The Toxicologist - Society of Toxicology

Reduction of Animals in Research established a group of toxicologists from the
UK’s major pharmaceutical companies and contract research organisations in order
to share practice and identify areas for application of the 3Rs whilst ensuring that
the scientific objectives and regulatory requirements of such studies are still met. A
cross company review of numbers of animals used in general toxicology and carcinogenicity
studies was carried out. The results showed there is some variation in
the numbers of animals used. The reasons for this have been explored and the information
used to develop a series of approaches where small changes in practice
may reduce animal use. We recommend these approaches are used where possible
but they will not be appropriate for all studies or programmes. Practical considerations
are given on: reducing the number of animals to obtain toxicokinetic (TK)
data; incorporating male fertility assessment into the six-month rodent toxicology
study; including fewer recovery animals; and, using transgenic mice, single control
groups and appropriate strains in carcinogenicity studies. The data collected
demonstrate that the largest influence on animal numbers in rodent toxicity studies
is for TK profiling. Therefore, the most significant contribution to reducing the
number of animals is likely to be the development of analytical techniques which
would allow analysis using smaller sample volumes.
1564 THE LIMITED VALUE OF ACUTE TOXICITY TESTS IN
SAFETY ASSESSMENT.
S. Robinson 1 , S. Creton 2 and K. Chapman 2 . 1 AstraZeneca, Macclesfield, Cheshire,
United Kingdom and 2 NC3Rs, London, United Kingdom.
A collaboration, led by the National Centre for the Replacement, Refinement and
Reduction of Animals in Research (NC3Rs) and AstraZeneca, analysed data from
70 compounds across therapeutic areas and demonstrated that acute toxicity studies
had no value in risk assessment before the first clinical trials in humans1. In addition,
consensus between clinicians, toxicologists, regulators and Poison Centres has
been reached that acute toxicity studies are not used for managing overdose of pharmaceuticals
and are of little value in treating human poisoning from chemicals2.
Therefore, the last remaining driver for acute toxicity studies for pharmaceuticals
has been removed. The impact of the pharmaceutical sector initiative has stimulated
efforts to review the value of acute toxicity testing in other sectors. A working
group, led by the NC3Rs, has highlighted circumstances where acute toxicity testing
of non-pharmaceutical chemicals is redundant and may be avoided3. In addition,
the European Partnership for Alternative Approaches to Animal Testing
(EPAA), has established a multi-stakeholder team (including AstraZeneca, NC3Rs,
ECVAM, the Humane Society and representatives of industry sectors) which has
demonstrated that the primary regulatory driver for conducting acute toxicity studies
across non-pharmaceutical sectors is classification and labelling 4. Further work
into the value of acute toxicity studies for classification purposes is ongoing. These
collaborations demonstrate the opportunities provided by creating a forum for a
wide range of stakeholders to review whether animal toxicity studies are providing
the data needed to make assessments of risk to human safety. The results will enable
consensus to be reached on how to reduce the number of animals used and make
the drug and chemical development process more efficient. 1 Robinson, S et al
(2008). Regulatory Toxicology and Pharmacology, 50(3), 345-352
2 Chapman, K et al (2010). Regulatory Toxicology and Pharmacology, in press. 3
Creton, S et al (2010). Critical Reviews in Toxicology, 40: 50-83. 4 Seidle T, et al
(2010) Toxicological Sciences, 116, 382-396
1565 RISK ASSESSMENT OF ACETALDEHYDE (A TOBACCO
SMOKE TOXICANT): INTEGRATION OF MARGIN OF
EXPOSURE (MOE) AND MODE-OF-ACTION (MOA)
EVALUATIONS.
F. H. Cunningham, S. Fiebelkorn and C. Meredith. Group R&D, British
American Tobacco, Southampton, United Kingdom.
Identification of tobacco smoke toxicants for the purpose of product regulation has
seen significant growth during recent years. Trends have been toward providing a
quantitative risk estimate of the contribution of individual toxicants to disease with
the aim of establishing priorities for risk reduction research. We previously proposed
adoption of the Margins of Exposure (MOE) model, as part of a quantitative
risk assessment paradigm. This model permits evaluation of both genotoxic and
carcinogenic compounds and we propose its application to toxicants found in tobacco
smoke. Our approach is to calculate MOE values from a range of published
studies to determine consistency within available data sets. Computed MOEs enable
segregation of toxicants into high and low priority groupings for risk reduction
research depending on their relationship to the critical MOE value of 10,000. We
suggest the integrated approach of using the MOE modeling technique in conjunction
with the preparation of a mode of action (MOA) review. The example given
here is for acetaldehyde where a proposed MOA consists of four key events eventually
progressing to the development of tumours, coinciding with increasing expo-
336 SOT 2011 ANNUAL MEETING
sure duration or dose. In line with the MOA, MOEs can be calculated for each of
the identified key events: Cytotoxicity (Degeneration with hyper/metaplasia) =
1733 – 2007.; Genotoxicity = 1.9 – 896.; Hyper/Metaplasia = 771 – 1810.;
Tumours = 165 – 1382. This integrated approach is the first step in combining risk
assessment methodologies to produce a more physiologically relevant outcome.
However, we also suggest that other tools, such as physiologically-based pharmacokinetic
(PBPK) modelling, be used to ascertain a toxicants importance to smokingrelated
diseases. Further work should also investigate the options surrounding cumulative
risk assessment, which may be of particular relevance to toxicants which
share structural and biological activity patterns. This may begin to account for
complex mixture exposure, as is the case for cigarette smoke.
1566 CONTINUOUS INTRAVENOUS INFUSION STUDIES
WITH IMPLANTED PORT CATHETER SYSTEMS IN
FREE RANGING CYNOMOLGUS MONKEYS—A 20
YEAR EXPERIENCE REPORT.
S. H. Korte, P. Nowak, S. Friderichs-Gromoll, J. Kaspareit and E. Buse. Covance
Laboratories GmbH, Muenster, Germany. Sponsor: G. Weinbauer.
Numerous pharmaceuticals and recently an increasing list of monoclonal antibodies
undergoing regulatory pre-clinical trials in non human primates (NHP) are administered
intravenously, often by continuous infusion. This overview summarizes
experience from 447 Cynomolgus monkeys between 1989 and 2009, which underwent
port-catheter system (PCS: PORT-A-CATH® and Covance patented port)
implantation and dosing for up to 90 days. In case of multiple 24 hour daily infusions
the maximum volume was 40 ml/kg, for once weekly infusions 60 ml/kg/24
h. The PCS was implanted with the catheter tip being inserted in the Vena cava
caudalis. Dosing (CADD-Micro® or Pegasus® Vario pump) commenced following
an adsorption test, jacket training, pump precision test and pre-study diagnostics.
Haematology screening just prior to the start of dosing (following the PCS implantation
plus a 2 week recovery period) confirmed the absence of haematological
changes. A 10 IU/mL Heparin lock and a once weekly system flush ensured the
free-flow of the PCS (dead space of 0.7 mL). Early problems such as (a) extraction
of the catheter out of the vein, (b) port area necrosis and (c) needle loss, were overcome
by (a) specialized training of animal handling, (b) better close body fixation
of jacket and (c) advanced taping of the needle. No adverse clinical signs or body
weight loss was noted. Microscopic findings post chronic catheterization were focally
confirmed and included: perivascular haemorrhage, acute-chronic
vasculitis/perivasculitis, hypertrophy/hyperplasia of the intima, perivascular edema,
thrombi and organized thrombi at the injection site (tip of catheter). The same
findings plus granulomatous inflammation (histiocytes and foreign body giant cells
around suture material) occurred at the entrance of catheter into the vein. In summary,
the presented work showed the long term feasibility of the implanted PCS
system and the cumulative experience increases the likelihood of a successful infusion
study in these primate species.
1567 ENVIRONMENTAL PREDICTORS OF U.S. COUNTY
MORTALITY PATTERNS ON A NATIONAL BASIS.
M. P. Chan 1 , R. S. Weinhold 2 , R. Thomas 3 , J. M. Gohlke 4 and C. J. Portier 5 .
1 NTP/NIEHS, Research Triangle Park, NC, 2 Independent Researcher & Journalist,
Colorado City, Co., 3 School of Public Health, University of California, Berkeley, CA,
4 School of Public Health, University of Alabama at Birmingham, Birmingham, AL
and 5 NCEH & ATSDR, CDC, Atlanta, GA.
A growing body of evidence has found that mortality rates are positively correlated
with social inequalities, air pollution, elevated ambient temperature, age, availability
of medical care and other factors. This study develops a model that uses indicators
for multiple factors to predict the mortality rates for selected diseases and life
expectancy by county across the United States (US). The model is then applied to
predict changes in mortality caused by changing environmental factors. A total of
3,110 counties in the US, excluding Alaska and Hawaii were studied. A subset of
519 counties from the 3,110 counties was chosen by using systematic random sampling
and these samples were used to validate the model. Step-wise and linear regression
analyses were used to estimate the linkage between environmental pollutants,
socio-economic factors, risk factors, social capital, weather, crime, social and
other factors to explain variations in county-specific mortality rates for cardiovascular
diseases, cancers, chronic obstructive pulmonary disease, all causes combined
and lifespan across five population density groups. Generally the estimated models
fit adequately for all mortality outcomes for all population density groups. The
model also adequately predicted risks for the 519 validation counties. Predictions of
changing mortality with changing environmental pollutant factors are used to illustrate
the predictive value of the model. This study confirms the complex inter-relationships
of multiple factors that influence mortality and lifespan, and suggests the