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Key value for chemical safety assessment

Toxic effect type:
dose-dependent

Effects on fertility

Description of key information

Short description of key information:
Male rats: Reduction of sperm number and motility (males). Effect occurs at toxic doses comparable with therapeutic clinical doses and above.

Justification for selection of Effect on fertility via oral route:
Effects on male fertility were noted. 


The fertility effect in the rat (sperm motility and number) is relevant at doses significantly above human exposure during therapy or workplace exposure. Clinical experience shows that in the course of high dapsone therapy methemoglobinaemia is very frequent at a comparable dose as in the rat study. In some studies rats showed also pale or blue extremities and other effects. There is a clear evidence that the fertility effects occur at doses which provoke clear signs of toxicity.


An absence of changes in the seminal vesicle and prostate weights indicate there was no significant effect on androgen status, suggesting the effects are not linked to endocrine disruption.


 


Overall Conclusions on reproduction from regulatory toxicity studies:


 


Based on the most sensitive endpoint measured (sperm motility), adverse effects were present at doses ≥ 3mg/kg/d (Norman A. See et al., 2005). They were not present at a dose level of 2 mg/kg/d (Norman A. See et al., 2005) and so this can be considered the NOEL for male reproductive effects. Since histopathological examination was not performed on the testes of rats dosed with 3 mg/kg/d it is not possible to correlate the changes in sperm motility with any spermatogenic abnormalities.


In the EOGRTs study, changes in epididymal sperm motility and degenerative changes in the testes were present at dose levels of ≥ 7.5 mg/kg/d (lowest dose of the study), while epididymal sperm morphology was abnormal in the only dose evaluated (30 mg/kg/d). Reduced numbers of implantation sites and decreased litter sizes in mated females were seen at all dose levels and correlate with the abnormal sperm parameters and spermatogenic abnormalities.  The highest dose level tested at which no effects on fertility have been noted is in the 0.5 mg/ kg bw/d dose level published in the 2005 pharmacology review by See et al. This value has been used for risk assessment.


 


The profile of changes in organ weights, histopathology, sperm evaluation and fertility parameters suggest that the male reproductive toxicity is mediated through adverse effects on testicular spermatogenesis, but may also be mediated through disturbances in the epididymis. It is not possible to distinguish the relative importance of the two pathways given the study design of the studies under review.


An absence of changes in the seminal vesicle and prostate weights indicate there was no significant effect on androgen status, suggesting the effects are not linked to endocrine disruption.


 


A limited number of published manuscripts are available in the public literature, due to Dapsone’s use as a therapeutic agent; those considered for the reproductive toxicity endpoint requirement have been summarized in ‘additional information’.


 


A no observed effect level for fertility or general toxicity could not be identified on the key reproductive toxicity study conducted in rats. The human epidemiological study referenced in section 7.10.2 is considered to represent the most appropriate value for use in risk characterization as it provides the lowest observed effect level and therefore the DNELs used for risk assessment have used 0.35 mg/kg bw/day as a starting point.


The most sensitive measured endpoint for dapsone-related male reproductive effects was sperm motility, the available regulatory guideline data does not allow conclusion as to whether these effects on motility are mediated through the epididymis or testis. Further to the regulatory requirement studies available, a limited number of published manuscripts are available in the public literature, due to Dapsone’s use as a therapeutic agent.


The main toxic effect of dapsone is methemoglobin formation. This effects occurs in humans rarely at a daily dose of 100 mg/person/day and becomes more frequent in patients with a metabolic disease. The effect is frequent and clinically relevant at about 400 mg/person/day (or ~ 6 mg/kg/day). Fertility effects have been noted in male rats at 3 mg/kg/day. The effects in male rats are a reduction of sperm number and motility.

Link to relevant study records
Reference
Endpoint:
toxicity to reproduction
Remarks:
other: Effect on the fertility of male rats
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2000
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Principles of method if other than guideline:
Treatment of males only. Fertility effects on females have been studied separately
GLP compliance:
yes (incl. QA statement)
Limit test:
no
Specific details on test material used for the study:
Dapsone
Lot 01110C
Species:
rat
Strain:
other: Rat/Crl:CD(SD)IGS BR VAF/Plus
Sex:
male
Route of administration:
oral: gavage
Vehicle:
CMC (carboxymethyl cellulose)
Remarks:
0.5%
Details on exposure:
The study was conducted in two stages, with an initial study that involved dosages of 0, 12, 30 and 75 mg/kg/day, and a second study that involved exposures at 0, 0.5, 2 and 12 mg/kg/day. Therefore there were two groups which received 0 mg/kg/day (vehicle control group) and two groups which received 12 mg/kg/day.
Details on mating procedure:
Only males were treated. Untreated females were used to confirm male reproductive potential.
Analytical verification of doses or concentrations:
yes
Duration of treatment / exposure:
F0 males were dosed with the test material 63 days prior to cohabitation with untreated females and continued through the day prior to sacrifice
Frequency of treatment:
daily
Remarks:
Doses / Concentrations:
0
Basis:
actual ingested
mg/kg bw/day
Remarks:
Doses / Concentrations:
0.5
Basis:
actual ingested
mg/kg bw/day
Remarks:
Doses / Concentrations:
3
Basis:
actual ingested
mg/kg bw/day
Remarks:
Doses / Concentrations:
12
Basis:
actual ingested
mg/kg bw/day
Remarks:
Doses / Concentrations:
30
Basis:
actual ingested
mg/kg bw/day
No. of animals per sex per dose:
25 males (treated) and 25 females (untreated)
Control animals:
yes, concurrent vehicle
Positive control:
none
Parental animals: Observations and examinations:
F0 male rats observed for viability and clinical signes twice daily. Body weight was recorded daily. F0 females were nonitred for body weight and clinical signs on gestation days 0, 7, 10 and 13. All F0 females were sacrificed on gestation day 13, cesarian sectioned, gross necropsied, and the numbers of corpora lutea, implantation sites, and viable and non-viable embryos was recorded. Following Completion of the cohabitation period, F1 males wer subjected to gross necropsy, the reproductive organs (each testis, each epididymidis, seminal vesicles and prostate) weighted, and sperm concentration and motility were evaluated.
Oestrous cyclicity (parental animals):
Females were not treated
Sperm parameters (parental animals):
Concentration and motility
Postmortem examinations (parental animals):
Gross pathology of males
Postmortem examinations (offspring):
not performed in this study
Statistics:
yes
Reproductive indices:
yes
Offspring viability indices:
yes
Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
Pale or blue extremities, salvation, poor grooming. Incidence proportional to exposure
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
BW gain significantly reduced > 75 mg/kg/day.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
BW gain significantly reduced > 75 mg/kg/day.
Food efficiency:
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Endocrine findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Other effects:
not examined
Description (incidence and severity):
Test substance intake: gavage
Reproductive function: oestrous cycle:
not examined
Description (incidence and severity):
only males treated
Reproductive function: sperm measures:
effects observed, treatment-related
Description (incidence and severity):
motility: Effects above 75 mg/kg/day; sperm number: no effect
Number of implantation sites in females and viable embryos significantly reduced if males were treated >12 mg/kg/day, presumably due to the numbers or effectiveness of sperm.
Key result
Dose descriptor:
NOAEL
Effect level:
>= 0.5 - < 3 mg/kg bw/day (actual dose received)
Based on:
act. ingr.
Sex:
male
Basis for effect level:
other: Effect is on the number of motile sperm
Clinical signs:
not examined
Mortality / viability:
no mortality observed
Body weight and weight changes:
not specified
Food efficiency:
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Sexual maturation:
not examined
Anogenital distance (AGD):
not specified
Nipple retention in male pups:
not specified
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
not examined
Histopathological findings:
not examined
Only male fertility tested.
Remarks on result:
not measured/tested
Reproductive effects observed:
not specified
Conclusions:
Dapsone impaired fertility in male rats at high doses. This was evident from reductions in fertility index (numbers of rats pregnant/number of rats mated), reduced sperm motility (percentage of observed sperm that were motile), and reduced numbers of implantations and viable embryos in the females that did become pregnant. Statistically significant reductions in percentage of motile sperm were observed at exposures of 3 mg/kg/day and above. 0.5 mg/kg/day was the apparent NOAEL in this study, although a non-significant trend toward a reduction in the percentage of motile sperm may have been apparent.
Executive summary:

In this study, groups of 25 male rats were treated via oral gavage for 63 days prior cohabitation with untreated females. The study was conduced in two stages, with an initial study that involved doses of 0,12,30 and 75 mg/kg/d and a second that included 0,0.5,3 and 12 mg/kg/d. therefore there were two groups of animals receiving vehicle control and 12 mg/kg/d. F0 males were observed for viability and clinical signs twice daily, body weight was recorded daily. F0 females were monitored for body weight and clinical signs on gestation days 0,7,10 and 13. All F0 females were sacrificed on gestation day 13, c-sectioned, gross necropsied and the numbers of corpora lutea, implantation sties and viable or non-viable embryos were recorded. Following completion of cohabitation, F1 males were subject to necropsy, the reproductive organs weighed and sperm concentration/mobility were evaluated.


Dapsone at high doses impaired fertility in male rats. This was evident from reductions in fertility index (numbers of rats pregnant/number of rats mated), reduced sperm motility (percentage of observed sperm that were motile), and reduced numbers of implantations and viable embryos in the females that did become pregnant. Statistically significant reductions in percentage of motile sperm were observed at exposures of 3 mg/kg/day and above. 0.5 mg/kg/day was the apparent NOAEL in this study, although a non-significant trend toward a reduction in the percentage of motile sperm may have been apparent.

Effect on fertility: via oral route
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEL
0.5 mg/kg bw/day
Study duration:
subchronic
Species:
rat
Quality of whole database:
A recent OECD 443 guideline study is available, the key endpoint value for which is higher than the previously available information from a pharmacology review by the US FDA.
The studies are not OECD-guideline studies, however were designed to investigate the fertility and teratogenicity endpoint similar to a guideline study. In addition, dapsone has been used as a pharmaceutical for > 60 years and the effects of dapsone are well reported in literature, a selection of which has been included in the present dossier.
Additional information

The most sensitive measured endpoint for dapsone-related male reproductive effects was sperm motility, the available data does not allow conclusion as to whether these effects on motility are mediated through the epididymis or testis. Further to the regulatory requirement studies available, a limited number of published manuscripts are available in the public literature due to Dapsone’s use as a therapeutic agent, the most relevant studies for reproductive toxicity have been summarised in 7.8.1 and further information is available in 7.12. 

Effects on developmental toxicity

Description of key information

No specific developmental toxicity effects on fetuses were observed across the available studies. No clear effect on development of offspring was obsevred in the F1 or F2 generations on the OECD Guideline 443 study conducted.

Link to relevant study records
Reference
Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2001
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
no guideline followed
Principles of method if other than guideline:
Oral developmental and perinatal/postnatal reproductive toxicity study in rats, including postnatal reproductive toxicity in rats with behavioral and functional evaluation. Pregnant females dosed daily throughout gestation and postpartum.
GLP compliance:
not specified
Specific details on test material used for the study:
USP Lot #01110D
Species:
rat
Strain:
Crj: CD(SD)
Route of administration:
oral: gavage
Vehicle:
CMC (carboxymethyl cellulose)
Analytical verification of doses or concentrations:
not specified
Frequency of treatment:
Daily
Duration of test:
F0 animals were sacrificed on day 28 post partum
Dose / conc.:
0 mg/kg bw/day
Dose / conc.:
3 mg/kg bw/day
Dose / conc.:
12 mg/kg bw/day
Dose / conc.:
30 mg/kg bw/day
No. of animals per sex per dose:
25
Control animals:
yes, concurrent vehicle
Maternal examinations:
Body weights, food consumption, clinical signs and duration of gestation. Gross necropsy following weaning.
Litter size, pup viability and nursing behaviour.
Fetal examinations:
F1 animals were evaluated for performance in a water filled M maze for overt coordination, swimming ability, learning and memory.
F1 males were monitored for the age of preputial separation and F1 females were monitored for the age of vaginal opening.

F1 animals were observed for changes in mating behaviour. F1 males testes and epididymides were weighed. F1 females were exhamined for numbers of corpora lutea, implantation sites and viable fetuses. F2 fetuses were weighed and examined for gross external alterations.
Clinical signs:
no effects observed
Mortality:
mortality observed, non-treatment-related
Description (incidence):
One high dose female was found dead during lactation. No other unscheduled deaths.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Significantly reduced in high dose group over the period of gestation. Mean body weight tended to be reduced in high dose females during the lactation perod.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
Mirrored body weight effects.
Food efficiency:
not specified
Ophthalmological findings:
not specified
Haematological findings:
not specified
Clinical biochemistry findings:
not specified
Urinalysis findings:
not specified
Behaviour (functional findings):
not specified
Immunological findings:
not specified
Organ weight findings including organ / body weight ratios:
not specified
Gross pathological findings:
no effects observed
Neuropathological findings:
not specified
Histopathological findings: non-neoplastic:
not specified
Histopathological findings: neoplastic:
not specified
Number of abortions:
no effects observed
Pre- and post-implantation loss:
no effects observed
Description (incidence and severity):
Reduced mean implantations at 75 mg/kg/d.
Total litter losses by resorption:
no effects observed
Early or late resorptions:
no effects observed
Dead fetuses:
effects observed, non-treatment-related
Description (incidence and severity):
The mean number of stillborn pups per litter was significantly higher with increased exposure to dapsone.
Changes in pregnancy duration:
not specified
Changes in number of pregnant:
not specified
Key result
Dose descriptor:
NOAEL
Effect level:
12 mg/kg bw/day
Basis for effect level:
body weight and weight gain
food consumption and compound intake
Fetal body weight changes:
no effects observed
Reduction in number of live offspring:
effects observed, non-treatment-related
Description (incidence and severity):
The mean number of stillborn pups per litter was significanty higher with increased exposure to dapsone but no effects were observed on pup viability post partum.
Changes in sex ratio:
no effects observed
Changes in litter size and weights:
no effects observed
Changes in postnatal survival:
no effects observed
External malformations:
no effects observed
Skeletal malformations:
no effects observed
Visceral malformations:
no effects observed
Dose descriptor:
NOAEL
Effect level:
30 mg/kg bw/day
Basis for effect level:
other: No effects observed in the abscence of maternal toxicity
Abnormalities:
no effects observed
Developmental effects observed:
no
Conclusions:
Treatment of pregnant rats resulted in maternal toxicity, but not effects on physical or behavioural development were noted in the offspring.
All clinical signs were considered incidental, body weight gain was significantly reduced in high dose females and food consumption mirrored body weight observations.
There was no effect of treatment on the duration of the destation period, the number of rats that delivered or the number of dams with pups dying post partum. The number of stillborn pips per litter was increased but only in the presence of effects on maternal body weight and food consumption. No effects were noted on pup viability postpartum.
Executive summary:

An oral gavage developmental and perinatal/postnatal reproduction toxicity study in rats, including a postnatal behavioural/functional evaluation, was conduced in groups of 25 female rats with dose levels of 0, 3, 12 and 30 mg/kg/d. F0 females were administered the test articles daily from gestation day 7 (seventh day following confirmed mating) through day 27 postpartum. F0 animals were sacrificed on day 28 postpartum. 25 F1 animals of each gender (pups of F0 animals) were selected on day 28 postpartum. At approximately 90 days of age the F1 animals were cohabited for up to 21 days with an F1 animal of the opposite gender and from a different litter. F1 males were sacrificed at the conclusion of the cohabitation period. F1 females were sacrificed on gestation day 21 and c-sectioned.


Body weight, clinical signs and food consumption were monitored daily. F0 animals were monitored for duration of gestation, litter size, pup viability and nursing behaviour. Gross necropsy was performed. F1 animals were evaluated on approx. day 70 postpartum for performance in a water filled M maze for overt coordination, swimming ability, learning and memory. F1 males were monitored for the age of preputial separation and F1 females observed for age of vaginal opening. F1 animals were observed for changes in mating behaviour. Reproductive organs were weighed and F1 females were observed for numbers of corpora lutea, implantation sites and viable fetuses. F2 females were weighed and examined for gross external alterations.


Little toxicity was overserved under the conditions of the study, although mean body weight gain was significantly reduced in high-dose F0 females over the period of gestation, indicating that a sufficiently high level of exposure was achieved for the data to be valid. The mean number of stillborn pups was slightly but statistically significantly higher in high dose treatment groups than control. No effects were observed on pup viability, physical development, behaviour, learning ability or reproduction.

Effect on developmental toxicity: via oral route
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
12 mg/kg bw/day
Study duration:
subacute
Species:
rat
Quality of whole database:
The studies are not OECD-guideline studies, however were designed to investigate the fertility and teratogenicity endpoint similar to a guideline study. In addition, dapsone has been used as a pharmaceutical for > 60 years and the effects of dapsone are well reported in literature, a selection of which has been included in the present dossier.
Additional information

The two studies together (Norman A See ATLS-137 and ATLS 120, which includes the evaluation of teratogenicity) indicate that no teratogenicity occurs.

Mode of Action Analysis / Human Relevance Framework

The clear evidence for male reproductive toxicity in rats for Dapsone. However, the available data is insufficient to fully understand the mechanisms of male reproductive toxicity. There is some indication that the hemotoxicity could be mediated by a common metabolic pathway in rat and human. This could potentially be the case for the reproductive toxicity as well but the current dataset does not allow for a final conclusion on this point. Nevertheless, based on the species similarity in the systemic toxicity, human relevance of the reproductive toxicity cannot be excluded either.

Justification for classification or non-classification

Toxicity to reproduction_Dapsone_QW56WJ EOGRTs



  • Dapsone produces degenerative changes in the testis and changes in sperm quality (morphology) and function (motility) in male rats treated with Dapsone.



  • Reduced male reproductive performance leads to reductions in the number of implantation sites and reduced litter size and/or number of viable embryos produced by (un)treated female rats.

  • Dapsone produces germ cell degeneration and spermatid retention in the testis. The EOGRT study demonstrated changes in sperm motility and testicular morphology at all dose levels tested (≥7.5 mg/kg/d). Sperm morphology was only examined at 30 mg/kg/d and it was abnormal.


 


Norman A See, 2000 21-794 ATLS-119 and ATLS-183



  • Dapsone impaired fertility in male rats at high doses. This was evident from reductions in fertility index (numbers of rats pregnant/number of rats mated), reduced sperm motility (percentage of observed sperm that were motile), and reduced numbers of implantations and viable embryos in the females that did become pregnant. Statistically significant reductions in percentage of motile sperm were observed at exposures of 3 mg/kg/day and above


Conclusion:



  • There is clear evidence for male reproductive toxicity for Dapsone.

  • Effects on sperm (motility and morphology) and germ cell degeneration in the testes are assessed to be the cause for reduced fertility (reduced number of implantation sites and reduced litter size).

  • There is no indication for an endocrine mode of action.

  • Although reproductive toxicity occurs at similar dose level as the systemic toxicity, a link between both could not be established.

  • Available data for Dapsone is insufficient to fully understand the mechanisms of male reproductive toxicity.

  • There is some indication that the hemotoxicity could be mediated by a common metabolic pathway in rat and human. This could potentially be the case for the reproductive toxicity as well but the current dataset does not allow for a final conclusion on this point. Nevertheless, based on the species similarity in the systemic toxicity, human relevance of the reproductive toxicity cannot be excluded either.


In summary, an effect was noted on fertility and reproduction in a recent OECD 443 guideline compliant GLP Extended One Generation Reproductive Toxicity Study in the rat. The findings are in line with findings from studies conducted to support the medical use of Dapsone and additional information from the public literature on Dapsone and related substances. Based on the overall Weight of Evidence, human relevance cannot be excluded.


Therefore, Dapsone (EC: 201-248-4) has been self-classified as follows:


UN GHS (Rev8 2019) 3.7.2.1./ CLP regulation (Regulation EC No. 1272/2008)


Category 1B, Presumed human reproductive toxicant

Additional information