Animal Testing Fails Over 90% Of the Time

Animal Testing Fails Over 90% Of the Time

At NZAVS, we proudly state that we have ethics and science on our side - animal testing fails over 90% of the time!

Below you can find scientific evidence that backs this claim — prepare to be shocked when you find out exactly how unreliable animal testing is.

Animal tests (preclinical trials) are sometimes conducted to try and prevent dangerous or ineffective new drugs from reaching human trials (clinical trials). We can see how well this is working by looking at the overall failure rates. I.e., the rate at which a potential drug shows promising results in animal tests but then fails in human trials. Spoiler alert, it isn't working well. 


There are many different studies and reports that provide overall failure rates of animal testing in different research fields, over different periods of time: 


  • A pharmaceutical analysis company reported success rates for drugs in clinical trials (human trials) of 14 major disease areas.
    • Hematology (the study of blood and blood disorders) had the highest approval rate (26.1%) and Oncology (cancer research) had the lowest (5.1%). The average success rate was 9.6%, analysing data from 2006-2015.1
    • The success rates were even lower when data from 2011-2020 was analysed — Hematology had the highest approval rate (23.9%) and Oncology had the lowest (3.6%). The average was 7.9%.2
  • Nature Reviews published their most recent data on Drug Discovery in 2019, reporting average success rates of 6 to 7 % for the years 2010 to 2017. These went as high as 16% with anti-infectives and as low as 3% when the therapeutic area was the nervous system.3
  • A review from 2013 reports on U.S. Food and Drug Administration (FDA) figures totalling a 96% failure rate despite efforts to make animal studies more effective. In fact, many vaccine clinical trials have also been terminated due to the negative side effects people experienced that were not predicted by animal testing, like brain swelling and organ failure.4
  • A 2018 analysis of the shortfalls in drug development found that the results from legislation-mandated animal tests in the early stages of drug development were hindering the cost-effectiveness of research. Leading only to a low 10% success rate for new drugs entering human trials, animal testing was deemed as a barrier to effective research.5
  • The US National Center for Advancing Translational Sciences states on its website: “Approximately 80 per cent of candidate drugs fail in human clinical trials because they are found to be unsafe or ineffective. More than 30 per cent of promising medications have failed in clinical trials because they are found to be harmful to human health (i.e., they have high toxicity), despite costly pre-clinical studies in animal and cell models.”6 In their infographics, they portray a failure rate of 95%.7
  • Wong and colleagues reported on their own data as well as data on two other clinical trials that entered into public registries. This data was from 2000-2015.8
    • from their own data: a drug from phase 1 has between 6.9 and 13.8% probability to gain approval (depending on calculation method and research field, numbers got as low as 3.4 for oncology and as high as 33.4 for infectious diseases)
    • In a separate comparison of studies in 2005-2015 regarding the use of biomarkers, studies had an average success rate of 5.7% (on average 10.3% when using biomarkers and 5.5% without biomarkers)
    • The other reported studies found between 9.6 and 19.0% success rate.
  • More than 90% of new drugs that seem to be safe and efficacious in animal tests are not effective in human trials and do not make it to clinical use, a 2014 review cites. They add: “Given the large amount of animal research being undertaken, some findings will extrapolate to humans just by chance.”9
  • A large meta-analysis from 2003 investigated 101 original research articles published from 1979 to 1983 (a subset of over 562 articles; these 101 articles clearly stated future clinical therapeutic or preventive applications in humans). Of these, only about half even resulted in further published research within 20 years, and only 5 were licensed for human use (equalling a success rate of 4.9%). Only one of the 101 has shown an extensive clinical advantages with expanding indications (equalling a truly useful rate of 1%).10
  • A 2015 study using the National Institutes of Health (NIH) drug database analysed 1,079 drugs, yielding a success rate of 24% and 6% for compounds developed with and without biomarkers, respectively.11
  • Using public sources and commercial databases, researchers gathered data about late-stage clinical trials between 1998 and 2008, which they followed up in 2015. 54% of drugs failed these trials, mostly due to inadequate efficiency (57% of the failures) and safety concerns (17% of the failures). Interestingly, results for unapproved drugs frequently remain unpublished.12
  • In Alzheimer's disease research using animals:
    • 99.6% of new medications developed in animals failed in humans between 2002 and 2012.13
    • a recent review published in 2022 found only two Alzheimer’s drugs approved since 2004 (aducanumab and oligomannate) which stand against 98 that failed in Phase II and III trials.14
  • There seems to be recent effort to soften the impression of failure:
    • Some researchers published their opinion, that trials being termination for toxicity reasons or because of inefficiency should not count as failure; we learn from them after all. They also propose that completed studies that did not “fail”, but lacked sufficient participants, should be counted as failure.15
    • A recent review of urological cancer trials found that 17% fail in Phase 2 and 3, so in the later stages of clinical trials. While that seems better than all the previous numbers, the study excluded studies that were suspended or withdrawn for any reason, or their status was unknown or studies without anticipated accrual data. And, of course, Phase 1 trials were skipped entirely.16

There don’t seem to be many recent, and no up-to-date, numbers. Any papers we found published in 2021/22 are either citing much older numbers or were portrayed above.

  • On a website defending animal-based research, numbers are cited in an article that was last edited on 06 April 2022. The numbers cited originate from a market research company and were likely paid for. The summed-up failure rate was 93.4%. Moreover, of all the drugs passing Phase 1 clinical trials in humans, 86% will fail in later stage trials.17
    • We think that if anyone would have an interest in a positive looking success rate of clinical trials, it would be the people defending animal testing. Therefore, while we cannot check their data is accurate, they are likely to be.