The new FDA draft guidance could help drug companies reduce unnecessary animal testing for certain cancer treatments, while still showing regulators that safety risks have been carefully assessed.
In May 2026, the FDA released new draft guidance outlining ways to modernize safety testing for certain cancer drugs.
The guidance focuses on some biologics and conjugated products used in oncology. Biologics are medicines made from living systems or designed to act on biological targets, such as antibodies. Conjugated products are therapies made by linking different components together, such as an antibody joined to a cancer-killing drug payload.
The guidance’s goal is to help drug developers use more efficient ways to assess safety before and during clinical development, while avoiding animal studies that may not add useful information.
The document is still a draft, meaning it is open for public comment and is not yet a final FDA recommendation.
A More Targeted Approach to Safety Testing
Before a new cancer drug is tested broadly in people, developers usually conduct nonclinical safety studies. These can include lab research and animal studies that look for possible toxicities, dose-related risks and other safety concerns.
But for some newer cancer drugs, traditional animal testing may not always be the most useful approach. Certain therapies are designed to interact with very specific human targets. If an animal species does not respond to the drug in a biologically relevant way, the study may offer limited insight into how the treatment would affect people.
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The FDA’s draft guidance suggests that, in some cases, companies may be able to use a more tailored strategy. That could mean using one relevant animal species instead of two, replacing some animal studies with a broader evidence-based assessment or avoiding animal toxicology studies when no relevant animal model exists.
The recommendations are informed by FDA analyses of cancer drug toxicology studies, as well as practices developed during the COVID-19 pandemic to reduce the use of non-human primates.
Using Existing Knowledge Instead of Repeating Animal Studies
An important part of the guidance is the use of a Weight of Evidence risk assessment. This means looking at the full body of available evidence instead of relying only on new animal studies.
That evidence can include lab and safety data from the investigational drug, what is already known about the drug’s target, published research on possible toxicities and safety findings from similar medicines. The FDA said these assessments may also include New Approach Methodologies, or newer tools and testing approaches that can provide additional safety information.
For drug targets or product classes that are already well understood, this type of assessment may sometimes replace a three-month animal toxicology study.
The draft guidance also allows companies to propose other ways to reduce animal use, such as study designs that do not require ending an animal’s life or evidence reviews that replace a new animal test. The FDA recommends that companies explain the science behind these choices and discuss them with the agency early.
Which Cancer Drugs Are Covered?
The new draft guidance gives different recommendations depending on the type of cancer drug and how much is already known about its safety risks.
For some biologics, animal studies should only use species that respond to the drug in a relevant way. If no suitable animal species exists, companies may be able to rely on a Weight of Evidence assessment instead.
For certain cancer immunotherapies, including PD-(L)1 blocking antibodies and CD3 bispecific T-cell engagers, this evidence-based approach may replace some three-month animal toxicology studies.
For antibody-drug conjugates, which use an antibody to deliver a toxic drug payload to cancer cells, rodent studies may be enough in some cases if the payload is already well characterized from other approved drugs.
FDA’s Gradual Move Away From Animal Testing
The cancer drug guidance follows an April 2026 FDA update saying the agency had met its first-year goals under a 2025 roadmap to reduce animal testing in drug development, including new guidance on non-human primate testing, Weight of Evidence approaches and the use of newer lab-based and computational tools.
In March 2026, the FDA released another draft guidance to help developers show when these newer methods are dependable enough to support drug development decisions.
FAQs
Is the FDA ending animal testing for cancer drugs?
No. The draft guidance outlines when some animal studies may be reduced, redesigned or replaced with other evidence, but it does not eliminate animal testing.
Does this FDA guidance apply to clinical trials in patients?
No. It focuses on nonclinical safety studies, including lab and animal-based work used to support cancer drug development before and during human testing.
What are nonclinical safety studies?
Nonclinical safety studies are tests done outside human trials to help researchers understand possible safety risks before a drug is tested more broadly.
Could this help cancer drugs reach patients faster?
Potentially. The FDA’s aim is to make parts of development more efficient by avoiding animal studies that may not add useful safety information.
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