Why is there so little research on diseases that are endemic in developing countries?

Why is there so little research on diseases that are endemic in developing countries?
What can be done to promote this research? What are the arguments for promoting
this research? Who should be involved in this promotion? Your audience is a director in
the World Bank’s Global Health Division. She is an epidemiologist by training and thus
already knows a lot about the incidence of tropical disease; but she is less familiar with
how pharmaceutical markets work.