Additional Study Information: The DIMENSION Study is evaluating the safety and effect on cognitive symptoms of an investigational oral drug in adults with early Huntington's disease. Cognitive symptoms may include difficulty paying attention or trouble thinking through steps of an activity or complex problems. Symptoms may also include difficulty planning, remembering, and staying on task, impaired judgment, and difficulty multi-tasking. There will be an open-label extension (OLE) study, which is planned to begin later in 2022. Participants who are interested can speak to the study team. To be eligible for the study, you must: be 25 to 65 years of age, have been diagnosed with early Huntington's disease, and be ambulatory (able to walk). The study doctor will discuss additional eligibility requirements. If you qualify and decide to participate: a study doctor will closely monitor you, your symptoms, and your overall health. All study-related procedures and the investigational drug will be provided at no cost. Transportation assistance may be available, if needed. You may invite a study partner to attend study visits and help you complete study activities. Your participation in the DIMENSION Study is completely voluntary. If you decide to participate in this research study, you are free to withdraw at any time, for any reason, without any penalty or effect on your medical care. Talk to your doctor if you have any questions about Huntington's or its symptoms.