Reports showing that in humans, intranasally administered insulin (51 amino acids) bypasses the bloodstream and reaches the cerebrospinal fluid within 30 minutes (73), modulates neuronal function (74), and reduces Alzheimer’s disease–associated changes in white matter (75) support the feasibility of using the nasal route for direct delivery of therapeutic peptides to the brain. The gene discussed is INS; the disease is early-onset autosomal dominant Alzheimer disease.