The Orphan Drug Act (ODA) was designed to spur the development of drugs for rare diseases. In principle, its design also incentivizes pharmaceutical firms to develop drugs for "rare" subdivisions of more prevalent diseases. I find that in response to this incentive, firms develop drugs for...

I study the impact of the Orphan Drug Act (ODA), which established tax incentives for rare disease drug development. I examine the flow of new clinical drug trials for a large set of rare diseases. Among more prevalent rare diseases, the ODA led to a significant and sustained increase in new...