5'-O-[bis(4-methoxyphenyl)benzyl]-2'-deoxy-N-(2-methyl-1-oxopropyl)guanosine

Endpoint summary

Description of key information

In an acute oral toxicity study in rats conducted according to OECD 423, the target substance N2-Isobutyryl-5’-O-(4,4’-Dimethoxytrityl)-2’-deoxyguanosine showed no mortality at the limit dose of 2000 mg/kg bw. Hence, the LD50 value is considered to exceed 2000 mg/kg bw.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017-12-08 to 2017-03-19

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 423 (Acute Oral toxicity - Acute Toxic Class Method)

Version / remarks:

adopted 17 December 2001

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test type:

acute toxic class method

Limit test:

yes

Specific details on test material used for the study:

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
In order to get the test item in a solution or suspension, which is applicable for dosing of the animals, aqua ad injectionem was first evaluated as vehicle and was subsequently considered to be adequate. This vehicle was chosen due to its non-toxic characteristics.
The test item was weighed out into a tared plastic vial on a precision balance.
Homogeneity of the test item in the vehicle was maintained by vortexing the prepared suspension thoroughly before each dose administration.
For all animals in the first step, 2002 mg of the test item was suspended with the vehicle to gain a final volume of 10 mL (i.e. 0.2 g/mL) and to achieve a dose of 2000 mg/kg body weight at a dose volume of 10 mL/kg body weight.
For all animals in the second step, 2008 mg of the test item was suspended with the vehicle to gain a final volume of 10 mL (i.e. 0.2 g/mL) and to achieve a dose of 2000 mg/kg body weight at a dose volume of 10 mL/kg body weight.
The dose formulations were made shortly before each dosing administration.

Species:

rat

Strain:

Wistar

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
-Source: Charles River, 97633 Sulzfeld, Germany
-Females non-pregnant and nulliparous: Yes
-Age at the beginning of the study: 8–10 weeks
-Body weight on the day of administration: Step 1: 154–168 g; Step 2: 151–159 g
-Fasting period before study: 16 to 19 hours
-Housing: The animals were kept in groups in individually ventilated cages (IVC), type III H, polysulphone cages on Altromin saw fibre bedding
-Diet: (e.g. ad libitum): ad libitum, food: Altromin 1324 maintenance diet for rats and mice
-Water (e.g. ad libitum): ad libitum, tap water, sulphur acidifid to a pH value of approximately 2.8 (drinking water, municipal residue control, microbiological controls at regular intervals)
-Acclimation period: at least 5 days under laboratory conditions

ENVIRONMENTAL CONDITIONS
-Temperature (°C): 22 +/- 3
-Humidity (%): 55 +/- 10
-Air changes (per hr): 10
-Photoperiod (hrs dark / hrs light): 12 / 12

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

VEHICLE
- Concentration in vehicle: 200 mg/mL
- Justification for choice of vehicle: The vehicle was chosen due to its non-toxic characteristics.
- Lot/batch no. (if required): 705820

DOSE VOLUME APPLIED: 10 mL/ kg body weight

CLASS METHOD (if applicable)
- Starting dose: The starting dose was selected to be 2000 mg/kg body weight

Doses:

2000 mg/kg body weight

No. of animals per sex per dose:

3 females per steps, 2 steps

Control animals:

no

Details on study design:

-Duration of observation period following administration: 14 days
-Frequency of observations and weighing: Animals were weighed on day 1 (prior to the administration) and on days 8 and 15. Clinical examination was made several times on the day of dosing (at least once during the first 30 minutes and with special attention given during the first 4 hours post-dose). Thereafter, animals were observed for clinical signs once daily until the end of the observation period.
-Necropsy of survivors performed: Yes, all animals were subjected to gross necropsy and examined macroscopically for gross pathological changes. In the absence of gross pathological changes no tissues were preserved for a possible histopathological evaluation.
- Other examinations performed: clinical signs: A careful clinical examination was made several times on the day of dosing (at least once during the first 30 minutes and with special attention given during the first 4 hours post-dose). Thereafter, the animals were observed for clinical signs once daily until the end of the observation period. Cageside observations included changes in the skin and fur, eyes and mucous membranes. Also respiratory, circulatory, autonomic and central nervous systems and somatomotor activity and behaviour pattern were examined. Particular attention was directed to observations of tremor, convulsions, salivation, diarrhea, lethargy, sleep and coma.

Statistics:

N.A.

Preliminary study:

N.A.

Key result

Sex:

female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Remarks on result:

other: no mortality occured at the limit dose of 2000 mg/kg bw

Mortality:

No mortality was observed for any of the test animals.

Clinical signs:

other: Reduced spontaneous activity, piloerection, hunched posture, moving the bedding, half eyelid closure, and prone position observed starting 30 minutes after dosing. Besides these clinical signs, no other abnormal cageside observations were made throughout

Gross pathology:

No macroscopic findings were observed in any animal of any step.

Other findings:

N.A.

Interpretation of results:

GHS criteria not met

Conclusions:

In an acute oral toxicity study in rats conducted according to OECD 423, no mortality occured at the limit dose of 2000 mg/kg bw. Hence, the LD50 value was determined to be greater than 2000 mg/kg bw.

Executive summary:

In an acute oral toxicity study (acute toxic class method, OECD 423), two groups of fasted, 8-11 weeks old, female Wistar rats (3 rats/group) were given a single oral application of the test item N2-Isobutyryl-5’-O-(4,4’-Dimethoxytrityl)-2’-deoxyguanosine (100% purity) in sterile water at the limit dose of 2000 mg/kg body weight and observed for 14 days. All animals survived until the end of the study with slight signs of toxicity of the test item. Throughout the 14-day observation period, the body weight gain of the test animals was within the normal range of variation for this strain. At necropsy, no treatment-related macroscopic findings were observed in any animal of any step. Based on the results from this study, the oral LD50 in rats is considered to exceed 2000 mg/kg bw.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

GLP guideline study

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

In an acute oral toxicity study (acute toxic class method, OECD 423), two groups of fasted, 8-11 weeks old, female Wistar rats (3 rats/group) were given a single oral application of the test item N2-Isobutyryl-5’-O-(4,4’-Dimethoxytrityl)-2’-deoxyguanosine (100% purity) in sterile water at the limit dose of 2000 mg/kg body weight and observed for 14 days. All animals survived until the end of the study with slight signs of toxicity of the test item. Throughout the 14-day observation period, the body weight gain of the test animals was within the normal range of variation for this strain. At necropsy, no treatment-related macroscopic findings were observed in any animal of any step. Based on the results from this study, the oral LD50 in rats is considered to exceed 2000 mg/kg bw.

Justification for classification or non-classification

Based on the available data, N2-Isobutyryl-5’-O-(4,4’-Dimethoxytrityl)-2’-deoxyguanosine does not warrant classification for acute toxicity. The LD50 value for the oral route was above the limit value for classification (2000 mg/kg bw).