Peptide 6 and in particular, Peptide 021, may be used to treat tauopathies, such as frontotemporal dementia with Parkinsonism linked to chromosome-17 (FTDP-17) tau, corticobasal degeneration, Pick disease, progressive supranuclear palsy, Guam Parkinsonism dementia complex, dementia pugilistica also known as traumatic encephalopathy or traumatic brain injury, ceroid neuronal lipofusinosis, Hallerworden Sptaz disease, Alzheimer's disease, and adults with Down syndrome.