Spending For Orphan Indications Among Top-Selling Orphan Drugs Approved To Treat Common Diseases.

The Orphan Drug Act of 1983 provides benefits to promote the development of treatments for rare diseases that have limited sales potential. Policy makers have questioned whether this purpose is furthered in the case of "partial orphan drugs" approved to treat both rare and common diseases, as many of these drugs are top sellers. In this study we used national commercial claims data to estimate the proportion of spending in the US on fifteen top-selling partial orphan drugs that was assigned to orphan indications in 2018. Of this spending, 21.4 percent was assigned to orphan indications, 70.7 percent to nonorphan indications, and 7.9 percent to neither orphan nor nonorphan indications (for example, off-label use). These findings support growing concerns regarding the costs of granting orphan drug benefits to the sponsors of top-selling partial orphan drugs.