Endocrine Disruptor Screening in Regulatory Submissions: OECD and EPA Guidelines
Endocrine disruptors are exogenous substances that interfere with the normal function of hormonal systems, potentially causing developmental, reproductive, neurological, or immune effects in humans and wildlife. Regulatory concern over endocrine-disrupting chemicals (EDCs) has led to the implementation of structured screening and testing frameworks by agencies such as the U.S. Environmental Protection Agency (EPA) and the Organisation for Economic Co-operation and Development (OECD). These frameworks are now a critical part of safety evaluation in IND and chemical risk assessments.
The EPA’s Endocrine Disruptor Screening Program (EDSP) and OECD’s Conceptual Framework classify testing into multiple levels. Tier 1 screens include in vitro assays (e.g., estrogen receptor binding and transcriptional activation) and short-term in vivo assays such as uterotrophic or Hershberger studies. These tests detect the potential for a compound to interact with estrogen, androgen, or thyroid pathways.
If Tier 1 screens indicate endocrine activity, Tier 2 tests—such as extended one-generation reproductive toxicity studies (EOGRTS) or amphibian metamorphosis assays—are used to characterize dose–response relationships, target organs, and developmental effects. These studies are resource-intensive and require robust design to differentiate endocrine-mediated effects from systemic toxicity.
In the context of IND-enabling toxicology, screening for endocrine disruption is particularly relevant for compounds with hormonal targets, steroid-like structures, or unexplained reproductive effects in early studies. Demonstrating the absence of endocrine activity through validated assays can reduce regulatory uncertainty and support a safer path to clinical development.
The inclusion of endocrine disruptor data in submissions demonstrates adherence to international safety standards and supports a precautionary approach to human health and environmental protection.