Because preclinical human trials with invermectin have only been done for breast cancer. The first trial was pulled, and a second one has begun. It has not as yet been found "safe", and has not been found to work well in peope teceivimg chemo. In fact there are stories of patients who did not tell their oncologists that they were also taking invermectin with terrible outcomes. Most testing that MAY indicate anything positive has occurred only at the cellular level in mice and petri dishes. Due to toxicity concerns, there is not much support for human trials. However, as with all science today's unknown could become tomorrows wonder drug. I wouldn't wait up for a decision, though. Personally, I'm not willing to be one of the first to trial a drug that works well on parasites alone at this point in time.