The FDA is seeking comments on draft guidance related to clinical trial enrichment: Enrichment Strategies for Clinical Trials to Support Approval of Human Drugs and Biological Products. The document is designed to provide guidance to industry on enrichment strategies that can be used in clinical trials intended so support effectiveness and safety claims in NDAs and BLAs. According to FDA, enrichment could lead to smaller studies, lower development costs, and help develop more personalized medicine. The guidance defines and discusses three types of enrichment strategies: decreasing heterogeneity, predictive enrichment, and prognostic enrichment. The guidance also discusses general clinical trial design considerations, provides examples of various potential clinical trial designs, and discusses potential regulatory considerations when using enrichment strategies in clinical trials. Comments may be submitted at www.regulations.gov until February 15, 2013.