Transgenic Models in Drug Discovery:An Industrial Perspective

The Research and Developmentactivities in the pharmaceutical industryand other biomedical arenas are turningincreasingly to the use of specificallydeveloped animal models, frequentlythe result of genetic manipulation.These transgenic animals will become aconstant part of the environment inR&D worldwide. This short articlehighlights some of the important generalissues surrounding the use of suchanimals and the quality concernsrelating to their creation andmaintenance. This is necessarybackground information for the qualityassurance professional working withscientists who deal with these modelsand wishing to contribute to theestablishment of high standards ofgood practice. In particular QA has arole in the review of contractspecifications to ensure that theexpectations of sponsors and suppliersare well met.

KEY WORDS: transgenic models; quality assurance

INTRODUCTION

Transgenic Alliance was created in 1992 by CharlesRiver Laboratories to meet the emerging demandfor transgenic services in Europe (mainly from

pharmaceutical companies but also from any bio-medical research institution with similar needs).Our experience in this field is small but veryintensive and relies on the enormous know-howaccumulated by our mother company (Iffa Credo)with ‘classical’ animal models. The goal of thisshort paper is to share not only our experience butalso our perception of the current environment. It ishoped that the information given here will encour-age QA professionals to seek greater knowledge inthis field as it is important that they play an activerole in helping to define good working practices inthis arena.

USE OF TRANSGENIC MODELS INDRUG DISCOVERY

Laboratory animals are used intensively in drugdiscovery and biomedical research. Their contribu-tion to the progress in understanding and curingdisease is undoubtedly a major one. The continuoussearch to improve the quality, consistency andreliability of experiments involving animals, com-bined with the related concern for animal welfare,has generated the birth of laboratory animal scienceand technology which addresses several topicssuch as:

d health and quality, and the monitoring of these(microbiology, parasitology, virology, infectiouspathology, serology, hygienic prophylaxia)

d genetic standardization and its monitoring(inbred and outbred stocks, genetics, geneticmonitoring, security and reference colonymanagement)

d environment control (nutrition and diet technol-ogy, control of housing conditions, caging andenrichment)

d experimental techniquesd animal care and handlingd anesthesia and euthanasia

Several historical milestones in the evolution oflaboratory animal science and technology are:

d gnotoxeny and isolator technologyd the creation and use of the SPF (Specific Patho-

gen Free) concept in breeding with associatedhealth monitoring schemes

Patrick HardyTransgenic Alliance, BP 0I09,F-69592 L’Arbresle Cedex, France

THE QUALITY ASSURANCE JOURNAL, VOL. 2, 19–23 (1997)

CCC/1087-8378/97/010019–05 $17.50© 1997 by John Wiley & Sons, Ltd. Accepted 24 February 1997

d the increasing use of inbred strains due to thedevelopment of immunology

d progress in rodent pathologyd the genetic management of outbred colonies

The latest significant evolution (some even call it‘revolution’ or ‘breakthrough’) has been the availa-bility of transgenic animals (expression of a trans-genic construct microinjected into the ovocytepronucleus), of target-mutants (gene alteration orinactivation following homologous recombination)and of conditional mutants (Cre-Lox constructs)which was made possible thanks to advances inmolecular biology and embryo technology.

In order to simplify the wording in this article, theword ‘transgenic’ (as an adjective) will, henceforth,cover all these categories of genetically modifiedanimals. However, one should bear in mind thatthese ‘novel systems’ are still laboratory animalsand that all the historical lessons and experienceaccumulated with the ‘classical’ animal models(outbred and inbred genetics, isolator technology,gnotoxeny, health and genetic monitoring, largescale SPF breeding), and other mutants (sponta-neous, induced), and pathological models remainhighly valuable. Considering the objectives of thisarticle, the animal welfare, ethical, public percep-tion and communication issues are not amplifiedhere. This does not mean, however, that they can beneglected. On the contrary, they are certainlyamongst the key factors which will trigger thefuture use of transgenic technology and models.

FIELDS OF USE AND QUALITYREQUIREMENTSTransgenic technology has stimulated severalindustrial areas for application: plant and livestockimprovement, use of ‘gene farming’ for therapeuticprotein production, vaccines engineering, xenog-rafts, development of gene therapy protocols etc.Here I will focus on a specific field: the ‘novelsystems for the study of human disease’. Most ofthe current applications are in fundamentalresearch: genetics, developmental biology, immu-nology, oncology, neuroscience and virology beingthe most common. A much smaller number ofmodels is used in drug discovery and related fields(mainly pharmacology and toxicology) which usu-ally require a significant ‘added value’ of suchmodels by comparison with the classical modelsand also requires much larger quantities (experi-mental lots must meet the requirements of statis-tical analysis).

The potential contribution of transgenic technologyand emerging models to the ‘rational drug discov-

ery approach’ is critical for the pharmaceuticalindustry which is currently facing issues such assky-rocketing R&D costs, pressure on marketprices, patent life, stockholders’ expectations andinternational competition. Any institution or com-pany involved in model creation or productionshould be aware of this environment of continuouschallenge.

“The potential contribution oftransgenic technology . . . to the. . . drug discovery approach iscritical”

When developing transgenic models for use inpharmaceutical R&D, the specific issues to beaddressed are those listed below. QA professionalsshould be aware of these issues so that they cancontribute to the promotion of good practices inthese areas.

d The need for more relevant models (the creationof new animal models or the improvement ofexisting ones) which will mimic human diseasesand the effects of selected reference drugs.

d The need to develop innovative toxicology mod-els able to increase the predictability of toxiceffects in humans, to allow an earlier detection oflesions and a consequent reduction in studyduration and cost (particularly in the fields ofoncogenicity and mutagenicity).

d The availability of consistent models over a longperiod of time.

d The absence of risk of transmitting knowninfectious diseases to man (zoonosis) and labo-ratory animal species, and of transmitting identi-fied infectious agents which could interfere withbreeding and research.

d Optimal life conditions and life span even withhighly sensitive animals.

d A fully standardized genetic background allow-ing a reliable and consistent expression of thetransgene or the mutation (the phenotype can begreatly affected and modified by the geneticbackground), the isogenicity of individuals withthe same line, a minimal genetic backgrounddrift from one generation to another and theavailability of a congenic control line. This crucialstep is too often neglected.

d The characterization and validation of the modelwith currently used investigation techniques andreference drugs.

d The quantity of animals available (number ofgroups and number of individuals per group)

20 Patrick Hardy

every week or every month with a defined sex,age or weight bracket, to meet the statisticalrequirements of studies. The breeding perform-ances, life span and reproductive life compatiblewith the expected breeding level and time lines.

d The breeding system which will optimize cost/productivity/quality, involving appropriatehousing and caging systems, genetic status(homozygous or hemizygous), mating schemes,diet etc.

d The possibility of signing a license agreement foraccess to the line, under reasonable and accept-able conditions (including financial ones), con-sidering the global estimated value of the models(which is by no means easy to evaluate inadvance).

d Practical access to the model, including problemsrelating to waiting lists, shipment conditions(concerning ‘animal welfare’ considerations andthe containment requirements of GeneticallyModified Organisms) and the cost of shipment.

The mission of a company specialized in this‘downstream development’ will be first to bridgethe gap between the acquisition of founders and theavailability of a standardized model, then to collab-orate with an expert body for its experimentalvalidation and characterization.

OPERATIONS RELATED TO HEALTHSTANDARDS

The following operations are usually carried out:

d reception and quarantine in negative pressureisolators

d assessment of health quality and sanitary risksd rederivation by aseptic hysterectomy or embryo

transfer (plus any additional relevantprocedure)

d transfer of a standard flora (like ‘Specific Patho-gen Free’ or ‘Specific and Opportunistic Patho-gen Free’)

d maintenance of a health security colony (liveand/or cryopreserved)

d breeding under adequate conditionsd regular health monitoring according to the

defined health status

OPERATIONS RELATED TO THEGENETIC STANDARD

Examples of operations related to the transgene orto the genetic background are listed below.

d Backcross to an inbred background (reduction ofgenetic variability, availability of a control line).

d Breeding to homozygosity.d Production of a transgenic ‘F1 hybrid’.d Production of multiple pathological models

(transgenic, target or spontaneous mutation,induction etc.).

d Genetic or phenotypic testing.d Maintenance of a genetic security colony (live

and/or cryopreserved).

OPERATIONS RELATED TO THESECURITY OF COLONIES

Independently, or in addition, the following arealso performed:

d main maintenance of a ‘breathing colony’ inisolator or in filter-top cage system

d collection, freezing and storage of cryopreservedembryos

d thawing and reimplantation of embryos

OTHER OPERATIONS

The following are also important considerationsaffecting the supply of valid transgenic models:

d import, licensing, collaboration agreementsd participation in the experimental validation proc-

ess and in model characterizationd improvement of breeding processes (productiv-

ity, cost)d expert, shipment organizationd establishment of production colonies closer to

investigator’s premises (in sister-companies)d individual animal identification, special diets or

treatment, aging

CUSTOMIZED DEVELOPMENT VERSUSSTANDARD ‘CATALOGUE’ MODELS

If the patents, industrial property rights, access feesand royalty issues are not preventing any furtherdevelopment, any line identified as a potentialpharmacological or toxicological model should, ofcourse, present a significant improvement overexisting models, have an expected life cycle of atleast 3 years and be suitable over a reasonably largefield of use. Quite often these conditions cannot befulfilled and the commercial breeding companywill not be in a position to finance the developmentof models and support their validation andcharacterization.

Transgenic Models in Drug Discovery 21

The most frequent alternative is customized devel-opment and breeding under exclusive and con-fidential agreements, totally supported by one orsometimes several interested sponsors. A futurefeature could be to arrange for full scale sponsoredproject development, starting with design andcreation, followed by the development, validationcharacterization, colony security and the pursual ofa large scale breeding programme. The currenttrend seems to favour the outsourcing of mosttransgenic services. Pharmaceutical companies, andeven some government institutions, are more andmore inclined to focus on their specific missions,leaving the creation of models to experts whomthey are prepared to support financially. Severalreasons bolster this attitude. It permits the companyto dedicate personnel and technical resources toresearch projects, to reduce capital expenditure, tobetter manage priorities, to meet the needs forflexibility (programmes are subject to frequentrevisions) and short set-up times. In addition thecosts are usually cheaper for outsourced projects,few companies have adequate animal resourcesavailable (size or quality), the management of thehealth risk is simplified, the administrative burdendue to regulations (use of animals in scientificprocedures, genetically modified organisms) isreduced and costs linked to the required permanentstructure and maintenance of specific expertise areeased.

AVAILABILITY OF EXISTING MODELS

Very often projects can be considerably impairedbecause models are not permanently available forreasons such as those given below.

d Inappropriate patent protection, licensing agree-ment or financial conditions prior to access to theuse of a line (for example, an excessive access feebefore any available validation evidence, orroyalties on any new drug developed using theanimal model etc.).

d Poor prolificity, early mortality impairing breed-ing, lethal homozygosity for knock-out lines,unavailability of founder animals because of thedemand. The international repositories shouldplay a key role in advising line owners and inmanaging the availability and distribution ofpotential models, so as to prevent the duplicationof line generations.

INTERNATIONAL COOPERATION

Considering that all parties involved in transgenicanimal generation and use are dedicated to a

common goal (i.e. improving public health andcuring human diseases), it is obvious that ourglobal efficiency and rate of success rely on identi-fying and using all available synergies and possibil-ities of collaboration. The Jackson Laboratory iscurrently the main international repository andexpert institution for inbred and mutant mouselines, and is facing, almost alone, the continuousflow of new mutants created in the world. To meetthe increasing demand for repository capacity withlimited resources and budget, and to fill the existinggaps (outbred stocks, other species like the rat), aclose collaboration should be developed betweenexisting and future centres in the USA, in Europeand in Japan. When considering the situation androle of government institutions and commercialbreeding companies, the potential synergies andcomplementarities are far more numerous thanpotential overlapping and areas of conflict.

DISCUSSION/CONCLUSION

In order to fully play their role in those industrieswhich develop, use or maintain transgenic animalmodels, Quality Assurance professionals shouldtake the time and trouble to inform themselves ofthe techniques and practices involved in this newscientific field. As in any other scientific area,particularly one subject to strict regulations, theindependent input from QA is essential and poten-tially highly valuable in helping to establish stan-dards of good practice. It is particularly worthnoting that since most development and breedingprojects are exclusive and confidential to onecompany (or sometimes to a few collaboratingfirms) the involvement of QA is critical for theevaluation of the exact requirements and expecta-tions of both contracting parties (e.g. type of geneticand/or phenotypic testing, expected level of pro-duction etc.). QA input is equally important foroptimal follow-up of the project.

“independent input from QA isessential . . . to establishstandards of good practice”

However, QA contributions can only be effective ifthe professionals are well informed about, thoughnot necessarily expert in, the discipline concerned.The intent of this short contribution has been toalert the QA professional to the principle issuesunderpinning this area of new but rapiddevelopment.

22 Patrick Hardy

REFERENCES

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Gnotoxenie) (1977). Definition d’une souris heteroxenique astatut sanitaire controle. Sci. Tech. Anim. Lab., 2: 9–12.Hardy, P. (1996). Optimization of the health management ofmouse transgenic colonies. SECAL Symposium, Vittoria.Lathe, R. (1996). Mice, gene targeting and behavior: more thanjust genetic background. Trends in Neuroscience, 19: 183–186.National Research Council (1991). Infections Diseases of Mice andRats, Washington D.C., USA: National Academy Press.Nielsen (January 1994). Communication. San Diego, California.Perrot, A. and Canard, G. (1991). SSCup Rodent ProductionMeans, Principles, Results, Iffa-Credo publication.Reetz, J.C., Wullenweber-Schmit, M., Kraft, V. and Hedrich, H.J.(1988). Rederivation of inbreed strains of mice by means ofembryo transfer. Laboratory Animal Science, 38 6: 696–701.Rouleau, A.M.J., Kovacs, P.R., Kunz, H.W. and Armstrong, D.T.(1993). Decontamination of rats embryos and transfer tospecific pathogen-free recipients for the production of abreeding colony. Laboratory Animal Science, 43 6: 611–615.

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