An investment operation is one which, upon thorough analysis, promises safety of principal and a satisfactory return. Operations not meeting these requirements are speculative. Ben Graham
Biotechnology companies are risky investments, typically these companies target a condition with a known cause. Biotechnology companies specializing in neuro-degenerative disorders pose the greatest risk, because most disorders have unknown causes, such as Alzheimer's and Parkinson's.
I previously argued Voyager Therapeutics' (VYGR): Parkinson's gene therapy VY-AADC would likely fail. Since that time, additional data from phase 1 clinical study has been published in the peer-reviewed journal Annals