Thoughts on the Proper Use and Interpretation of Clinical Pathology Data in Preclinical Safety Testing: A Canadian Perspective* RUDOLF W. MUELLER
Toxicology Research Division, Health and Welfare Canada, HPB, Sir Frederick G. Banting Building, Tunney’s Pasture, Ottawa, Ontario, Canada KIA 0L2
Keywords. Regulations; animals; hematology; clinical chemistry; toxicity testing I would like to express my thanks for the invitation to take part in this workshop and to be able to discuss important aspects of research pertaining to and leading to regulatory activities. In spite of being specialized in morphologic pathology, I hope to be able to contribute to the discussion that focuses on the role of clinical pathology. As a research scientist, I am working within the Department of Health and Welfare, in the Health Protection Branch. The pathology-related research is carried out in 2 bureaus: the Bureau of Chemical Safety and the Bureau of Drug Research. Both provide expertise in the regulatory process. Similar to the Food and Drug Administration, very few veterinary pathologists and clinical pathologists are in regulatory positions. This fact is quite important for the understanding of differing opinions on interpretation of results in the preclinical studies. I would like to discuss selected aspects that I have encountered while working in the present department. There is no question that clinical pathology, comprising clinical chemistry and hematology, is an integral part of the pathology assessment of the in vivo studies. Like gross pathology and histopathology, it is a vital part of any study using animal models. The value of results obtained within the disciplines mentioned is greatly enhanced by an interpretative input, combined with the drawing of
conclusions. This sented in an tistical data.
means
that results would be preform rather than as sta-
interpretative
How, then, are clinical pathology data presented in submissions to regulatory bodies? It is not rare that animal data are submitted in several separate packages that present themselves as rather large, separate piles of paper or books. In addition, many computer programs presently used in data collection do not allow the easy switching back and forth between the data packages. Thus, the question arises of who is going to produce the Comprehensive Preclinical Review, the cornerstone of any new submission. It is there that input can be enhanced or diminished, especially since the actual reviewer might not be a person used to the interpretation of animal experiments. It is certainly fortunate that in the Health Protection Branch each submission is reviewed on its own merit. The assessment of clinical pathology data is therefore to be seen in the context of a given study rather than merely in the fulfillment of a requirement for regulatory purposes. Or, in other words, the question is asked whether or not tests used and data obtained do adequately explain observations of clinical and pathological nature? For instance, page 2 of the 1990 Canadian guidelines (2) for new drug submissions states the following: &dquo;These guidelines should not be considered immutable or definitive. They are subject to revision when future developments in science and medicine require it.&dquo; To further underline the significant value regulators attribute to clinical pathology, I quote some lines from the same document: &dquo;Before initiating studies in non-rodents, baseline values should be obtained for
* Address correspondence to: Dr. Rudolf W. Mueller, Toxicology Research Division, Health and Welfare Canada, HPB, Sir Frederick G. Banting Building, Tunney’s Pasture, Ottawa, Ontario, Canada K 1 A OL2. Presented at the International Workshop on Clinical Pathology Testing in Preclinical Safety Assessment, George Washington University, Washington, D.C., July 27, 1991.
526
527
hematology, clinical chemistry, and urinalysis. These parameters should be determined periodically both in rodents and non-rodents during the study as well as terminally. Such determinations should be performed in all non-rodents and in a sufficient number of rodents per group to permit meaningful statistical analysis.&dquo; At this point I would like to know who would look at the statistical analysis: Is it the regulatory body, or is the analysis integrated in the comprehensive review, of course with interpretation ? In practice, it is mostly a combination of the 2, and this fact, not surprisingly, may give rise to a lot of discussions and misunderstandings. The value of clinical pathology data depends greatly on laboratory practices and the setting of normal limits. Historical data, probably more so than in histopathology, are of questionable value. Just the variety of analytical equipment will lead to a wide spread of margins within and among laboratories. Clinical pathology is established as an integral part of the safety assessment of traditional xenobiotics, especially in short- and medium-term toxicity, helping to define target organs of significance in long-term studies. At the same time, normal values and ranges can be set for the statistics to be studied. In long-term studies, the guidelines require observations on clinical chemistry, hematology, and urinalysis. Fortunately again the tests to be used are not unnecessarily and narrowly specified by the regulatory guidelines (1). The role of clinical pathology in the definition of a maximum tolerated dose could
be quite important. One only has to look at the rather difficult-to-interpret definition of maximum tolerated dose put forward, for instance, by McConnell (3): &dquo;The maximum tolerated dose is the highest dose of the test agent during the chronic study that can be predicted not to alter the animals longevity from effects other than carcinogenicity.&dquo; It is clear that with regard to the present regulatory situation clinical pathology needs to gain a higher level of importance. A precondition for this to happen will be an improved reliability of the tests. Clinical pathology may play a key role in the safety testing of biologics, as previously discussed. I would like to quote Zbinden (4), who clearly expresses my thoughts on this subject: &dquo;Toxicity testing of biotechnology products requires a flexible approach, taking into consideration all available chemical, pharmacological and biochemical information.&dquo; REFERENCES 1.
Canada, Minister of Supplies and Services (1988). Bio-
Tech : User’s Guide to Regulations. Cat. No. EN 40357/1988 E, ISBN 0-662-16353-2. 2. Canada, Minister of Supplies and Services (1990). Toxicologic Evaluation: Drugs Directorate Guidelines. Cat. No. H42-2/ 15. 3. McConnell EE (1989). The maximum tolerated dose: The debate. J. Am. Toxicol. 8: 1115-1120. 4. Zbinden G (1990). Safety evaluation of biotechnology products. Drug Safety 5(suppl. 1): 58-64.
Toxicology Research Division, Health and Welfare Canada, HPB, Sir Frederick G. Banting Building, Tunney’s Pasture, Ottawa, Ontario, Canada KIA 0L2
Keywords. Regulations; animals; hematology; clinical chemistry; toxicity testing I would like to express my thanks for the invitation to take part in this workshop and to be able to discuss important aspects of research pertaining to and leading to regulatory activities. In spite of being specialized in morphologic pathology, I hope to be able to contribute to the discussion that focuses on the role of clinical pathology. As a research scientist, I am working within the Department of Health and Welfare, in the Health Protection Branch. The pathology-related research is carried out in 2 bureaus: the Bureau of Chemical Safety and the Bureau of Drug Research. Both provide expertise in the regulatory process. Similar to the Food and Drug Administration, very few veterinary pathologists and clinical pathologists are in regulatory positions. This fact is quite important for the understanding of differing opinions on interpretation of results in the preclinical studies. I would like to discuss selected aspects that I have encountered while working in the present department. There is no question that clinical pathology, comprising clinical chemistry and hematology, is an integral part of the pathology assessment of the in vivo studies. Like gross pathology and histopathology, it is a vital part of any study using animal models. The value of results obtained within the disciplines mentioned is greatly enhanced by an interpretative input, combined with the drawing of
conclusions. This sented in an tistical data.
means
that results would be preform rather than as sta-
interpretative
How, then, are clinical pathology data presented in submissions to regulatory bodies? It is not rare that animal data are submitted in several separate packages that present themselves as rather large, separate piles of paper or books. In addition, many computer programs presently used in data collection do not allow the easy switching back and forth between the data packages. Thus, the question arises of who is going to produce the Comprehensive Preclinical Review, the cornerstone of any new submission. It is there that input can be enhanced or diminished, especially since the actual reviewer might not be a person used to the interpretation of animal experiments. It is certainly fortunate that in the Health Protection Branch each submission is reviewed on its own merit. The assessment of clinical pathology data is therefore to be seen in the context of a given study rather than merely in the fulfillment of a requirement for regulatory purposes. Or, in other words, the question is asked whether or not tests used and data obtained do adequately explain observations of clinical and pathological nature? For instance, page 2 of the 1990 Canadian guidelines (2) for new drug submissions states the following: &dquo;These guidelines should not be considered immutable or definitive. They are subject to revision when future developments in science and medicine require it.&dquo; To further underline the significant value regulators attribute to clinical pathology, I quote some lines from the same document: &dquo;Before initiating studies in non-rodents, baseline values should be obtained for
* Address correspondence to: Dr. Rudolf W. Mueller, Toxicology Research Division, Health and Welfare Canada, HPB, Sir Frederick G. Banting Building, Tunney’s Pasture, Ottawa, Ontario, Canada K 1 A OL2. Presented at the International Workshop on Clinical Pathology Testing in Preclinical Safety Assessment, George Washington University, Washington, D.C., July 27, 1991.
526
527
hematology, clinical chemistry, and urinalysis. These parameters should be determined periodically both in rodents and non-rodents during the study as well as terminally. Such determinations should be performed in all non-rodents and in a sufficient number of rodents per group to permit meaningful statistical analysis.&dquo; At this point I would like to know who would look at the statistical analysis: Is it the regulatory body, or is the analysis integrated in the comprehensive review, of course with interpretation ? In practice, it is mostly a combination of the 2, and this fact, not surprisingly, may give rise to a lot of discussions and misunderstandings. The value of clinical pathology data depends greatly on laboratory practices and the setting of normal limits. Historical data, probably more so than in histopathology, are of questionable value. Just the variety of analytical equipment will lead to a wide spread of margins within and among laboratories. Clinical pathology is established as an integral part of the safety assessment of traditional xenobiotics, especially in short- and medium-term toxicity, helping to define target organs of significance in long-term studies. At the same time, normal values and ranges can be set for the statistics to be studied. In long-term studies, the guidelines require observations on clinical chemistry, hematology, and urinalysis. Fortunately again the tests to be used are not unnecessarily and narrowly specified by the regulatory guidelines (1). The role of clinical pathology in the definition of a maximum tolerated dose could
be quite important. One only has to look at the rather difficult-to-interpret definition of maximum tolerated dose put forward, for instance, by McConnell (3): &dquo;The maximum tolerated dose is the highest dose of the test agent during the chronic study that can be predicted not to alter the animals longevity from effects other than carcinogenicity.&dquo; It is clear that with regard to the present regulatory situation clinical pathology needs to gain a higher level of importance. A precondition for this to happen will be an improved reliability of the tests. Clinical pathology may play a key role in the safety testing of biologics, as previously discussed. I would like to quote Zbinden (4), who clearly expresses my thoughts on this subject: &dquo;Toxicity testing of biotechnology products requires a flexible approach, taking into consideration all available chemical, pharmacological and biochemical information.&dquo; REFERENCES 1.
Canada, Minister of Supplies and Services (1988). Bio-
Tech : User’s Guide to Regulations. Cat. No. EN 40357/1988 E, ISBN 0-662-16353-2. 2. Canada, Minister of Supplies and Services (1990). Toxicologic Evaluation: Drugs Directorate Guidelines. Cat. No. H42-2/ 15. 3. McConnell EE (1989). The maximum tolerated dose: The debate. J. Am. Toxicol. 8: 1115-1120. 4. Zbinden G (1990). Safety evaluation of biotechnology products. Drug Safety 5(suppl. 1): 58-64.
