Nitrilotrimethylenetris(phosphonic acid)

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

No data. Dates of treatment were 27.12.1978 to 19.01.1979

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1979

Report date:

1979

Materials and methods

Test guideline

Guideline:

other: FDA "Guidelines for reproductive studies for evaluation of drugs for human use", segment II (teratological study)

Deviations:

not specified

Remarks:

Treatment on GD 6 - 15; no record of gravid uterine weight; number corpora lutea not recorded; no analytical confirmation of exposure levels.

Principles of method if other than guideline:

Study was used to assess the teratogenic and/or embryotoxic potential of the test substance.

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Nitrilotrimethylenetris(phosphonic acid)

EC Number:

229-146-5

EC Name:

Nitrilotrimethylenetris(phosphonic acid)

Cas Number:

6419-19-8

Molecular formula:

C3H12NO9P3

IUPAC Name:

{[bis(phosphonomethyl)amino]methyl}phosphonic acid

Test material form:

solid - liquid: aqueous solution

Remarks:

clear; 22.5% active acid

Details on test material:

neutralised to pH 7.5.

Result expressed as active acid.

Test animals

Species:

rat

Strain:

Sprague-Dawley

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Analytical verification of doses or concentrations:

no

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1:2
- Length of cohabitation: Overnight
- Further matings after two unsuccessful attempts: No data
- Verification of same strain and source of both sexes: No data
- Proof of pregnancy: vaginal plug referred to as day 0 of pregnancy.

Duration of treatment / exposure:

GD 6 - 15

Frequency of treatment:

daily

Duration of test:

16 days

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

100 mg/kg bw/day (actual dose received)

Doses / concentrations 2

Dose / conc.:

500 mg/kg bw/day (actual dose received)

Doses / concentrations 3

Dose / conc.:

1 000 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

24 mated females/dose

Control animals:

yes, concurrent vehicle

Details on study design:

Sex: female
Duration of test: 21 d

Results and discussion

Results: maternal animals

Effect levels (maternal animals)

Key result

Dose descriptor:

NOAEL

Effect level:

500 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

other: No adverse maternal toxicity effects were observed.

Maternal abnormalities

Abnormalities:

no effects observed

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Effect levels (fetuses)

1

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No adverse teratogenic effects observed.

2

Key result

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No adverse fetotoxic effects observed.

Fetal abnormalities

Abnormalities:

no effects observed

Overall developmental toxicity

Developmental effects observed:

no

Any other information on results incl. tables

MATERNAL TOXIC EFFECTS BY DOSE LEVEL AND BY SEX
Effects with dose level: 0/100/500/1000 mg/kg bw/day

Mortality
- one female from 100 mg/kg bw/day group moribund and sacrificed on GD6 (first day of treatment)

Body weight
- no significant differences in maternal body weight gain between groups
- body weight gain GD6-15: 50/49/50/44
- 12% (non-significant) reduction in body weight gain at 1000 mg/kg bw/day on GD6-15
Comment: individual body weight gain for dam 822 (high dose) on GD6-15 = 22 g; mean gain for controls = 50 g; mean gain for high dose group = 44 g. Body weight gain for this dam on GD 0-6 (preceding treatment) and on GD 15-21 (post-treatment) was similar or greater than mean bwt gain for control and high dose group.

Clinical observations, physical signs
- none present

Necropsy findings
- few adverse changes present, no treatment related effects 

Reproductive parameters
- pregnancy rate comparable between groups (100% in control, mid and high dose groups, 95.6% at 100 mg/kg bw/day), no treatment-related changes.
- mean number of corpora lutea (17.2/16.0/16.7/16.8), implantations (14.5/14.7/14.0/13.7) and implantation efficiency (84.3%/91.8%/84.0%/81.2%) comparable; significant 7% decrease in corpora lutea and significant 7.5% increase
in implantation efficiency at 100 mg/kg bw/day (P<0.05 in both instances) considered unrelated to treatment by authors
- mean number live fetuses comparable: 14.3/13.9/13.5/12.9 (no dead fetuses in any group)
- mean number resorptions: 0.2/0.8(P<0.05)/0.5/0.8(P<0.05); all values within historical control range
- non-dose related, non-significant increase in dams with 2 or more resorptions in treated groups (0%/22.7%/8.3%/20.8%);
within historical control range

FETAL DATA
Effects with dose level: 0/100/500/1000 mg/kg bw/day
- body weight by sex: males 5.54/5.43/5.71/5.49; females 5.25/5.17/5.34/5.16 (no significant effect)

Crown-rump length: males 4.2/4.2/4.3 (P<0.01)/4.2; females 4.1/4.1/4.2 (P<0.01)/4.1 (increase at 500 mg/kg bw/day
considered biologically insignificant by authors)

Sex: males/litter 6.9/7.0/6.6/6.0; females 7.4/6.9/7.0/6.9 (no significant effect)

Sex ratio (m:f): 92.4%/102.0%/94.6%/87.3% (no significant effect)

Variation in ossification: fetuses 80.2%/83.5%/79.3%/84.3%; litters 95.8%/100.0%/100.0%/100.0% (no significant effect)

External malformations: 
- incidence: 0 fetuses from 339 examined/0 from 305 examined/0 from 325 examined/6 from 315 examined
-  in the high dose group, one female (no. 822) had 6 fetuses (from a total litter of 16) with a syndrome of
defects that included: flexed forepaws, shortened and thickened torso, abdominal distension and exaggerated
forward flexure of the head (see maternal body weight, above). Remaining high dose fetuses (n = 309) unremarkable.

Total skeletal malformations 
- total fetuses examined: 177/158/169/159
- per fetus: 4.0%/1.9%/3.0%/1.3% (no significant effect)
- per litter: 20.8%/13.6%/20.8%/8.7% (no significant effect)
- type of skeletal malformations control: angulated ribs, cervical rib, wavy rib
100 mg/kg bw/day: angulated rib, cervical rib, angulated and wavy rib
500 mg/kg bw/day: cervical rib, angulated and wavy rib, 7 lumbar vertebra
1000 mg/kg bw/day: 5 lumbar vertebra, fused sternebrae 

Total soft tissue malformations
- total fetuses examined: 162/147/156/150
- per fetus: 4.3%/8.2%/4.5%/4.0% (no significant effect)
- per litter: 16.7%/40.9%/29.2%/20.8% (no significant effect)
- type of soft tissue malformation
control: distended renal pelvis, renal pelvis, ureter, baldder
100 mg/kg bw/days: as control + fold in retina
500 mg/kg bw/day: as control + ectopic kidney
1000 mg/kg bw/day: as control + fold in retina, anophthalmia, malrotation of heart
- malrotation of the heart occurred in high dose 2 fetuses, both from litter No. 822 (see "maternal body weight"  and
"external malformations", above)

Visceral malformations
- per fetus: 0.6%/1.3%/0.6%/1.9% (no significant effect)
- per litter: 4.2%/9.1%/4.2%/12.% (no significant effect)
- type of visceral malformation control: distended ureter
100 mg/kg bw/day: distended ureter +/- renal pelvis 500 mg/kg bw/day: as control
1000 mg/kg bw/day: as control + malpositioned testis

Applicant's summary and conclusion

Conclusions:

In a well documented pre-GLP teratology study (FDA segment II teratological study; reliability score 2) ATMP-H (Dequest 2000) was not embryotoxic or teratogenic when administered to rats at 100 or 500 mg/kg bw/day by gavage on GD6-15. At 1000 mg/kg bw/day, six fetuses from a single litter showed common multiple malformations in presence of a 50% decrease in individual maternal body weight gain (possibly indicative of concurrent maternal toxicity); all other high dose fetuses were normal. The clear absence of any comparable effect in other high dose litters and lack of dose-response indicates that 1000 mg/kg bwt/day was a probable no-effect level for embryotoxicity and fetotoxicity. The maternal NOAEL was 500 mg/kg bw/day.

Executive summary:

In a well documented pre-GLP teratology study (FDA segment II teratological study; reliability score 2) ATMP-H was administered by oral gavage to pregnant Charles River CD rats (24/dose), at dose levels of 100, 500 and 1000 mg/kg bw/day, on gestation days 6 to15. Control animals received the vehicle (water) only. Dams were sacrificed on gestation day 21 and recovered fetuses evaluated for external, soft-tissue and skeletal malformations. Maternal mortality, pregnancy rate, body weight gain, uterine implantation data, fetal size, sex data, ossification variation data and teratological evaluations were evaluated. High dose females gained less weight than the controls during the dosing period. A statistically significant increase in the number of resorptions was observed in the low and high dose animals (not the mid-dose). There was also an increase in the number of dams with two or more resorptions. However, the resorption data were within the range of historical values for the laboratory, so it was concluded that there was not a treatment-related effect. There were no teratogenic effects in the low and mid dose group. In the high dose group six fetuses from a single litter had common multiple malformations that included flexed forepaws, shortened and thickened torso, abdominal distention and exaggerated flexure of the head. Soft tissue examination revealed two of these fetuses had a malformation defect of the heart. The remaining high dose fetuses were generally unremarkable. Soft tissue and skeletal malformation data from the high dose group were similar to the control group. Although a possible teratogenic effect could not be excluded, it was most likely that the effects were secondary to maternal toxicity. Therefore the maternal NOAEL was 500 mg/kg bw/day, and the NOAEL for fetotoxicity and teratogenicity was >1000 mg/kg bw/day.