Drug Testing 101

The Problem

High Drug Prices, Slow Approvals, Serious Side Effects, and missing on life-saving drugs American consumers face several dilemmas when it comes to the drugs they need: extraordinarily high costs for drugs, inordinately long wait periods in bringing the drugs to market, and, even after the drugs are approved for common use, serious side effects for consumers often result from taking the drugs. The existing drug development paradigm also mislabels many toxic drugs as safe. Vice versa, many perfectly safe drugs in humans are discarded just because they fail animal tests in preclinical stages. The FDA Modernization Act 2.0 opened the door for use of nonanimal human-relevant test methods, but FDA needs to act to implement the new law in regulatory practice.

The Solution

The FDA Modernization Act 2.0 removed the mandate for animal testing and allows drug sponsors to use modern, innovative, human-relevant test methods. FDA regulations must be updated to reflect the new law and Congressional intent, and FDA must make a clear pathway for regulatory acceptance of nonanimal methods. These modifications will provide drug sponsors with state-of-the-art tools to better predict how humans will respond to their drugs in clinical trials, thereby reducing attrition, shortening time to market potentially in half, saving millions of dollars, and providing safer and more effective drugs for American consumers.

The FDA Modernization Act 3.0 requires the FDA to publish a final rule to implement the FDA Modernization Act 2.0 and establish clear guidelines for non-animal test methods that can better predict drug safety and efficacy, and speed the time to market for new treatments and cures.

Animal testing requirements in the US for human drugs dates back to 1938. 82 years later, the requirements remain the same.
Adverse drug reactions (ADRs), taken as prescribed is the 4th leading cause of death in the US. A major contributing fact to ADRs is the inadequacy of preclinical animal tests.
Lack of toxicity in animals in preclinical tests provides nearly no insight into the possibility of toxicity in humans.
A recent study shows 63% of ADRs in humans had no counterpart in animals.
95% of drugs found safe and effective in animals later fail in human clinical trials.
Animal tests slow down the drug development process, delaying needed treatments. It takes an average of 10 years to bring a new drug to market.
We have been using animal biology to test drugs for nearly a century. The current system based on animal tests is broken. The focus needs to turn to human biology.
Human-relevant cell-based assays, organs-on-a-chip, human-on-a-chip models, and sophisticated computer modeling have been developed to more accurately predict human response to new drugs, yet FDA does not officially acknowledge these superior models in their regulations, requiring drug sponsors to use inferior animal models.
Resistance to change and complacency must give way to innovation and modern technology.
Using modern human-relevant microphysiological organ chip systems could cut drug development time in half and cut R & D costs fivefold, resulting in substantially lower drug prices.
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Read our Fact Sheet

on the FDA Modernization Act 3.0


Examples of Human Relevant Technology in the Battle Against COVID-19

Tamara Drake, Center for a Humane Economy, Center for Responsible Science

Human Tissues, organs-on-a-chip, organoids, immune models are being used in multiple scenarios for COVID-19 research.  According to the World Health Organization, “The ideal animal model for studying routes of virus transmission, pathogenesis, antiviral therapy, vaccine and immune responses has yet to be found. “

Current Regulatory Scheme causes confusion for drug developers, is at odds with the FDA Modernization Act 2.0

Deliberate Ambiguity by the FDA impacts Public Health, Industry, and Innovation

Recognizing the need to improve the drug development paradigm, Congress passed the FDA Modernization Act 2.0 to amend the FFDCA to eliminate the mandate for animal tests and allow for the use of human-relevant nonclinical test methods. Unfortunately, dozens of outdated FDA regulations and guidance documents do not comport with the new law and facially require drug sponsors to submit data from animal tests before investigational drugs are used in human trials. Agency regulations are promulgated in accordance and conformity with Congress’s statutory language and intent; therefore, if a rule conflicts with a statute, the statute will prevail, and the rule will be set as void to the extent it conflicts with the enabling statute. As the amended FDCA now stands, FDA’s current regulations related to animal testing are no longer compliant with the statutory language.

The requirement for animal tests before human clinical trials dates back to 1938 with the passage of the FFDCA[i], later to be included in the Nuremburg Code and the Helsinki Act.  The latter included language requiring human experiments be “designed and based on the results of animal experimentation and a knowledge of the natural history of the disease.” The statement was written by Andrew Ivy, a relentless proponent of animal research, but wasn’t based on scientific evidence that such a requirement would improve safety or efficacy of human drug development.[ii]

The acceptance of alternate methods can, in many instances, produce better human health outcomes and quicker approvals. As a matter of moral concern for patients and for animals and out of a concern for cost and efficiency, FDA should revamp its regulations to comport with the revised FFDCA to allow for better, faster, safer testing methods and not require outdated ones.   

  • Adverse reactions to drugs, taken as prescribed, is the 4th leading cause of death in the United States.[iii] Adverse events from properly prescribed drugs cause 1.9 million hospitalizations per year, and 128,000 of these are fatal.[iv]
  • A major contributing factor to adverse drug reactions (ADRs) is the inadequacy of preclinical animal tests: one recent study showed that 63% of ADRs had no counterpart in animals, and less than 20% had a positive corollary in animals.[v]
  • Including non-animal test methods will make preclinical testing more efficient and accurate in predicting human health outcomes, getting safer, more effective drugs into the marketplace sooner to help people with health challenges or crises.
  • Better testing methods will minimize the exposure of clinical trial participants and patients to serious adverse events and death during human clinical trials and beyond.
  • The current regulations stifle research and testing into a wide range of health conditions because the companies make a judgment that they cannot make profits from drugs with limited market potential. Companies must invest in drugs with high market potential because they must make high-risk, 10-year, billion-dollar investments in research to bring a single drug to market. This corporate screening process leaves health concerns experienced by a smaller subset of the public to do without life-saving treatments.

[i] Wax PM. Elixirs, diluents and the passage of the 1938 Federal Food, Drug and Cosmetics Act. Ann Intern Med 1995;122:456–61.
[ii] National Institutes of Health. Regulations and Ethical Guidelines. Reprint from: Trials of War Criminals before the Nuremberg Military Tribunals under Control Council Law no. 10, Vol. 2. 1949 1. Washington, DC: U.S. Government Printing Office, 1949:181–2. Available at: https://history.nih.gov/research/downloads/nuremberg.pdf
[iii] Lazarou J, Pomeranz B, Corey PN. Incidence of adverse drug reactions in hospitalized patients: A meta-analysis of prospective studies. JAMA 1998;279:1200–1205.
[iv] Id.
[v] Bailey J, Thew M, Balls M., An analysis of the use of animal models in predicting human toxicology and drug safety. Alternatives to  Laboratory Animals, 2014;42:189–99.

FDA regulations require drug developers to rely on traditional animal tests that place immense and unnecessary financial and regulatory burdens on companies for no good reason. This results in delays in the approval process, costing millions of dollars.  It typically takes 10 years to bring a new drug to market with an average cost between $1 billion and $2.6 billion.[i],[ii] 

  • Use of modern test methods would improve results and lower attrition rates. Between 90 and 95% of drugs found safe in preclinical tests fail during human clinical trials due to toxicities not predicted by traditional animal tests or because of lack of efficacy.
  • When costs are added for withdrawn and restricted drugs, along with failures during development, for a new drug, the cost is an estimated average of $4 billion and could reach as high as $12 billion.[iii]
  • Failing 90 to 95% of the time after spending millions or billions of dollars imposes extraordinarily onerous burdens on companies and then those costs are passed on to consumers in the form of higher drug prices, marring the public perceptions of companies.  Yet, drug sponsors have no choice but to follow these archaic regulations.
  • To lower drug costs, restrictive regulations must be changed to give drug sponsors the ability to innovate and get better drugs approved years earlier and at less cost for companies and consumers.

[i] DiMasi, J, Grabowski, H.G., Hansen, R., Innovation in the pharmaceutical industry –New estimates of R&D costs, Journal of Health Economics, Volume 47, 20-33 (2016)
[ii] A Tough Road: Cost to Develop One New Drug is $2.6 Billion; Approval Rate for Drugs Entering Clinical Development is Less Than 12%, Policy and Medicine, 2019.
[iii] Herper, M., The Truly Staggering Cost of Inventing New Drugs, Forbes Magazine (2012)

  • Studies show that while toxicity in animals may also be present in humans these tests are not consistent or reliable and provide nearly no insight into the possibility or likelihood of toxicity or the absence of toxicity in humans.[i]
  • In one protocol, researchers studied six drugs to determine which of the 78 adverse effects that occurred in humans would occur in dogs or rats. Effects that are undetectable in animals (e.g. headaches) were not taken into account. Less than half (46%) of the remaining side effects were detected in the animals — slightly less than the expected results from flipping a coin. In other words, animal tests were wrong 54% of the time.
  • A 2006 review of 76 animal studies, found that approximately 20% were contradicted in humans and only 37% were ever replicated in humans.[ii]
  • A review of 221 animal experiments found agreement in human studies just 50% of the time, tantamount to a coin flip.[iii]
  • Another study of drug registration files was conducted to determine whether post-marketing serious adverse reactions to small molecule drugs could have been detected on the basis of animal data. Of 93 serious adverse reactions related to 43 small molecule drugs, only 19% were identified in animal studies as a true positive outcome.[iv]
  • An analysis of 2,366 drugs concluded that “results from tests on animals (specifically rat, mouse and rabbit models) are highly inconsistent predictors of toxic responses in humans, and are little better than what would result merely by chance — or tossing a coin — in providing a basis to decide whether a compound should proceed to testing in humans”. [v] Similar results were found for nonhuman primates and dogs.[vi]
  • Vioxx appeared safe and even beneficial to the heart in animal tests, but was withdrawn from the global market in 2004 after causing an estimated 320,000 heart attacks, strokes and cases of heart failure worldwide — 140,000 of them fatal.[vii] Nine of 11 studies on mice and rats had shown Vioxx or other COX-2 inhibitors to be safe for animal hearts and blood vessels. In fact, six different animal studies — in four different species — showed Vioxx was actually protective against heart attacks and vascular disease.[viii] Litigation related to these adverse reactions has cost billions to the manufacturer.
  • There have been at least 200 treatment-related (non-disease progression) deaths in human clinical trials the US in the last six years.[ix]
  • Human-relevant cell-based assays, organs-on-a-chip, human-on-a-chip models, and sophisticated computer modeling have been developed to more accurately predict human response to new drugs, yet FDA does not officially acknowledge these superior models in their regulations, requiring drug sponsors to use inferior animal models.
  • Market growth for non-animal tests is outpacing traditional animal tests, but FDA has yet to embrace the new technology in their regulations. The global market for laboratory animal models is predicted to grow at a compound annual growth rate (CAGR) of 5.6% for the period of 2018 to 2023. For the same period, cell-based assays are predicted to grow at a compound annual growth rate (CAGR) of 10.2%, and organ-on-a-chip assays should grow at a compound annual growth rate (CAGR) of 39.9%.[x]

[i] Bailey, J., Thew, M., Balls, M., An Analysis of the Use of Dogs in Predicting Human Toxicology and Drug Safety, Alternatives to Laboratory Animals, 2013, 41(5), pp. 335-350., Bailey J, Thew M, Balls M., An analysis of the use of animal models in predicting human toxicology and drug safety. Alternatives to  Laboratory Animals, 2014;42:189–99.,  Bailey, J., Thew, M., Balls, M., Predicting Human Drug Toxicity and Safety Via Animal Tests: Can Any One Species Predict Drug Toxicity in Any Other, and Do Monkeys Help? Alternatives to Laboratory Animals, 2015, 43 (6), pp,393-403.
[ii] Hackam DG, Redelmeier DA. Translation of research evidence from animals to humans. JAMA 2006;296:1731–2.
[iii] Perel P, Roberts I, Sena E, et al. Comparison of treatment effects between animal experiments and clinical trials: systematic review. BMJ 2007; 334:197–203.
[iv] Van Meer, P,J., Kooijiman, M., Gispen-de Wied, CC., Moors, E.H., Schellekens, H. The Ability of Animal Studies to Detect Serious Post Marketing Adverse Events Is Limited, Regulatory Toxicology and Pharmacology, 2012, 64 (3), pp. 345-349.
[v] Bailey J, Thew M, Balls M., An analysis of the use of animal models in predicting human toxicology and drug safety. Alternatives to  Laboratory Animals, 2014;42:189–99.
[vi] Bailey, J., Thew, M., Balls, M., Predicting Human Drug Toxicity and Safety Via Animal Tests: Can Any One Species Predict Drug Toxicity in Any Other, and Do Monkeys Help? Alternatives to Laboratory Animals, 2015, 43 (6), pp,393-403.
[vii] Congressional Testimony of David J. Graham, MD, MPH,  Food and Drug Administration, November 18, 2004
[viii] PCRM (Physician’s Committee for Responsible Medicine). 2005. Animal Research on Trial. Good Medicine 14:13.
[ix] Center for Responsible Science, 2019.
[x] Organ-on-a-Chip: Global Markets, 2019, BCC Research , https://www.bccresearch.com/market-research/biotechnology/organ-on-a-chip-markets-research-report.html, Accessed May 13, 2020.

Types of Testing

Safety Pharmacology:
Under the current regulatory scheme, rats, dogs, non-human primates and guinea pigs are used to determine whether a drug causes on- or off-target serious acute effects on critical organ systems (e.g., cardiovascular, respiratory, gastrointestinal, and central nervous system). Dose responses identified in these studies serve to establish a safety margin for the first in human (FIH) dose regimen. Follow-up experiments aimed at understanding the mechanism behind an observed specific toxicity can be undertaken to address the relevance of the finding to human risk 

Examples of Alternatives to animal tests:

  • Cardiovascular system: Comprehensive In Vitro Proarrhythmia Assay (CiPA)
  • Central Nervous system:
    • Microbrains
    • brain organoids
    • bioimaging
    • Integrated video electroencephalography.
  • Respiratory System:
    • In vitro air-liquid interface (ALI) cell culture models,
    • Emulate lung-on-a-chip
  • Gastrointestinal, renal and other:
    • intestinal cell organoids
    • HurelTox (primary hepatic cell-based)
    • Hurel Microlivers
    • gut-on-a-chip, etc.
    • Emulate Liver Chip
    • General Toxicity Services
    • Emulate Duodenum Intestine Chip
    • Emulate Proximal Tubule Kidney-Chip

Examples of General Toxicity:
  Two species are required (rodent, non-rodent) for single-dose and repeated-dose toxicity studies to evaluate drug safety encompassing drug pharmacodynamics (what the body does to the drug), pharmacokinetics (what the drug does to the body), and toxicology.

Current method:
Rodent and non-rodent
Acute: 7 to 20 rats + dogs or primates
Subchronic: 20 rodents, 8 dogs or primates, up to 90 days
Chronic:  120 rats + 32 dogs or primate


  • Microphysiological Systems (organ-on-a-chip using human cells-including all listed above)
  • Organotypic cultures

Carcinogenicity: Two rodent species are used under the current FDA requirements. Rats are tested for 18 to 24 months in mice and 24 to 30 months in rats. Up to 400 of each species are used to assess cancer risk for pharmaceuticals intended to treat chronic conditions.

Examples of Alternatives:

  • Mining for cancer correlations in human genomic databases
  • Correlative gene expression signatures
  • In silico methods
  • Application of hallmarks of cancer and key characteristics of carcinogens
  • Weight of Evidence (WOE) evaluation of carcinogenic risk for small and large molecules before determining the need for a two-year rodent bioassay

Developmental and Reproductive Toxicity (DART)

Current method: 2,500 rats for reproductive toxicity in two generations, 900 rabbits, 1,300 rats for birth defects for an estimate of 4,700 animals for each drug.
Nonhuman primates for biologics

Alternatives: (Not non-animal tests — alternatives need to be developed)

  • Embryonic stem cell assays (mouse and rat)
  • Whole embryo culture assay (rat, mouse, rabbit)
  • Zebrafish studies
  • Frog embryo teratogenesis assay (FETAX)
  • Stem cell assays with “omics” approaches

FDA does not recommend the DRAIZE test, but has refused to issue guidance. Drug sponsors continue to use these tests despite the fact that FDA claims that these tests are no longer submitted.

Current method: A study shows that 94% of skin irritation testing uses the Draize method for and 60% for eye irritation, even though FDA claims they don’t require it and that it isn’t used in their regulatory space.


  • In vitro reconstructed human cornea-like epithelium
  • Reconstructed human tissue skin models

for drugs which are either applied to the skin or accumulate in the skin and/or the eye.

Current method: guinea pig, rat and mouse. Many with non-pigmented skin except for drugs that bind significantly to melanin.


  • 3T3 Neutral Red Uptake test
  • Reconstructed 3D human skin models

Each lot of vaccine or drug must be tested for impurities and contaminants.  Currently, rabbit and horseshoe crabs are used.  Hundreds of thousands of animals are used each year.  These tests can be replaced with the Monocyte Activiation Test (using human blood), and Recombinant Factor C (fFC).

Examples of Alternative Disease Models
  • Hesperos Human-on-a-Chip® System Used to Model Preclinical Stages of Alzheimer Disease and Mild Cognitive Impairment
  • Kidney Microphysiological Analysis Platforms to Optimize Function and Model Disease
  • Micropysiological Organ-on-a-Chip system to model Amyotrophic Lateral Sclerosis and Parkinson’s disease
  • Microphysiological system of Cerebral Organoid and blood vessel for disease modeling and neuropsychiatric drug screening
  • Multi-tissue platorm for modeling systemic pathologies
  • Systemic inflammation in microphysiological models of muscle and vascular disease
  • Lung-on-a Chip models for efficacy testing
  • Polycystic ovary syndrome (PCOS) and androgen-related disease modeling and drug testing in multi-organ integrated reproductive platform
  • 3-D in vitro disease model of atrial conduction
  • Microphysiological systems to model vascular malformations
  • Tissue chip modeling of synovial joint pathologies: effects of inflammation and adipose-mediated diabetic complications
  • Head and neck cancers: engineered salivary gland tissue chips
  • Microphysiological system for kidney disease modeling and drug efficacy testing
  • Neurovascular and cardiac microphysiological models for drug development for tuberous sclerosis complex and other pediatric epileptogenic diseases.
  • Integrated tissue chip system (intestinal, liver, pancreatic human cells) for modeling diabetes
  • Tumor–on-a-Chip devices to model cancer
  • Human primary airway epithelial cell-based model integrated into a high-throughput platform (PREDICT96-ALI)