**D-SPARK: A Clinical Trial of D-Serine for Parkinson's Disease** This study tests if a substance called D-serine can help people with Parkinson's disease, a condition that affects movement. **Parkinson's disease (PD)** is a brain disorder that affects movement, causing tremors, stiffness, and balance problems. This trial is **randomized, double-blind, and placebo-controlled.** This means participants are randomly placed into groups, neither participants nor researchers know who gets the real treatment or a fake one (placebo). Participants will take D-serine, or a placebo, for 58 weeks, followed by 12 weeks without any treatment. They will have tests to see how well D-serine works, including movement tests and brain scans. This study involves 100 people diagnosed with PD within the last 5 years. **Key Points:** - **Duration:** 58 weeks of treatment, plus 12 weeks of follow-up. - **Tests and Visits:** Movement tests, brain scans, blood samples, and cognitive assessments. - **Eligibility:** Must be diagnosed with PD within 5 years, aged 40-80, and not have severe other health issues. The study could show that D-serine helps reduce PD symptoms, potentially benefiting patients and their families.