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Administrative data

Description of key information

Repeat dose short-term, sub-chronic and chronic toxicity studies are available. The results show that balsalazide disodium, and hence balsalazide acid, are of low toxicological concern.

The short term toxicity studies performed in rats and dogs did not produce any treatment related effects up to the highest dose tested (2000 mg/kg bw/day). In the longer term studies, 26 and 96 weeks in rats, adverse effects were seen in the stomach, kidney and bladder. However, these effects indicated low systemic toxicity of the test substance and hence balsalazide acid. In the 96 week study, these effects manifested themselves at dose levels of 100 and 500 mg/kg bw/day.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Referenceopen allclose all

Endpoint:
repeated dose toxicity: oral, other
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Read across is considered possible due to the almost identical structural formulae of the two substances and their treatment in the body.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Read across is proposed between balsalazide disodium salt dihydrate (CAS No.150399-21-6) and balsalazide acid (CAS No. 80573-04-2).

3. ANALOGUE APPROACH JUSTIFICATION
Balsalazide disodium salt dihydrate is a prodrug used as a registered pharmaceutical for the effective treatment of inflammatory bowel diseases and has been used without any major recorded adverse side effects for many years. Toxicological studies are available on balsalazide disodium salt dihydrate and are considered to be directly relevant to balsalazide acid due to the almost identical structural formulae of the two substances and their treatment in the body.
Following ingestion of balsalazide salt dihydrate, in the acidic pH of the stomach (approximately pH 4-5 in rats and pH 2 in humans), the salt will be converted to the free acid. Following transit to the intestinal tract, the more alkaline pH (approximately pH 6.5-8 in rats and pH 5-8 in humans) will result in conversion of the free acid to the salt equivalent. Therefore, the substance available for absorption in the small intestine will be the same regardless of the form ingested originally.
If absorption of either substance into the bloodstream was to occur, the buffering effect of the blood would also ensure that the substances would be in the same form prior to reaching any organs.
Hence, the toxicological studies on balsalazide salt dihydrate can be used to predict the toxicological effects of balsalazide acid.

4. DATA MATRIX
Please see attached justification.
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across: supporting information
Remarks on result:
other: read across
Critical effects observed:
not specified
Endpoint:
short-term repeated dose toxicity: oral
Remarks:
14-day
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Qualifier:
no guideline followed
Principles of method if other than guideline:
No guideline is specified in the report.
GLP compliance:
no
Species:
rat
Strain:
Wistar
Sex:
male/female
Route of administration:
oral: gavage
Vehicle:
water
Details on oral exposure:
The volume of administration was 2 mL/rat.
Duration of treatment / exposure:
Animals were treated for 14 consecutive days.
Frequency of treatment:
Daily
Dose / conc.:
2 000 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
10 animals per sex per group
Control animals:
yes, concurrent vehicle
Observations and examinations performed and frequency:
MORTALITY:
- Time schedule: Daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily

BODY WEIGHT: Yes
- Time schedule for examinations: Twice weekly

FOOD CONSUMPTION: Yes
- Food intakes were recorded weekly

WATER CONSUMPTION: Yes
- Time schedule for examinations: Daily

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Just before sacrifice
- Anaesthetic used for blood collection: Not specified
- Animals fasted: Not specified
- Blood was collected from the abdominal aorta

CLINICAL CHEMISTRY: Yes
- See above

URINALYSIS: Yes
- Time schedule for collection of urine: Urine samples were taken during the last week of treatment.
Sacrifice and pathology:
At the end of the study period all surviving rats were sacrificed and subjected to complete necropsy and histological examinations.
Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, non-treatment-related
Description (incidence and severity):
Body weight gain was significantly increased (46%) in treated males, while in females body weight gain was reduced by 10% when compared to control values.
Food consumption and compound intake (if feeding study):
effects observed, non-treatment-related
Description (incidence and severity):
In males food intake was increased by 19% compared to control.
Water consumption and compound intake (if drinking water study):
effects observed, non-treatment-related
Description (incidence and severity):
Water intakes were increased by 139% and 22% in treated males and females, respectively.
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Dose descriptor:
NOAEL
Effect level:
> 2 000 mg/kg bw/day (actual dose received)
Sex:
male/female
Remarks on result:
not determinable due to adverse toxic effects at highest dose / concentration tested
Critical effects observed:
no
Conclusions:
Based on the results of the study, 2000 mg/kg bw of Balsalazide for 14 days did not produce any toxicity in rats (both sexes).
Endpoint:
short-term repeated dose toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Qualifier:
no guideline followed
Principles of method if other than guideline:
No guideline is specified in the report.
GLP compliance:
yes
Species:
dog
Strain:
Beagle
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Age at study initiation: 6 - 7 months old
- Weight at study initiation: Males: 7.0 - 11.95 kg; Females: 6.95 - 9.35 kg
Route of administration:
oral: gavage
Vehicle:
methylcellulose
Details on oral exposure:
The volume of administration was 5 mL/kg.
Duration of treatment / exposure:
28 days
Frequency of treatment:
Daily
Dose / conc.:
120 mg/kg bw/day (actual dose received)
Dose / conc.:
600 mg/kg bw/day (actual dose received)
Dose / conc.:
2 000 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
3 animals/ sex/ dose group
Control animals:
yes, concurrent vehicle
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly

FOOD CONSUMPTION:
- Time schedule: Daily

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes
- Time schedule for examinations: Daily

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Pre-test and during week 4 (from jugular vein)

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Pre-test and during week 4 (from jugular vein)

URINALYSIS: Yes
- Time schedule for collection of urine: Pre-test and during week 4 (24 hour urine samples)
- Animals fasted: Yes

OTHER: ECG tracing was obtained at pre-test and during week 4 of the study period.
Sacrifice and pathology:
At the end of the treatment period, all animals were sacrificed and subjected to complete necropsy and histopathological examinations.
Other examinations:
Part of the blood and urine samples were saved for measuring drug and its metabolite levels.
Clinical signs:
effects observed, non-treatment-related
Description (incidence and severity):
Yellow/ orange faeces were seen in treated dogs. This is due to the colouration of the test article.
Mortality:
mortality observed, non-treatment-related
Description (incidence):
One dog from low dose group died on Day 1 of the study due to dosing error. This dog was replaced with another naive dog and the treatment was started from day 2 onwards.
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
no effects observed
Water consumption and compound intake (if drinking water study):
no effects observed
Ophthalmological findings:
no effects observed
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
effects observed, treatment-related
Description (incidence and severity):
Urinary potassium levels were decreased by 30% in males and 63% in females of high dose treated group when compared to control values. Additionally urinary chloride levels were decreased by 56% in high dose treated females compared to control values.
Organ weight findings including organ / body weight ratios:
effects observed, non-treatment-related
Description (incidence and severity):
One male dog of the high dose group had a very enlarged prostate. The Sponsor considered that this was not treatment related.
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Dose descriptor:
NOEL
Effect level:
> 2 000 mg/kg bw/day (actual dose received)
Sex:
male/female
Remarks on result:
not determinable due to absence of adverse toxic effects
Critical effects observed:
no

Toxicokinetic data:

Maximum plasma levels of BSZ were reached within 2 hours. The median Cmax on Day 1 was 0.595, 1.55 and 3.65 nmol/mL, respectively, in the low, mid and high dose groups. The plasma levels declined progressivly with time and were still measurable at 8 hours (low and mid doses) and 24 hours (high dose). There was no apparent accumulation of BSZ over time. The urinary recovery of BSZ was <1% of the dose.

The urinary recovery for 4 -ABA was 0.5 - 5.2% of the dose. The urinary recovery for 4 -ASA was 1.3 - 10.5%.

The median plasma AUC of NASA was 7.3, 26.6 and 28.6 nmol.h/mL on day 27 and urinary recoverywas 0.054 - 0.57% of the dose. Plasma and urinary levels of NABA were below the limit of detection.

Conclusions:
The highest dose tested (2000 mg/kg bw/day) was the no-effect dose and no target organ of toxicity was identified.
Endpoint:
sub-chronic toxicity: oral
Remarks:
26 week
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Qualifier:
no guideline followed
Principles of method if other than guideline:
No guideline is specified in the report.
GLP compliance:
yes
Species:
rat
Strain:
other: CRl:CD (SD) BR
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Age at study initiation: 39 days old
- Weight at study initiation: Males: 190.8 - 224.1 g; Females: 137.5 - 183.4 g
Route of administration:
oral: gavage
Vehicle:
methylcellulose
Remarks:
1%
Details on oral exposure:
Volume of administration: 10 mL/kg bw
Duration of treatment / exposure:
26 weeks
Frequency of treatment:
Daily
Dose / conc.:
120 mg/kg bw/day (actual dose received)
Dose / conc.:
600 mg/kg bw/day (actual dose received)
Dose / conc.:
3 000 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
20 animals per sex per dose group
Control animals:
yes, concurrent vehicle
Observations and examinations performed and frequency:
MORTALITY: Yes
- Time schedule: Daily

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly

FOOD CONSUMPTION: Yes
- Time schedule for examinations: Weekly

WATER CONSUMPTION: Yes
- Time schedule for examinations: Weekly

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: Pre-dosing and week 25
- Dose groups that were examined: All animals at pre-dose and on all animals in the control and high dose groups in week 25 of the study.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Weeks 4, 13 and 26
- Blood samples were collected from the orbital sinus

CLINICAL CHEMISTRY: Yes
- See above

URINALYSIS: Yes
- Time schedule for collection of urine: Weeks 4, 12 and 25 (18 hour urine samples were collected)
- Metabolism cages used for collection of urine: Not specified
- Animals fasted: Yes
Sacrifice and pathology:
At the end of the treatment period, all animals were sacrificed and subjected to complete necropsy. Histopathological examinations were conducted on all tissues of control and high dose groups, all gross lesions and kidney, stomach and bladder from low and mid dose groups.
Description (incidence and severity):
Clinical signs such as salivation and paddling motions were seen in all high dose treated rats.
Mortality:
mortality observed, non-treatment-related
Description (incidence):
A total of 6 animals (3 from control group, 1 from low dose group and 2 from high dose group) died or sacrificed during the study period. These deaths were considered not to treatment related.
Description (incidence and severity):
At the end of the treatment priod, only high dose treated males body weight gains were reduced by 9% when compared to the control values.
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
Water intakes were increased by 32-35% and 45-60% in high dose treated males and females, respectively, compared to their respective control values.
Ophthalmological findings:
no effects observed
Haematological findings:
no effects observed
Description (incidence and severity):
In high dose treated rats (both sexes) serum cholesterol and serum phospholipid levels were decreased by 25-30% and 20-26%, respectively, when compared to their control values.
Description (incidence and severity):
In high dose treated males, increases in urinary volume (107%), sodium (725%), potassium (78%) and chloride (1005) excretion were seen. Increased electrolyte excretion was also seen in high dose treated females but the magnitude of increase was lower than that seen in high dose males. Increased incidences of blood and protein were seen in the urine of high dose treated rats (both sexes).
Description (incidence and severity):
Only kidney weights were increased by 12% in high dose treated rats of both sexes.
Description (incidence and severity):
Cecal distention (males: 2/20 in mid dose and 16/20 in high dose; females: 13/20 in high dose) and thickening of the fundic region of the stomach (males: 3/20 in high dose and females: 2/20 in high dose) were seen in treated rats.
Description (incidence and severity):
Examination revealed gastritis in the stomach, corticomedullary mineralisation and papillary urothelial hyperplasia/ mineralisation in the kidneys and urothelial hyperplasia in the bladder of mid and high dose treated rats. The cecal distention noted macroscopically was not associated with any histopathological changes.
Dose descriptor:
NOEL
Effect level:
120 mg/kg bw/day (actual dose received)
Sex:
male/female
Basis for effect level:
gross pathology
histopathology: non-neoplastic
Critical effects observed:
yes
Lowest effective dose / conc.:
600 mg/kg bw/day (actual dose received)
System:
urinary
Organ:
bladder
Treatment related:
yes
Dose response relationship:
not specified
Relevant for humans:
not specified
Critical effects observed:
yes
Lowest effective dose / conc.:
600 mg/kg bw/day (actual dose received)
System:
gastrointestinal tract
Organ:
stomach
Treatment related:
yes
Dose response relationship:
not specified
Relevant for humans:
not specified
Critical effects observed:
yes
Lowest effective dose / conc.:
600 mg/kg bw/day (actual dose received)
System:
other: renal
Organ:
kidney
Treatment related:
yes
Dose response relationship:
not specified
Relevant for humans:
not specified
Conclusions:
The results of the study indicate that the stomach, kidney and bladder are the target organs of toxicity and the lowest tested dose (120 mg/kg bw/day) is the no effect dose.
Endpoint:
sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
documentation insufficient for assessment
Qualifier:
no guideline followed
Principles of method if other than guideline:
No guideline is specified in the report.
GLP compliance:
no
Specific details on test material used for the study:
- Test material: Balsalazide [5-(carboxyethylcarbamoyl-4-phenylazo)-salicylic acid disodium salt; C17 H13 N3 O6 Na2 . 2H2O, MW 437]
- Appearance: Yellow, crystalline, nonhygroscopic stable dihydrate
- Water solubility: Highly soluble in water (up to 22% w/v)
- Purity: 99.5%
Species:
rat
Strain:
Wistar
Remarks:
Biorex
Sex:
male/female
Route of administration:
oral: unspecified
Duration of treatment / exposure:
90 days
Frequency of treatment:
Daily
Dose / conc.:
100 mg/kg bw/day (actual dose received)
Dose / conc.:
500 mg/kg bw/day (actual dose received)
Dose / conc.:
1 000 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
10 animals per sex per dose
Observations and examinations performed and frequency:
Full haematology and blood chemistry were determined at postmortem and the animals were examined for any gross abnormalities.
Sacrifice and pathology:
The animals were examined for any histological abnormalities. Twenty-eight tissues including bone marrow smears were studies histologically.
Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
not specified
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Dose descriptor:
NOAEL
Effect level:
> 1 000 mg/kg bw/day (actual dose received)
Sex:
male/female
Remarks on result:
not determinable due to absence of adverse toxic effects
Critical effects observed:
no
Conclusions:
No adverse effects or mortality were observed during the study. Therefore, the NOAEL is >1000 mg/kg bw.
Endpoint:
chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Qualifier:
no guideline followed
Principles of method if other than guideline:
No guideline is specified in the report.
GLP compliance:
no
Species:
rat
Strain:
Wistar
Remarks:
Biorex
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Weight at study initiation: Male mean weight: 143 g; Female mean weight: 148 g
Route of administration:
oral: feed
Vehicle:
unchanged (no vehicle)
Duration of treatment / exposure:
Rats were treated with 0, 100, 500 and 1000 mg/kg bw/day for 12 or 27 weeks.
Additionally, 15 rats/ sex each were included in control and high dose groups for 6 weeks recovery study.
Furthermore, 15 rats/ sex each were also included in control, low and mid dose groups in which treatment continued for 96 weeks.
Frequency of treatment:
Daily
Dose / conc.:
100 mg/kg bw/day (actual dose received)
Dose / conc.:
500 mg/kg bw/day (actual dose received)
Dose / conc.:
1 000 mg/kg bw/day (actual dose received)
Remarks:
Not used in the 96 week study
No. of animals per sex per dose:
10 - 15 animals per sex per dose group
Control animals:
yes, plain diet
Observations and examinations performed and frequency:
MORTALITY: Yes
- Time schedule: Daily

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly

FOOD CONSUMPTION: Yes
- Time schedule for examinations: Weekly

WATER CONSUMPTION: Yes
- Time schedule for examinations: Weekly

OPHTHALMOSCOPIC EXAMINATION: Yes / No / Not specified
- Time schedule for examinations:
- Dose groups that were examined:

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Just before sacrifice blood was collected from the abdominal aorta.
- Anaesthetic used for blood collection: Not specified
- Animals fasted: Not specified

CLINICAL CHEMISTRY: Yes
- See above

URINALYSIS: Yes
- Time schedule for collection of urine: Week prior to autopsy (24 hour urine samples)
- Metabolism cages used for collection of urine: Not specified
- Animals fasted: Not specified
- Animals: 5 rats/ group

OTHER: Blood pressure and heart rate were monitored in the control and high dose group rates after 6, 12, 27 and 96 weeks of treatment and after 6 weeks recovery period in rats treated for 27 weeks.
Sacrifice and pathology:
At the end of the treatment/ recovery period all surviving animals were sacrificed and subjected to complete necropsy and histopathological examinations.
Other examinations:
Fertility tests were also performed. For further details please refer to the summary in IUCLID Section 7.8.1.
Clinical signs:
no effects observed
Mortality:
mortality observed, non-treatment-related
Description (incidence):
A total of 58 rats (21 in control group, 19 in low dose group, 17 in mid dose group and 1 in high dose group) died or were killed during the study period. All these deaths were considered not to be treatment related.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
During the first 27 weeks of treatment, body weight gains in both sexes were not affected by the treatment. At the end of the 96 weeks of treatment, body weight gains were reduced by 21% and 15% in low and mid dose treated males and 15% and 30% in corresponding females when compared to the control values (high dose was not used for the 96 week treatment).
Food consumption and compound intake (if feeding study):
no effects observed
Water consumption and compound intake (if drinking water study):
effects observed, non-treatment-related
Description (incidence and severity):
Dose related increases in water consumption were seen in treated rats. The Sponsor attributed this to the high sodium content in the drug.
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
effects observed, non-treatment-related
Description (incidence and severity):
A one unit increase in urinary pH was evident in high dose treated rats. Urinary pH at 6 weeks after the recovery period in rats which were treated for 27 weeks were comparable in all groups.
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
No treatment related effects were seen in rats treated for 27 weeks. However, at the end of 96 weeks of treatment, relative kidney weights were increased by 17% and 45% and relative testes weights were reduced by 28% and 25% in 100 and 500 mg/kg treated group, respectively. Additionally, the relative weights of adrenals and kidneys were increased by 41% and 23% in 500 mg/kg/day treated females.
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
At the end of 27 weeks of treatment, no drug related effects were seen. At the end of 96 weeks of treatment, 2 out of 7 male rats treated with 500 mg/kg/day had pale soft kidneys with haemorrhagic foci and mottled kidneys were seen in 4/7 and 1/6 mid dose (500 mg/kg/day) treated males and females, respectively.
Histopathological findings: non-neoplastic:
effects observed, non-treatment-related
Description (incidence and severity):
No treatment related effects were seen. Tumours such as basophilic adenoma in pituitary (control = 0/30, low dose = 1/30 and mid dose = 1/30) was seen in treated rats. This is a common tumour and the incidence is very low, therefore can be considered as spontaneous findings.
Details on results:
The data indicated that a dose of up to 1000 mg/kg/day for 27 weeks did not produce any drug related effect in rats. However, dose levels of 100 and 500 mg/kg/day for 96 weeks did produce a decrease in body weight gain, an increase in kidney weights and some gross changes in kidneys which were not evident by microscopic examinations.

Although these effects are treatment related they are not considered significant for classification as the LOAEL of 100 mg/kg bw/day is an order of magnitude higher than the adjusted (using Haber's rule) classification limits for STOT-RE 2 classification.
Dose descriptor:
NOAEL
Effect level:
> 1 000 mg/kg bw/day (actual dose received)
Sex:
male/female
Remarks on result:
not determinable due to absence of adverse toxic effects
Remarks:
27 weeks treatment
Dose descriptor:
LOAEL
Effect level:
100 mg/kg bw/day (actual dose received)
Sex:
male/female
Basis for effect level:
body weight and weight gain
organ weights and organ / body weight ratios
gross pathology
histopathology: non-neoplastic
Remarks on result:
other: 96 weeks treatment
Dose descriptor:
NOAEL
Effect level:
< 100 mg/kg bw/day (actual dose received)
Sex:
male/female
Remarks on result:
other: 96 weeks treatment
Critical effects observed:
yes
Lowest effective dose / conc.:
100 mg/kg bw/day (actual dose received)
System:
other: renal
Organ:
kidney
Treatment related:
yes
Dose response relationship:
not specified
Conclusions:
No treatment related effects were seen in rats following 27 weeks of treatment. However, treatment related effects were seen in dose levels of 100 and 500 mg/kg/day following 96 weeks of treatment but are not considered to trigger classification of balsalazide acid.
Endpoint:
chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Qualifier:
no guideline followed
Principles of method if other than guideline:
No guideline is specified in the report.
GLP compliance:
yes
Species:
dog
Strain:
Beagle
Details on test animals and environmental conditions:
TEST ANIMALS
- Age at study initiation: 5 - 7 months old
- Weight at study initiation: Males: 6.40 - 8.95 kg; Females: 5.15 - 7.35 kg
Route of administration:
oral: gavage
Details on oral exposure:
The volume of administration was 5 mL/kg bw.
Duration of treatment / exposure:
52 weeks
Frequency of treatment:
Daily
Dose / conc.:
120 mg/kg bw/day (actual dose received)
Dose / conc.:
600 mg/kg bw/day (actual dose received)
Dose / conc.:
2 000 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
6 animals per sex per dose group
Control animals:
yes, concurrent vehicle
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly

FOOD CONSUMPTION:
- Time schedule for examinations: Daily

WATER CONSUMPTION: Yes
- Time schedule for examinations: Daily

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Pre-test and weeks 1, 6, 13, 26, 39 and 52 (from jugular vein)

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Pre-test and weeks 1, 6, 13, 26, 39 and 52 (from jugular vein)

URINALYSIS: Yes
- Time schedule for collection of urine: Pre-test and weeks 1, 6, 13, 24, 38 and 50 (24 hour urine samples)
- Animals fasted: Yes

OTHER: ECG tracing was obtained at pre-test and during weeks 26 and 52 of the study period.
Sacrifice and pathology:
Two dogs/ sex/ group were used for 26-week interim sacrifice.
At the end of the treatment period, all animals were sacrificed and subjected to complete necropsy and histopathological examinations.
Other examinations:
Part of the blood and urine samples were saved for measuring drug and its metabolite levels.
Clinical signs:
effects observed, non-treatment-related
Description (incidence and severity):
Yellow/ orange vomit was seen in treated dogs.
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
no effects observed
Water consumption and compound intake (if drinking water study):
no effects observed
Ophthalmological findings:
no effects observed
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
effects observed, non-treatment-related
Description (incidence and severity):
Urinary sodium levels were increased by 43%, 109% and 326% in low, mid and high dose treated males and by 70% and 85% in mid and high dose treated females when compared to the control values. The Sponsor attributed this to the high sodium content of the drug.
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Dose descriptor:
NOEL
Effect level:
> 2 000 mg/kg bw/day (actual dose received)
Sex:
male/female
Remarks on result:
not determinable due to absence of adverse toxic effects
Critical effects observed:
no

Toxicokinetic data:

Plasma levels of the drug and its metabolites wwere not determined. The urinary excretion of BSZ was very low (0.062 - 0.152%) as compared to total 5 -ASA ranging from -4.18% to 11.97% of the dose. The urinary excretion of 4 -ABA was -1.6 - 6.7% of the dose.

Conclusions:
The highest tested dose (2000 mg/kg bw/day) was the no effect dose and no target organ of toxicity was identified.
Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LOAEL
100 mg/kg bw/day
Study duration:
chronic
Species:
rat
System:
other: renal
Organ:
kidney

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Mode of Action Analysis / Human Relevance Framework

The mode of action of toxicity and its relevance to humans has not been assessed. However, the sodium salt of balsalazide acid has been authorised for use as a pharmaceutical for the treatment of inflammatory bowel disease.

Additional information

Justification for classification or non-classification

The only adverse effects of repeated exposure to balsalazide acid (in the form of balsalazide disodium salt) were seen in the 96 week oral repeated dose toxicity study in rats, where dose levels of 100 and 500 mg/kg/day produced a decrease in body weight gain, an increase in kidney weights and some gross changes in the kidneys. These effects were considered to be treatment-related and hence the LOAEL was assigned as 100 mg/kg bw/day.

However, these effects are not considered to trigger classification of balsalazide acid as STOT-RE 2. According to the Guidance on the Application of the CLP Criteria (Version 5.0, July 2017), the guidance value for STOT-RE category 2 classifications is 10 – 100 mg/kg bw/day based on 90 day oral repeated dose toxicity studies in rats. When Haber’s rule is used to adjust these standard guidance values for a 96 week study, the equivalent classification range is then 1.5 – 13 mg/kg bw/day. Since the lowest dose tested in the 96 week study was at least an order of magnitude above this range, there is no available test data to justify classification. Therefore, balsalazide does not need to to be classified for repeated dose toxicity (STOT-RE).