Poorly conducted animal studies are putting patients at risk and wasting drug company money and the animals themselves, it is claimed.
The British Association's Festival of Science in York heard evidence from
consultant neurologist Dr Malcolm Macleod of the Stirling Royal Infirmary
that most drug tests on animals did not allow for sources of bias.
Many, he said, failed to adopt basic principals of good practice, such
randomisation and double-blinding and as a result, drugs under development often appeared more effective than they really were.
He noted one study published earlier this year in Trends in Neuroscience listing 880 drugs that were tested in animal models of stroke of which 550 seemed to work in animals. Yet when transferred into human trials, of the 114 tested, only one was effective.
He set out to determine why the animal studies were such poor predictors of success and looked at how 288 animal trials were conducted and found that only 36% randomised the animal subjects and just 29% of the researchers were completely blind during the trial.
"This goes some way to explaining why stroke drugs tested in animals do not appear to work nearly so well in humans," Dr Macleod said. "It is certainly the case that human health in clinical trials would be better served with higher quality animal data."
As an example, he cited the effectiveness of a stroke drug called NXY-059,
made by AstraZeneca. Animals studies found that it improved outcome by more than 50% but when these tests were properly randomised and blinded – ie the researchers themselves were aware whether animals had been given medication or placebo – the improvement was between 25%-30%.
He added that sample size was also an issue in animal testing and calculated that between 40 and 50 animals were necessary for a trial to be viable. On average he found, however, that just eight animals per trial were used and this is too small a number from which to draw firm conclusions.
Professor Michael Bracken, an epidemiologist at Yale University, said that
such flaws were critically compromising the value of 'in animal' research. "This lack of advanced scientific methods leaves many questions about the
value of animal research unanswered, and exposes patients and research
volunteers to clinical trials that could be based on flawed animal studies,"
he told the Independent newspaper. By Michael Day