MAPT and early-onset autosomal dominant Alzheimer disease: These secretomes contain an array of tau fragments with little or no detectable full-length protein.39 Therapeutic targeting of different forms of extracellular tau with selective antibodies has become a major area of clinical development in the potential treatment of Alzheimer’s disease.85,86 It is a matter of some controversy whether to target the N-terminus, mid-region or C-terminus of tau.