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FDA Will No Longer Require Animal Tests Before Human Trials for All Drugs

The new legislation is a big adjustment in decades-old drug testing requirements.

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Senate staff members and their dogs look on as Sen. Rand Paul (R-KY) speaks at a press conference on his FDA Modernization Act on Capitol Hill on October 07, 2021 in Washington, DC.
Senate staff members and their dogs look on as Sen. Rand Paul (R-KY) speaks at a press conference on his FDA Modernization Act on Capitol Hill on October 07, 2021 in Washington, DC.
Photo: Anna Moneymaker (Getty Images)

Animal testing will no longer be a mandated part of the Food and Drug Administration’s approval process for all new drugs. Since 1938, pharmaceutical makers seeking FDA approval have had to successfully put their medications through multiple animals trials before proceeding to human tests.

Now, though, drug companies will have the option of either animal or non-animal tests—in a shift that animal rights groups and some pharma companies have long advocated for. Meanwhile, researchers’ reactions are mixed: Some say the move is unlikely to trigger immediate change, others are excited by the possibilities, while others still have safety concerns.


What’s in the new legislation?

The new FDA adjustment comes as part of a massive package of spending legislation signed into law by President Biden on December 29. In addition to determining this year’s budget for the Department of Defense and other federal agencies, the 2023 Consolidate Appropriations Act (H.R. 2617) included a section on “modernizing” clinical trials. And within that, a subsection on alternatives to animal testing, which amends the existing law.


Instead of animal testing, new drugs can now move onto human trials following successful rounds of “non clinical tests,” an umbrella term that includes animal tests but also allows for technological advances like computer simulations, organ chips, and 3-D printed body parts to replace animals.

From the bill:

Nonclinical Test Defined.—For purposes of this section, the term `nonclinical test’ means a test conducted in vitro, in silico, or in chemico, or a nonhuman in vivo test, that occurs before or during the clinical trial phase of the investigation of the safety and effectiveness of a drug. Such test may include the following:

(1) Cell-based assays.

(2) Organ chips and microphysiological systems.

(3) Computer modeling.

(4) Other nonhuman or human biology-based test methods, such as bioprinting.

(5) Animal tests.

The federal budget package also includes $5 million for FDA research aimed at reducing animal testing and developing new, improved testing methods.

Kentucky Senator Rand Paul co-sponsored the FDA Modernization Act 2.0 with New Jersey Senator Corey Booker, and Sen. Paul celebrated its inclusion in the appropriations package and passage in a statement last week. The act “will accelerate innovation and get safer, more effective drugs to market more quickly by cutting red tape that is not supported by current science,” he said.

How does animal testing in drug trials work, currently?

Until now, the FDA has generally required that proposed medications go through toxicity tests on a rodent species (i.e. lab rat or mouse), as well as one non-rodent like a monkey or dog. But the overwhelming majority of drugs that move past these tests into human trials still end up being deemed unsafe or ineffective. Nearly 95% of drugs that enter human trials fail to obtain FDA approval, according to one 2019 study, meaning animal testing doesn’t seem to be much of an effective filter. A rat’s internal biology is different from that of a dog, which is, in turn, different from a human’s.


“Animal models are wrong more often than they are right,” said Don Ingber, a bioengineer at Harvard University, to Science. (As a caveat: Ingber’s research lab developed organ chip technology, which is currently being commercialized by the company Emuluate, in which Ingber owns stock and has a board seat, according to the publication.)

Not to mention the hefty cost, potential cruelty, and guaranteed death that comes along with animal testing. Tens of millions of animals (overwhelmingly rodents) are used in laboratory studies and drug testing in the U.S. every year. Nearly all are killed at the conclusion of experiments.


What happens next?

Foregoing rigorous pre-human trials altogether is a recipe for disaster and increased human suffering—so that’s not going to happen. However, most of the tech-based substitutes for animal testing aren’t yet ready to take over pharma trials, Jim Newman, communications director at Americans for Medical Progress—an organization that advocates for animal research—told Science. These replacement methods are “in their infancy,” he said, and won’t be able to supplant animal models for “many, many years.” As a result, he doesn’t expect the FDA to change much about its requirements or protocols very quickly.


Aliasger Salem, a pharmacology researcher at the University of Iowa, echoed Newman’s skepticism of new, substitute technologies, in a report from NPR. “Companies need to be aware of the limitations of those technologies and their ability to identify or not identify potential toxicities,” Salem said. “You don’t want to shift to systems that might not capture all of the types of toxicities that have been seen in the past,” he added.

Likely, the transition from animal testing to alternatives will be slow, and animal testing will still be used in many drug trials. The FDA did not immediately respond to Gizmodo’s questions or request for comment, but told NPR it will “implement all applicable provisions in the [new bill] and continue to work with stakeholders to encourage the development of alternative testing methods.”