3.2.  Limitations and more of the same
A large number of drugs approved by the FDA in the past 10 years are new formulations of existing drugs referred to as ‘me too drugs’. While in some cases these drugs have offered some improvements over older versions, in many cases improvements remain marginal with slight changes in side effects or activity profiles [34]. Since these drugs have identical mechanism of action to older versions their innovative value and overall benefit is oftentimes insignificant [35]. Additionally, the molecular effects of several marketed drugs remain unknown despite their proven effectiveness. For example, acetaminophen is used by millions to treat mild to moderate pain while lithium is a first-line treatment for biopolar disorder. Yet the exact molecular target and mechanism of action remain unknown [36,37]. Many diseases particularly those affect the nervous system like Alzheimer, Parkinson’s, and depression lack accurate biomarkers [38,39]. While progress is being made, the lack of reliable biomarkers remains another impediment for the accurate diagnosis, prognosis and effective drug development against these diseases.