterine horns
- absolute number per group
- mean per group
- early resorptions < 2 mm
- late resorptions > 2 mm
Weight of placentae
- individual data per fetus
- mean per litter
- mean per group
- mean per sex and group
Weight of fetuses
- individual data per fetus (alive and dead)
- mean per litter
- mean per group
- mean per sex and group
Fetuses
- number per dam (alive)
- number per dam (dead)
- number of fetuses (alive + dead) per sex and dam
- distribution in the uterine horns
- absolute number of fetuses alive per group
- mean number of fetuses alive per group
- male/female ratio (alive + dead)
Runts
- number per dam
- number per group

Fetal examinations:

The fetuses were removed and the following examinations performed:
(a) Macroscopic inspection (gross evaluation) of the placentae for example for focal indurations or abnormal appearance (e.g. size, colour, shape).
(b) The number of fetuses (alive and dead) and placentae (location in the uterus and the assignment of the fetuses) was determined.
(c) Sex and viability of fetuses were determined. Animals are said to be viable when they are found alive (spontaneous breathing, spontaneous movement).
(d) Number and size of resorptions were determined.
(e) Corpora lutea in the ovaries, implantations and location of fetuses in the uterus were determined.
(f) Weights of fetuses and weights of the placentae were determined (fetuses were considered as runts if their weight was less than 70% of the mean litter weight).
(g) The ano-genital distance (AGD) of all live fetuses was determined using a scale.
(h) All fetuses (dead and alive) were inspected externally for damages, especially for malformations7.
(i) The fetuses were sacrificed by an ether atmosphere.
(j) Examination of fetuses and determination of number and kind of retardations,
variations or malformations:
1) 50% of the number of fetuses in each litter were examined for skeletal anomalies. The thorax and peritoneal cavity (without damage to ribs and sternum) were opened and the location, size and condition of the internal organs were determined.
Then the skeleton was double-stained with Alcian blue for the examination of cartilage and with Alizarin red to reveal ossifications (according to
DAWSON). The skeletal system was examined (determination of the number and type of retardations, variations as well as malformations).
2) The remaining 50% of the number of fetuses in each litter were examined for soft tissue anomalies. Body sections were made and examined
according to WILSON.
The fetuses were allocated to the evaluation of DAWSON or WILSON on an alternating basis.
(k) External fetal sex (as determined by gross examination) was compared with internal (gonadal) sex in all fetuses (examined for both skeletal and soft tissue malformations).
(l) Indication of incomplete testicular descent/cryptorchidism was noted in male fetuses.

Statistics:

Parametrical data:
The statistical evaluation of the parametrical values was done by Provantis using the following settings:
Homogeneity of variances and normality of distribution were tested using the BARTLETT's and SHAPIRO-WILK's test. In case of heterogeneity and/or nonnormality of distribution, stepwise transformation of the values into logarithmic or rank values was performed prior to ANOVA. If the ANOVA yielded a significant effect (p ≤ 0.05), intergroup comparisons with the control group were made by the DUNNETT’s test (p ≤ 0.01 and p ≤ 0.05).
Non-parametrical data:
The statistical evaluation of non-parametrical values was done using the FISHER or Chi2 test.

Historical control data:

Yes, 2004 to 2017, results of the 52 last embryotoxicity studies in Sprague-Dawley rats

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

no effects observed

Description (incidence and severity):

No changes were noted for the treatment groups (20, 60 or 200 mg PPDA/kg b.w./day). All animals of all groups, including the control revealed normal behaviour, external appearance and faeces.

Mortality:

no mortality observed

Description (incidence):

No premature deaths were noted in the control group and in the dose groups (20, 60 or 200 mg PPDA/kg b.w./day).

Body weight and weight changes:

no effects observed

Description (incidence and severity):

No test item-related differences in body weight were noted between the dams of the control group and the dams of the dose groups (20, 60 and 200 mg PPDA/kg b.w./day). In the high dose group (200 mg PPDA/kg b.w./day), a slight reduction in the body weight was noted on GD 9 and GD 10 (1.7% and 2.2% below the value of the control group, not statistically significant).No test item-related differences were noted for the net body weight gain throughout the study period from GD 0 to 21 or over period after start of dosing from GD 6 to GD 21 between the dams of the control group and the dams of the dose groups (20, 60 or 200 mg PPDA/kg b.w./day). However, a small decrease in the body weight gain was observed in the intermediate and high dose group (60 and 200 mg PPDA/kg b.w./day) over the treatment period from GD 6 to GD 20 (2.7% and 2.9% below the control group, not statistically significant) on GD21. This was however, not statistically significant. Therefore, regarded to be not adverse. The reduced body weight and body weight gain are transient effects after start of the treatment and were not considered to be of toxicological relevance. The described observations were noted without any other clinical symptoms and the
effect of the reduced food intake over this period. In accordance to the publication from Lewis et. al. (2002) this observation is excluded in the assessment of the NOAEL.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

No test item-related difference was noted between the control group and the dose group of 20 mg PPDA/kg b.w./day. For the intermediate dose group (60 mg PPDA/kg b.w./day), a decrease in food consumption was noted between GD 7 and GD 8 (7.9% below the value of the
control group, not statistically significant) and in the high dose group (200 mg PPDA/kg b.w./day) from GD 7 to GD 10 (14.8% or 7.8% below the value of the control group, statistically significant between GD 7 and GD 8 at p ≤ 0.05). These transient decreases in food consumption were considered to be test item-related, but without any toxicological relevance, as they were small and fully reversible within very few days (see Lewis et. al. (2002)). Statistically significantly increased values for the food consumption were noted for the low dose group (20 mg PPDA/kg b.w./day) between GD 10 to GD 11 (11.6% above the value of the control group, p ≤ 0.01) and for the high dose group from
GD 20 to GD 21 (10.5% above the value of the control group, p ≤ 0.05). However, these differences were only transient effects and an increased food consumption was not considered to be test item-related.

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

no effects observed

Description (incidence and severity):

No test item-related changes in drinking water consumption were noted between
the dams of the control group and the dams of the treatment groups by visual
appraisal.

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

No test item-related differences were noted for the concentrations of T3, T4 and TSH in the dose groups (20, 60 or 200 mg PPDA/kg b.w./day) on GD 21.
At 60 and 200 mg PPDA/kg b.w./day, a statistically significant decrease was noted for the concentration of the thyroid hormone T3 (25.0% and 28.2% below the value of the control group, both statistically significant at p ≤ 0.05). However, histopathologic examination of the thyroids displayed no changes and also no differences were noted for the thyroid weights. The decreased T3 levels, that were noted for the animals were not considered to be of toxicological relevance and were not employed for the determination of the NOAEL. Such an assessment is in accordance with a publication by Siglin, J.C., 2000. Dose levels with significant thyroid hormone levels, but without changes in the thyroid weight and histopathology or other indicators of toxicity (e.g. adverse clinical signs) were not considered for determining the NOAEL.
It is generally known that histopathological examination of the thyroids is usually more sensitive than hormone levels (Beekhuijzen et al., 2016). The validation report of OECD 407 (OECD, 2006) states that “Thyroid histopathology was consistently the most reliable and most sensitive endpoint for the detection of thyroid modulation. Thyroid weight was reliable, but was somewhat less sensitive when
compared to thyroid histopathology. Circulating thyroid hormone levels (T3, T4, and TSH) were not always reliable and sensitive, but standard operating procedures for blood sampling and for thyroid hormone analyses were not standardized to reduce stress induced variability, respectively. Circulating T4 levels were the most promising of the three thyroid hormone values.” Therefore, the decreased serum concentrations of T3 were considered to be spontaneous and not test item-related.

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

Thyroid weights:
No test item-related differences were noted between the control group and the female animals dosed with 20, 60 or 200 mg PPDA/kg b.w./day.

Gross pathological findings:

no effects observed

Description (incidence and severity):

No pathologic changes were noted for the dams of the low and high dose groups (20 or 200 mg PPDA/kg b.w./day) during the macroscopic inspection of the organs and tissues.
In the intermediate dose group (60 mg PPDA/kg b.w./day), dam no. 53 was noted with a dilatation of the right renal pelvis. However, the single occurrence of one dilated renal pelvis was considered to be spontaneous.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

In the dose groups (20, 60 or 200 mg PPDA/kg b.w./day), no test item-related pathologic changes were noted during microscopical evaluation of the thyroids. The central microfollicular structures of the thyroids contained cells in the follicle lumen. Furthermore, squamous cell cysts were observed in the thyroid and focal C-cell complexes of minimal size were found in the interstitium. However, these findings were considered to be artefacts or coincidental findings and therefore, not test item-related. No histomorphological differences were noted between the left and right lobe of the
thyroids and also no differences were noted between the thyroids of the control
animals and the thyroids of the animals dosed with PPDA.

Other effects:

not examined

Maternal developmental toxicity

Number of abortions:

no effects observed

Pre- and post-implantation loss:

no effects observed

Description (incidence and severity):

No test item-related influence on the reproductive parameters (number of
implantation sites, fetuses, resorptions and the index of pre- and post-implantation
loss) were noted between the dams of the control group and the dams of the dose
groups (20, 60 or 200 mg PPDA/kg b.w./day).

Total litter losses by resorption:

no effects observed

Early or late resorptions:

no effects observed

Dead fetuses:

no effects observed

Changes in pregnancy duration:

no effects observed

Changes in number of pregnant:

no effects observed

Effect levels (maternal animals)

Key result

Dose descriptor:

NOAEL

Effect level:

200 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

other: no effects observed

Maternal abnormalities

Key result

Abnormalities:

no effects observed

Results (fetuses)

Fetal body weight changes:

no effects observed

Reduction in number of live offspring:

no effects observed

Changes in sex ratio:

no effects observed

Changes in litter size and weights:

no effects observed

Changes in postnatal survival:

not examined

External malformations:

no effects observed

Description (incidence and severity):

No macroscopically visible external malformations were noted for the fetuses of the intermediate and high dose group (60 or 200 mg PPDA/kg b.w./day) during the external inspection at laparotomy.

Skeletal malformations:

no effects observed

Description (incidence and severity):

No skeletal malformations were noted for the fetuses of the control group and the test item-treated groups (20, 60 or 200 mg PPDA /kg b.w./day) during the skeletal examination according to DAWSON.
Skeletal variations were noted for the ribs (ribs wavy) and the sternum (misaligned to a slight degree).
No test item-related difference in the incidence of the observed skeletal variations in comparison to the control group was noted for the fetuses of the treatment groups (20, 60 or 200 mg PPDA/kg b.w./day).
No test item-related increase in the incidence of skeletal retardations at 20, 60 or 200 mg PPDA/kg b.w./day was noted during skeletal examination according to DAWSON.

Visceral malformations:

no effects observed

Description (incidence and severity):

The macroscopic inspection of the organs and tissues for gross alterations at laparotomy revealed no malformations or variations for the fetuses of the control group and the fetuses of the dose groups (20, 60 or 200 mg PPDA/kg b.w./day).
No malformations were noted for the fetuses of low and intermediate dose group (20 or 60 mg PPDA/kg b.w./day) during the soft tissue examination according to WILSON.
During the examination of the organs and tissues according to WILSON, variations were noted for the brain (haemorrhage), the kidneys (uni- or bilateral dilatation of
the renal pelvis, hydro-ureter or nephroptosia) and the liver (haemorrhagic focus/foci).
No test item-related differences and no statistically significant differences in the incidences of the observed variations were noted between the control group and the dose groups (20, 60 or 200 mg PPDA/kg b.w./day).
No unclassified observations were noted for the control group and for the
intermediate dose group (60 mg PPDA/kg b.w./day).
An unclassified observation in form of a thoracic cavity filled with blood was noted for one fetus (no. 43-12) of the low dose group (20 mg PPDA/kg b.w./day) and for one fetus (no. 89-16) of the high dose group (200 mg PPDA/kg b.w./day). This observation was considered to be a preparation-induced artefact and not test item-related.

Other effects:

no effects observed

Description (incidence and severity):

Testicular development
The examination of the testicular development revealed no malposition and no absence of testes in the control group and the dose groups (20, 60 or 200 mg PPDA/kg b.w./day).

Effect levels (fetuses)

Key result

Dose descriptor:

NOAEL

Effect level:

200 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no effects observed

Fetal abnormalities

Key result

Abnormalities:

no effects observed

Overall developmental toxicity

Key result

Developmental effects observed:

no

Applicant's summary and conclusion

Conclusions:

In this prenatal developmental toxicity study, the test item Phenyl phosphorodiamidate (PPDA) was administered orally to female rats at dose levels of 20, 60 or 200 mg/kg b.w./day from the 6th to 20th day of pregnancy.
Under the test conditions, the no-observed-adverse-effect level (NOAEL) was 200 mg PPDA/kg b.w./day for the dams.
The no-observed-adverse-effect level (NOAEL) for the fetal organism was above 200 mg PPDA/kg b.w./day.
Under the conditions of the study, Phenyl phosphorodiamidate (PPDA) did not show any teratogenic potential for rats.

Executive summary:

In this prenatal developmental toxicity study, the test item Phenyl phosphorodiamidate (PPDA) was administered orally to female rats at dose levels of 20, 60 or 200 mg/kg b.w./day from the 6th to 20th day of pregnancy.

A reduced body weight was noted for the female animals of the high dose group 200 mg PPDA/kg b.w./day on GD 9 and GD 10.

There was no test item-related influence on the net body weight gain in the test groups compared to the control group during the treatment period (GD 6 to GD 20) on GD 21. However, the female animals treated with 60 and 200 mg PPDA/kg b.w./day, showed a slight reduction in the body weight gain right after start of the treatment. This effect was fully reversible within a few days.

A test item-related reduction was noted for the food consumption from GD 7 to GD 8 in the intermediate dose group (60 mg PPDA/kg b.w./day) and from GD 7 to GD 10 for the dams dosed with 200 mg PPDA/kg b.w./day.

As no other clinical symptoms were noticed and all above mentioned effects were only marginal and fully reversible, these observations arenotconsidered as adverse effects.These observations are transient effects after start of the treatment and werenotconsidered to be of toxicological relevance.The observations were noted without any other clinical symptoms and the effect of the reduced food intake over this period. In accordance to the publication from Lewiset. al.(2002) this observation is excluded in the assessment of the NOAEL.

No test item-related premature death was noted for any dose group.

No test item-related changes in behaviour, external appearance or faeces were noted for the treatment groups.

No test item-related pathologic changes, no test item-related differences for the thyroid weights and no test item-related changes in the serum thyroid hormone concentration were noted for the dose groups.

Therefore, under the present test conditions, the no-observed-adverse-effect level (NOAEL) was 200 mg PPDA/kg b.w./day for the dams.

The reproductive parameters (number of implantation sites, number of resorptions and number of fetuses) were not influenced by the test item. The placental and fetal weights of the dose groups were not influenced by the test item.
No test item-related deaths of fetuses and no test item-related malformations, variations or retardations were noted.

 

The no-observed-adverse-effect level (NOAEL) for the fetal organism was above 200 mg PPDA/kg b.w./day.

Under the conditions of the study, Phenyl phosphorodiamidate (PPDA) did not show any teratogenic potential for rats.