Study to Evaluate the Safety, Tolerability, Efficacy, and PK of FHL-301 in Parkinson's Disease Patients.

This is a phase 2, double-blind, multi-center, placebo-controlled clinical study to evaluate the safety, tolerability, efficacy, and PK of FHL-301 in adult patients with early-stage PD. Following screening, qualifying patients who meet all inclusion and exclusion criteria will enter the study and be randomized 1:1 to receive FHL-301 or Placebo at a starting dose of 200 mg BID (30 minutes before the morning and evening meals) during the 3-week titration period. To determine the tolerance of each participant for FHL-301, titration will increase by 200 mg BID every week until the maximum dose of 600 mg BID or the highest tolerated dose of 1200 mg daily is reached and maintained for 1 week. Thereafter, patients who complete the dose Titration Phase of the study will enter the Maintenance Phase and remain on the final titrated dose for up to 48 weeks post titration. If at any stage during the titration phase the participant cannot tolerate the increased dose, the dose will be decreased by 100 mg BID weekly until the highest tolerated dose is reached.