This is a Phase I, investigator-initiated, first-in-human study to evaluate the safety, tolerability, and pharmacokinetics of MF1, a novel agent that is expected to inhibit α-synuclein related pathogenesis in α-synucleinopathies, primarily Parkinson's disease (PD). MF1 aims to address the unmet medical need in PD, which affects about 1% of individuals aged 60 years and older in Japan and is projected to reach 43 million patients worldwide by 2050.

The trial consists of three parts: Part A (single ascending dose) and Part B (multiple ascending dose) in healthy Japanese male adults, and Part C (multiple dose) in patients with idiopathic PD. Part A is a randomized, double-blind, placebo-controlled, single-center study assessing single oral doses , including a food-effect evaluation. Part B is a randomized, double-blind, placebo-controlled, single-center study with once-daily dosing for 7 days. Part C is an open-label, multicenter study in 4-8 PD patients (MDS 2015 criteria, Hoehn & Yahr stage ≤3) receiving once daily for 14 days, with or without stable background antiparkinsonian therapy.

The primary objective is to assess safety and tolerability; secondary objectives include characterization of plasma, urine, and cerebrospinal fluid pharmacokinetics and assessment of food effect. Exploratory pharmacodynamic endpoints include biomarkers such as α-synuclein, neurofilament light chain, UCHL-1, FABP3, GFAP, and other neurodegeneration markers.

Key exclusion criteria include clinically significant systemic diseases, seizure history, serious infections (HBV, HCV, HIV, syphilis), recent suicidal ideation or attempts, and recent use of other investigational products.

• α-Synucleinopathies are a group of progressive neurodegenerative diseases caused by the pathological aggregation and prion-like propagation of α-synuclein protein, culminating in selective neuronal loss. Parkinson's disease (PD) represents the most prevalent form, affecting approximately 1% of individuals aged 60 years and older in Japan, with the global burden projected to reach 43 million patients by 2050. Despite decades of research, currently approved therapies remain restricted to symptomatic management targeting dopaminergic deficits and do not address the underlying mechanisms of α-synuclein misfolding, oligomerization, or cell-to-cell spread. No disease-modifying, neuroprotective, or neurorestorative therapy has been approved to date, representing a critical unmet medical need.
• MF1 is a novel investigational agent designed to target the pathophysiological mechanisms underlying α-synucleinopathy. Preclinical studies have demonstrated that MF1 inhibits α-synuclein aggregation and reduces neuroinflammatory cascades associated with dopaminergic neurodegeneration. Based on its mechanism of action, MF1 is expected to be a novel therapeutic agent targeting these pathological mechanisms, with the potential to confer both neuroprotective effects and clinically meaningful symptomatic benefits, thereby addressing this unmet medical need.
• This First-in-Human (FIH) Phase I trial employs a stepwise dose-escalation approach across three sequential parts to characterize the safety, tolerability, and pharmacokinetic (PK) profile of MF1. The three-part sequential dose-escalation design, incorporating single ascending doses (Part A) and multiple ascending doses (Part B) in healthy adult volunteers, followed by evaluation in a patient cohort (Part C), is consistent with established first-in-human (FIH) best practices and ensures systematic safety data review prior to advancement to each subsequent study part.
• The restriction to healthy Japanese males aged 18-44 years with BMI 18.5 to <25.0 kg/m² in Parts A and B is intended to minimize confounding variables during initial safety and PK characterization. Given that MF1 is intended for a patient population with a higher average age and potential co-morbidities, Part C enrolls patients with idiopathic PD under a more inclusive age range (40-84 years) and permits concomitant use of select stable antiparkinsonian medications to reflect real-world treatment conditions. The restriction to Hoehn & Yahr stage ≤3 ensures that participants retain sufficient functional capacity for protocol compliance and limits confounding from advanced disease-related physiological changes.
• Food effect assessment in Part A is incorporated to characterize the influence of food intake on oral bioavailability of MF1, which will inform dosing recommendations for subsequent studies. CSF sampling in a subset of participants is planned to assess CNS penetration of MF1, a critical pharmacological prerequisite for a CNS-targeted agent. Exploratory pharmacodynamic assessments include established fluid biomarkers of neuronal injury and glial activation (α-synuclein, Nf-L, UCHL-1, FABP3, GFAP), which will provide mechanistic evidence of target engagement and serve as early signals for neuroprotective activity.
• The primary objectives of Part C are to assess the safety and tolerability profile in a small number of elderly subjects and to obtain pharmacokinetic data in this patient population, which will serve to support rational dose selection for subsequent phases of clinical development.

Inclusion Criteria:

(Parts A and B)

• 1)Healthy Japanese male adults aged >=18 and <45 years at the time of informed consent.
• 2) Subjects with a body mass index (BMI) of >=18.5 and <25.0 kg/m2 at screening.
• 3) Subjects who have received sufficient explanation regarding the study from the principal investigator or subinvestigator, have understood the objectives of the study, voluntarily agreed to participate, and have provided written informed consent of their own free will.

(Part C)

• 1) Patients diagnosed with idiopathic Parkinson's disease according to the International Parkinson and Movement Disorder Society (MDS) Clinical Diagnostic Criteria (2015).
• 2) Patients with Parkinson's disease classified as Stage 3 or below according to the modified Hoehn and Yahr staging scale.
• 3) Patients who are either untreated or have been receiving one of the following treatments at a stable dosage regimen for at least 8 weeks prior to screening, with no planned changes during the study period: selegiline up to 5 mg twice daily, rasagiline up to 1 mg once daily, or immediate-release carbidopa/levodopa up to 25/100 mg three times daily.
• 4) Patients with an average Bristol Stool Scale score of <=3 from the date of informed consent to eligibility assessment, or patients with fewer than two bowel movements per week.

If the period between informed consent and eligibility assessment is less than one week, information prior to informed consent will also be collected to assess bowel conditions for at least one week in total.

• 5) Male or female patients aged >=40 and <85 years at the time of informed consent.
• 6) Patients with a BMI of >=18.5 and <32.0 kg/m2 at screening.
• 7) Female patients who are postmenopausal for at least one year at the time of informed consent, including menopause resulting from hysterectomy or oophorectomy.
• 8) Patients who have received sufficient explanation regarding the study from the principal investigator or subinvestigator, have understood the objectives of the study, voluntarily agreed to participate, and have provided written informed consent of their own free will.

Exclusion Criteria:

(Parts A and B)

• 1) Subjects with clinically significant cardiovascular, neurological, pulmonary, hepatic, renal, metabolic, gastrointestinal, urological, immunological, endocrine, or psychiatric disorders, or any other abnormalities that may affect safety, increase seizure risk, lower seizure threshold, or confound study results.
• 2) Subjects with current or past diseases or surgical histories involving the gastrointestinal tract, liver, kidneys, or other organs that may affect drug absorption, metabolism, or excretion.
• 3) Subjects who used any medication, including over-the-counter drugs, within 7 days prior to the day before the first administration of the investigational product.
• 4) Subjects with seizure disorders such as epilepsy, or a history thereof.
• 5) Subjects with allergies or a history of allergies to drugs or foods.
• 6) Subjects with allergic predisposition who are considered unsuitable for participation by the principal investigator or subinvestigator.
• 7) Subjects with current or past alcohol or drug dependence.
• 8) Subjects who donated >=400 mL of whole blood within 12 weeks, >=200 mL of whole blood within 4 weeks, or blood components within 2 weeks prior to investigational product administration.
• 9) Subjects who tested positive at screening for HBs antigen, HCV antibody, HIV antigen/antibody, or syphilis serology (TP antibody test or RPR test).
• 10) Subjects unwilling to use appropriate contraception from the time of informed consent until the final study visit.
• 11) Subjects who answered "Yes" to Question 4 or 5 regarding suicidal ideation on the Columbia-Suicide Severity Rating Scale (C-SSRS) at screening, or who had a history of suicidal behavior within 6 months prior to screening.
• 12) Subjects who received investigational treatment in another clinical trial within 4 months prior to investigational product administration.
• 13) Subjects judged unsuitable for study participation by the principal investigator or subinvestigator based on findings from screening or admission assessments, observations, or examinations.

(Part C)

• 1) Patients with drug-induced parkinsonism, metabolic neurogenetic disorders, encephalitis, Parkinson-plus syndromes, or other atypical parkinsonian syndromes.
• 2) Patients with freezing of gait.
• 3) Patients with a history of stereotactic brain surgery for Parkinson's disease (e.g., pallidotomy, deep brain stimulation, or fetal tissue transplantation).
• 4) Patients with clinically significant cardiovascular, neurological, pulmonary, hepatic, renal, metabolic, gastrointestinal, urological, immunological, endocrine, or psychiatric disorders other than Parkinson's disease, or any other abnormalities that may affect safety, increase seizure risk, lower seizure threshold, or confound study results.
• 5) Patients with current or past diseases or surgical histories involving the gastrointestinal tract, liver, kidneys, or other organs that may affect drug absorption, metabolism, or excretion.
• 6) Patients with seizure disorders such as epilepsy, or a history thereof.
• 7) Patients currently receiving antiplatelet agents or anticoagulants.
• 8) Patients with allergies or a history of allergies to drugs or foods.
• 9) Patients with allergic predisposition who are considered unsuitable for participation by the principal investigator or subinvestigator.
• 10) Patients with current or past alcohol or drug dependence.
• 11) Patients who donated >=400 mL of whole blood within 16 weeks, >=200 mL of whole blood within 4 weeks, or blood components within 2 weeks prior to investigational product administration.
• 12) Patients who tested positive at screening for HBs antigen, HCV antibody, HIV antigen/antibody, or syphilis serology (TP antibody test or RPR test).
• 13) Patients unwilling to use appropriate contraception from the time of informed consent until the final study visit.
• 14) Patients who answered "Yes" to Question 4 or 5 regarding suicidal ideation on the Columbia-Suicide Severity Rating Scale (C-SSRS) at screening, or who had a history of suicidal behavior within 6 months prior to screening.
• 15) Patients who received investigational treatment in another clinical trial within 4 months prior to investigational product administration.
• 16) Patients judged unsuitable for study participation by the principal investigator or subinvestigator based on findings from screening or admission assessments, observations, or examinations.

De-identified individual participant data (IPD) underlying the primary and key secondary outcome analyses may be shared with qualified researchers and collaborating pharmaceutical companies for the purpose of further development of the investigational product and related scientific research. IPD will be made available after completion of the primary analysis and publication of the main results of this trial, subject to approval by the investigator. Data will be provided in a de-identified format in which direct identifiers are removed and indirect identifiers are processed according to our institutional data protection policy, so that individual participants cannot reasonably be re-identified. Access to IPD will require a written research proposal, a data use agreement specifying the scope of use, data security measures, and prohibition of attempts at re-identification or unauthorized sharing of the data.