We discovered that a small dose of the FDA-approved anti-HIV drug efavirenz (EFV) allosterically activated CYP46A1 in mouse brain (Mast et al., 2014), and that EFV treatment of 5XFAD mice, a model of rapid amyloidogenesis in AD (Oakley et al., 2006), led to multiple brain effects. Here, CYP46A1 is linked to Alzheimer disease.