OBJECTIVES: The 1983 Orphan Drug Act (ODA) was designed to provide incentives to the development of drugs for diseases affecting 200,000 or fewer people in the United States. Since then, some drugs have sought, and been approved for, multiple Orphan Drug designations, some of them for multiple subgroups of individuals with a same clinical condition. We examined drugs with multiple Orphan Drug approvals for the prevalence of the conditions they intended to treat, aiming to examine whether the total size of their target population exceeded the original intent of the ODA.

METHODS: We utilized the FDA Orphan Drug Database to identify drugs with three or more approved indications. We reviewed the medical literature and disease registries to identify the prevalence of each approved indication.

RESULTS: There were 26 drugs with three or more approved indications among 415 different drugs with orphan approvals (6%). Drugs had an average of 4.3 indications for an average of 3.5 different conditions. Thirteen (50%) of the examined drugs had aggregated target populations of over 200,000 individuals. These drugs tended to have higher number of approvals and conditions than those with aggregated populations under 200,000 (avg ±sd: 4.62±2.17 vs. 4.00±1.41 approvals; 3.92±2.02 vs. 3.15±1.03 conditions).

CONCLUSIONS: About half of the drugs with multiple orphan indications are approved for target populations greater than what was foreseen in the ODA. While these numbers do not reflect actual drug utilization, they support the need for further studies addressing whether the ODA incentives may be utilized by drugs targeting broader markets.