Safety, PK and Biodistribution of 18F-OP-801 in Patients With ALS, AD, MS, PD and Healthy Volunteers

Inclusion Criteria: 1. Has the ability to understand and sign the written ICF and local medical privacy authorization forms, which must be obtained prior to the conduct of any study related procedures. 2. Female subjects of non-childbearing potential must be either surgically sterile (hysterectomy, bilateral tubal ligation, salpingectomy, and/or bilateral oophorectomy at least 26 weeks before the Screening Visit) or postmenopausal, defined as spontaneous amenorrhea for at least 2 years, with follicle-stimulating hormone (FSH) in the postmenopausal range at screening, based on the local laboratory's defined ranges. 3. Female subjects of childbearing potential (i.e., ovulating, premenopausal, and not surgically sterile) and all male subjects must agree to practice abstinence from sexual intercourse or use a medically accepted contraceptive regimen (including hormonal contraceptives) during their participation in the study and for 90 days (males) or 6 months (females) after Day 1. Medically accepted contraceptive methods are defined as those with 90% or greater efficacy and are as follows: 1. Male subjects: condoms or surgical sterilization of subject at least 26 weeks before the Screening Visit (i.e., vasectomy). 2. Female subjects: 1. Surgical sterilization at least 26 weeks before the Screening Visit (includes hysterectomy or bilateral tubal ligation, bilateral oophorectomy, or salpingectomy); 2. Intrauterine device or diaphragm with spermicide for at least 12 weeks before the Screening Visit; or 3. Hormonal contraception (oral, implant, injection, ring, or patch) for at least 12 weeks before the Screening Visit. 4. If male, subjects must agree to abstain from sperm donation through 90 days after the Day 1 Visit. 5. Female subjects may not be pregnant, lactating, or breastfeeding. 6. Female subjects of childbearing potential must have negative result for pregnancy test at Screening and Check-in. 7. Subjects must have an estimated glomerular filtration rate (eGFR) of \>45 mL/min/1.73m2 at Screening. 8. C-reactive protein level ≤10 mg/dL. 9. Subjects must be willing and able to abide by all study requirements and restrictions. Inclusion Criteria Specific to ALS Subjects: 10. Adult (Age 18 to 80, inclusive) at the Screening Visit 11. Sporadic or familial ALS diagnosed as possible, laboratory-supported probable, probable, or definite as defined by the modified El Escorial criteria. 12. Forced vital capacity (FVC) of ≥50%; or if in the opinion of the investigator can lay flat for up to 90 minutes. If FVC has been performed within the past 6 months, this data may be used at the discretion of the investigator. 13. For ALS subjects, medication changes within 30 days prior to the Screening Visit should be discussed with the Medical Monitor. Inclusion Criteria Specific to AD Subjects 14. Adult (Age 40 to 80, inclusive) at the Screening Visit 15. Clinical diagnosis of early stage dementia, Alzheimer type, plus positive Aβ and tau PET imaging, cerebrospinal fluid (CSF) and/or plasma biomarkers consistent with 2018 NIA-AA criteria 16. MMSE score \>20 at Screening 17. AD medication changes within 30 days prior to the Screening Visit should be discussed with the Medical Monitor. Inclusion Criteria Specific to MS Subjects: 18. Adult (Age 18 to 70, inclusive) at the Screening Visit 19. MS medication changes within 30 days prior to the Screening Visit should be discussed with the Medical Monitor. Inclusion criteria specific to subjects with RRMS: 20. Diagnosis of RRMS based on 2017 McDonald criteria 21. If not newly diagnosed, subjects should have at least 1 documented relapse in the last 24 months. 22. "Active disease" subjects should have at least 1 Gadolinium-enhancing (Gd+) T1-weighted brain or spinal cord lesion at Screening MRI. 23. "Disease in remission" subjects should have no Gd+ T1-weighted brain or spinal cord lesions at Screening MRI and stable clinical symptoms for at least 3 months prior to Day 1. 24. EDSS score between 2.0 and 5.5 inclusive at Screening Inclusion criteria specific to subjects with progressive MS: 25. Diagnosis of PPMS or SPMS based on 2017 McDonald criteria 26. EDSS score between 3.0 and 6.5 inclusive at Screening 27. No evidence of relapse in the prior 6 months 28. Neurological exam and symptom stability for ≥30 days prior to Day 1 29. Documented evidence of disability progression in the past 24 months not temporally related to a relapse Inclusion Criteria Specific to PD Subjects: 30. Adult (Age 55 to 80, inclusive) at the Screening Visit 31. Diagnosis of definite, idiopathic Parkinson's disease according to UK Parkinson's Society Brain Bank diagnostic criteria 32. PD medication changes within 30 days prior to the Screening Visit should be discussed with the Medical Monitor. Overall Exclusion Criteria - For All Subjects: Subjects meeting any of the following criteria will be excluded from this study: 1. Body weight \>120 kg 2. Evidence of clinically significant or past medical history of hematologic, renal, endocrine, pulmonary, cardiac, gastrointestinal, hepatic, psychiatric, neurologic, immunologic, allergic disease (including multiple or clinically significant drug allergies) or any other condition that, in the opinion of the Investigator, might significantly interfere with the absorption, distribution, metabolism or excretion of study drug or place the subject at an unacceptable risk as a participant in this study 3. History of recurrent kidney or liver malignancy 4. Pacemaker or defibrillator or any non-removable metallic foreign objects in the body not compatible with MRI 5. Inability to lie in a PET/CT or PET/MRI scanner for up to 90 minutes at a time 6. Laboratory results (serum chemistry, hematology, coagulation and urinalysis) outside the normal range at Screening and Check-In and considered clinically significant in the opinion of the Investigator. Any elevation of aspartate transaminase (AST) and alanin