Registration Dossier

Administrative data

Endpoint:
additional toxicological information
Type of information:
other: Expert review
Adequacy of study:
supporting study
Study period:
2010
Reliability:
other:
Rationale for reliability incl. deficiencies:
other: The study represents an in-depth expert review of hematological data from a 90-day oral gavage study in rats.
Cross-reference
Reason / purpose:
reference to same study

Data source

Reference
Reference Type:
other: Expert review
Title:
Unnamed
Year:
2010
Report Date:
2010

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Hematological data from a 90-day repeated dose (gavage) toxicity study of dimyrcetol (CAS 18479-58-8) in Sprague-Dawley rats were re-evaluated for the purposes of: (1) confirming hematological findings; (2) providing interpretation of treatment-related findings and adverse effects as the basis of assigning a NOAEL value; and (3) providing an interpretation as to the relevance of any findings to humans and to human risk assessment.
GLP compliance:
no
Remarks:
not applicable

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Type:
Constituent
Details on test material:
Name of test material (as cited in study report): Dimyrcetol
- Physical state: clear, colorless liquid
- Analytical purity: 99% (Certificate of Purity)
- Impurities: None identified
- Purity test date: 15 December 2005
- Lot/batch No.: SM/4103311 and SM/5073201
- Expiration date of the lot/batch: December 2006
- Stability under test conditions: Solutions in corn oil determined to be stable for at least 14 days
- Storage condition of test material: room temperature in the dark until 6 January 2006, thereafter approximately 4 deg C in the dark
- Other: The integrity of the supplied data relating to the identity, purity and stability of the test material was the responsibility of the Sponsor.

Statement from the Test Article Supplier (International Flavors and Fragrances, Lot SM 410331)
Dimyrcetol is a fragrance ingredient manufactured by IFF. It is not a single component but a mixture of two chemical entities, 2,6-dimethyl-7-octen-2-ol formate and 2,6-dimethyl-7-octen-2-ol. The percentage of each component from the certificate of analysis dated December 15, 2005, is 54.8% and 44.2%, respectively. These two components derive from the chemistry used to manufacture dimyrcetol. It is an equilibrium mixture of tertiary formate and tertiary alcohol.

Results and discussion

Any other information on results incl. tables

For this re-evaluation, all clinical laboratory data (group mean and individual data) was examined, alone and in context with other in-life and pathology data and provided reference intervals (RI; normal ranges), as presented in the Tables and Appendices of the original report.

Statistically significant differences between hematological data from control animals compared to treated animals were detected for platelet counts (males at ≥ 50 mg/kg/day); aPTT (males at 1000 mg/kg/day; females at ≥ 500 mg/kg/day); Hgb concentration and HCT (females at 1000 mg/kg/day); and RBC (females at ≥ 500 mg/kg/day). The data for these analytes plus WBC are presented as mean ± 2SD and as range of values, with statistically significance differences indicated in Tables 1 (males) and 2 (females).

Erythron

Interpretation of erythroid results requires evaluation of HGB, RBC, HCT, MCV, MCHC and MCH. The hemoglobin concentration and the haematocrit provide the most solid information for determining red blood cell mass and oxygen carrying capacity and are the best measures for detecting a change. When these two results from weeks 7 and 13 are compared, only rat no. 37 (Group 2) shows a real decrease in her erythron, with a 1.1 g/L drop in HGB and decrease in HCT by 4.3%. Group 5 female rat no. 76 (data not presented in table) showed a reverse effect, with a 1 g/L increase in HGB and 3.1% increase in HCT. These two rats, no. 37 at week 13 and no. 76 at week 7, are the only individuals to have an HCT, 38.3% and 38.6% respectively, that is lower than the historical RI of 38.9%. Hemoglobin concentrations below the historical RI (< 14.2 g/L) were identified in four individuals: rat no. 32 (Group 2; 13.9 g/L at both time points; not presented in table); rat no. 37 (Group 2; 13.8 g/L at week 7); rat no. 76 (Group 4; 13.5 g/L at week 7); and rat no. 91 (Group 5; 14.1 g/L at week 13). See Table 3.

HGB concentration and HCT for Group 5 females and RBC for Groups 4 and 5 females were statistically significantly lower (p<0.05) than concurrent control values at week 13. The results from the individual/group with the lowest HCT at week 13 are listed in Table 3 with individual results presented in bold for week 7 (in parentheses) and week 13, beneath the group mean ± 2 SD and the range and with the historical RI.

Based on this detailed review of the erythroid data, demonstrating that the majority of individual values were within the historical RI, and that a slight reduction in the erythron is commonly seen in treated animals relative to concurrent controls, the difference detected with statistical analysis is not considered to represent a treatment related effect for HBG concentration, HCT or RBC.

Platelets

Platelet counts flagged as statistically significantly decreased, relative to concurrent control results, occurred in males at ≥ 500 mg/kg/day week 7 and at ≥ 50 mg/kg/day week 13; no significant differences were identified for female rats. To be both conservative and comprehensive in identifying the incidence and severity of low platelet counts, the individual data were reviewed and each rat with a count less than the lowest concurrent control value (week 7 or week 13) was identified. Platelet counts from these individuals from both samplings were noted and compared to concurrent control results and the historical RI (see Table 4).

Platelet counts below the concurrent control range occurred in all four treatment groups for both sexes at week 7, and all but Group 2 males at week 13. For males the incidence of platelet counts less than the lowest concurrent control result, Groups 2-5, was 2, 2, 2 and 4 for week 7, and 0, 3, 3 and 4 for week 13. For female rats, Groups 2-5, the incidence was 1, 2, 1 and 1 for week 7, and 2, 2, 1 and 1 for week 13. None of the results from the male rats was outside of the historical RI. Four values from female rats, one value/group, fell below the historical RI. Rats that had low platelet counts below the concurrent control range at both week 7 and 13 occurred in male rats nos. 43 (Group 3), 70 (Group 4), and 81, 88 and 89 (Group 5). Dramatic improvement in individual platelet counts was appreciated for male rat no. 21 (Group 2) and for female rats nos. 36 (Group 2), 58 (Group 3), 76 (Group 4) and 91 (Group 5). No individual had a significant decrease in platelet count from week 7 to week 13.

There is an increased incidence in the number of treated rats with platelet counts that are both below the concurrent control range and less than the historical control mean. However, the values from treated male rats are comparable to male Control rat no. 1, there is no clinical, post mortem or histological observation of hemorrhage, and the difference detected by statistical analysis is minimal and has no medical or clinical significance. Based on this review, the minimal decrease in platelet counts in males is not considered to represent a treatment related effect.

Bone Marrow Findings

Histopathology results indicate that the incidence of higher grades of severity of adipose infiltration of the marrow was greater in relation to males at 1000 mg/kg/day. This finding was considered indicative of marrow hypoplasia. No effect was found in the females.

Granulocytes and monocytes spend the shortest time in circulation, measured in hours; platelets circulate for days and erythrocytes circulate for months. The minimal decrease in circulating platelets is discussed above and not considered to be a compound related finding. Without evidence of leucopenia or neutropenia (see Tables 2 and 3) or a decrease in the erythron, and no increase in extramedullary hematopoiesis, there is nothing tangible in the laboratory data to corroborate the hypoplastic diagnosis. 

Based on the review of information available, the possibility that the diagnosis of bone marrow hypoplasia may be a misinterpretation. Bone marrow composition varies with the site sampled and there may be enough variation in the sections studied to have suggested a difference that was relative rather than absolute. Therefore, when all data are considered and noting that a similar effect was not identified in the female rats, the bone marrow is not considered to be a target organ and findings are more likely incidental and are not considered a treatment related effect.

Activated Partial Thromboplastin Time (aPPT)

Activated partial thromboplastin time showed a statistically significant difference between results of treated rats to control rats in both sexes at week 7 (see Tables 1 and 2). In the author’s experience, the aPTT test results vary less than ± 1.5 seconds in a healthy individual. Therefore, the delta for each pair of aPTT results was determined. Results (n and individual animal numbers) were divided into three groups: no change (∆ ≤ 1.5 s), increased (∆ > +1.5 s; week 13 value > week 7), or decreased (∆ > +1.5 s; week 13 value < week 7) and are presented in Table 5. A decrease (shortening) in aPTT for males was identified in 4, 0, 6, 7 and 3 individuals, Groups 1-5; for females, aPTT decreased in 4, 4, 3, 1 and 2, Groups 1-5. Fewer individuals had an increased (prolonged) change: in males, 2, 1, 1, 0 and 2, Groups 1-5 while in females, 1, 3, 3, 3, and 3, Groups 1-5.

Because nearly every data point fell within the historical RI and no meaningful effect could be identified when individual values were paired, the significance of detecting a statistical difference between results from treated rats and those of concurrent control rats needs to be carefully considered, particularly because significance was only detected at week 7. If a true hypercoagulable state existed, this finding should have repeated at week 13, and histopathological lesions of thrombi or thromboembolic disease would likely have been identified. Based on this review, the difference in the minimal shortening of the aPTT detected with statistical analysis is not considered to represent a treatment related effect.

Applicant's summary and conclusion

Conclusions:
Oral (gavage) administration of Dimyrcetol (CAS 18479-58-8) in corn oil at doses of 0, 10, 50, 500 or 1000 mg/kg/day to male and female Sprague-Dawley Cr1:CD-(SD) IGS BR strain rats did not produce any treatment related effects in the hematology or hemostasis data.
Executive summary:

Hematological and related information from a 90 -day oral (gavage) study in Sprague-Dawley rats with dimyrcetol at doses of 0, 10, 50, 500 or 1000 mg/kg bwt/day were reviewed. In the case of the hematology endpoints HGB, RBC, HCT, MCV, MCHC and MCH, the majority of measured values from female rats were within historical RI and group mean results were considered unremarkable. Reduced platelet counts in some male and female rats were recorded, and in male rats, platelet counts from otherwise healthy rats were on the lower end of the historical RI. Based on dramatic increases in platelet counts in some rats from week 7 to 13, and the presence of similar low counts in a male control (untreated) rat, the minimal decreases in platelet counts were not considered to represent a treatment-related effect. Based on several observations including: aPPT results that were well controlled and differing by no more than +/- 1.5 seconds; inconsistent changes within dosed groups; no accompanying histopathological lesions consistent with hypercoagulation (thombi; thromboemboli); and nearly all data points falling with historical RI values, it was concluded that aPTT results did not represent a treatment-related effect. The review of information relating to possible bone marrow effects was considered inadequate for a diagnosis of bone marrow hypoplasia in male rats. In particular, the bone marrow was not considered to be a target organ and findings were most likely incidental in nature. This conclusion is strengthened by the lack of similar effects in female rats.