The Food and Drug Administration (FDA or Agency) is announcing the availability of a draft guidance for industry entitled “Optimizing the Dosage of Human Prescription Drugs and Biological Products for the Treatment of Oncologic Diseases.” This guidance is intended to assist sponsors in identifying the optimal dosage(s) for human prescription drugs or biological products for the treatment of oncologic diseases during clinical development prior to submitting an application for approval for a new indication and usage. This guidance does not address selection of the starting dosage for first-in-human trials nor does it address dosage optimization for radiopharmaceuticals, cellular and gene therapy products, microbiota, or cancer vaccines.