Patient description: A 22-year-old Caucasian man came to the Clinic with a history of tremors since a year ago. The tremor was first in his right hand while holding something. Later the tremor became continuous and extended to both hands and legs and even at rest. The Kayser-Fleischer' ring was detected in the ophthalmologic exam. The physical exam revealed jaundice, hepatosplenomegaly and hypotonia of the upper limbs. He had a constant smile on his face, however, he has aggressive behavior according to his parents' explanation. His laboratory study was significant for a low serum caeruloplasmin (0.05 g/l), and a raised 24 hour urine copper excretion (120 μg/24 h). Wilson disease was confirmed by high liver copper concentration (305 μg/g dry weight of liver).

Clinical trial eligibility criteria: eligible ages (years): 18.0-80.0,  Essential Tremor Participant has a diagnosis of ET, defined as isolated tremor syndrome consisting of bilateral upper limb action tremor for at least 3 years prior to screening, with or without tremor in other locations and absence of other neurological signs, such as dystonia, ataxia, or parkinsonism, isolated focal tremors (eg, voice, head), task and position-specific tremors, sudden tremor onset or evidence of step-wise deterioration of tremor Participant scores at least 1.5 for each of the six items that comprise the combined total upper limb (total performance subscale part 4) with the total score for the dominant upper limb (the sum of the three items for either the right or left upper limb, whichever is dominant) being at least 5.5, at both Screening and predose on Day 1 Participant is willing to discontinue medications taken for the treatment of ET within 14 days or 5 half-lives prior to receiving IP. Medications taken for the treatment of ET that were discontinued prior to receiving IP may be resumed following Day 29 Participant has no clinically significant findings, as determined by the investigator, on Screening and pre-dose Day 1 physical examination including mental state examination (MSE) and neurologic examination, 12-lead electrocardiogram (ECG), or screening clinical laboratory tests  Participant has a presence of known causes of enhanced physiological tremor Participant has had recent exposure (14 days prior to Day 1) to tremorgenic drugs Participant has had direct or indirect injury or trauma to the nervous system within 3 months before the onset of tremor Participant has had a previous procedure for the treatment of ET, deep brain stimulation, brain lesioning, or magnetic resonance (MR)-guided procedure, eg, MR-guided focused ultrasound Participant has historical or clinical evidence of tremor with psychogenic origin (including but not limited to eating disorders, major depression, etc.) Participant has history of suicidal behavior within 2 years or answers "YES" to questions 3, 4, or 5 on the Columbia-Suicide Severity Rating Scale (C-SSRS) at Screening or at Day 1 or is currently at risk for suicide in the opinion of the investigator Participant has used any known moderate or strong cytochrome P450 3A4 and/or inducers within 14 days or 5 half-lives (whichever is longer) prior to Day 1 or consumed grapefruit juice, grapefruit, Seville oranges, pomegranates, tangelos, or St. John's Wort or products containing these within 30 days prior to Day 1. Use of mild cytochrome inhibitors and/or inducers may be permitted Participant has concurrent or recent exposure (14 days or 5 half-lives, whichever is longer, prior to the Day 1 visit) to sedative/hypnotic drugs, stimulants, highly-caffeinated beverages or dietary supplements containing high doses of caffeine, or recent increase above regular daily consumption of caffeine Participant currently uses or has used within 14 days or 5 half-lives (whichever is longer) prior to Day 1, any prescription or over-the-counter medication that is a substrate of the OATP1B1 transporter