tert-butyl 3,5,5-trimethylperoxyhexanoate

Toxicity to reproduction

Administrative data

Endpoint:

extended one-generation reproductive toxicity - with developmental immunotoxicity (Cohorts 1A, 1B without extension, and 3)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2021-2022

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2022

Report date:

2022

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 443 (Extended One-Generation Reproductive Toxicity Study)

Version / remarks:

25 June 2018

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.56 (Extended One-Generation Reproductive Toxicity Study)

Version / remarks:

15 July 2014

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Justification for study design:

SPECIFICATION OF STUDY DESIGN FOR EXTENDED ONE-GENERATION REPRODUCTION TOXICITY STUDY WITH JUSTIFICATIONS

- Premating exposure duration for parental (P0) animals: 10 weeks, as requested by ECHA.
- Basis for dose level selection: Based on a pre-test conduced with TBPND; furthermore, results from a subchronic toxicity study in rats and a OECD 422 study were taken into consideration for dose level selection.
- Exclusion of extension of Cohort 1B; not requested by ECHA based on available data
- Exclusion of developmental neurotoxicity Cohorts 2A and 2B; not request by ECHA based on available data
- Inclusion of developmental immunotoxicity Cohort 3, as requested by ECHA
- Route of administration: oral (gavage)

Test material

Test material information

Constituent 1

Reference substance name:

tert-butyl peroxyneodecanoate

EC Number:

247-955-1

EC Name:

tert-butyl peroxyneodecanoate

Cas Number:

26748-41-4

Molecular formula:

C14H28O3

IUPAC Name:

Reaction products of neodecanoic acid (or neodecanoyl chloride derived from neodecanoic acid) and tert-butyl hydroperoxide

Test animals

Species:

rat

Strain:

Wistar

Details on species / strain selection:

The rat is regarded as suitable species for reproduction studies and the test guideline is designed to use the rat. The Wistar rat was selected due to a wide range of experience with this strain of rat in reproduction toxicity studies and well-known fertility parameters.

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Toxi-Coop Zrt. Cserkesz u. 90. H-1103 Budapest, Hungary
- Females nulliparous and non-pregnant: yes
- Age at study initiation: P0 males and females: not older than 9 weeks
- Weight at study initiation: (P) Males: The weight variation in animals involved at the starting point of the study will not exceed ± 20 % of the mean group weight of each sex.
- Fasting period before study: no
- Housing: Type III polypropylene/polycarbonate
Before mating: 2 animals of the same sex/cage
Mating: 1 male and 1 female/cage
Pregnant females will be housed individually.
Males after mating: 2 animals/cage
F1 offspring (after weaning): 2 animals of the same sex/cage
- Diet: ad libitum, ssniff® SM R/M-Z+H "Autoclavable complete feed for rats and mice
- Water: ad libitum, tap water
- Acclimation period: 15 days

ENVIRONMENTAL CONDITIONS
- Temperature: 22 ± 3°C
- Humidity: 30-70 %
- Air changes: > 10 per hr
- Photoperiod: 12/12 hrs dark / hrs light

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

vegetable oil

Remarks:

Sunflower oil (Helianthi annui oleum raffinatum)

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: The test item was formulated in the vehicle in concentrations of 25, 75 and 225 mg/mL. Formulations were prepared in the formulation laboratory of Test Facility not longer than for three days before the use. Analysis of formulations was performed in the Analytical Laboratory of Test Facility. Five samples were taken from different places from each concentration (Groups 2, 3 and 4) and measured on 5 occasions. Similarly, five samples were taken from the control solution (Group 1) from different places and analyzed.
VEHICLE
- Justification for use and choice of vehicle: The test item is not stable in water. Therefore, sunflower oil was used for preparing formulations appropriate for oral administration. Sunflower oil is a suitable vehicle to facilitate formulation analysis for the test item.
- Concentration in vehicle: 25, 75 and 225 mg/mL
- Amount of vehicle: 2 mL/kg bw

Details on mating procedure:

- M/F ratio per cage: 1:1
- Length of cohabitation: max. 2 weeks
- Proof of pregnancy: sperm in vaginal smear referred to as day 0 of pregnancy
- After successful mating each pregnant female was caged: single

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

A sufficient stability and homogeneity in the chosen vehicle have been verified over the range of relevant concentrations at the appropriate frequency of preparation. Recovery was 98 and 102 % of nominal concentrations at 1 and 500 mg/mL in sunflower oil, respectively. TBPND proved to be stable at room temperature for four hours (recovery was 105 % of starting concentration at 1 mg/mL and 100 % at 500 mg/mL) and at 5 ± 3°C for 3 days (recovery was 98 % of starting concentration at 1 mg/mL and 101 % at 500 mg/mL).

Duration of treatment / exposure:

Parental males were dosed for 70 days pre-mating and up to 14 days mating and until to the weaning of offspring. Overall treatment period is therefore up to 18 weeks for male parental animals.
Parental females were dosed for 70 days pre-mating, through up to 14 days mating period and throughout pregnancy and at least up to and including post-partum day 21 or up to the day before sacrifice. The day of birth (viz. when parturition is complete) is defined as day 0 post-partum. Overall treatment period is therefore up to 18 weeks for female parental animals.
Dosing of F1 offspring selected for follow-up examinations began on PND 22 up to post-natal day 90 (Cohort 1A) or at least up to post-natal day 97 (Cohort 1B).
F1 animals selected for determination of primary IgM antibody response to a T-cell dependent antigen in Cohort 3, were administered and observed individually up to and including the day before euthanasia on PND 61 ± 3.

Frequency of treatment:

daily, 7 days/week

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

50 mg/kg bw/day (nominal)

Doses / concentrations 2

Dose / conc.:

150 mg/kg bw/day (nominal)

Doses / concentrations 3

Dose / conc.:

450 mg/kg bw/day (nominal)

No. of animals per sex per dose:

P0: 26
F1, Cohort 1A: 20
F1, Cohort 1B: 20
F1, Cohort 3: 20

Control animals:

yes, concurrent vehicle

yes, historical

Details on study design:

- Dose selection rationale: The dose setting is based on findings obtained in previous studies with TBPND in rats (OECD 422, OECD 421, OECD 408)
- Fasting period before blood sampling for clinical biochemistry: yes

Positive control:

not applicable

Examinations

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily
- Pertinent behavioral changes, signs of difficult or prolonged parturition and all signs of toxicity including mortality were recorded including onset, degree and duration of signs.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: More detailed examinations were made at the times of weekly weighing, prior to and during the mating and until necropsy. Detailed clinical observations were made on all animals outside the home cage in a standard arena once prior to the first exposure and once weekly thereafter. Observations were performed on the skin, fur, eyes and mucous membranes, autonomic activity (lachrymation, piloerection, pupil size, respiratory pattern, occurrence of secretions and excretions), circulatory and central nervous system, somatomotor activity and behavior pattern, changes in gait, posture and response to handling. Special attention will be directed towards the observation of tremors, convulsions, salivation, diarrhea, lethargy, sleep and coma.

BODY WEIGHT: Yes
- Time schedule for examinations: Parental males were weighed on the first day of dosing (Day 0) and weekly thereafter. Parental females were weighed on the first day of dosing (Day 0) then weekly, on gestation days 0, 7, 14 and 21 and on post-partum days 0 (within 24 hours after parturition), 4, 7, 14 and 21. Body weight of the female animals were additionally weighed on gestation day 10 in order to give accurate treatment volumes, but these data were not be evaluated statistically. F1 animals selected for follow-up examinations were weighed on post-natal day 22, then twice a week during the two weeks following weaning (on PND 25, 29, 32, 36, 39 and 42), and once weekly thereafter (Cohorts 1A, 1B and Cohort 3). For selected F1offspring, the body weight was recorded on the day when they attain puberty (completion of balano-preputial separation or vaginal patency). Fasted body weight was measured on the day of necropsy for all animals (P and F1)

FOOD CONSUMPTION AND COMPOUND INTAKE: Yes
- The food consumption was determined weekly by reweighing the non consumed diet with a precision of 1 g during the treatment period except mating phase as follows:
- by weekly interval during premating and post-mating periods for P male animals and for F1 animals (Cohorts 1A, 1B and Cohort 3) after weaning;
- by weekly interval during premating period, on gestation days 0, 7, 14 and 21, on lactation days 0, 7, 14 and 21, then weekly if needed, for P female animals

WATER CONSUMPTION AND COMPOUND INTAKE: No

URINALYSIS: Yes
The following parameters were evaluated in selected test animals of P and F1 Cohort 1A generation:
Nitrite (NIT), pH, Glucose (GLUC), Urobilinogen (UBG), Bilirubin (BIL), Ketone (KET), Blood, Leucocytes (LEU), Specific Gravity (SG), Protein (PROT), Volume (VOL), Sediment (SED), Colour, Clarity

HEMATOLOGY/BLOOD COAGULATION
The following parameters were measured in all selected animals of P and F1 Cohort 1A generation:
White blood cell (leukocyte) count (WBC), Red blood cell (erythrocyte) count (RBC), Hemoglobin concentration (HGB), Hematocrit (HCT), Mean Corpuscular (erythrocyte) Volume (MCV), Mean Corpuscular (erythrocyte) hemoglobin (MCH), Mean Corpuscular (erythrocyte) hemoglobin concentration (MCHC), Platelet (thrombocyte) count (PLT), Reticulocytes (RET), Differential white blood cell count, Activated partial Thromboplastin Time (APTT), Prothrombin Time (PT).

CLINICAL CHEMISTRY
The following parameters were measured in all selected animals of P and F1 Cohort 1A generation:
Alanine Aminotransferase activity (ALT), Aspartate Aminotransferase activity (AST), Total Bilirubin concentration (TBIL), Creatinine concentration (CREA), Urea concentration (UREA), Glucose concentration (GLUC), Cholesterol concentration (CHOL), Sodium concentration (Na+), Potassium concentration (K+), Albumin concentration (ALB), Total protein concentration (TPROT)

DETERMINATION OF SERUM LEVELS OF THYROID HORMONES
Blood samples were collected for determination of serum levels of thyroid hormones (FT3, FT4, TSH) as follows:
- from 10 parent animals/sex/ group

Oestrous cyclicity (parental animals):

Estrous cycle was monitored by examining vaginal smears from each parental female animal daily for two weeks before the mating starts.Vaginal smears were also prepared and estrous cycle was monitored daily during the mating period until evidence of copulation. Vaginal smear was prepared on the day of the necropsy of parental animals.Vaginal smears were examined for all F1 Cohort 1A females selected for follow-up examinations after the onset of vaginal patency until the first cornified smear is recorded thus determining the time interval between these events. Estrous cycle of F1 adult female animals was examined for a period of two weeks commencing on PND77 and PND84 in Cohort 1A and Cohort 1B, respectively, including necropsy days. Vaginal smears were stained with 1 % aqueous methylene blue solution. After drying, the smears were examined with a light microscope.

Sperm parameters (parental animals):

Sperm parameters were measured in all control and high dose male animals in P generation and in F1 generation in Cohort 1A. The one-side testes and epididymides were used for examinations. The weights of one-side testes and epididymides were determined and recorded. Sperm from the ductus deferens was collected for evaluation of sperm motility and morphology at the necropsy. Both numbers of motile and immotile sperms were recorded. Two samples were prepared from each animal. For the determination of the sperm motility, the mean percentage of motile sperms were determined. A morphological evaluation of ductus deferens sperms sample was performed from the same animals. Sperm was examined as fixed, wet preparations and classified as either normal or abnormal (isolated heads, misshapen heads and/or tails). The epididymis was used for enumeration of cauda epididymis sperm reserves. The total number of sperm in homogenization was enumerated. The testis and epididymidis were frozen and enumeration were performed later.

Litter observations:

STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: yes
- maximum of 10 pups/litter (5/sex/litter as nearly as possible); excess pups were killed and discarded.

PARAMETERS EXAMINED
The following parameters were examined in F1 offspring:
number and sex of pups, stillbirths, live births, postnatal mortality, presence of gross anomalies, weight gain, physical or behavioural abnormalities, anogenital distance (AGD), presence of nipples/areolae in male pups on PND13, FT3, FT4 and TSH in surplus pups at PND 4 (pooled by litters) and in pups not selected for Cohorts on post-natal day 22.

Sexual maturity of selected F1 animals was examined by observing balano-preputial separation (between post-natal days 25 and 35; or until PND40) or vaginal patency (between post-natal days 28 and 40; or until PND45). The body weight was determined on the day when balanopreputial separation or vaginal patency is completed

GROSS EXAMINATION OF DEAD PUPS:
yes, for external and internal abnormalities; possible cause of death was determined for pups born or found dead

ASSESSMENT OF DEVELOPMENTAL NEUROTOXICITY: No

ASSESSMENT OF DEVELOPMENTAL IMMUNOTOXICITY: No

ASSESSMENT OF IMMUNOTOXICITY : Yes, Cohort 3

Animals of Cohort 3 were administered daily from weaning up to the day before the termination. The following observations will be conducted:
- Checking of mortality/ morbidity – twice daily;
- General clinical observations – daily;
- Detailed clinical observations were made outside the home cage in a standard arena once prior to the first exposure and once weekly thereafter.
- Body weight measurement – on PND 22, then twice a week during the two weeks following weaning and once weekly thereafter;
- Food consumption – on PND 22 and weekly thereafter
- Blood sampling for T-cell dependent antibody response assay (TDAR) on PND 56±3 and PND 61±3;
On PND 61±3 the primary IgM antibody response to a T-cell dependent antigen – keyhole limpet hemocyanin (KLH) – is assessed after subcutaneous immunization of all Cohort 3 animals with KLH (0.2 mL at a concentration of 1.5 mg/mL on PND56±3; prior dosing with test-item). Anti-KLH IgM antigen concentrations in serum was measured before immunization and 5 days after immunization using a validated ELISA method (Rat Anti-KLH IgM ELISA kit, Life Diagnostics, Inc.). Responses typically peak five days after immunization.

DETERMINATION OF SERUM LEVELS OF THYROID HORMONES
Blood samples were collected for determination of serum levels of thyroid hormones (FT3, FT4, TSH) as follows:
- in surplus pups at PND 4 (pooled by litters)
- from 10 adult F1 male and female animals/group (Cohort 1A ) at termination
- from 10 F1 pups/group not selected for cohorts on PND22

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: after mating period
- Maternal animals: on PND 22.

GROSS NECROPSY
- Gross necropsy consisted of external and internal examinations including the cervical, thoracic, and abdominal viscera.

HISTOPATHOLOGY / ORGAN WEIGHTS
The following tissues were prepared for microscopic examination and weighed, respectively, for high dose and control animals:

Organ weights (all parental (P) animal and all adult F1 animals of Cohort 1A):
- uterus (with oviducts and cervix)
- ovaries
- testes
- epididymides
- prostate (dorsolateral and ventral parts combined)
- seminal vesicles with coagulating glands as one units (with their fluids)
- brain
- liver
- kidneys
- heart
- spleen
- thymus
- pituitary
- thyroid glands (post-fixation)
- adrenal glands

The organs were fixed in 4% buffered formaldehyde solution. Paired organs were weighed together except for organs with macroscopically visible difference in size between the two organs. Absolute organ weight was recorded and reported.

Full histological examinations was performed on the above listed organs and tissues of control and high dose treated parental animals. Reproductive organs were examined in all animals suspected of reduced fertility (not mated, non pregnant or not delivered) in the low and mid dose group.

SPLENIC LYMPHOCYTE SUBPOPULATION ANALYSIS
At termination, weighing of the lymph nodes and splenic lymphocyte subpopulation analysis was performed in 10 male and 10 female Cohort 1A animals from each group (1 male or 1 female per litter; all litters represented by at least 1 pup; randomly selected) as follows:
- weighing of the lymph nodes associated with and distant from the route of exposure (submandibular and popliteal lymph nodes);
- splenic lymphocyte subpopulation analysis: CD4+ (Helper T cells) and CD8+ (Cytotoxic T cells) T lymphocytes, B lymphocytes and natural killer (NK) cells were identified by a validated flow cytometry method. Immuno-staining and immunophenotyping of spleen lymphocytes were carried out after preparation of single cell suspensions from one half of each provided spleen. For further information please refer to the attached background material.

Postmortem examinations (offspring):

SACRIFICE
- Offspring selected for Cohort 1A and Cohort 1B: on post-natal days 91and 98, respectively
- Offspring selected for Cohort 3 on PND 61±3
- Offspring not selected: on post-natal day 22

GROSS NECROPSY
- Gross necropsy consisted of external and internal examinations including the cervical, thoracic, and abdominal viscera.

HISTOPATHOLOGY / ORGAN WEIGTHS
Organ weights ( all adult F1 animals of Cohort 1A):
- uterus (with oviducts and cervix)
- ovaries
- testes
- epididymides
- prostate (dorsolateral and ventral parts combined)
- seminal vesicles with coagulating glands as one units (with their fluids)
- brain
- liver
- kidneys
- heart
- spleen
- thymus
- pituitary
- thyroid glands (post-fixation)
- adrenal glands

In animals of Cohort 1B, the weight of following organs was determined:
- uterus (with oviducts and cervix)
- ovaries
- testes
- epididymides
- prostate (dorsolateral and ventral parts combined)
- seminal vesicles with coagulating glands as one units (with their fluids)
- brain,
- pituitary

For 10 male and 10 female pups per group, not selected for Cohorts, – from as many litters as possible – brain, spleen and thymus was weighed.

In animals of Cohort 3, the body weight and weight of following organs was determined:
- thymus
- spleen
- brain

Full histological examinations was performed on the above listed organs and tissues of control and high dose treated adult F1 animals in Cohort 1A. In adult F1 animals in Cohort 1B, the uterus (with oviducts and cervix), ovaries, testes, epididymides, prostate (dorsolateral and ventral parts combined), seminal vesicles with coagulating glands as one unit (with their fluids), brain, pituitary will be processed to the block stage. In the ovaries of F1 adult females of control and high dose groups, a quantitative evaluation of primordial and small growing follicles, as well as corpora lutea was performed.

Detailed histological examination of testis was conducted with special emphasis on stages of spermatogenesis in the F1 male gonads and histopathology of interstitial testicular cell structure. Rete testis – where feasible – caput, corpus, and cauda of the epididymides were examined. All gross lesions were examined histologically. The fixed tissues were trimmed, processed (dehydrated), embedded in paraffin, sectioned with a microtome (at a thickness of 2-4 µm), placed on glass microscope slides, stained with hematoxylin and eosin and examined by light microscopy.

Statistics:

The homogeneity of variance between groups was checked by Bartlett’s
homogeneity of variance test. Where no significant heterogeneity is detected, a one-way analysis of variance (ANOVA) was carried out. If the obtained result was significant, Duncan Multiple Range test was used to access the significance of intergroup differences. Getting significant results at Bartlett’s test the Kruskal-Wallis analysis of variance was used and the inter-group comparisons were performed using Mann-Whitney U-test. Chi2 test was performed if feasible.

Reproductive indices:

Copulatory Index (Measure of animals ability to mate):
Males: Number of males with confirmed mating / Total number of males cohabited x 100
Females: Number of sperm positive females / Total number of females cohabited x 100

Fertility Index (Measure of male’s ability to produce sperm that can fertilize eggs and measure of female’s ability to become pregnant):
Males: Number of males impregnating a females / Total number of males with confirmed mating x 100
Females: Number of pregnant females / Number of sperm positive females x 100

Gestation Index (Measure of pregnancy that provides at least one live pup):
Number of females with live born pups / Number of pregnant females x 100

Offspring viability indices:

Formulas for Calculation of Pup Mortality and Sex Ratio Indices:

Post-implantation mortality: Number of implantations – Number of liveborns / Number of implantation x 100

Post-natal mortality: Number of liveborns – Number of live pups on PND 13 / Number of liveborns x 100

Survival Index: Number of live pups on PND 13 / Number of liveborns x 100

Sex ratio: Number of pups examined – Number of pups males (females) / Number of pups examined x 100

Results and discussion

Results: P0 (first parental generation)

Effect levels (P0)

Dose descriptor:

NOAEL

Based on:

test mat.

Sex:

male/female

Remarks on result:

other: Study not yet finalized. Study results will be reported in an update.

Target system / organ toxicity (P0)

Key result

Critical effects observed:

not specified

Results: F1 generation

Effect levels (F1)

Dose descriptor:

NOAEL

Generation:

F1

Based on:

test mat.

Sex:

male/female

Remarks on result:

other: Study not yet finalized. Study results will be reported in an update.

Target system / organ toxicity (F1)

Critical effects observed:

not specified

Overall reproductive toxicity

Reproductive effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

The study on ongoing and final results will be presented in an update. Preliminary findings are as follows:
Body weight: The body weight was lowered in male animals at 450 mg/kg bw/day (approximately -12 % terminally) but not in females.
Mating: The mating was successful: 26/26, 26/26, 26/26, 26/26 respectively to groups control, 50, 150, 450 mg/kg bw/day.
Pregnancy: Pregnancy was achieved in all groups with no difference compared to the control group: 25/26, 26/26, 24/26, 24/26, respectively to groups control, 50, 150, 450 mg/kg bw/day
Necropsy: 23/26 renal alteration (pale, enlarged or soft kidneys) in male animals at 450 mg/kg bw/day – thus, histological processing was performed on the kidneys of all animals.
Histopathology: chronic progressive nephropathy in male animals: 13/26 at 150 mg/kg bw/day and 26/26 at 450 mg/kg bw/day;
Based on daily observations, development of offspring was not essentially affected at any dose level. Evaluation, processing of additional data and histological processing of F1 animals are is in progress.
Based on first results for histopathology, the ovaries had a normal structure i.e., characteristic of the species, age and phase of the active sexual cycle in the control and 450 mg/kg bw/day groups. The cortical region of ovaries contained primary, secondary and tertiary follicles and corpora lutea, indicating the active maturation of oocytes and ovulation. The epithelial capsule and ovarian stroma was normal in all cases as well. The number of developing follicles and the number of follicular atresia was similar in the control and treated animals.