Some 500,000 people worldwide die from hepatitis C virus every year because available remedies are unaffordable. So it is good to see expensive medicines against this virus, along with anticancer agents, included on the latest World Health Organization (WHO) Model Lists of Essential Medicines (see go.nature.com/wzah9w). However, simply listing these drugs is unlikely to make them more affordable, particularly in the developing world (see also www.msfaccess.org).

Health authorities must drive home the ethical obligation of pharmaceutical companies to cut the cost of life-saving medicines in accordance with the Doha Declaration of 2001, especially given that even some wealthy countries cannot afford them. To support this, governments and national health authorities should not grant patents on medicines that could be made more affordable.

Authorities should insist that drug firms make their costing information publicly available. This would include their investment in research and development compared with marketing expenditure, and details of differences between the actual cost and the retail price of medicines.

Such measures would enable the public to judge to what extent drug prices are the result of investment in innovation, rather than of satisfying shareholders and supporting marketing.