(R)-α-phenylethylammonium (-)-(1R, 2S)-(1,2-epoxypropyl)phosphonate monohydrate

Repeated dose toxicity: oral

Administrative data

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

September 15, 1994 - November 11, 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Title:

Unnamed

Year:

1995

Report date:

1995

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

EU Method B.7 (Repeated Dose (28 Days) Toxicity (Oral))

Deviations:

no

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

(R)-α-phenylethylammonium (-)-(1R, 2S)-(1,2-epoxypropyl)phosphonate monohydrate

EC Number:

418-570-8

EC Name:

(R)-α-phenylethylammonium (-)-(1R, 2S)-(1,2-epoxypropyl)phosphonate monohydrate

Cas Number:

25383-07-7

Molecular formula:

C11H20NO5P

IUPAC Name:

(R)-α-phenylethylammonium (-)-(1R, 2S)-(1,2-epoxypropyl)phosphonate monohydrate

Details on test material:

- Name of test material (as cited in study report): Fosfomycin PEA salt
- Physical state: white crystalline powder
- Lot/batch No.: 4177
- Expiration date of the lot/batch: June, 1997
- Storage condition of test material: room temperature, in the dark
- Other: manufacturing date: June 10, 994

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Italia S.p.A
- Age at study initiation: About 4 weeks
- Weight at study initiation: Males: 75-85 g. Females: 60-70 g
- Housing: 3 or 2 animals per cage; wire cages measuring 40.5x38.5.18h cm, with stainless steel feeders.
- Diet (e.g. ad libitum): Ad libitum (4 RF 21 GLP Top Certificate feed)
- Water (e.g. ad libitum): Ad libitum (from the municipal water main, filtered)
- Acclimation period: Two weeks in a quarantine room.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 2 ºC
- Humidity (%): 55 ± 10 %
- Air changes (per hr): 20 per hour (filtered on HEPA 99.97 %)
- Photoperiod (hrs dark / hrs light): 12 h dark / 12 h light (7 a.m. - 7 p.m.)

IN-LIFE DATES: From: males: September 15, 1994; females: September 16, 1994
To: males: October 13, 1994; females: October 14, 1994

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: Deionized water

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: Every day, an exact amount of test article was weighed in a suitable graduated container and was made up to final volume with vehicle to obtain the final concentration of 50 mg/ml (Group 4). Part of this solution was diluted 1:3.33 with vehicle down to the concentration of 15 mg/ml (Group 3). Part of this solution was further diluted 1:3 with vehicle down to the concentration of 5 mg/ml (Group 2). Solutions were administered within 4 hours from the preparation and were kept away from light.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Concentration checks were performed by RBM on formulates prepared on September 16, 1994 (week 1) and October 7, 1994 (week 4).
Measured concentrations:
Week 1: 4.44 mg/ml (nominal: 5 mg/ml), 13.64 mg/ml (nominal: 15 mg/ml), 53.27 mg/ml (nominal 50 mg/ml)
Week 4: 4.53 mg/ml (nominal: 5 mg/ml), 14.99 mg/ml (nominal: 15 mg/ml), 52.40 mg/ml (nominal 50 mg/ml)

Duration of treatment / exposure:

28 days

Frequency of treatment:

Once a day, seven days a week

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 50, 150 and 500 mg/kg/day
Basis:
actual ingested

No. of animals per sex per dose:

10 animals per sex in groups 1 and 4 (0 mg/kg/day (control) and 500 mg/kg/day).
5 animals per sex in groups 2 and 3 (50 mg/kg/day and 150 mg/kg/day)

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The dose levels administered in the study were selected on the basis of data obtained in a previous dose-range-finding study in the same species treated with the test article Fosfomycin PEA salt administered by oral route at the doses of 0, 150, 500 and 1000 mg/kg/day for two consecutive weeks (RBM Exp. no 940330).
- Rationale for animal assignment (if not random): On arrival (35M+35F), all animals were clinically observed and 20% of them were weighed. During the acclimation period of two weeks their health status was assessed by daily clinical observations. In view of the normal health of all the animals, the entire group was deemed fit for the experiment with the exception of one female which was discarded since it showed an eye abnormality at the pre-test ophthalmological examination. Before commencement of the treatment all the animals were weighed: animals at the extreme of the body weight range were discarded. The required number of rats (30M+30F) was allocated to the dosage groups by means of a computerized stratified sequenced randomization program.
- Rationale for selecting satellite groups: At the end of the 4-week treatment period, 5 animals/sex in each groups 1 (0 mg/kg/day, control) and 4 (500 mg/kg/day, dose with the highest identification numbers) were kept off treatment for the post-exposure recovery period.
- Post-exposure recovery period in satellite groups: 4 weeks
- Section schedule rationale (if not random): Yes (see examinations below)

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: inspections for mortality were made twice a day (early in the morning and late in the afternoon) and clinical observations daily.
- Cage side observations checked: mortality, physical appearance, behaviour and clinical signs.

DETAILED CLINICAL OBSERVATIONS: Yes (physical appearance, behaviour and clinical signs)
- Time schedule: Daily

BODY WEIGHT: Yes
- Time schedule for examinations: Prior to the beginning of the treatment period (on day 0, the day before the first administration) and then at weekly intervals throughout the study period.

FOOD CONSUMPTION:
- Food consumption for each animal determined: Yes (body weight gain in g/animal/day, for each 7-day period).

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

OPHTHALMOSCOPIC EXAMINATION: Yes (conjunctiva, cornea, anterior chamber, iris, lens, vitreous body and fundus)
- Time schedule for examinations: Before the start of the treatment (day-2 for males and day -3 for females) and at the end of the dosing period (week 4; day 28 for males and day 27 for females). On recovery animals: at the end of 4-week recovery period (day 54 for males and day 53 for females)
- Dose groups that were examined: All groups: 0, 50, 150, 500 mg/kg/day and recovery animals from 0 and 500 mg/kg/day.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: At the end of treatment period (week 5; day 29); recovery animals (week 8, day 55 for males and 54 for females)
- Anaesthetic used for blood collection: Yes (ether)
- Animals fasted: Yes
- How many animals: All animals
- Parameters checked: Erythrocytes, Hemoglobin, Leukocytes, WBC differential count, Hematocrit, Mean corpuscular volume (MCV), Mean corpuscular hemoglobin (MCH), Mean corpuscular hemoglobin concentration (MCHC), Platelets, Prothrombin time.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: At the end of treatment period (week 5; day 29); recovery animals (week 8, day 55 for males and 54 for females)
- Animals fasted: Yes
- How many animals: All animals
- Parameters checked: Glucose, Urea, Creatinine, Bilirubin total, Cholesterol total, Alkaline phosphatase (SAP), serum glutamic oxaloacetic transaminase (SGOT or AST), serum glutamic pyruvic transaminase (SGPT or ALT), Triglycerides, Total protein, Serum protein electrophoresis, A/G ratio, Sodium, Potassium, Calcium, Inorganic phosphorus, Chloride.

URINALYSIS: Yes
- Time schedule for collection of urine: At the end of treatment period (week 5; day 29); recovery animals (week 8, day 55 for males and 54 for females)
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes
- Parameters checked: Diuresis, Specific gravity, Semiquantitative examination (Leukocytes, Nitrites, pH, Protein, Glucose, Ketone bodies, Urobilinogen, Bilirubin, Blood), Microscopic examination (Epithelial cells, Leukocytes, Erythrocytes, Crystals, Casts, Bacteria, Other abnormal components).

NEUROBEHAVIOURAL EXAMINATION: Yes (as clinical signs)

Sacrifice and pathology:

GROSS PATHOLOGY: Yes. At the end of the treatment and recovery periods, each animal was fasted overnight (about 16 h); the fasted body weight was recorded before killing. The following organs were removed and those indicated by "*" were also trimmed and weighed. Individual organ weight/fasted body weight ratios were calculated:
Skin and mammary gland, urinary bladder, prostate, testes*, epididymides, seminal vesicles, vagina, uterus, ovaries*, spleen*, stomach, intestine: duodenum, jejunum, ileum, cecum, colon, rectum; mesenteric lymph nodes, pancreas, liver*, kidneys*, adrenals*, submandibular salivary glands and lymph nodes, sternum with bone marrow, heart*, thymus, lungs, aorta, trachea, esophagus, thyroid with parathyroids, eyes, Harder's lacrimal glands, tongue, brain-coronal sections at three levels*, pituitary*, skeletal muscle: biceps femoris, peripheral nerve: sciatic nerve, spinal cord: thoracic, cervical and lumbar, vertebrae, femur including articular surface, gross lesions.

HISTOPATHOLOGY: Yes. All or part of each of the above organs were fixed in 10% buffered neutral formalin, except eyes that were fixed in Davidson's fluid.
Histology of organs and tissues of all animals in control and high dose groups sacrified at the end of the treatment:
Urinary bladder, prostate, testes, epididymides, ovaries, spleen, stomach, intestine: duodenum, colon, mesenteric lymph nodes, liver, kidneys, adrenals, heart, lungs, eyes, Harder's lacrimal glands, gross lesions.
Histology of organs and tissues of all animals in low and intermediate dose groups sacrificed at the end of the treatment and in animals sacrificed after the recovery period:
Liver, kidneys, mesenteric lymph nodes, lungs and gross lesions. Only in males: Testes, epididymides and prostate. Only in females: spleen, eyes and Harder's lacrimal gland.
The organs to be histologically examined were post-fixed, for about 5 minutes in Davidson's fluid, embedded in paraffin blocks, sectioned and stained with hematoxylin and eosin.

Statistics:

The parameters statistically examined were: body weight, body weight gain, food consumption, hematology, blood chemistry, urinalysis (except semi-quantitative analysis and microscopic examination of the sediment), organ weights (absolute and relative to body weight).
Data were analised by Barlett's homogeneity of variance:
if homogeneous, ANOVA was applied. If significant (p <0.05): Dunnett's multiple comp. test.
if not homogeneous, TRANSFORMATIONS (inverse, logarithm decimal, square and square root):
if transformation was successfully: ANOVA and Dunnett's test.
if not homogeneous: Kruskal-Wallis non parametric ANOVA: if significant (p<0.05), Mann Whitney's "U" test.
When comparing two groups (recovery period), variance homogeneity was verified with de F ratio, and statistical comparison with Student's T test.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Some test article-induced clinical changes were seen during the treatment period at the dose of 500 mg/kg/day; they included salivation after gavage (seen in most animals), fur loss (seen in one male and in most females), lacrimation and/or eyelid swelling (seen in a few males and in half of the females), chromodacryorrhea (observed in two females), abdomen dilation and poor conditions (seen in a few females).
At 150 mg/kg/day the only clinical finding was one episode of salivation after gavage seen in one male at the end of the administration period.
No clinical signs were observed at 50 mg/kg/ in either sex.
Reversibility of the above-mentioned clinical changes was ascertained in the recovered animals previously treated at the highest dose of the test article.

Mortality:

no mortality observed

Description (incidence):

No animals died during the study.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

No effects on body weight were seen at 50 and 150 mg/kg/day in either sex.
A decrease in body weight was observed during the treatment period at the dose of 500 mg/kg/day, this change being moderate in males (-19% vs control) and only mild in females.
Recovery was evident on treatment discontinuation.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

A moderate decrease in food consumption was observed in males of the high dose groups mainly in the first half of the treatment period. Only a transient decrease, confined to the first week of dosing, was found in males which received the intermediate dose.
No changes in food consumption were found in males of the low dose group.
Regarding the females, the only change of note was a negligible decrease in food consumption observed at the highest dose during the first week of treatment. No treatment-related changes were found at the two lower doses.
Food consumption data of recovered animals of both sexes appeared comparable to those of the control.

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

effects observed, treatment-related

Description (incidence and severity):

After 4 weeks of treatment, 3 females of the 500 mg/kg/day dose group showed corneal changes consisting of opacity and/or vascularization; moreover, one female of this group had atrophy of the eyes.
No eye modifications were seen in treated males or in females of the two lower dose groups.
Reversibility of corneal changes was achieved on discontinuation of treatment.

Haematological findings:

no effects observed

Description (incidence and severity):

After 4 weeks of treatment, hematology profiles were found to have been unaffected in treated females. In males, the only finding worth mentioning was a dose-related but negligible increase in the hematocrit value, observed in all treated groups. At the end of the recovery period there were no modifications of note in either sex.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

At the end of the treatment period, slight modifications in the serum protein pattern consisting of an increase in albumin percentage and A/G ratio with concomitant decrease in the globulin percentage (β and γ globulins appeared mainly involved) were found in all treated groups of both sexes. These changes showed dose-relationship in males only.
Males treated at 150 and 500 mg/kg/day had a dose-related increase in total cholesterol serum levels (44-90% vs controls) while females of the same dose groups showed an increase in triglycerides (levels about twice as much as the controls).
In females of the high dose group there was also an increase in alkaline phosphatase and in GPT serum activities, with some individual values out of the range of normality; moreover serum protein concentration appeared slightly reduced.
Minor electrolyte changes, i.e. increase in calcium (two higher doses) and decrease in chloride (all doses) in both sexes, decrease in sodium (all doses) and increase in inorganic phosphorus (high dose) in female only, were observed. Such modifications, always slight in degree, were regarded as possible trends.
On discontinuation of the treatment, the following slight biochemistry changes were still observed in the recovered animals; increase in albumin percentage (concomitant with a decrease in globulin percentage) and in total cholesterol for males, decrease in total protein and increase in organic phosphorus for females.

Urinalysis findings:

no effects observed

Description (incidence and severity):

A slight decrease in the pH of urine was found at the end of the treatment period in the 500 mg/kg/day dosed animals of both sexes.
No changes in urine parameters were observed after recovery in either sex.

Behaviour (functional findings):

not specified

Description (incidence and severity):

As clinical signs.

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

At the end of the treatment period, a few changes were seen that were considered related to the test article administration. These were, on the whole, slight increases in mean weights of liver and kidneys in males and females of the intermediate and high dose groups, (usually being statistically significant), a slight decrease in absolute valued of testes in males and in spleen in females of the high dose group.
At the end of recovery, the only change seen was an evident decrease in weights of testes in the group previously treated with 500 mg/kg/day, while other organs affected at the end of the treatment period showed complete recovery.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

At the end of treatment, compound-related changes were noted. Some males of the intermediate dose group and all males of the high dose group had slight congestion of the cortico-medullary junction of the kidney. One male each of the two high dose groups had pale kidneys, and one male of the high dose group had pale liver. All males of the high dose group had a slight decrease in size of the prostate and seminal vesicles, while only one rat showed a slight decrease in size of tested. All females of the high dose group sacrificed at this time had moderate alopecia; two of this group had a decrease in size of spleen. One female of this group was thin, and decreased size of genital organs and paleness of Harder’s lacrimal gland were noted. Slight eye opacity was also seen in one female.
At the end of the recovery period, the only change still seen was an evident decrease in size of testes in most males previously treated at 500 mg/kg/day; one male of this group also had a slight decrease in size of epididymides.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

The following changes were seen at the end of the treatment period and considered related to administration of the test article:
Dose-related in frequency and degree of hepatic centrilobular hypertrophy in males and females of the intermediate and high dese groups.
Presence of hyaline droplets in tubules of the renal cortex or the papilla seen in all treated male groups and in females of the intermediate and high dose group. One male treated at 500 mg/kg/day had slight tubule dilation, and one male of the high dose group also showed slight congestion of the cortico-medullary junction.
Atrophy of lymphatic tissue (mesentreic lymph nodes and/or spleen) in a few rats of the high dose group.
Presence of vacuolated histiocytes in lungs in a few rats of the high dose group; one female had a moderate presence of histiocytes and two rats had slight presence of fibrin.
Testicular changes in all males of the high dose group, consisting in a slight increase in vacuolation and/or degeneration of the tubular epithelium. Epididymides of all rats showed decreased number and degeneration of spermatic elements, with vacuolation of tubular epithelium. A decrease in secretory material was seen in seminal vesicles and in a few cases in prostate of these males. These changes were not observed in rats treated with the intermediate and low doses.
Moderate to severe acute inflammation of the cornea, associated with conjunctivitis or degeneration of the corneal epithelium, in two females of the high dose group. One female of this group also had decreased secretory material in the Harder’s lacrimal gland, with an increase in apoptotic figures.
Decrease in number of hair follicles of the skin in a few females of the high dose group.
Most of these changes were considered of mild toxicological relevance as they appeared completely reversible after the recovery period. In particular, hepatic hypertrophy may be regarded as a functional metabolic response to the high doses of test compound administered, rather than a toxic effect. The only relevant change still noted at the end of the withdrawal period was in testes and epididymides in male’s tubule epithelium, but other changes seen at the end of treatment were now seen to a more severe degree. Most of these testes also had severe decrease in spermatogenesis; a few cases of multinucleated spermatids and tubule mineralization were seen. As a consequence an evident decrease in number of spermatic elements with varying degrees of degeneration was seen in epididymides.

Histopathological findings: neoplastic:

not specified

Other effects:

no effects observed

Details on results:

Doses of 50 and 150 mg/kg bw/day induced only mild effects.
At 500 mg/kg bw/day, the test article caused clinical changes and some moderate to severe alterations involving liver, kidneys, male gonads and accessory glands and several other tissues. Also the eye appeared to have been involved. Degenerative changes of testes even more severe, were still found after recovery; however, no mortality occurred.

Effect levels

Key result

Dose descriptor:

NOAEL

Effect level:

150 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: clinical signs; ophthalmoscopic examination; gross pathology; histopathology.

Target system / organ toxicity

Key result

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

Although the absolute no effect level (NOEL) could not be established, Fosfomycin PEA salt when administered to rats for 4 consecutive weeks by oral route, the no adverse effect level (NOAEL) could be considered 150 mg/kg/day.

Executive summary:

A 4 weeks repeated dose toxicity study of the test article Fosfomycin PEA salt on Sprague Dawley rats was performed following the EU Method B.7. The test article was administered by oral route dissolved in deionized water, once a day for 4 consecutive weeks to groups of Sprague Dawley rats at the doses of 50, 150 and 500 mg/kg/day (groups 2, 3 and 4 respectively). The control group (group 1) received the vehicle alone. The volume of administration was kept constant at 10 mg/kg/day in all groups. Experimental groups 1 and 4 consisted of 10 males and 10 females, while groups 2 and 3 consisted of 5 males and 5 females. Clinical observations, ophthalmological and hematological examinations, blood chemistry tests and urinalyses were carried out. At the end of the 4 -week dosing period 5 animals/sex from each of the groups 1 and 4 (those with the highest identification numbers) were kept off treatment for 4 weeks for recovery evaluation and then sacrificed, while the remaining animals from each sex/group were killed for pathology investigations. Although the absolute no effect level (NOEL) could not be established, Fosfomycin PEA salt when administered to rats for 4 consecutive weeks at the doses of 50 and 150 mg/kg/day induced only mild effects. Therefore the no adverse effect level (NOAEL) could be considered at 150 mg/kg/day. At 500 mg/kg/day the test article caused clinical changes and some moderate to severe alterations involving liver, kidneys, male gonads and accessory glands and several other tissues. Also the eye appeared to have been involved. Degenerative changes of testes even more severe, were still found after recovery; however no mortality occurred.