GENERATION HD2. A Study to Evaluate the Safety, Biomarkers, and Efficacy of Tominersen Compared With Placebo in Participants With Prodromal and Early Manifest Huntington's Disease.

Open to people ages 25-50

-Huntington's disease (HD) gene expansion mutation carrier status with a CAP score of 400-500 inclusive

Either:

• Prodromal HD (defined as DCL 2 to 3, Independence Scale (IS) ⩾70, and ⩾TFC8); or
• Early manifest HD (defined as DCL 4, Independence Scale (IS) ⩾70, and ⩾TFC8);
• Total body weight > 40 kg and a body mass index within the range of 18-32 kg/m2
• Study Companion

• Current or previous use of an ASO (including small interfering RNA) or any HTT lowering therapy (including tominersen)
• Anti-platelet or anticoagulant therapy within 14 days prior to screening or anticipated use during the study, including, but not limited to, aspirin (unless </= 81 mg/day), clopidogrel, dipyridamole, warfarin, dabigatran, rivaroxaban, apixaban, and heparin
• History of gene therapy, cell transplantation, or brain surgery
• Hydrocephalus
• Pregnancy or breastfeeding, or intention of becoming pregnant during the study or within 5 months after the final dose of study drug
• History of attempted suicide or suicidal ideation with plan (i.e., active suicidal ideation) that required hospital visit and/or change in level of care within 12 months prior to screening