Tau promotes the assembly and maintains the structure of microtubules in neuronal cells3,4,5. While the fetal brain contains a single isoform of tau (Tau-352) the adult brain has several isoforms. Tau is both phosphorylated and O-GlcNAcylated6. The normal brain tau contains 2-3 moles of phosphate/mole of the protein. In Alzheimer disease tau is hyperphosphorylated, containing 3-4-fold more phosphate/mole of the protein than the normal tau7,8 and is the major protein subunit of paired helical filaments (PHF) that form the neurofibrillary tangles (NFT). NFT accumulation correlates with the clinical progression of Alzheimers disease. Tau 4G11 (TA-1001) is a rPeptide exclusive Tau Monoclonal Antibody that binds 4 out of the 6 Tau isoforms. It specifically binds Tau-381, Tau-410, Tau-412, and Tau-441 which all contain at least one amino terminal insert.