Reproductive toxicity testing of pharmaceutical compounds to support the inclusion of women in clinical trials.

1. The potential for toxicity to reproduction and the developing fetus is an important concern requiring attention during the development of new medicines. However, there are differences in the opinions of the regulatory authorities in Europe, Japan and the USA regarding the nature and amount of data from reproductive toxicity tests that should be available at the various stages of clinical development. 2. Forty-one companies or their subsidiaries from Europe, Japan and the USA provided data for a questionnaire-based study, carried out in 1994, to ascertain the practices of pharmaceutical companies and their views on an ideal approach to the timing of reproduction and development toxicity studies in relation to clinical investigation. 3. Differences were identified in the stage of drug development at which animal studies were completed, the sequence of completion of specific studies, and the extent of reproduction testing completed to support the inclusion of women in clinical trials. 4. A harmonised, but flexible, guidelines, encompassing the timing of reproductive toxicity studies in relation to clinical trials, would permit better integration between clinical and non-clinical studies in an international drug development programme.

The timing of preclinical toxicological studies: pharmaceutical company approaches to toxicity testing in support of initial clinical investigations.

The completion of preclinical toxicity studies to support the first administration to humans is a time-critical step in the clinical development of medicines, and is complicated by differences in national regulatory requirements. A questionnaire-based study was carried out in 1994 to ascertain pharmaceutical companies' actual practices and views on an ideal approach to the timing of different types of nonclinical safety studies in relation to clinical investigation. Forty-one companies or their subsidiaries from Europe, Japan, and the United States responded by providing data. A range of preclinical packages were indicated as being used by companies prior to initiating Phase I clinical trials. The selection of studies tended to be based on the recommendations of the regulatory authority of the region in which the respondents were located. Differences were evident regarding the extent of genetic toxicity testing, the duration of repeat-dose toxicity studies, and the need for male fertility testing to support the first single administration of a compound to humans. In an ideal situation, the respondents would have preferred to conduct shorter duration repeat-dose toxicity studies prior to the first single administration to humans than was their actual practice in 1994. A harmonized guideline on the timing of toxicity studies in relation to clinical trials will allow better integration between clinical and nonclinical studies in an international development program. However, the diversity in the responses has demonstrated the need for flexibility in any future guideline.

Genotoxicity testing: current practices and strategies used by the pharmaceutical industry.

Current guidelines and recommendations for genotoxicity testing of pharmaceuticals are disparate, both in terms of the most appropriate tests to use and the protocols to follow. Recent attempts have been made to standardise genotoxicity testing procedures, coinciding with the current review of the OECD guidelines and the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH). However, as with other aspects of non-clinical safety assessment of pharmaceuticals, guidelines have been prepared by evaluation of general chemical data due to the lack of specific information on pharmaceuticals. To address this, a project was undertaken to collect and collate information specifically pertaining to the genotoxicity testing of pharmaceuticals in order to obtain a clear understanding of international strategy and procedures in the pharmaceutical industry. It is clear that the practices and regional variations are strongly influenced by national guidelines and do not necessarily follow companies' preferences. However, there is a surprising amount of variation in approach between companies on some issues. This is evident in how companies define a genotoxin. This ranges from a positive result in an in vivo assay as indicative of a genotoxin (43%) to any positive result in vitro or in vivo (30%). Indeed many companies (particularly in Japan) will terminate development on the strength of a clear positive result in an Ames test. There is much debate within the ICH process concerning tests to detect gene mutations in mammalian cells as part of a primary test battery. This survey shows that in general, the pharmaceuticals industry has severe doubts about these assays. Thirty-seven (78%) of the 47 participating pharmaceutical companies include an in vitro test to detect gene mutation in mammalian cells as part of their routine test battery. The HPRT test using Chinese hamster cells has the most widespread use, although there is only limited use of such tests in Japan. Compound development has been affected by the results of such tests, but usually only in terms of clarification of equivocal results in other genotoxicity tests in the test battery. The majority (63%) of companies do not support its use as a primary regulatory requirement, and 83% do not consider the mouse lymphoma assay (L5178Y) an acceptable replacement for in vitro mammalian cytogenetics. In conclusion, this survey has provided valuable information on the current modus operandi of the international pharmaceutical industry for consideration in current harmonisation initiatives.

The value of information generated by long-term toxicity studies in the dog for the nonclinical safety assessment of pharmaceutical compounds.

Data on 117 pharmaceutical compounds in the CMR toxicology database have been analyzed to determine what new toxicological information was provided by the dog in chronic (6 months or longer) toxicity testing. For more than half of the 117 compounds, all salient effects in the dog were seen for the first time within 3 months. For just under one-third of the compounds, any effects that occurred for the first time beyond 3 months in the dog were also seen in studies in the rat. Only 13 of the 117 compounds showed new and possibly important effects in the chronic study. No particular therapeutic class nor any other single circumstance was implicated in these 13 cases. Types of late-onset findings in the dog occurring with more than 1 compound included nonspecific effects or hypertrophic/hyperplastic changes. There may be several reasons, pragmatic as well as scientific, why it can sometimes be desirable to carry out chronic repeat-dose studies of 6 months or longer in the dog. However, the results of this retrospective evaluation have demonstrated that in the large majority of cases analyzed, long-term toxicity studies in the dog provide relatively little qualitatively new toxicological information not already gained from a short-term (3 month) study in the dog in conjunction with short- and long-term studies in the rat.

New chemical entity output of the international pharmaceutical industry from 1970 to 1992.

A database has been established that contains confidential information, together with publicly available data, on various aspects of the development of 1106 new chemical entities and biological compounds (including products of biotechnology) first marketed as medicines since 1970 on one or more of 20 major international markets. These data have been used to examine the performance of the European, U.S., and Japanese pharmaceutical industries by examining the numbers and types of new medicines reaching the marketplace from 1970 to 1992 and the companies responsible for introducing them. Although the European marketing companies dominate in total numbers first marketed over this period, there has been a significant decline in their annual output. In contrast, the Japanese companies have shown a significant increase in the number of new compounds marketed annually. However, European marketing companies remain the most successful in terms of sales because they are responsible for first marketing approximately 50% of the top 50 products by international sales in 1992. The main therapeutic areas of output by all three regions have remained relatively unchanged over the 23-year period: cardiovascular system (21%), nervous system (18%), and anti-infectives (16%). This article provides insight into the changing status of the international pharmaceutical industry over the last 23 years in terms of output from research and development.

An international appraisal of the minimum duration of chronic animal toxicity studies.

1. There are international differences in regulatory guidelines for the appropriate duration of chronic, two species repeat-dose animal tests for new medicines intended for long-term use in man, ranging from 6 months in Europe to 12 months in Japan and the USA. 2. An adequate data base is necessary to support any challenge to the scientific rationale behind regulatory guidelines with regard to the design, duration and relevance of toxicity tests of new medicines. 3. The Centre for Medicines Research has established an international toxicology data base which has been expanded to enable a comparison of data obtained within 6 months, with information from longer periods, for 154 studies. 4. Although new findings were revealed after 6 months for 9/75 cases for which pathology data are available at 6 and 12 months or longer, and 21/80 with data at 1 or 3 (but not 6 months) and 12 months or longer, in no instance did these influence the decision to drop or further develop the compounds in question. 5. These data suggest that a 6-month period of dosing is all that is routinely required for evaluating the chronic toxic (excluding carcinogenic) potential of a new chemical entity intended for therapeutic use.

The need for a control animal pathology database: an international survey.

1. The sensitivity of long-term toxicity tests is impaired due to the 'background noise' of spontaneous lesions which are unrelated to treatment. 2. The need for a comprehensive source of computerized information concerning the occurrence and incidence of spontaneous lesions in control animals has been highlighted by initiatives in Europe and the USA. It is, however, essential to identify the potential users, and the type of information required for such a database to be of value. 3. This information has been acquired following an international survey of the pharmaceutical industry in Europe, Japan and the USA, including responses from 48 toxicologists and toxicopathologists representing 38 company groups. 4. Thirty-eight respondents indicated that they would use a historical control database that was regularly updated with the majority of respondents suggesting that they currently use external sources (Breeder's data, the literature, other companies) occasionally to acquire information on control animal pathology data. 5. The majority (94%) of the respondents indicated that a control animal database should contain information on both neoplastic and non-neoplastic lesions for use in evaluating long-term studies, in particular carcinogenicity studies. 6. The survey confirms the need for a historical control animal pathology database wider then those currently available.

Proposal for international guidelines for reproductive and developmental toxicity testing for pharmaceuticals.

1. A Workshop was organized by the Centre for Medicines Research in London, 13th-15th May 1991 to discuss the current situation concerning tests for reproductive and developmental toxicity required for new drug development, and whether a unified series of guidelines could be developed which would satisfy Regulatory Authorities and Scientists worldwide. 2. The international group of experts invited to participate in this meeting reached a consensus regarding the desirability of developing new and flexible guidelines. An approach was proposed based on the state of the art of scientific knowledge in the field of reproductive and developmental toxicology coupled with the minimum use of experimental animals, and taking into consideration the European proposal for a new guideline which has been open for discussion since 1989. 3. Although time did not permit detailed discussion of all study designs, several which are considered to provide acceptable tests for reproductive and developmental toxicity of new therapeutic candidates have been proposed for further discussion. These include the possibility of considerable reduction in duration and size of studies, and numbers of animals used where there is an indication that a low hazard potential exists. 4. Whichever of the combinations are ultimately used in the premarketing assessment, it is most important that the investigators justify in detail the rationale underlying the choice of studies undertaken. This should take into account the specific properties of the drug molecule and its proposed clinical use. 5. This paper reflects the discussions which took place at the Workshop and its publication has been agreed to by the participants. It is intended that it could be used as the basis for discussions of a harmonized approach to reproductive and developmental toxicity testing of pharmaceuticals. As such, it will be made available to regulatory agencies, trade associations and other appropriate groups for their consideration and acceptance, modification or scientific augmentation.

Harmonization of guidelines for toxicity testing of pharmaceuticals by 1992.

In the past there has been considerable disagreement between various regulatory authorities regarding the type and design of animal tests that should be required before a new medicine can be used ethically and safely in the clinic. However, regulatory variations have largely been removed within politically and geographically similar regions (e.g., the U.S.A., the European Community, the Nordic countries) and there now appears to be a consensus regarding the value of harmonizing international requirements. In order to assist the process of harmonization, a detailed table of preclinical toxicity requirements in the U.S.A., Canada, Japan, and the European Community for each test (acute, subacute, chronic, carcinogenicity, mutagenicity, reproduction) has been compiled. This has been circulated to the relevant regulatory authorities to ensure that it accurately reflects current requirements. The major differences between authorities were found to be the duration of chronic, repeated-dose tests and the design of reproduction studies. International pharmaceutical companies were asked to complete a questionnaire, indicating how they design their preclinical testing program to comply with varying regulatory requirements. Most of the respondent companies indicated that chronic tests of longer than 6 months were conducted solely to comply with some regulatory requirements. Many companies repeat reproduction studies in order to comply with Japanese requirements. This emphasizes the need to harmonize these guidelines and discussions are currently underway to attempt to develop protocols acceptable to the FDA, the EC, and the Japanese Ministry of Health and Welfare.

A critical appraisal of the duration of chronic animal toxicity studies.

One method of assessing the contribution of studies of longer than 6 months to a safety evaluation program is to compare retrospectively the findings in toxicity tests carried out for 6 months or less with those observed after 6 months. The Centre for Medicines Research has therefore established a databank comprising animal toxicological data obtained from pharmaceutical companies in Europe. Twenty-one companies have provided data for 124 compounds (214 studies), including 88 studies of 65 compounds where comparable short-term (less than or equal to 6 months) and long-term (greater than 6 months) data are available. The results from the 88 studies show that, excluding the possibility of identifying carcinogens, tests of longer than 6 months have not added to the overall safety evaluation of these compounds.

The questionable value of long-term animal toxicity studies: a regulatory dilemma.

Recommendations for the minimum period of repeated dose administration to animals to support marketing authorization of pharmaceuticals vary from 6 months in the EEC to 18 months in Canada. The value of studies lasting longer than 6 months has not, however, been established. In order to enable retrospective analyses to be carried out, the Centre for Medicines Research has established a toxicology databank containing comprehensive data from repeated dose animal safety evaluation studies on 124 compounds, provided by 21 pharmaceutical companies in Europe (Lumley and Walker 1985a). There are 214 case studies (1 compound tested in 1 species for 1 or more time periods), and in 100 of these tests lasted for longer than 6 months. In 88 long-term studies comparable short-term data are available and these have been analysed to determine what new findings, if any, became apparent after 6 months. The data do not support the need for animal toxicity studies of longer than 6 months, apart from those designed to investigate carcinogenicity. Safety evaluation studies should be of value in predicting adverse drug reactions for man. Unless it can be established that these longer-term studies more accurately define potential target organ effects, the scientific rationale for conventional long-term studies must be questioned.

The value of chronic animal toxicology studies of pharmaceutical compounds: A retrospective analysis.

Extensive animal studies are carried out during the development of new medicines to assess toxicity and predict their safety for use in man. There are, however, differences of opinion concerning the nature of safety evaluation studies required prior to marketing. Any prospect of rationalizing the number and design of animal studies must stem from a reappraisal of conventional animal testing procedures and better use of available data on the toxicity of compounds previously investigated. The Centre for Medicines Research has therefore established a toxicology databank containing comprehensive data from repeated-dose animal safety evaluation studies provided by pharmaceutical companies. Thirteen companies within the United Kingdom have provided toxicological data for 32 pharmaceutical compounds studied in the rat, dog, or primate, resulting in 45 case studies for which both short-term (less than or equal to 6 months) and long-term (greater than 6 months) tests had been completed. A comprehensive analysis of these studies has been carried out to determine what new findings, if any, become apparent in studies after 6 months. The results do not support the need for animal toxicity studies of longer than 6 months duration, apart from those designed to investigate carcinogenicity.

A toxicology databank based on animal safety evaluation studies of pharmaceutical compounds.

Thirteen UK pharmaceutical companies have provided comprehensive toxicological data from repeated-dose animal safety evaluation studies of 74 pharmaceutical compounds. These data comprise a unique toxicology database and this paper describes its establishment including the problems encountered, its current size with over 35 000 data fields, its content and potential value for retrospective analyses. Increasing reliance on animal studies for predicting the safety of medicines in man necessitates a reappraisal of conventional animal testing procedures and better use of the considerable volume of data in the archives of regulatory authorities and pharmaceutical companies. This reappraisal may be achieved by the use of computer-based toxicology databanks.

Chemosensitization in vitro: potentiation of melphalan toxicity by misonidazole, metronidazole and nitrofurazone.

Misonidazole, metronidazole and nitrofurazone can enhance the cytotoxicity of melphalan in vitro if the cells are subjected to a hypoxic pretreatment with the drug prior to exposure of melphalan in air. Potentiation of melphalan is dependent upon the concentrations of the nitro compound and the duration of the hypoxic pretreatment. On a concentration basis, nitrofurazone was most effective at enhancing melphalan toxicity and metronidazole was the least effective. This potentiating activity correlates with the electron affinity of each drug.