TAC1 and early-onset autosomal dominant Alzheimer disease: This mutation results in the loss of the C‐terminal region of the endopeptidase neprilysin (NEP) protein (OMIM #120520), which inactivates a broad spectrum of peptide substrates, such as enkephalins, neurokinin A, substance P, bradykinin, endothelin, somatostatin, and more others, including amyloid‐β (Aβ) protein, which accumulates in Alzheimer's disease (AD).