November 20, 2023

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 Dr. Rand Paul Urges FDA to Update Animal Testing Guidance in Accordance with the FDA Modernization Act 2.0

WASHINGTON, D.C. Recently, U.S. Senator Rand Paul (R-KY), led a bipartisan group of nine senators in sending a letter to the U.S. Food and Drug Administration (FDA) to ensure the FDA is updating its animal testing regulations following the enactment of the FDA Modernization Act 2.0 last year. The legislation ended an outdated FDA mandate that required investigational new drugs to be tested on animals in pre-clinical trials. The legislation did not ban animal testing, but it allowed drug sponsors to use modern alternative methods to demonstrate a drug’s safety and effectiveness where they were suitable.

Dr. Paul was joined in sending the letter by Senators Cory Booker (D-NJ), Mike Braun (R-IN), Angus King (I-ME), Roger Marshall (R-KS), Tim Kaine (D-VA), John Kennedy (R-LA), Ben Ray Luján (D-NM), and Eric Schmitt (R-MO).

You can read the full letter HERE or below and can read more about the Senators’ efforts published in Reason HERE.

Dear Dr. Califf:

We write to you about the investigational new drug development work of the FDA in the wake of the enactment of the FDA Modernization Act 2.0. 

That legislation, which Congress passed and the President signed into law at the end of 2022 with uncommon unanimity, removes FDA’s mandate for animal testing of all new drug candidates and allows an applicant for new drug market approval to use methods other than animal testing to establish a drug’s safety and effectiveness.  During one of your appearances before the U.S. Senate Committee on Health, Education, Labor, and Pensions, you spoke favorably about the shift toward human-based biology, noting that alternative methods may include cell-based assays, organ chips and micro-physiological systems, computer modeling, bioprinting, and a growing variety of other New Approach Methodologies (NAMs).

As you are aware, agency regulations are promulgated in accordance and conformity with Congress’s statutory language and intent. Yet in the aftermath of the enactment of the FDA Modernization Act 2.0, the FDA’s regulations related to animal testing no longer fully conform with applicable law. For example, federal regulations governing submission of Investigational New Drug (IND) applications require that amendments to an IND “should be supported by additional information, including the results of animal toxicology studies or other human studies as appropriate.” Further, regulations governing the IND Investigator’s Brochure call for a summary of “pharmacological and toxicological effects of the drug in animals and, to the extent known, in humans.” These and other regulatory provisions no longer reflect the full scope of the governing statute and should therefore be updated as expeditiously as possible.

The above examples are just a sampling of a larger set of inconsistencies between the amended statute and FDA regulations. We therefore write to ask what specific steps the FDA is taking to update its animal testing regulations, and what its timeline is for implementation of a revised regulatory framework.  Please respond with this information within 30 days of the date of this letter.

Thank you for your attention to this important matter.


The FDA Modernization Act 2.0 was introduced by Dr. Paul and Sen. Cory Booker (D-NJ) last year and was unanimously passed by the Senate and signed into law in 2022. 

In 1938, Congress passed the U.S. Federal Food, Drug, and Cosmetic Act, mandating animal toxicity testing. Since then, science and data has shown that in some products, animal testing is a highly inconsistent predictor of toxic responses in humans, all while animal testing on any single pharmaceutical product often requires killing hundreds of animal test subjects. 

Dr. Paul and Sen. Cory Booker also previously introduced the first FDA Modernization Act in October 2021, and in the spirit of the bill, Dr. Paul hosted a Puppy Press Conference with Sen. Mike Braun (R-IN) and Sen. John Kennedy (R-LA). You can read more about the FDA Modernization Act 2.0 HERE.



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