Sure, but the US or US-based businessmen are hardly the only actors lobbying and if you look at the trade balances of basically all African countries, Chinese interests are far more successful in exploiting African markets than US concerns. Add to this that several African countries have basically no diplomatic relationship and/or are openly hostile to the US and it makes no sense at all that they would forego a cheap and self-sufficient remedy to malaria (if it existed), just to please big Pharma.