How reliable is animal testing?; Podium

From a speech by the organ transplant expert to the Doctors for Responsible Medicine Conference in London

TAKING MEDICATION is a daily routine for many. Lives are routinely saved by medicines such as antibiotics, vaccines, and chemotherapeutic agents. Drugs such as painkillers and anaesthetics daily improve the lives of millions more.

Before being marketed, these miracle drugs are tested first on animals, and then in clinical trials on human volunteers. The animal tests are intended to evaluate new medications for toxicity, carcinogenicity, teratogenicity, side-effects and sometimes, efficacy. Human trials are then undertaken to verify that the animal tests have accurately predicted the effects and side- effects of the new drugs on humans. Human clinical trials take place in many forms.

Humans who are very sick can be given an untried medication that may help them. This occurs in patients with potentially fatal diseases such as cancer or Aids. If the patient is likely to die from their disease, then they are thought to have nothing to lose and potentially much to gain from trying the new drug. Co-ordinators of human trials can also ask for volunteers, to take the medication and then undergo blood tests and report side-effects. The humans volunteering for clinical trials are assured that the risk they are taking is minimal. After all, the drugs have already passed animal trials.

Does animal experimentation really contribute to the safety of those volunteering to test new medicines? How reliable is animal testing in terms of human safety? Let's look at the example of Thalidomide.

Thalidomide may be the best-known medication that harmed humans even after extensive animal testing. Like all drugs, it was tested on animals prior to being released. However, not until phocomelia had been recognised in babies whose mothers had taken the drug, did it undergo extensive animal tests for teratogenesis.

The researchers working with Thalidomide had done experiments on rats, but had not produced the characteristic limb abnormalities seen in humans. After clinicians warned that they suspected Thalidomide of causing this devastating birth defect in children, researchers raced back to the lab to see if their clinical brethren were correct.

Despite testing Thalidomide on scores of species, breeds, and strains of animals, phocomelia was infrequently seen. Testing on more than 50 types of animals did not consistently produce the side-effects that crippled thousands of children. There is no way to know whether the rabbit, the beagle or the chimp will respond as does man, until one knows how man responds. By then, the horse is well out of the barn.

Animal testing of new medications is not predictive. There is little value in confirming that a negative outcome occurs in certain other species after babies have been crippled or humans have died. The dead and crippled are unlikely to be comforted by the fact that they react as New Zealand white rabbits do but differently from guinea-pigs! There is no single animal that makes a good bellwether. An animal that responds like humans to one medication will not necessarily respond the same way to another medicine.

How well the animal test predicts outcomes in humans depends on the animal species picked. However, you don't know which one to pick until after you know what the medication does to humans.

In America, the Food and Drug Administration is charged with assuring that medications released to the public are safe. It oversees clinical trials after the medications have been tested on animals. Certainly, they would not depend on animal tests unless they had great confidence in them. One high-ranking FDA official stated: "Most of the animal tests we accept have never been validated. They evolved over the past 20 years and the FDA is comfortable with them."

Animal testing of new medicines has delayed the marketing of life-saving medications like penicillin, for years. It has the potential to prevent others from ever making it to patients who need them. It has also resulted in human beings being harmed by unsafe medications that had received a clean bill of safety in animal tests. Humans participating in clinical trials are at risk because of the false sense of security perpetuated by those who profit from the release of new medications. This includes pharmaceutical companies, pharmaceutical sales people, animal experimenters, and those who sell supplies and animals for that process.

The informed consent given to those participating in clinical trials should clearly state that the testing of new medications on animals offers no safety for the humans undergoing clinical trials.