First of all, if a pharma company had an annual income of 2bn from HIV treatments, and that companies CEO went forward with a HIV cure that is only predicted to earch 3bn overall; that CEO could essentially be removed from his position, as that would not be in the best interest of the company and shareholders.

Also, there does not need to be an evil twist where someone deliberately holds back a developed cure. It is much easier to cut/steer the research in ways that favor treatment/management options, ensuring that a cure would only be found be accident.