Beta-site APP-cleaving enzyme 1 (BACE1) inhibitors have a long history of failure in patients with Alzheimer’s disease. Clinical development of verubecestat, elenbecestat, lanabecestat, umibecestat, atabecestat and LY-3202626 were all discontinued. The drugs largely showed that inhibiting BACE1 reduced amyloid beta (AB) in both cerebrospinal fluid and plasma, reduced AB plaques on PET scans and reduced phosphorylated tau. Unfortunately, patients had early cognitive worsening, and there were signs of lowering of brain volume and increases in psychiatric adverse events.