On December 2, 2025, the U.S. Food and Drug Administration (FDA) issued new draft guidance identifying specific monoclonal antibody product types for which six-month non-human primate toxicity studies may be reduced or eliminated. This release represents a significant step in the agency’s ongoing effort to modernize nonclinical drug evaluation and reduce reliance on traditional animal testing.
Shift Toward Human-Relevant Assessment Models
The FDA noted that this draft guidance reflects the agency’s continued progress in implementing more efficient and scientifically advanced approaches to drug safety evaluation. Rather than relying on extended non-human primate studies, the agency aims to integrate risk assessments that incorporate human-relevant scientific tools. These include computational toxicology methods, organoid systems, and real-world human safety data, which together provide a more precise understanding of how a product may behave in humans.
Leadership Perspectives on the Transition
Commenting on the agency’s new direction, FDA Commissioner Marty Makary, M.D., M.P.H., emphasized the importance of shifting away from longstanding animal-based systems. He stated that modern science offers more effective and humane ways to evaluate drug safety, potentially reducing the time required to bring new drugs to market and lowering research and development costs. These efficiencies, he added, could ultimately help lower drug prices for patients.
The agency highlighted the substantial resources historically required for nonclinical programs. A typical monoclonal antibody development program could involve more than 100 non-human primates, often macaques, with costs reaching approximately $50,000 per animal. Yet many products that successfully complete animal testing still fail to obtain FDA approval due to safety or efficacy challenges in humans, underscoring the need for more human-centered evaluation models.
Richard Pazdur, M.D., Director of the FDA’s Center for Drug Evaluation and Research, noted that integrating knowledge-based risk assessments can help regulators make more informed decisions while maintaining the high safety standards expected by patients. He emphasized that incorporating advanced, human-relevant methodologies reflects both scientific progress and the agency’s responsibility to adopt the most effective tools available for drug evaluation.
A Key Component of the FDA’s Roadmap to Reduce Animal Testing
The newly issued draft guidance aligns with the FDA’s broader roadmap to reduce animal testing in nonclinical safety studies, particularly for certain monoclonal antibodies. Once finalized, the guidance will supplement the FDA’s May 2012 S6 Addendum, which outlines approaches to scientific flexibility, product-specific evaluation, and risk assessment in biotechnology-derived pharmaceuticals.
The FDA reaffirmed its commitment to ongoing collaboration with national and international partners, including the National Institutes of Health, the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM), and other regulatory bodies worldwide. These partnerships aim to validate and expand innovative non-animal testing methodologies across therapeutic areas.
Stakeholder Engagement and Public Dialogue
In July 2025, the FDA hosted a public workshop focused on identifying scientifically meaningful approaches to reduce animal testing while ensuring patient safety. The workshop brought together researchers, industry sponsors, and patient advocates. Their perspectives contributed to shaping both the newly released draft guidance and the FDA’s broader long-term strategy for transitioning away from animal testing in drug development.
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Written by Nare Hovhannisyan, MD