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# Guide on Reducing Animal Studies for Cancer Products
- URL: https://www.fdaweb.com/guide-on-reducing-animal-studies-for-cancer-products/
- Published: 2026-05-29T12:00:00.000Z
- Updated: 2026-09-14T13:40:12.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5161224

FDA has issued a [draft guidance](https://www.fda.gov/media/192723/download?ref=fdaweb.com) that proposes streamlined nonclinical safety testing approaches for certain oncology biologics and conjugated therapies, a move the agency said could reduce animal use and speed cancer drug development without compromising patient safety. The document, titled “Oncology Pharmaceuticals: Streamlined Nonclinical Safety Studies for Biologics and Conjugated Products,” outlines circumstances in which sponsors could rely on shorter toxicology programs, single-species studies or weight-of-evidence (WoE) risk assessments instead of traditional long-term animal testing.

FDA said the recommendations were informed by analyses of toxicology data for oncology products, including CD3 bispecific antibodies and antibody-drug conjugates (ADCs), as well as practices adopted during the COVID-19 pandemic to reduce reliance on non-human primates.

Under existing international guidelines, chronic toxicology assessments for cancer therapies are often based on three-month studies in one or two animal species. The new draft guidance expands on those principles by identifying specific product classes where additional streamlining may be appropriate.

For PD-(L)1 blocking monoclonal antibodies, FDA says sponsors could use a WoE risk assessment instead of conducting a dedicated three-month toxicology study. The agency also said one-month studies for those products could potentially be conducted without animal sacrifice if supported by adequate justification and supplemental evidence.

Similarly, for CD3 bispecific T-cell engagers, FDA says chronic toxicity assessments could rely on WoE analyses in place of three-month animal studies.

The guidance also proposes more flexible approaches for ADCs containing well-characterized cytotoxic payloads. In cases where the payload is considered the primary driver of toxicity, FDA says sponsors could conduct three-month toxicology studies solely in rodents, regardless of whether the ADC binds to the target antigen in that species.

FDA notes WoE assessments may incorporate nonclinical and clinical data, published literature on molecular targets, known toxicities from related drug classes and data from “new approach methodologies,” including alternative testing systems.

The agency says sponsors developing products outside the categories specifically addressed in the guidance could still propose alternative toxicology approaches, including non-sacrificial studies, reduced-animal study designs or WoE-based strategies, provided they submit adequate scientific justification.

The draft guidance was prepared by FDA’s Oncology Center of Excellence.