Four years ago NNVC took early data to the FDA, a workshop for discovery and the process for approval. The FDA is aware of NNVC and its technology, but are skeptics at heart. The officers of this company are following FDA guidelines.
Yes, four years is a long time, but keep in mind that nearly all drug testing came to a halt in 2007 due to uncertainty about funding amid budget cuts in both private and public sectors. Pre-clinical and clinical testing is only this year getting back up to pre-2007 levels of activity. NNVC isn't alone in losing a year or more of advancement.