3a,4,5,6,7,7a-hexahydro-4,7-methano-1H-indenyl propionate

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

Cyclaprop and its toxicity to reproduction: Absence of toxicity to reproduction based on read across from Cyclacet in an oral gavage OECD TG 421 in which a NOAEL of ≥1000 mg/kg bw/day was derived. In addition, Cyclacet did not show effects on Reproductive organs in a dietary 90-day study according to OECD TG 408, with a NOAEL of 1500 mg/kg bw.

Effect on fertility: via oral route

Endpoint conclusion:

no adverse effect observed

Study duration:

subacute

Species:

rat

Quality of whole database:

The reproduction/developmental toxicity screening study and available repeated dose toxicity studies are of sufficient quality and are sufficiently adequate for this dossier.

Additional information

For Cyclaprop, toxicity to reproduction is derived from the close structural analogue Cyclacet. The summary of the experimental information available is presented first and thereafter the read across rationale.

Cyclacet and its fertility and developmental toxicity in an OECD TG 421 study

The potential adverse effects of the test material on reproduction including offspring development were studied in an OECD 421 Reproduction/Developmental Toxicity Screening Test following GLP. The test material was administered by gavage to three groups, each of ten male and ten female Wistar rats, for up to forty-six consecutive days (including a two week maturation phase, pairing, gestation and early lactation for females), at dose levels of 100, 300 and 1000 mg/kg bw/day. A control group of ten males and ten females was dosed with vehicle alone (Arachis oil BP). Adult males were terminated on Day 43, and all females and surviving offspring on Day 5 post partum. 

Clinical signs, bodyweight change, dietary intake and water consumption were monitored during the study. Pairing of animals within each dose group was undertaken on a one male: one female basis within each treatment group on Day 15 of the study, with females subsequently being allowed to litter and rear their offspring to Day 5 of lactation. During the lactation phase, daily clinical observations were performed on all surviving offspring, together with litter size and offspring weights and assessment of surface righting reflex. All animals were subjected to a gross necropsy examination and histopathological evaluation of reproductive tissues was performed.

Results on systemic toxicity: There were no unscheduled deaths and no clinically observable signs of toxicity detected. No adverse effect on bodyweight change, food consumption or food efficiency was detected for treated animals when compared with controls. No toxicologically significant macroscopic abnormalities were detected, no treatment-related effects were detected in the organ weights measured, and no treatment-related microscopic changes were observed.

Results on fertility: There were no treatment-related effects on mating, conception rates, and gestation lengths. Of the litters born, litter size, bodyweight gain and litter weight at birth and on day 1 and 4 were comparable to controls.

Results on developmental toxicity: No clinically observable signs of toxicity were detected for offspring from all treatment groups. In conclusion, the oral administration of the test substance to rats by gavage, for a period of up to forty six consecutive days at dose levels of 100, 300 and 1000 mg/kg bw/day did not result in any treatment-related systemic or reproductive effects.

Conclusion: The NOAEL for systemic and reproductive toxicity was therefore considered to be >=1000 mg/kg bw/day.

Cyclacet reproductive parameters in a 90-day (OECD TG 408) study

No fertility effects were seen in the 90 -day oral repeated dose toxicity studies, further confirming the absence of effects on fertility.

The assessment of reproductive toxicity of Cyclaprop using read across from Cyclacet

Introduction and hypothesis for the analogue approach

Cyclaprop is a propyl ester attached to a tricyclodecenyl fused ring structure. For this substance no reproductive toxicity data are available. In accordance with Article 13 of REACH, lacking information should be generated whenever possible by means other than vertebrate animal tests, i.e. applying alternative methods such as in vitro tests, QSARs, grouping and read-across. For assessing the reproductive toxicity but specifically fertility toxicity of Cyclaprop the analogue approach is selected because for one closely related analogue reliable fertility toxicity information is available from a Reproscreen OECD 421 study.

Hypothesis: Cyclaprop has similar reproductive toxicity compared to Cyclacet resulting in a similar NOAEL because the analogue Cyclacet, with a one methyl shorter chain length, has not shown any reproductive toxicity in the Reproscreen toxicity test (oral route: OECD TG 421) up to the limit dose. The information from the source chemical Cyclacet is sufficiently reliable and the chemical is very similar in structure to read across towards Cyclaprop.

Available experimental information: The source chemical Cyclacet has been tested in a Reproscreen (OECD TG 421, GLP) up to 1000 mg/kg bw and in a 90-day repeated dose toxicity study (OECD TG 408 under GLP) up to 1500 mg/kg bw, in which no effects were seen on male and female reproductive organs. Both studies receive a reliability score of 1.

Target chemical and source chemical(s)

Chemical structures of the target chemical source chemicals are shown in the data matrix as are the physico-chemical properties and toxicological information, thought relevant for reproductive and developmental toxicity.

Purity / Impurities

Cyclaprop is a reaction mass containing a mixture of two very similar isomers (5-yl and 6-yl). The impurities are all below 1%.

Analogue approach justification

According to Annex XI 1.5 read across can be used to replace testing when the similarity can be based on a common backbone and a common functional group. When using read across the result derived should be applicable for C&L and/or risk assessment and it should be presented with adequate and reliable documentation.

Analogue justification: For Cyclaprop the nearest neighbour is used, which is Cyclacet and this substance has one methyl group less in the alkyl chain and has experimental reproductive toxicity.

Structural similarities and differences: The target and the source chemicals, the Cycla-esters, have a tricyclodecenyl fused ring structure with an unsaturated bond in the right ring. On the left ring an ester bond is attached with a short alkyl chain (< C4). The alkyl chain of Cyclaprop (C3) is one methyl group longer than of Cyclacet (C2). These differences between the target and source chemicals are not expected to behave differently compared to the target organs because the alkyl side chains (propyl versus acetyl) are not expected to influence significantly the reproductive toxicity of these chemicals.

Toxico-kinetic: The target and source substances have similar toxico-kinetic characteristics because the difference is one methyl group in the alkyl chain with respect to absorption, distribution and excretion via all exposure routes. Cyclaprop and Cyclacet will both metabolize into the Cycla-alcohol as a first metabolite and propionic acid and acetic acid, respectively, as the second metabolite. This metabolisation is illustrated in the figure below.

Fig. 1: The metabolisation pathway of the Cycla-esters. The R group can be a straight alkyl chain C2-C4 (Figure can be seen in the read across documentation attached at the endpoint summary of IUCLID 7.8).

MoA: The key metabolite of both Cyclaprop and Cyclacet is the Cycla-alcohol and this alcohol will have the same reproductive toxic MoA.

Similarities in results for toxicological endpoints between the target and the source chemical(s): In the data matrix a summary of the other toxicological data are presented to show that there are no toxicological differences between the target and the source chemical. The acute oral and dermal toxicity data show limited acute toxicity, both are not irritating, and both are negative in the Ames test and therefore reproductive toxicity resulting from genotoxicity is not expected.

Remaining uncertainties: There are no remaining uncertainties, which are not already addressed above.

Data matrix

The relevant information on physico-chemical properties and toxicological characteristics are presented in the Data Matrix at the end of this section.

Conclusions for reproductive toxicity

For Cyclaprop no reproductive toxicity is available but for a close analogue Cyclacet such information is available which can be used for read across with the focus on fertility. When using read across the result derived should be applicable for C&L and/or risk assessment and be presented with adequate and reliable documentation, which is presented here. For Cyclacet (acetyl side chain), a well conducted Reproscreen test is available (Reliability 1) with a NOAEL of >=1000 mg/kg bw for reproductive toxicity including fertility and developmental toxicity (as well as systemic toxicity). Based on the read-across approach described here, this information can be directly applied to Cyclaprop.

Final conclusion: Cyclaprop has a NOAEL of >=1000 mg/kg bw for reproductive toxicity with the focus on fertility (and developmental toxicity) based on read across and OECD TG 421 endpoints.

 

Data matrix for the read across to Cyclaprop from Cyclacet for reproductive toxicity

Common names	Cyclaprop	Cyclacet
	Target	Key source
Chemical structures
Cas no 5-yl Cas no of the generic	68912-13-0	2500-83-6 54830-99-8
EC number	272-805-7	911-369-0
Empirical formula	C13H18O2	C12H16O2
REACH registration	Registered	Registered
Molecular weight	206	192
Physico-chemical data
Physical state	liquid	liquid
Melting point (^oC)	< -20	< -20
Boiling point (^oC)	263	247
Water solubility (mg/l)	57	186
Log Kow	4.4	3.9
Human health endpoints
Toxico-kinetics: metabolisation	Cycla-alcohol and propyl-acid	Cycla-alcohol and acetic acid
Acute oral tox (mg/kg bw)	>5000 OECD TG 401)	2750 (OECD TG 401)
Acute dermal tox (mg/kg bw)	>5000 (OECD TG 402)	>5000 (OECD TG 402)
Skin irritation	Not irritant (OECD TG 404)	Not irritant (OECD TG 404)
Eye irritation	Not irritant (OECD TG 405)	Not irritant (OECD TG 405)
Genotoxicity – Ames test	Negative (OECD TG 471)	Negative (OECD TG 471)
Repeated dose toxicity (mg/kg bw/day)	RA from Cyclacet	NOAEL 1500 (OECD TG 408)
Reproductive toxicity including fertility and developmental toxicity – reproscreen study	Read across from Cyclacet	NOAEL 1000 for both endpoints (OECD TG 421)

Effects on developmental toxicity

Description of key information

In the decision letter from ECHA of 21 October 2021 (CCH-D-2114569822-39-01/F) a Pre-natal developmental toxicity study (Annex IX, Section 8.7.2.; test method: OECD TG 414) by oral route, in one species (rat or rabbit) with Cyclaprop was requested. The deadline for submission is January 26th 2023, but unfortunately, the test report will not be available before that date. Quotations from several labs were requested, but due to non-availability of some labs, it took some time to find the right lab to perform the study on the shortest notice. The OECD 414 study was initiated on 8 August 2022 and the final results are expected to be available by the end of February 2023. The dossier will be updated as soon as possible after receiving the final reports. A letter from the test lab showing the timelines is attached to this endpoint summary.

 

Cyclaprop and its developmental toxicity: Absence of developmental toxicity based on read across from Verdox in a dietary OECD TG 414 study in which the NOAEL≥444 mg/kg bw/day was derived. In addition, no developmental toxicity is seen in a reproduction/developmental toxicity screening study (rats, oral gavage, OECD TG 421) with Cyclacet.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Species:

rat

Quality of whole database:

The prenatal developmental toxicity study with Verdox, and the reproduction/developmental toxicity screening study with Cyclacet are of sufficient quality and are sufficiently adequate for this dossier.

Additional information

For Cyclaprop, developmental toxicity is derived from the close structural analogue Verdox and Cyclacet. The summaries of the experimental information available are presented first and thereafter the read across rationale.

The Cyclacet experimental information on developmental toxicity (from the OECD TG 421) is included in the fertility section above.

Prenatal developmental toxicity study with Verdox

Introduction: A prenatal developmental toxicity study was performed according to OECD TG 414 and GLP. The substance was administered to female Wistar Han IGS rats (Crl:WI(Han)) at dose levels of 800, 2500 and 7700 mg/kg in diet (corresponding to 55, 166 and 444 mg/kg bw total dose).The dose levels were selected based on the results of a 14 -day dose range finding (DRF) study for a previously performed 70 -90 -days extended OECD TG 422 study. In the DRF the dose of ca 15400 mg/kg diet (nominal 1000 mg/kg bw) was used. In this DRF at this high dose decrease in food consumption and body weight was seen and these effects were related to the palatability of the test item Verdox. Verdox is a fragrance which can smell awkwardly and is therefore not tasty either. At this 15400 mg/kg diet in the DRF, the relative liver weight increased ≥17% in males and females, which was considered to be due to metabolic saturation. This liver weight increase is also expected in combination with Verdox’s molecular weight (196 g/mol) and physico-characteristics, which indicate full and fast oral absorption. The dietary 80 -90 -day Repeated dose / Reproscreen study with the highest dose of 7500 mg/kg diet (converted to nominal 500 mg/kg bw) showed decrease in body weight gain (ca. 15%), which was considered test item related but not adverse. Based on this, the 7500 mg/kg diet was sufficiently high to present (absence of adverse) effects for the OECD TG 414 study and not muddle the outcome of the study due to potential palatability issues. In this Combined Repeated dose / Reproscreen (OECD TG 422) study the relative liver weights in males were increased around 14%, which we related to increased metabolic capacity and considered this sufficiently high to set the maximum dose levels at 7500 mg/kg diet in the follow up OECD TG 414 study.

Method: The 24 females/ dose level were exposed from gestation day 0 (defined by a sperm-positive vaginal smear) to necropsy at gestation day 21. A control group on plain diet was included. Analysis of the test diets showed that the test substance was homogeneously distributed in the test diets and that the concentrations were close to intended. Based on the limited stability in the test feeds, the feed was replaced daily with fresh portions from the freezer. Clinical observations and feed consumption were measured daily. Body weight was determined on gestation days 0, 6, 9, 12, 15, 18 and 21. At gestation day 21, the animals were sacrificed and cesarean section was performed. On the maternal animals gross pathology was performed and weights of reproductive organs were recorded. In addition, the number and distribution of implantations, fetuses and resorptions was recorded. Fetuses were weighed and examined for external observations and then sacrificed and processed for visceral or skeletal fetal evaluations.

Results: During the study no mortalities or morbidity was observed. Statistically significant decreased mean body weight and body weight gain in the 7700 mg/kg diet group which were related to decreased food intake in the in this dose-group. The test substance is a fragrance and probably reduced palatability of the high-dose diet resulted in a lower food intake. Hence the reduced food intake and the accompanying lower body weights in the high-dose group are considered to be due to reduced palatability rather than to the test substance per se, and are not considered to be adverse. No effects on maternal reproductive organ weights (full and empty uterus, ovary weight) fertility and litter parameters (pre- and post-implantation loss, number of live fetuses and resorptions), placenta weight and fetus sex ratio were observed. No treatment related effects on external, visceral and skeletal observations were observed. In the high dose group, a decrease in mean fetus weight in the 7700 mg/kg diet group was observed. This effect is considered to be related to the decrease of maternal food intake and maternal body weight. In view of the minor effect on fetal body weight as compared to the maternal effects and in absence of a delay in ossification this fetal body weight decrease is not considered to be adverse.

Conclusion: As the maternal effects on body weight and food consumption observed in the high dose group are considered related to the palatability of the test substance and are not considered adverse, the No Observed Adverse Effect Level (NOAEL) for maternal toxicity is ≥ 7700 mg/kg diet (corresponding to a dose level of 444 mg/kg bw/day). In absence of effects on ossification the slight effect on fetus weight in the high dose group was not considered adverse and therefore the NOAEL for developmental toxicity is ≥7700 mg/kg diet (corresponding to a dose level of 444 mg/kg bw/day). The substance is therefore not considered to be a developmental toxicant.

Developmental toxicity of Cyclaprop (Cas no. 68912-13-0) using read across from Verdox (Cas no. 20298-69-5) and Cyclacet (54830-99-8)

Introduction and hypothesis for the analogue approach

Cyclaprop has a tricyclodecenyl fused ring backbone structure to which a propyl ester is attached. For this substance no information on developmental toxicity in rat is available. In accordance with Article 13 of REACH, lacking information should be generated whenever possible by means other than vertebrate animal tests, i.e. applying alternative methods such as in vitro tests, QSARs, grouping and read-across. The analogue approach is selected since for the structurally related analogue Verdox a reliable rat developmental toxicity test is available that can be used for read-across to assess the developmental toxicity of Cyclaprop. In addition, information of the analogue Cyclacet is added, which was tested in a Reproscreen study (OECD TG 421) to support the read across.

Hypothesis: Cyclaprop has the same developmental toxicity as Verdox based on structural, repeated and reproductive toxicity similarity using Cyclacet as a bridging substance.

Available information: The analogue Verdox is tested in a dietary OECD TG 414 study (Rel. 1) in which no effects were seen at ≥444 mg/kg bw. In addition, for Cyclacet a gavage OECD TG 421 screening study for reproductive toxicity is available, showing absence of fertility and developmental effects ≥1000 mg/kg bw (Rel. 1).

Target chemical and source chemical(s)

The information on substance target and the analogue information from Cyclaprop, Verdox and Cyclacet are presented in the data matrix. Also, relevant physico-chemical properties are listed there.

Purity / Impurities

Cyclaprop is a reaction masses containing a mixture of two very similar isomers (5-yl and 6-yl). The impurities are all below 1%.

Analogue approach justification

According to REACH Annex XI 1.5, read-across can be used to replace testing when the similarity can be based on a common backbone and a common functional group. When using read-across the result derived should be applicable for C&L and/or risk assessment and it should be presented with adequate and reliable documentation, which is presented below.

Analogue selection: For Cyclaprop the analogue Verdox is selected being a close analogue for which a developmental toxicity (OECD TG 414) is available.

Structural similarities and differences: Cyclaprop, Cyclacet and Verdox have a hydrocarbon backbone to which the same ester functionality is attached. These backbones have the same number of carbons. Cyclaprop and Cyclacet contain an unsaturated bond which is absent in the structure of Verdox. This double bond is not adjacent to the ester and is therefore not impacting the ester reactivity. In addition, Verdox and Cyclacet are acetic esters while Cyclaprop is a propionic ester.

Toxico-kinetic: Absorption via all routes will be similar in view of similar appearance, molecular weights and physico-chemical parameters. The lower water solubility and higher log Kow of Verdox compared to Cyclaprop will not make a difference in absorption because it is still in the range for good oral absorption (Martinez and Amidon, 2002). Metabolism: Small chain straight alkyl esters such as Cyclaprop, Cyclacet and Verdox, which are not hindered by adjacent bulky groups are likely to be fully metabolised in the gut by micro-organisms or in the liver by human carboxylesterase (hCE-2) into a secondary cyclohexyl alcohol and its respective acid (EFSA, 2012, 2008)). These secondary alcohols and the acetic/propionic acids are expected to be more water soluble and have lower Log Kow values. The secondary alcohols will be glucuronated and easily be excreted via the kidney. These substances also will be conjugated with the alpha-2u globulin which can sediment in the kidneys as is shown in the repeated dose toxicity studies. The propyl and acetic acids are natural constituents of the body and processed as such.

Mode of Action (MoA): Cyclaprop will have the same developmental toxicity MoA compared to Verdox and Cyclacet resulting in absence of adverse developmental toxic effects in view of the similarities of the toxicity profile. In addition, to what is presented above, both Cyclacet and Verdox showed no adverse effects up to the highest dose tested in OECD TG 421 and extended OECD TG 422 (> 80-days) for fertility and developmental toxicity, respectively confirming the similar absence of repeated dose and reproductive toxicity effects of these two source substances, which can be extrapolated to Cyclaprop. The systemic male rat alpha-2u hydrocarbon nephropathy seen in Cyclacet and Verdox in repeated dose toxicity studies will also anticipated for Cyclaprop.

Uncertainty of the prediction: There are no remaining uncertainties other than those addressed above.

Data matrix

The relevant information on physico-chemical properties and toxicological characteristics are presented in the data matrix.

Conclusions on hazard and risk assessment

For Cyclaprop no developmental toxicity is available but for two analogues Cyclacet and Verdox screening information (OECD TG 421) is available. For Verdox also a developmental toxicity study according to OECD TG 414 (Rel. 1) is available, which can be used for read across. When using read across the result should be applicable for classification and labelling and risk assessment as well as presented with reliable and adequate documentation, which is presented here. For Verdox absence of developmental and systemic toxicity is seen in this OECD TG 414 study, resulting in a NOAEL of >=444 mg/kg bw and this result can be used for Cyclaprop. This absence of toxicity is supported with information form the Reproscreen studies of Cyclacet and Verdox which showed NOAELs of >=1000 mg/kg bw.

Final conclusion: Cyclaprop does not show developmental toxicity: NOAEL of≥444 mg/kg bw.

Data matrix to support the read across to Cyclaprop from Verdox for developmental toxicity

Common names	Cyclaprop	Verdox	Cyclacet
	Target	Key source	Supporting source
Chemical structures
Cas no 5-yl Cas no of the generic	68912-13-0	20298-69-5	2500-83-6 54830-99-8
EINECS	272-805-7	243-718-1	911-369-0
REACH registration	Registered	Registered	Registered
Empirical formula	C13H18O2	C12H22O2	C12H16O2
Molecular weight	206	198	192
Phys-chem properties
Physical state	Liquid	Liquid during handling	Liquid
Log Kow	4.4	4.75	3.9
Water solubility (mg/l)	57	10	186
Human health
Repeated dose toxicity (mg/kg bw)	RA to Cyclacet	≥423 (OECD TG 408)	≥1500 (OECD TG 408)
Reproductive screening test (mg/kg bw)	RA to Cyclacet	≥437 (> 80-day extended OECD TG 422)	≥1000 (OECD TG 421)
Developmental toxicity (mg/kg bw)	RA to Verdox	≥444 (OECD TG 414)	RA to Verdox

References

EFSA, 2008, Scientific Opinion, Flavouring Group Evaluation 47, (FGE.47), Bicyclic secondary alcohols, ketones and related esters from chemical group 8, Scientific Opinion of the Panel on Food Additives, Flavourings, Processing Aids and Materials in Contact with Food (Question No EFSA-Q-2008-051)

Adopted on 22 May 2008.https://efsa.onlinelibrary.wiley.com/doi/epdf/10.2903/j.efsa.2008.743

 

EFSA, 2012, (FGE.87Rev1): Consideration of bicyclic secondary alcohols, ketones and related esters evaluated by JECFA (63 rd meeting) structurally related to bicyclic secondary alcohols, ketones and related esters evaluated by EFSA in FGE.47 (2008), EFSA Journal 2012, 10(2), 2564

 

Verdox, 2018, ECHA dissemination site, EC no.243-718-1.

Justification for classification or non-classification

Based on the absence of adverse effects on fertility and developmental toxicity the substance does not need to be classified for reproduction toxicity according to EU CLP (EC 1272/2008 and its amendments).