RecruitingPhase 2Drug trialLow-dose Carbon Monoxide (HBI-002) Trial to Evaluate Safety, Tolerability, PK, and Biomarkers in Parkinson's DiseaseA phase 2a multicenter, randomized, double-blind, placebo-controlled multiple dose study to evaluate the safety, tolerability, pharmacokinetics, of HBI-002, an oral low-dose carbon monoxide (CO) liquid drug product, administered daily over 14 days in subjects with Parkinson's disease (PD).