Orphan drugs are defined as drugs that are:

Orphan drugs are specifically designated for the treatment of rare diseases, which affect a small percentage of the population. These drugs often receive special regulatory status to encourage their development due to the limited financial incentive for companies to invest in treatments for diseases that affect few patients. The rarity of the condition means that the potential market is not large enough to justify the high research and development costs associated with bringing a new drug to market.

In various regions, including the United States and the European Union, orphan drug designations come with benefits such as tax incentives, assistance with the drug development process, and an extended period of market exclusivity. This framework aims to ensure that patients with rare conditions have access to necessary therapies, populations that are often overlooked in the pharmaceutical industry.

Other options do not accurately reflect the definition of orphan drugs. For instance, drugs used for common diseases do not fit within this classification, as the focus of orphan drug designation is solely on rare diseases. Similarly, while some orphan drugs may not be commercially available yet, that does not form the core definition. Lastly, the use of drugs primarily in clinical trials does not inherently relate to the concept of orphan drugs, as drugs in trials may target various conditions, not specifically rare diseases.