To the Editor The article by Dr Wouters and colleagues¹ compared their estimate of the mean cost of developing a new drug with that found in a study by myself and colleagues.² Their base case mean cost per approved new drug of $1.6 billion (in 2018 US dollars) stands in contrast to our estimate of $2.8 billion (2018 US dollars). The authors acknowledged that their sample was nonrepresentative in a number of drug characteristics (including therapeutic class) and by firm size (primarily small firms). Given that our sample consisted of midsized to large firms, their results could be viewed as complementary. Wouters and colleagues¹ also noted that their information came from public sources, whereas our estimates were based in part on proprietary information.