In Reply Dr Lopert and Mr Welch and Dr Green make the point that the Gilead purchase of Pharmasset does not accurately reflect the true costs of development of sofosbuvir. We agree.
Our point was simply that the $11 billion price was the most that one could say that it cost Gilead to bring sofosbuvir to market, and even then their return on investment is extraordinary.
In addition, Lopert and Welch call for a formal cost-effectiveness analysis. We agree and are currently undertaking that research.