MAPT and Cognitive impairment: Because histological analysis and tau positron emission tomographic studies have revealed that cognitive impairment correlate better with tau and neuronal loss than with Aβ pathology (Bondareff et al., 1989; Bobinski et al., 1996; Gomez-Isla et al., 1996; Guillozet et al., 2003; Schöll et al., 2016; Schwarz et al., 2016; Bejanin et al., 2017), AD drug discovery research has increasingly shifted from Aβ to tau protein (Giacobini and Gold, 2013), with some reaching clinical trial stages.