This clinical study is testing a new drug called **SUL-238** for people with early, untreated Parkinson's Disease (PD). The study uses a special scan called **MRS** (like an MRI) to see how the drug affects brain chemicals related to energy called phosphates. The drug is compared to a **placebo**, which looks like the drug but has no active ingredients. The study will last for about 12 weeks, including a 4-week treatment period. During this time, participants will take SUL-238 or the placebo daily and visit the clinic every two weeks for checkups. Participants will also need to keep a diary about their symptoms and any side effects. **Key Points:** - Duration: Approximately 12 weeks, with 4 weeks of daily treatment. - Clinic Visits: Every two weeks during treatment and a final visit 28 days after the last dose. - Participants must fast (no eating) before some doses and tests. This study checks if SUL-238 improves brain energy and what side effects might occur. Participants must be at least 40 years old, recently diagnosed with PD, and willing to follow study rules.