The NAD-HD Study: A Study to Investigate Efficacy and Safety of Nicotinamide Riboside Compared With Placebo in Huntington's Disease

Inclusion Criteria: * Confirmed HD gene expansion carrier status with a diagnostic genetic test confirming ≥36 CAG-repeats in HTT. * Clinically manifest HD with objective neurological signs corresponding to Diagnostic Confidence Level 4 based on the Total Motor Score of the UHDRS. * Early or mid-stage disease corresponding to Shoulson-Fahn stage 1-340 and Total Functional Capacity (TFC) \> 2. * Ability to walk indoors unassisted or by the help of walking aids only as determined at screening and baseline visits. * Ability to write and perform pen-and-paper tests (SDMT, SWRT, MoCA) and complete questionnaires (HADS-SIS, SF-12) included in the study protocol. * Ability to follow up telephone appointments and reliably attend study visits independently or with the assistance of a reliable partner (family member, friend, or assistant). * Ability to tolerate blood draws. * Participants who are women of childbearing potential should use an approved method for highly effective birth control throughout the study intervention period * Capable of giving signed informed consent Exclusion Criteria: * Presence of other co-morbid neurological or psychiatric disorders considered clinically significant by the investigator, including, but not limited to psychotic disorders, brain tumor or inflammatory neurological disease. * Attempted suicide or active suicidal ideation within 12 months prior to screening. * A history of alcohol or substance use within a 12 month period prior to the baseline…