A blood NfL increase in presymptomatic gene carriers could be a good biomarker to include these individuals in clinical trials, and a non-interventional study as preparation for pivotal clinical trials is ongoing, with the aim of qualifying blood NfL as an endpoint for the prevention of familial forms of FTD (ClinicalTrials.gov identifier: NCT04516499). The gene discussed is NEFL; the disease is frontotemporal dementia.