Comment from Julie OConnor

Docket No. FDA-2026-D-2839. Dear FDA, I am writing to support the continued reduction and replacement of animal testing in the development of cancer medicines. I welcome the FDA’s draft guidance, which proposes reducing the use of non-human primates for certain oncology toxicology studies. This is an important step forward and demonstrates recognition that some traditional animal studies are no longer necessary. However, I believe the guidance should go further. Rather than largely replacing monkey studies with rodent studies and treating animal testing as a default approach, the FDA should prioritize scientifically validated, human-relevant non-animal methods wherever possible. Modern approaches, including computational models, advanced cell-based systems, organ-on-chip technologies, and other New Approach Methodologies (NAMs), have the potential to provide information that is more directly relevant to human biology. Despite decades of reliance on animal testing, cancer remains one of the areas with the highest rates of clinical failure during drug development. Published evidence has shown that rodent toxicology studies identify only around 43% of the toxicities later observed in humans. Where more predictive human-relevant approaches are available, these should form the primary basis of safety assessment. I therefore encourage the FDA to strengthen the final guidance by: Making integrated weight-of-evidence (WoE) assessments incorporating human-relevant methods the default approach to safety assessment. At minimum, a WoE assessment should accompany every animal test. Requiring animal studies only where there is clear scientific justification that they will provide information that cannot be obtained through available non-animal approaches. Encouraging greater regulatory adoption of validated NAMs to improve both patient safety and animal welfare.