Longitudinal Investigation of I2BS in PD

Inclusion criteria * All subjects must be judged by the investigator able to understand the nature, design, and procedures of the study and must be able to provide a signed and dated informed consent in accordance with Good Clinical Practice (GCP), International Conference on Harmonization (ICH), and local regulations. * All subjects must be willing and able to comply with scheduled visits, required study procedures and laboratory tests. * All subjects must be able to travel to the research sites for the study procedures. * Age 25 years or older. * For female subjects: They must be either of non-childbearing potential (either surgically sterile or post- menopausal - defined as 12 months of spontaneous amenorrhea), or, if of childbearing potential, subjects must demonstrate to be non-pregnant (as demonstrated by negative urine β-HCG test at screening), non-breastfeeding. * All subjects must comply with highly effective contraceptive measures. A highly effective contraceptive measure is defined as a measure that can achieve a failure rate of less than 1% per year when used consistently and correctly. These methods are listed in more detail below: Oral, intravaginal, or transdermal combined (estrogen and progestogen containing) hormonal contraception associated with inhibition of ovulation; Oral, injectable, or implantable progestogen-only hormonal contraception associated with inhibition of ovulation: Intrauterine device (IUD) Intrauterine hormone-releasing system (IUS) Bilateral tubal occlusion Vasectomised partner Sexual abstinence * For sexually active male subjects, they must agree to use condoms to protect their partners from becoming pregnant for the duration of the study and for 3 months after the last administration of PET or SPECT ligands. They must also agree to ensure that they and their partners are routinely using a medically approved contraceptive method. It is important that male subjects not impregnate others for the duration of the study and for 3 months after the last administration of PET or SPECT ligands. * All subjects must have adequate visual and auditory acuity according to investigator's judgement to complete the psychological testing. * All subjects must have no use of medications with known interaction with I2BS (e.g. idaxozan, efaroxan, yohimbine, atomoxetine, atipamezole, mianserin, mirtazapine, clonidine, guanfacine, guanabenz, guanethidine, xylazine, tizanidine, tedetomidine, methyldopa, fadolmidine, dexmedetomidine) * For subjects taking any drugs that might interfere with dopamine transporter SPECT imaging (neuroleptics, metoclopramide, alpha methyldopa, methylphenidate, reserpine, or amphetamine derivative) must be willing and able from a medical standpoint to hold the medication for at least 5 half-lives prior to screening DaTSCANä imaging. Exclusion criteria * Subjects lacking capacity according to investigator's judgment; * Subjects with a clinical diagnosis of dementia as determined by the investigator; * Subjects with current or a recent history of drug or alcohol abuse/dependence; * Current treatment with anticoagulants (e.g. warfarin, heparin) that might preclude the arterial cannulation and the safe completion of the lumbar puncture. * Condition that precludes the safe performance of routine lumbar puncture, such as prohibitive lumbar spinal disease, bleeding diathesis, or clinically significant coagulopathy or thrombocytopenia. * Negative Allen test in both hands, * Use of any of the following drugs that might interfere with dopamine transporter SPECT imaging: neuroleptics, metoclopramide, alpha methyldopa, methylphenidate, reserpine, or amphetamine derivative, within 5 months of Screening. * Use of any medications with known actions on I2BS (e.g. idaxozan, efaroxan, yohimbine, atomoxetine, atipamezole, mianserin, mirtazapine, clonidine, guanfacine, guanabenz, guanethidine, xylazine, tizanidine, tedetomidine, methyldopa, fadolmidine, dexmedetomidine); * Use of investigational drugs or devices within 60 days prior to Baseline (dietary supplements taken outside of a clinical trial are not exclusionary, e.g., coenzyme Q10). * History of cancer within the last 5 years, with the exception of non-metastatic basal cell carcinoma of the skin. * Subjects with current or recent history of drug or alcohol abuse/dependence. * Contraindication to MRI, such as presence of metal devises or implants (e.g. pacemaker, vascular- or heart- valves, stents, clips), metal deposited in the body (e.g. bullets or shells), or metal grains in the eyes; * Claustrophobia or history of back pain that makes prolonged laying on the PET, SPECT, or MRI scanner intolerable. * Previously obtained MRI scan with evidence of clinically significant neurological disorder (in the opinion of the Investigator). * Presence of any clinically significant medical condition (including cardiovascular, respiratory, cerebrovascular, hematological, hepatic, renal, gastrointestinal, or other disease) that, based on the judgment of the investigator, is clinically unstable, is likely to deteriorate during the course of the study, could put the patient at risk because of participation in the study, could affect the subject's ability to complete the study, or could influence the study results; * History of suicidal behavior or active suicidal ideation; * Pregnancy or breastfeeding or intent to become pregnant in the next 18 months;