Julianne Moore in her Oscar winning role in ‘Still Alice’ and the death of Sir Terry Pratchett this month have brought into sharp focus the need to find treatments for Alzheimer’s disease.
Yet, two recent reviews have illustrated that the current approach of testing potential treatments on animals is highly unsuccessful and a new way is needed.
According to these recent reviews, the huge majority of Alzheimer’s disease drugs fail in human trials despite promising results in the preceding animal tests.
One review found that out of 244 new Alzheimer’s drugs tested in humans in the decade between 2002 and 2012, only one was approved for marketing.1 The researchers found that (excluding 14 compounds currently in final phase 3 human trials) the success rate for Alzheimer’s drugs in the last decade had been just 0.4% - a staggering 99.6% failure rate.
Another review looking at the same entire database of human trials reported that by March 2014 in total there had been over 1,200 trials of potential Alzheimer’s drugs.2 Yet there remains only five drugs available for Alzheimer’s patients. Sadly, these drugs are not able to cure or slow the development of the disease but are only used to help treat the symptoms. Furthermore, the drugs only work in about 50% of patients and the beneficial effects are short-lived (they may work for only 6-12 months).
The researchers blamed the convention of relying on animal tests to provide evidence that the drug might work. Looking at 28 specific drugs that had apparently ‘worked’ in animal experiments, they found that 57% went on to have no effect in human patients and 25% were actually found to be dangerous. One drug increased the rate of dementia while another led to brain infection and swelling.
Dr Mark Mattson, professor of neuroscience at Johns Hopkins University said, “Quite a bit of work is still in animals models. We need studies in humans and we need to understand how to diagnose this disease early and prevent it”.3
Please see our Alzheimer’s Disease briefing for more information and criticisms of animal experiments.
1. Alzheimer’s disease drug-development pipeline: few candidates, frequent failures. (2014). Alzheimer’s Research & Therapy, 6(4): 37. Original article can be found here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4095696/
2. Animal models of Alzheimer’s disease: historical pitfalls and a path forward. (2014). ALTEX, 31(3): 279-301. Original article can be found here: http://www.ncbi.nlm.nih.gov/pubmed/24793844
3. Mark Mattson discusses the relationship between energy metabolism and Alzheimer’s. (2011). Science Watch, Jul: http://archive.sciencewatch.com/ana/st/alz2/11julSTAlz2Matt/