Erythromycin

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian germ cell study: cytogenicity / chromosome aberration

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

January 4 to May 31, 1988

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study conducted per protocol similar to OECD protocol. Study conducted in accordance with GLP.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1988

Report date:

1988

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method B.22 (Rodent Dominant Lethal Test)

Version / remarks:

in vivo mammalian germ cell study: cytogenicity / chromosome aberration

Principles of method if other than guideline:

The study was conducted in accordance with Department 468 Standard Operating Procedure No.
0468-12-407

GLP compliance:

yes

Type of assay:

rodent dominant lethal assay

Test material

Test material information

Constituent 1

Reference substance name:

Erythromycin

EC Number:

204-040-1

EC Name:

Erythromycin

Cas Number:

114-07-8

Molecular formula:

C37H67NO13

IUPAC Name:

6-{[4-(dimethylamino)-3-hydroxy-6-methyltetrahydro-2H-pyran-2-yl]oxy}-14-ethyl-7,12,13-trihydroxy-4-[(5-hydroxy-4-methoxy-4,6-dimethyltetrahydro-2H-pyran-2-yl)oxy]-3,5,7,9,11,13-hexamethyloxacyclotetradecane-2,10-dione (non-preferred name)

Test animals

Species:

mouse

Strain:

CD-1

Sex:

male

Details on test animals or test system and environmental conditions:

All groupscontained 10 male mice. CD-1 mice were used in this study because mice are commonly used for dominant lethal testing and because of the availability of historical data developed in our laboratories using this species and strain. The oral route of administration was used since the intende d clinical route of administration for ABBOTT-56268 is oral.

The CD-1 strain mice4 (50 males and 1200 females) used in this study were selected from at least 75 males and 1250 females.The mice were about 8 weeks old upon arrival and over 12 weeks old at the start of treatment or mating.Female mice were received from the supplier at approximately 3-week intervals. All mice were examined by a veterinarian upon arrival in the animal facility .

Prior to the start of the treatment period the following procedure was completed for all mice .

1. Acclimation to the laboratory for at least 5 days.

Mice were accepted into the study on the basis of the following criteria.

1. Completion of item 1 above.
2. Acceptable physical condition .
3. Acceptable body weight of 28 grams or above for males at the time of animal selection




During the treatment and mating periods, male mice were housed individually in hanging metal, mesh- bottom cages, equipped with feeders and water bottles. Female mice were housed in group cages un til used for breeding.

Animal cages, racks and cage mats were changed regularly . Animal rooms were cleaned regularl y.Ambient temperature was maintained at 72 ± 5°F. Temperature and humidity were recorded daily.Rooms were on a 14-hour daily light cycle. The basal ration was Certified Rodent Chow® meal.6 Food and tap water were available ad libitum

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

Hydroxypropylmethylcellulose

Details on exposure:

Formulation and Treatment: All test formulations were prepared fresh every 5 to 7 days. ABBOTT-
56268 was suspended at concentrations of 3000, 1000 and 300 mg ABBOTT-56268 per 60 ml of
0.2% hydroxypropylmethylcellulose for the high-dose , intermediate-dose and low-dose groups, r espectively. Cyclophosphamide was dissolved at a concentration of 13 mg cyclophosphamide per
10 ml of water for the positive control. Hydroxypropylmethylcellulose (0.2%) was used as the vehicle control.All formulations were prepared at room temperature. Cyclophosphamide was prepared daily.

All compounds were administered to male mice by oral gavage for five consecutive days. The dosage volume for all groups was 20 ml/kg.

Duration of treatment / exposure:

All compounds were administered to male mice by oral gavage for five consecutive days. During treatment, Individual body weights were recorded for each male mouse on each day of treatment. Observations on the physical condition of all treated male mice were made twice daily during the five- day treatment
period (approximately 2 and 24 hours after treatment). During the mating period, both male and female mice were observed at least once daily

Frequency of treatment:

ABBOTT-56268 was administered by oral gavage to CD-1 male mice for 5 consecutive days at do sages of 0, 100, 333, and 1000 mg/kg/day. The acute oral
LD50 of ABBOTT-56268 in mice has been reported to be above 5 g/kg for male mice. In a range-find ing study using pregnant mice,2 a dose of 1000
mg/kg resulted in decreased body weight gain. In a range-finding study using male mice, a dose of
1000 mg/kg resulted in decreased body weight
and decreased food consumption . Dosages of 3000 and 5000 mg/kg resulted in animal deaths during the dosing period. The dosages chosen for this study were 1000, 333 and 100 mg/kg/day. The intermediate and low dosages represent 1/3 and 1/10 of the high dosage, respectively.

Post exposure period:

Beginning the day of the final treatment , each male mouse was allowed the opportunity to mate with three untreated virgin female mice on seven consecutive nights. The mating procedure was repeated with new groups of three untreated virgin female mice each week for eight successive weeks.

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day (nominal)

Doses / concentrations 2

Dose / conc.:

100 mg/kg bw/day (nominal)

Doses / concentrations 3

Dose / conc.:

333 mg/kg bw/day (nominal)

Doses / concentrations 4

Dose / conc.:

1 000 mg/kg bw/day (nominal)

No. of animals per sex per dose:

10 males per dosage.
After the treatment period , each male mouse was allowed to mate with three female CD-1 mice per week for a period of eight weeks.

Control animals:

yes, concurrent vehicle

Positive control(s):

cyclophosphamide at dosage of 25 mg/kg/day; dissolved at a concentration of 13 mg cyclophos phamide per 10 ml of water for the positive control.

Examinations

Tissues and cell types examined:

There were no treatment-related deaths or clinical signs. There were no treatment-related effects
on body weights of the males during drug treatment. No statistically significant differences were det ected for number of fertile males per number of males mated or for number of pregnant females per n umber of females mated. Females from the positive control group had significantly more pregnancies with dead implants than did controls for the first three mating weeks

Details of tissue and slide preparation:

No statistically significant pairwise differences were detected for ABBOTT-56268-treated mice in this test for either male or female based analyses of the numbers of viable fetuses or implantation sites per pregnant female, or the numbers of viable fetuses, dead fetuses, early resorptions {mutagenic index), late resorptions or dead implants per implantation site.However, a statistically significant posi
tive trend was detected for numbers of late resorptions during the first mating week . This appeared to be due to a higher number of late resorptions in the 1000 mg/kg/day). This was not thought to be an indication of mutagenic activity since it is primarily an increase in early resorptions that is considered to result from mutagenic activity in this test.There was no corresponding increase in early resorptions.

Evaluation criteria:

Analysis of the Data
The following indices were calculated for each mating week for each group:
• Number of pregnant females/number of females mated
• Number of fertile males/number of males mated
• Number of live implantations per pregnancy
• Number of dead implantations per pregnancy
• Number of pregnancies with dead implants versus total number of pregnancies

Mutagenic effect expressed as a mutagenic index {M.I.) = early resorptions/total implantations X 100

Mutagenic indices were calculated each week for each male using the pooled data from all females mated to each male . The mutagenic indices of female mice mated to ABBOTT-56268-treated males were compared to the mutagenic indices of females mated to vehicle control-treated males.

Statistics:

Statistical methods and statistical analyses of results were used.

Results and discussion

Test results

Sex:

male/female

Genotoxicity:

negative

Toxicity:

no effects

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

Statistically significant positive responses in the mutagenic index occurred in the first three mating weeks for the Tpc (cyclophosphamide) group only. This was accompanied by statistically significant decreases
in numbers of viable fetuses per pregnant female or per implantation site, statistically significant dec reases in numbers of implantation sites per pregnant female {female-based analysis) and by statisti cally significant increases in numbers of dead implants per implantation site. These positive resul
ts with cyclophosphamide indicate that the test system as employed in this study was capable of detecting a mutagenic agent

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): negative
There was clearly no increase in early resorptions in any ABBOTT-56268-treated group. Therefore, ABBOTT-56268 was concluded to be negative for mutagenic activity in the mouse dominant lethal test.