While the trending decrease in CSF levels of NfL, a marker of axonal damage that is elevated in CSF47 and plasma48 of individuals with mild cognitive impairment, Alzheimer’s dementia, and other neurodegenerative disorders49, further suggests a benefit due to 3TC treatment, we note that the trending change in NfL due to 3TC treatment is discordant between CSF and plasma. The gene discussed is NEFL; the disease is Cognitive impairment.