Primate testing in Europe
Welfare and suffering related to specific studies
This study used 72 monkeys, in 4 groups. Dosing was by mainly by injection into the muscles, and into the veinon one occasion, followed by a range of observational procedures such as regular bleeding, and the animals were killed and sent for necropsy at varying times. This was carried out for 4 days, 14 days or 13 weeks, up to 26 weeks, dependant upon the study.
This used 4 monkeys. The test compound was administered to each monkey over the course of three months, on three separate occasions, intravenously (into vein), by inhalation and subcutaneously (under the skin). On each occasion, the monkeys were dosed and then bled for 17 days. After this they were given a break before the next dosing. Over the total period, each monkey was bled 84 times. At the end of this study, the four animals were killed, but none were taken for necropsy.
The test substance was given daily by oral gavage, over a period of 52 weeks. The monkeys were removed from their cages, restrained by two people, and a third pushed a tube down the throat to deliver the product being tested. A “flush” substance is given after the compound. Some of the monkeys vomited every time they were dosed, particularly the control animals.
The fact that both the test and the control monkeys were vomiting indicates that the oral gavage procedure itself, rather than the test substance, was causing the problem. It has been noted elsewhere that, especially with primates, “gavaging is unpleasant for the animals, requires highly skilled staff, and, in the case of unanaesthetized animals, carries a risk of injury to both the animals and the operator”, and, the observation that non-human primates will “forcefully resist such intervention”.
The investigator became concerned that the animals were being dosed “right on the limit”, reporting, “monkeys are dosed at a volume of 10ml/kg”; it is advised that the oral administration volume for rhesus macaques is 10ml/kg.
Other laboratories have refined their methods to avoid the use of oral gavage and minimise the stress suffered by the animals (such as the dough-type feed carrying the compound, described earlier), but not it would seem, HLS.
As mentioned earlier (in ‘procedures, restraint, handling’), it is important to bear in mind that these monkeys were undergoing dosing every day for an entire year, so they would anticipate what was about to happen to them. The long-term consequences of these experiences can affect experimental outcomes.
During this year-long study, several animals suffered prolapses, which appear to be the result of fear due to anticipation of the procedures (see earlier: Procedures, restraint, handling).
The overall level of suffering on this study was severe, prolonged and could have been mitigated.
HLS managers need to review their training and procedures, in light of modern thinking, for example “Primates should be trained to co-operate with restraint and handling using positive reinforcement techniques”.
HuMab (anti-inflammatory (painkiller) drug
This study involved 36 monkeys; 3 groups given rising doses and one control group. Each group included “recovery animals” who underwent an 8 week recovery period. The animals were dosed once fortnightly, on days 1, 15, 29, 43, 57, 71, 85 and 99. Recovery animals survived until day 155.
On dosing days the animals were caught, restrained, a needle inserted into either the vein in the back of the leg or in the arm. The dose was injected over a couple of minutes and the animal returned to its cage.
On 22.09.07, two of the animals on this study were noted to have ophthalmic abnormalities. Abnormalities in the eye were one of the conditions being screened for regularly, therefore it had been anticipated that the animals might undergo ocular changes during the tests. It is possible that an ophthalmic abnormality, of any severity, would be capable of causing distress to the animal concerned. It has been noted that the primate’s “sensory emphasis is visual. Their forward facing eyes and highly developed visual centres in the brain are associated with the three dimensional, stereoscopic, colour vision that primates have”.
Blood Clotting drug
This protocol involved 56 cynomolgus macaques, in 7 groups. The test substance was administered by intravenous injection in the vein in the back of each monkey’s leg using an infusion pump. Groups 1 to 5 were given increasing doses of the test compound, groups 6 and 7 also received a clotting factor.
One week prior to study, all the monkeys were bled; the night before dosing, they were fasted. On the dosing day they were removed from their cages, restrained by two people and a third inserted a cannula into a vein at the back of the leg. The animals were placed in restraint chairs, connected to the pump and the substance infused over 2-15 minutes. Half of the animals were then returned to their cages. At the end of the day they were fasted. The following morning, they were removed from their cages, bled, sedated, killed and sent to necropsy. Blood had been taken from the other animals when the cannula was initially inserted. They then had blood samples taken at 12 points over the next 24 hours. Two weeks after dosing, this second group was fasted overnight, bled, sedated, killed and sent to necropsy.
On 10.09.07 the animals were fasted and bled, but a fault with analysis equipment meant the animals had to be bled again the following day, so they were re-fasted. Although a common procedure in laboratories, fasting would have caused some distress, as animals become accustomed to routine meal times.
On 19.09.07, one female was trembling during dosing, indicating distress. It is known that biochemical changes in the body as a result of stress can influence the outcome of a test “Stress responses in the animal result in the release of hormones and other substances to counteract the stress, which can cause anomalous experimental results”. Primates suffer stress when placed in a restraint chair, even when they become used to it, and it is known that they “show rapid behavioural changes when learning a restraint procedure”.
This monkey’s distress could have been reduced with adequate planning and training; “techniques that reduce or eliminate adverse effects not only benefit animal welfare but can also enhance the quality of scientific research, since suffering in animals can result in physiological changes which are, at least likely to increase variability in experimental data and, at worst, may even invalidate the research. Staff should be given formal training in these operant conditioning techniques”.
For the second group, a total of 12 bleeds were taken after the initial dosing. It is surprising that over a test of such duration no effort appears to have been made to train the monkeys in order to avoid some restraint and manhandling, and therefore reduce stress for animals and workers, whereas others have advised, “The initial time investment pays off in a safe handling procedure that no longer requires a second person to control the resisting subject”.
Replacing regulatory safety testing on primates
There are an increasing number of modern non-animal techniques to study human health and test products. These are generally faster, more accurate and, being based on humans, avoid the potentially disastrous consequences of species differences. Modern science requires precision, down to the molecular level, yet we continue to use primates when we are aware of the significant differences between ourselves and other primates. For example:
- Gout is caused by excess uric acid which is produced in monkeys, apes and humans; but only humans get gout.
- Herpes B virus in monkeys may cause lesions on the face, lips, mouth, body. Monkeys can carry the virus without suffering the disease; in humans, the disease is rare but is almost always fatal.
- Drs Palfreyman, Charles and Blander in ‘Drug Discovery World’ observed: “One of the major challenges facing the drug discovery community is the poor predictability of animal-based strategies . . . many drugs have failed in later stages of development because the animal data were poor predictors of efficacy in the human subject . ...One of the overriding interests of the pharmaceutical and biotechnologies industry is to create alternative development strategies that are less reliant on poor animal predictor models of human disease . . .”.
- Studies have shown that on average, effects in humans differ from those in laboratory monkeys a third of the time. Even if the way drugs break down and are excreted are similar in monkeys and humans, metabolism rates differ radically.
The consequences can be either disastrous in terms of human health or missed opportunities, for example:
- An anti-Parkinson’s disease drug, tolcapone (Tasmar); withdrawn from the market in 1998 after links to deaths from liver disease. Similarly, the antidepressant Seroxat was also linked to liver damage, in 1997.
- The safety of donepazil for Alzheimer’s came under review in 1999 resulting in updating of product information, and clinical trials of a potential Alzheimer’s vaccine were suspended when participating patients began experiencing side-effects to the nervous system[164,165]. The vaccine had been hailed as “revolutionary ..following encouraging tests on animals”.
- The therapeutic effects of the appetite suppressant fenfluramine for autism and its potential to reduce suicidal tendencies were discovered in people and could not have been predicted in animal experiments.
- The drug chloramphenicol does not have the adverse effect in monkeys and dogs that it has in humans.
- The drug azauracil caused no apparent toxic effects in monkeys; in humans, it produced unpleasant effects that caused its use to be stopped.
Such differences were grimly illustrated when the UK drug trial for test drug TGN1412 was almost fatal to human volunteers who suffered multiple organ failure caused by an uncontrollable immune reaction. Side effects included: Soaring body temperatures; dilated blood vessels; falling blood pressure; swollen neck and head; limbs turning purple; permanent damage to immune system; fingers and toes requiring amputation; early signs of cancer; early stage lupus. The laboratory tests on monkeys gave doses of the drug 500 times that given to the human volunteers, without side effects. Now many agree that this disaster could have been avoided by using microdosing, which involves giving ultra-low, safe doses of new compounds to human volunteers and samples of blood or urine can then be analysed by Accelerator Mass Spectrometry (AMS). AMS can show how compounds are absorbed, distributed, metabolised and excreted by the human body.
And this is not the only advanced non-animal technique, ready to replace primate use, others include:
- advanced scanning techniques
- computer database and analytical programmes – DfW, high throughput screening
- computer modelling
- QSARs (chemical structure-activity relationships)
- studies in human cell, tissue and organ cultures
- 3-D tissue engineering
- Political and Public Support for Replacement of Primate Tests
- Drug development and safety testing using animals
- Advanced Techniques to Replace use of Primates
- The Investigation
- Suppliers and Travel
- The Primate Environment and Animal Welfare at Huntingdon Life Sciences (HLS)
- (HLS) Husbandry-related welfare issues
- (HLS) Health and sickness
- (HLS) Procedures, handling and restraint
- (HLS) Welfare and suffering related to specific studies
- (HLS) Critique of studies observed at HLS
- Replacing primates