Efficacy, Safety, Tolerability, and Biomarker Effects of GT-02287 in Early Parkinson's Disease

Inclusion Criteria: * Able and willing to provide written informed consent and willing to comply with the requirements and restrictions of the study * Willing to undergo PD-related genetic testing and analysis * Any sex, ≥30 and ≤85 years of age * Body mass index of ≥18 and ≤40 kg/m2 and a body weight of at ≥55 kg and \<120 kg at Screening * Diagnosis of PD based on MDS criteria * Within 5 years of PD diagnosis * Positive SAA in CSF at Baseline * Hoehn \& Yahr 1-2.5, inclusive * Naïve to pharmacological treatment for PD with no initiation of dopaminergic treatment expected during the first 9 months of the study or on stable PD medication for ≥3 months prior to Screening, including ≥4 weeks at the same dose(s) immediately before Screening with no changes to dose(s), or medication(s) expected during the first 9 months of the study * Not pregnant or breastfeeding * If participant is either of childbearing potential or produces potentially viable sperm, participant must agree to use 2 forms of contraception (barrier method and a second highly effective form of birth control/contraception, as defined in the protocol) if engaging in potentially reproductive intercourse (with a partner who produces potentially viable sperm or is of childbearing potential, respectively) * Agreeing not to participate in another investigational study while taking part in this study Exclusion Criteria: * Other neurological disorders, including but not limited to Alzheimer's disease, amyotrophic lateral sclerosis, frontotemporal dementia, progressive supranuclear palsy, corticobasal syndrome, Huntington's disease, multiple system atrophy, dementia with Lewy bodies, secondary (e.g. drug-induced) parkinsonism, multiple sclerosis, or epilepsy * PD-associated LRRK2 pathogenic variant or other PD-associated genetic mutations other than GBA1 * Severe motor fluctuations and/or disabling dyskinesias based on the investigator's clinical assessment * Deep-brain stimulation * Hallucinations, delusions, or other psychotic symptoms requiring antipsychotic medication Use of dopamine antagonists (antipsychotics) or anticholinergic medications * Dementia by clinical diagnosis and/or a MoCA score of ≤20 and/or a history of behavioral impairment * Hypersensitivity to GT 02287 or any of its excipients * Concomitant medications including drugs metabolized primarily by CYP3A4 that have a narrow therapeutic window, substrates of BCRP that have a narrow therapeutic window, strong or moderate inhibitors or strong inducers of CYP3A4 that could affect the metabolism and plasma levels of GT 02287, including herbal supplements and certain foods. * Concomitant disease including, but not limited to cardiovascular conditions, diabetes, autoimmune disease, cancer, active infectious disease, psychotic disorders and symptoms, depressive symptoms, drug and/or alcohol misuse as defined in the protocol * Clinically significant abnormalities in laboratory test * Contraindications to lumbar puncture (LP) including current treatment with anticoagulants or any other contraindications that might preclude safe completion of the LP * Blood donation \>500 mL within 3 months * Malabsorption or relevant disorder which may impact the absorption of GT-02287 * Participation in any interventional clinical study within 3 months or 5 half-lives, whichever is longer, prior to Screening