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Additional toxicological data

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Endpoint:
additional toxicological information
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From 18 MAY 1999 to 20 SEPTEMBER 2001
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study was carried out according to OECD 432 and under GLP. Some deviations in the protocol relative to OECD guideline 432 were evident, however they are expected not to influence the outcome of the study.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2001
Report Date:
2001

Materials and methods

Type of study / information:
The neutral red uptake phototoxicity assay in Balb/c 3T3 mouse fibroblasts was used to assess the phototoxicity and cytotoxicity potential of HHCB to Balb/c 3T3 mouse fibroblasts (3T3).
Test guideline
Qualifier:
according to
Guideline:
other: OECD 432
Deviations:
yes
Remarks:
See any other information on materials and methods
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): 99AC90
- Physical state: Colorless, semi-viscous liquid
- Analytical purity: >95% (IFF personal communication with RIFM)
- Storage condition of test material: RT/ 2-8°C
- Other: The test article was protected from exposure to light.

Results and discussion

Any other information on results incl. tables

Preliminary test

A preliminary assay was performed using eight doses (ranging from 100 ag/ml to 0.03 ug/mL in 1/2 log steps) of the test article. Based upon the results of the preliminary assay, eight doses were selected for the definitive test.

Definitive test

Table 1 presents the concentrations dosed for the test article in the valid definitive trials.

Test substance Dose spacing Conc (+UVA) ug/mL (Conc) (-UVA) ug/mL
HHCB 1/4 LOG 100-1.77 100-1.77

Table 2 presents the IC50 results and Mean Photo Effect (MPE) and Photo-Irritation Factors (PIF) for the definitive test.

Assay replicate IC50 (-UVA) ug/mL IC50 (+UVA) ug/mL MPE PIF
1 15.9 11.9 0.016 1.32
2 6.54 6 0.016 1.12

MPE = mean photo effect (a material is considered nonphototoxic if the MPE < 0.1 and phototoxic if the MPE > or equal to 0.1.

PIF = photo irritancy factor (a material is considered phototoxic if the PIF > 5).

The visual observations of the treated cultures in the preliminary and definitive trials supported the neutral red uptake results. The average IC50 value for the test article, in the absence of UVA exposure, from the first 4 definitive trials (under cooler conditions) was 65.2 ug/mL (counting the >100 ug/mL values as 100 ug/mL). The average IC50 value for the test article, in the absence of UVA exposure, from the last two trials (wanner conditions) was 11.2 ug/mL. The positive control, chlorpromazine, was held in the same manner but was less temperature sensitive. It showed little change in the average IC50 value from the first four trials (27.1 ug/mL) to the last two trials (30.1 ug/mL). It should be understood that the impact of temperature on the solubility of the test article has not been tested directly but is consistent with its relatively poor solubility.

Applicant's summary and conclusion

Conclusions:
In conclusion. the data presented in this study suggest that HHCB is not phototoxic in this assay system.
Executive summary:

In the present GLP compliant study according to the OECD guideline 432 / adopted EU-SSCNFP guideline, Balb/c 3T3 mouse fibroblasts were exposed to 50 µl aliquots of HHCB (purity not reported in report, confirmed to be >95% pure undiluted material, IFF personal communication with RIFM) in Hank’s Balanced Salt Solution (HBSS) containing 0.5% ethanol (concentrations of 1.77 – 100 µg/ml) for 1 hr followed by irradiation with UVA light for 50 minutes for a total irradiation dose of 5 J/cm2. Duplicate slides were kept in the dark for the 50-minute period. After the irradiation period, the test solutions were decanted from the plates and the cells were washed with HBSS. Assay medium was then added to the cells and the cells were incubated for 24 hr at which time the assay medium was decanted from the cells and 100 µl of filtered Neutral Red solution added. After a 3 hr incubation, the cells were washed, scored for Neutral Red uptake and the IC50, the Mean Photo Effect (MPE) and Photo-Irritation Factor (PIF) were calculated. The average (over 2 runs) IC50 for HHCB was 8.84 µg/ml with and 11.2 without irradiation. The MPE was 0.016 (0.1 is considered non-photoirritant ) for each run and the PIF was 1.32 and 1.12 (2.0 is considered non-photoirritant ). Chlorpromazine was tested as a positive control. The average IC50was 30.1 µg/ml with irradiation and 1.84 without. The MPE was 0.64 for each run and the PIF was 18.36 and 13.62.