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Chapter 1

Definitions, History and Regulatory Framework for Rare Diseases and Orphan Drugs

The term orphan drug is a formal regulatory term used to describe a drug product that has been granted orphan status by a regulatory agency. Orphan designation is reserved for medicines that are intended to treat diseases with prevalence below the threshold set for rare diseases, which in the US is any disease or condition affecting fewer than 200 000 people. In Europe, a condition is considered rare if it affects fewer than 1 in 2000 people. There is considerable diversity among conditions defined as rare and they include neurological conditions, infectious diseases, rare cancers, autoimmune disorders, respiratory, muscle and blood disorders and a wide range of inherited genetic disorders. It has been estimated that there are more than 7000 rare diseases known but only around 5% of these have therapies available and the unmet medical need within rare diseases remains high. Across the thousands of highly heterogeneous rare diseases that are known, there is no unifying classification that links them all, with the exception that they affect a relatively small number of people, and the vast majority have no effective therapy available. Outside of the rare disease field, there is considerable misconception and misunderstanding surrounding rare diseases and orphan drugs; what these terms mean, what is classed as an orphan drug, what this designation entails and how many orphan drugs exist for which rare diseases. This chapter seeks to clear up these misconceptions and make clear to the reader what the terms orphan drug and rare disease mean, and detail the breadth of research, drugs and clinical activity taking place in this important field.

Publication details

Print publication date
14 Aug 2014
Copyright year
Print ISBN
ePub eISBN

From the book series:
Drug Discovery