A Dose Range Finding Study With Open-Label Extension to Evaluate the Safety of Oral LMI070/Branaplam in Early Manifest Huntington's Disease

Inclusion Criteria * Signed informed consent must be obtained prior to participation in the study. * Clinically diagnosed Stage 1 or 2 Huntington's disease with a diagnostic confidence level (DCL) = 4 and a United Huntington's Disease Rating Scale (UHDRS) Total Functional Capacity (TFC) \>8 at screening. * Genetically confirmed Huntington's disease, with presence of ≥40 cytosine-adenineguanine (CAG) repeats in the huntingtin gene. * Male and female participants between 25 to 75 years of age, inclusive, on the day of Informed Consent signature. Exclusion Criteria * Prior participation in clinical trial investigating a huntingtin-lowering therapy (unless participant received only placebo). * Participants taking medications prohibited by the protocol. * Any medical history, lumbar surgery or condition that would interfere with the ability to complete the protocol specified assessments. * Participant has other severe, acute or chronic medical conditions including unstable psychiatric conditions, or laboratory abnormalities that in the opinion of the Investigator may increase the risk associated with study participation, or that may interfere with the interpretation of the study results. * Any surgical or medical condition which might put the participant at risk in case of participation in the study. The Investigator should make this determination in consideration of the participant's medical history and/or clinical or laboratory evidence at the Screening visit.