MAPT and Cognitive impairment: For example, NAP (davunetide, AL-108) failed in the pure 4R tauopathy progressive supranuclear palsy (PSP) [46], but showed efficacy in increasing cognitive scores in patients with amnestic mild cognitive impairment (mixed 3R + 4R tauopathy) [15, 47] involving differential interaction with Tau 3R/4R splice variants [28].