A Two-Part Single and Multiple Ascending Dose Trial of the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of LBT-3627 in Healthy Participants and in Participants With Parkinson's Disease.

Evaluate the safety and tolerability of LBT-3627 in both a single and multiple ascending dose study.

Phase Ia will explore safety and tolerability first in healthy volunteers then followed by Parkinson's patients after a single dose. Dose levels will escalate per cohort.

Phase Ib will explore safety and tolerability in Parkinson's patients after multiple doses. Dose levels will escalate per cohort.

Both cohorts (Healthy Volunteers and Parkinson's Disease)

Key inclusion criteria

• Male or female, 30-89 years inclusive at screening
• BMI 18-32 kg/m²
• Vital signs, ECG (QTcF <450 ms male / <470 ms female), and safety labs without clinically significant abnormality; no orthostatic hypotension
• Women of non-childbearing potential, or using highly effective contraception per protocol

Key exclusion criteria

• Immunomodulators / steroids - HV: any (incl. OTC) within 90 days; PD: systemic within 60 days and topical/nasal-inhaled OTC within 7 days (both waivable only with Sponsor approval)
• Vaccine within 60 days (HV) / 45 days (PD) of first dose
• CoQ10 within 5 days
• Inadequate renal function (CrCl ≤ 60 mL/min; ≤ 79 if HV under 40), or LFTs / bilirubin > 1.5× ULN
• Clinically significant cardiovascular, hepatic, renal, neurological, or psychiatric disease
• Active infection requiring systemic anti-infectives within 14 days; positive HBV/HCV/HIV serology

Parkinson's Disease participants - additional key inclusion criteria

• PD diagnosis by a neurologist/geriatrician, 6 months to < 11 years before first dose, per MDS clinical diagnostic criteria
• Hoehn & Yahr stage 1-3
• If on levodopa: stable ≥ 2 months and able to withhold ≥ 12 hours (overnight) around dosing/assessments; if not, remain treatment-naïve through end of study

Parkinson's Disease participants - additional key exclusion criteria

• Prior PD brain surgery, focused ultrasound, or neuromodulation; no anti-amyloid/anti-tau biologics
• Antibiotics within 30 days; OTC pre/probiotics; ≥ 3 unexplained falls in 12 months

Note: Additional protocol-defined criteria apply.