If this is like a homework question, i would say cancer. if it is you trying to understand more throughly, then the answer is anything and everything.
RNAi drugs are drugs that mimic RNAi strands, thereby, more effectively and easily entering into the bodies cells. They are thought to be much more effetive and therefore a person would need . The problem with these though, the analytical techniques need to test the drugs for quality and purity, and also for toxins and such is still in its infancy.