Partial orphan cancer drugs: FDA approval, clinical benefit, trials, epidemiology, price, beneficiaries, and spending

•The Orphan Drug Act (ODA) incentivizes drug development for rare diseases with limited sales potential. However, orphan drugs frequently turn into multi-billion dollar blockbusters, particularly those used to treat rare and common diseases: “partial orphans”.•This is the first study to analyze the development, US Food and Drug Administration (FDA) approval, epidemiology, and economics of full, partial, and non-orphan cancer drugs.•We show that the clinical benefit, trials, and epidemiology of partial orphan cancer drugs are more similar to non-orphans than full orphans.•However, partial orphans receive all of the ODA’s incentives and are swiftly extended to new indications; resulting in greater prices, beneficiaries, and gross spending.•Establishing a maximum revenue threshold for the ODA’s benefits alongside indication-specific pricing could reduce expenditure on partial orphan drugs.