The aim of this clinical trial is to explore the potential of novel 2nd generation tau PET radiotracers as biomarkers in cases suggestive of progressive supranuclear palsy (PSP), an atypical form of parkinsonism.

Phase II, uncontrolled, single-center, uncontrolled, drug-controlled clinical trial for the evaluation of a diagnostic test (PI-2620).

Inclusion Criteria:

For all patients:

• Patients of both sexes between 40 and 80 years of age.
• The subject must be able to comply with the protocols and procedures necessary for the development of the clinical trial.
• Conformity of the subject or his/her legal representative to voluntarily participate in the study by signing the informed consent form.
• In women, postmenopausal status (one year without menstruation without other medical causes) or negative pregnancy test. Subjects (women and partners of male of childbearing age must accept the commitment to practice sexual abstinence or use highly effective contraceptive methods (hormonal contraceptives that inhibit ovulation, IUD, surgical sterilization) from their inclusion in the study up to one month after the PET scan.

For PSP patients:

• Have a clinical diagnosis of probable soPSP or PSP according to current diagnostic criteria (Höglinger et al. current diagnostic criteria (Höglinger et al. 2017).
• Magnetic resonance imaging (MRI) study that rules out any other relevant neurological pathology. relevant neurological pathology.

For Parkinson patients:

• To have a clinical diagnosis of Parkinson's disease according to established criteria (Postuma et al. 2015).
• Magnetic resonance imaging (MRI) study that rules out any other relevant neurological pathology.

For control patients:

- Absence of clinical history of neuropsychiatric disease.

Exclusion Criteria:

For all patients:

• Diagnosis of relevant central nervous system disease such as:

Huntington's disease, normotensive hydrocephalus, cerebrovascular disease, frontotemporal dementia, Alzheimer's disease, history of major or recurrent traumatic brain injury, history of epilepsy or seizures history of major or recurrent traumatic brain injury, history of epilepsy or seizures(except febrile seizures in childhood without current antiepileptic medication).

• Presence of terminal illness or illnesses that may put the patient's health at risk by participating in the the patient's health by participating in the study or influencing the results of the study or the patient's or on the patient's ability to participate in the study.
• Abuse of alcohol or other legal or illegal drugs (except nicotine).
• Pregnancy.
• Known allergy to PI-2620 or any of the other components of the radiopharmaceutical.
• Any contraindication or impediment to the performance of the PET/CT study with PI-2620.

with PI-2620.

• Subjects who are not capable of understanding and/or complying with the guidelines necessary for the performance of the test (e.g.: interrogation, physical examination, attending the lumbar puncture, attending the visits, etc.) and who do not have responsible accompanying persons who understand and are committed to complying with these guidelines.
• Subjects who do not cooperate or are not capable of complying with the required procedures required for this clinical trial, such as (but not limited to): social disorders that anticipate an evident lack of collaboration, psychopathy, drug or alcohol abuse.
• Subjects or their legal representatives who do not sign the informed consent.
• Legal incapacity and/or circumstances that prevent the subject or his/her legal representatives from understanding the nature, objectives, potential and possible consequences of the trial.
• Treatment with any other investigational drug in the 30 days prior to inclusion.

For PSP patients:

- Diagnosis or suspicion of any parkinsonian syndrome other than PSP such as idiopathic Parkinson's disease, pharmacological parkinsonism, essential tremor, primary dystonias or any other cause that may produce symptoms similar to those of Parkinson's disease.