MINUTES - 7TH FEBRUARY 2002
Present:
| Chairman: Professor P Farmer |
Members: |
Secretariat: Dr R J Fielder (Scientific DH) Dr D Benford (Scientific FSA) Mr J Battershill (Scientific DH) Mr S Robjohns (Minutes) Mr K N Mistry (Administrative) |
| Assessors: Mr A Browning (VMD) Dr D Shillaker (PSD) Dr A Smith (HSE) Dr D Jones (MCA) |
In attendance: Dr D Renshaw (FSA, item 8) Dr G Smith (HO, item 7) |
CONTENTS
| Item | Paragraph |
|
1. |
Announcements/Apologies for absence | 1-4 |
2. |
Minutes of meeting held on 11 October 2001 | 5 |
3. |
Minutes of meeting held on 9 January 2002 | 6 |
4. |
Matters arising from the meeting on 11th October 2001 | |
| 4.1 P53 mutations and tobacco-induced carcinogenesis 4.2 SHE cell transformation assay: ILSI/HESI data 4.3 Statement on dimetridazole |
8 8 |
|
| 5. | Matters arising from the meeting on 9th January 2002 | 31 |
| 5.1 Dichlorvos | 10-21 |
|
| 6. | Possible nitrosation of nicotine patches (MUT/02/7) | 22-25 |
| 7. | PAVA: Use as an incapacitant spray (MUT/02/6) | 26-34 |
| 8. | Flunixin meglumine (MUT/02/3) | 35 |
| 9. | Consideration of OST Code of practice for Scientific Advisory Committees (MUT/02/5) | 36-42 |
| 10. | Committee procedures in light of BSE inquiry report (MUT/02/4) | 43-45 |
| 11. | Glossary of terms used by COT/COC/COM (MUT/02/8) | 46-47 |
| 12. | Draft Annual Report 2001 (MUT/02/9) | 48 |
| 13. | Any other business | 49 |
14. |
Date of next meeting | 50 |
ITEM 1: ANNOUNCEMENTS/APOLOGIES FOR ABSESENCE
1. The Chairman welcomed Dr G Smith from the Home office in attendance for item 7, and Dr D Renshaw from Food Standards Agency (FSA) attending for item 8.
2. The COM was informed that interviews had been held for two new members of the Committee with expertise in cytogenetics and aneuploidy and that recommendations have been made for consideration by CMO and the Chairman of the FSA. It was anticipated that an announcement would soon be made, and that two new members might be able to attend the next meeting.
3. Members were reminded of the need to declare any interests before discussion of items.
4. An apology for absence was received from Dr N Gooderham.
ITEM 2: MINUTES OF THE MEETING OF 11th OCTOBER (MUT/MIN/2001/4)
5. The minutes were approved with minor amendments.
ITEM 3: MINUTES OF THE MEETING OF 9th JANUARY 2002 (MUT/MIN/2002/1)
6. The minutes had been previously agreed and had been sent to industry together with the Committee's draft statement; they were circulated for information only.
ITEM 4: MATTERS ARISING FROM THE MEETING OF 11th OCTOBER 2001
4.1 P-53 mutations in tobacco induced carcinogenesis
7. A critique of a paper by Rodin and Rodin (Proc Natl Acad Sci, US, 97 12244-12249, 2000) on the importance of p53 mutations in tobacco induced carcinogenesis was tabled for information. This review paper had been sent to Mutagenesis for consideration for publication.
4.2 SHE cell transformation assay: ILSI/HESI data
8. Members were informed that the COM statement on the Syrian Hamster Embryo Cell Transformation assay and a statement by the COC on alternative cancer tests, had been sent to International Life Sciences Institute and Health and Environmental Sciences Institute (ILSI/HESI) for consideration at their meeting on the 10th January 2002. ILSI/HESI had made an initial suggestion of a joint publication on their research programme on alternative cancer models with separate sections containing the views of ILSI/HESI and the COC/COM. The COM was awaiting a formal response.
4.3 Dimetridazole
9. The Committee was told that the draft COM Statement had been forwarded to the companies Meryl (license holder for marketing the product) and BASF (who owned most of the data ). Meryl had responded and had offered to provide full copies of the previously requested three in-vivo mutagenicity studies on dimetridazole in sufficient time to allow a paper to be drafted for consideration by the COM at its next meeting on the 25th April 2002. Members agreed that this was satisfactory.
ITEM 5: MATTERS ARISING FROM THE MEETING ON 9th JANUARY 2002
5.1 Dichlorvos
10. Members confirmed the declarations of interest stated at the 9 January 2002 meeting. Professor Ashby declared a non personal interest and left the room for the discussion on dichlorvos.
11. The Chairman informed members that the revised statement which had been amended following the 9 January 2002 meeting had been forwarded to the data holders and additional comments had been received on 4 February 2002. The Chairman asked for comments on the new documents.
12. Members noted that the comments covered many issues which the Committee had considered in detail before including the weight of evidence to be attributed to the results from the Plesta study, the purity and source of test material used in the Plesta study, the finding of positive results in the Mutaä Mouse test system using dermally applied acetic acid, the possibility of a threshold for dichlorvos, use of unvalidated mutagenicity tests in hazard identification and the possible mechanisms of forestomach tumours seen in mice dosed with dichlorvos by gavage. The Committee agreed that the most pragmatic way forward would be undertake appropriate in-vivo testing in the lacZ Mutaä Mouse test system in order to fully evaluate the potential in-vivo mutagenicity of dichlorvos.
13. Apart from some references to results from skin micronucleus tests using 12-o-tetradecanoylphorbyl-13-acetate (TPA), there was no new data for the Committee to assess. Members were aware that there were other mutagenicity data on TPA and confirmed their view of the Tungal skin micronucleus study with dichlorvos, namely that although the study had not been fully evaluated the results were indicative of an in-vivo site of contact mutagenic effect.
14. Overall the COM concluded that there was no compelling reason to alter the statement. The Chairman informed the Committee that the Chair of COC and the animal pathologist from COC had forwarded e-mails to the secretariat confirming that they felt it would not be appropriate to alter the statement at this juncture but would be the case if results from additional testing of dichlorvos became available.
15. The Chairman invited Professor Ashby to return to the room to provide generic advice on the conduct of mutagenicity tests in transgenic animals.
16. The Committee gave detailed consideration to what further testing would be required to fully clarify the mutagenicity of dichlorvos and in particular the potential for site of contact mutagenicity. The Chairman noted that the Chairman of ACP had asked for advice in respect of the additional testing designed to allow conclusions to be reached with regard to the mechanism of the forestomach tumours reported in the NTP bioassay in mice.
17. Members agreed that further mutagenicity studies in the transgenic lacZ Mutaä Mouse system using both oral (gavage and diet) and dermal routes of administration were required in order to investigate potential site of contact effects. With regard to oral administration Members felt that the selection of dose levels, vehicle (corn oil) and dietary levels of dichlorvos should reflect the conditions used in the NTP/NCI bioassays. Members agreed that tissues examined (forestomach/ oesophagus) should also reflect the tissues where evidence of carcinogenicity had been reported. The duration of exposure has been subject to recent discussion at international working groups.There is general acceptance that daily doses for 14-28 days followed by a 7 day expression period is sufficient for identification of mutagenic effects. There would need to be pilot studies, to investigate the degree of gastrointestinal irritancy. Such studies would assist with dose level selection. Members agreed that MNNG should be used as a positive control.
18. Members had a detailed discussion of the potential conduct of the dermal studies. It was important to select a vehicle that allowed absorption but did not exacerbate irritancy. Overall it was felt that acetone, as used in the Tungal et al study of skin micronuclei would be suitable. There would need to be pilot studies to determine the degree of irritancy and these might inform on dose level selection.
19. The Committee felt that additional supporting information could be gleaned from undertaking appropriate studies to investigate dermal penetration and measurement of DNA adducts. However such additional investigations would be time consuming and were felt not essential to the conduct of the mutagenicity studies suggested by COM.
20. The Committee recognised that these would be difficult studies to plan and undertake and agreed to review and provide advice on protocols should the ACP consider that further studies would be appropriate.
21. With regard to evaluation of the data, the Committee agreed that equivocal and or positive results in any one of the studies in transgenic mouse systems would confirm the provisional hazard assessment of site of contact mutagen. Clearly negative studies by oral and dermal routes would provide sufficient reassurance that dichlorvos is not an in-vivo mutagen at the site of contact. Negative results in the oral transgenic mutagenicity assays would provide sufficient reassurance that the mechanism of forestomach tumour induction was non-genotoxic.
ITEM 6: POSSIBLE NITROSATION OF NICOTINE PATCHES (MUT/02/07)
22. Professor Tweats declared an interest in this item and left the room for the duration of the discussion.
23. At the COM meeting on 23rd July 2001 a member had requested the views of the Medicines Control Agency (MCA) on the possible nitrosation of nicotine derived from nicotine patches applied to the skin, and any mutagenic and subsequent carcinogenic risk.
24. MCA presented a paper to the Committee in response to this request. Members heard that nicotine from patches is absorbed through the skin and passes in to the systemic blood system, and is distributed throughout the body. Blood plasma concentrations rise more slowly from the use of these products than from cigarettes. Nicotine is continually released throughout the time of exposure. Nicotine has not been shown to be carcinogenic to animals. There was the possibility that nicotine could be demethylated and subsequently (or concomitantly) nitrosated to form N-nitroso-nornicotine, which is a genotoxic carcinogen. Although the amount of nitrosamine generated in this way was unknown, the MCA considered that is was likely to be minimal and very much less than the levels of other nitrosamines and other carcinogens present in tobacco smoke. In the licensing of a medicinal product one aspect to be considered was the benefit to health which had to be compared with any risk attributed to the use of the medicinal product. The MCA view was that the benefits clearly outweighed the risks in this case.
25. Members agreed that any concern over the risk of nicotine related mutagenicity and cancer from skin patches due to nitrosation is likely to be very small or insignificant in tobacco users who are or have been exposed to high concentrations of many carcinogens. It was noted that similar arguments also applied to chewing gum containing nicotine.
ITEM 7: PAVA: USE AS AN INCAPACITANT SPRAY (MUT/02/6)
26. No interests were declared.
27. Members were informed that the Sussex Police Force had recently started to use an incapicitant spray based on pelargonyl vanillylamide (PAVA) as an alternative to CS spray. PAVA is the synthetic equivalent to capsaicin the active ingredient of natural peppers. It is permitted as a food flavour (at up to 10 ppm). It is also used in human medicine topically as a rubifacient. The Home Office, who have the policy lead in this area, had asked the COT for advice on the health effects of PAVA spray. The COT gave initial consideration to this at their meeting on 4th December 2001, and requested that the COM provide advice on the mutagenicity data. This comprised a package of 3 in-vitro studies and one in-vivo study that had been commissioned by Sussex Police. The COM advice will be included in an overall statement on the health effects of PAVA spray which it was hoped would be agreed at the next meeting of the COT on 27th February.
28. The Committee noted that the structure of PAVA had a structural alert which could give rise to reactive oxygen species derived following possible formation of quinone intermediates. This might result in mutagenicity, particularly in-vitro and it was therefore incorrect to state that it did not have a structural alert.
29. Consideration was given to the data from the 3 in-vitro assays and members agreed that these studies had been carried out to an acceptable standard.
30. It was agreed that PAVA gave a clear negative in the assay for gene mutation in bacteria. However, members considered that a clear positive result was obtained in the cytogenetic assay in the presence of S-9, although effects seen in the absence of S-9 were not reproducible.
31. Members agreed that results from the mouse lymphoma assay should be regarded as equivocal/weakly positive. There was a marginal increase in mutant fraction at some dose levels, but with no clear dose-response. However, the lack of a positive trend of increasing mutation with increasing concentration could have been the result of the dose levels being set very close to each other.
32. Regarding the in-vivo bone marrow micronucleus test the COM considered that this was clearly negative. The top dose used was as high as could be tested, resulting in a number of deaths in the female animals. Although there was no evidence of any cytoxicity in the bone marrow, it was felt that the systemic toxicity seen indicated that the compound or metabolites reached the bone marrow. Members were informed that the compound was widely distributed following absorption, and would reach the bone marrow via the blood. Members noted a few numerical errors in tabulated results, which did not effect the overall conclusion that negative results were obtained in this study, but asked the study directors should be made aware of these discrepancies.
33. Members noted that according to the COM Guidance for a compound clearly positive in any of the 3 recommended in-vitro assays, a negative result in a single tissue would not provide sufficient data to conclude that the chemical was inactive in somatic cells in-vivo. Thus data from a second in-vivo assay was needed to provide adequate reassurances in this regard.
34. The COM agreed that an in-vivo liver UDS assay would be an appropriate assay in a second tissue, and that a negative result in this test would provide the adequate reassurance necessary. The Committee agreed the following conclusions for inclusion in the COT statement:
i) The structure of PAVA suggests the possible formation of reactive oxygen species from the phenol moiety, and other possible active metabolites which may be mutagenic.
ii. Data are available from 3 in-vitro studies done to current standards. The assay for gene mutation in bacteria gave negative results. Equivocal/weakly positive results were obtained in the mouse lymphoma assay. A clear positive result was however obtained in the assay for chromosome damage in CHO cells in the presence of the exogenous metabolic activation system which was not limited to concentrations producing excessive toxicity. These in-vitro data indicate that PAVA has mutagenic potential.
iii. Negative results were obtained in a bone marrow micronucleus test, PAVA being given orally at up to dose levels that produced marked toxicity (some lethality).
iv. As noted in the COM guidelines, in the case of substances positive in vitro a negative result in a single tissue will not provide sufficient data to conclude that the chemical is inactive in vivo. Thus data from a second in-vivo assay are necessary to provide adequate reassurance that the mutagenic potential identified in the in-vitro studies cannot be expressed in vivo. In this regard members felt that data from an in-vivo liver UDS assay would be appropriate in this case and that negative results in this assay would provide the necessary reassurance.
ITEM 8: FLUNIXIN MEGLUMINE AND MEGLUMINE (MUT/02/3)
35. The minutes of this item are now published as paragraphs 51 to 56.
ITEM 9: CONSIDERATION OF OST CODE OF PRACTICE FOR SCIENTIFIC ADVISORY COMMITTEES (MUT/02/5)
36. A copy of the new "Code of Practice" for Scientific Advisory Committees published by the Office of Science and Technology (OST) on 19th December 2001 was provided to members for information and comment.
37. Members agreed that in general the COM procedures complied with most of the guidance given by OST. However, there were a number of areas that required consideration.
38. The Committee agreed that it was difficult to publish a detailed forward plan, as much of the work of the Committee was reactive in response to requests for advice from Other Government Department/Agencies, often at short notice. It was noted that the agenda was normally set by the secretariat in response to such requests but that members could make suggestions for consideration at anytime.
39. Regarding 'horizon scanning' members believed that generic issues were often identified by the secretariat and members, but acknowledged that systematic searching of the literature to identify all relevant research was not possible.
40. The Committee considered that improving communications of its advice to the public was difficult because of its specialist and very technical nature. The Chairs of the COC/COM had both agreed with the proposal in the OST to publish more background papers. A 'what's new' section had also been placed on the COM website, which would help improve communication. Members agreed that lay summaries of completed statements should be drafted as appropriate when particularly complex subjects were under discussion.
41. It was agreed that a glossary of technical terms could help with public understanding and that COM would contribute to a joint COT/COC/COM glossary presently being reviewed by the COT (see item 11).
42. With respect to dealing with dissenting views members agreed that it should be made clear in the minutes and statements when consensus had not been reached, and the dissenting view published alongside the statement agreed by the majority.
ITEM 10: CONSIDERATION OF COMMITTEE PROCEDURES IN LIGHT OF GOVERNMENT RESPONSE TO THE BSE INQUIRY REPORT (MUT/02/4)
43. The report of the BSE Enquiry published in October 2000 included a number of findings relating to the role of scientific advisory committees and the Government's assessment and use of scientific advice. The Government's interim response to the Enquiry's report - issued in February 2001 was put out for public consultation (9 February to 30 April 2001).
44. An appended paper (CC/01/26) had previously been submitted to the COT for discussion on October and the COC on November 2001. The paper outlines points made in the Government's final response to the BSE Enquiry report and incorporates views expressed during the consultation exercise. This paper was presented to the COM for information and comment, and members were invited to consider whether the committee needed to change its mode of working.
45. This item was considered in conjunction with the previous item (OST report on procedures for Scientific Advisory Committees). The COM was satisfied with the approach set out in the document, and noted that the areas of discussion overlapped with those identified in the OST paper.
ITEM 11: GLOSSARY OF TERMS USED BY THE COT/COC/COM (MUT/02/8)
46. There has been an increasing recognition of the importance of terminology and definitions and thus a need to review and expand the glossary of terms used by the COT/COC/COM. A paper on this had been circulated to the COT and was now being provided to the COM (and COC). The COT had questioned a number of terms and member's comments on these were requested.
47. The COM agreed to set up a small working group and report comments to the Chairman. The group would consider the relevant terms and provide their views to the Committee at a later date. All members were invited to forward comments by post/e-mail to the secretariat.
ITEM 12: COM ANNUAL REPORT FOR 2001 (MUT/02/9)
48. A draft annual report, drawn up from the agreed minutes and statements, was provided to the Committee. Members were requested to send written comments to the Secretariat.
ITEM 13: ANY OTHER BUSINESS
49. Members were informed that the ACP had referred a review of malathion to the COM and COC.
ITEM 14: DATE OF NEXT MEETING
50. 25th April 2002
ACTIONS
| Item | Action | Responsibility |
| Item 5 Dichlorvos | Draft letter to ACP and circulate to Members. | Chairman/ Secretariat |
| Item 7 PAVA | Draft conclusion and circulate to members | Secretariat |
| Item 8 Flunixin meglumine | Revise interim statement but await further data for next meeting | Secretariat |
ADD PARAGRAPHS 51 TO 56 on 28 MARCH 2003
ITEM 8: FLUNIXIN MEGLUMINE AND MEGLUMINE (MUT/02/3)
51. The three compounds, flunixin, flunixin meglumine, and meglumine had been initially considered separately at the COM meeting on 11th October 2001 (MUT/01/28). A draft statement without a discussion or conclusions section had been circulated to members.
52. At the 11th October 2001 meeting the Chairman had asked a number of members to consider the full reports of some of the mutagenicity studies and provide evaluations. Members had agreed that further consideration of a number of reports was required before conclusions could be agreed.
53. One member had reviewed an in-vitro CHO chromosome aberration assay with flunixin-meglumine and concluded that a clear positive response had been obtained, which was tempered by not knowing the degree of cytotoxicity at the 'positive' concentrations. On commenting on the mouse lymphoma assays, Members were informed that the studies were old and therefore had limitations but some positive results had been produced, including in the presence of exogenous metabolic activation. Overall these data couldn't be discounted.
54. At the meeting of 11th October 2001 members had agreed that results of the mouse in-vivo bone marrow micronucleus assay on meglumine had been inconsistent. One member had offered to carry out additional testing with meglumine to help clarify the position. This member provided an interim report to the Committee.
55. One old study had reported a positive result in a bone-marrow micronucleus assay in BSI mice using intraperitoneal doses of 500 or 1000 mg/kg bw meglumine (sampling time 6h after last dose). A repeat trial in this old study using 1000 mg/kg bw was also positive. A separate in-vivo micronucleus study involving intraperitoneal administration of up to 600 mg/kg bw meglumine to CD1 mice had given negative results (sampling time 24h after last dose).
56. To help determine whether meglumine was active in the micronucleus assay investigations were performed using male mice. Animals were given two doses of 1000 mg/kg bw by intraperitoneal injection (doses spaced 24h apart). Sampling times were 6h and 24h after the last dose to cover the positive and negative responses described above. The results corresponded with the previous studies with a positive response obtained at the 6h time point and a negative response at the 24h time point. It was also difficult to explain why a positive result was obtained after 6 hours and not after 24 hours. These data were however, consisitent with the earlier studies. Further investigations of the time response were to be conducted and presented at the next meeting.