A Study to Evaluate the Efficacy and Safety of Safinamide Mesilate as Add-on Therapy to Levodopa in Parkinson's Disease Participants With Motor Fluctuation in South Korea

1. Male or female, age greater than or equal to (>=) 19 years at the time of informed consent

2. Participants who meet the clinical diagnostic criteria of Movement Disorder Society (MDS) diagnostic criteria 2015 for Parkinson's disease, have motor fluctuations with >=1.5 hours of "off" time throughout the day which is confirmed at the time of Screening, and take levodopa 3 or more times a day

3. Parkinson's Disease participants who are receiving levodopa without Catechol O-methyltransferase (COMT) inhibitor and/or Monoamine oxidase-B (MAO-B) inhibitor

4. Be able to maintain an accurate and complete diary with the help of a caregiver as needed, recording "on" time, "on" time with dyskinesia, "off" time, and time asleep

5. Be able to provide written informed consent

6. Participants whose cognitive function, at the discretion of an investigator, is at a level appropriate to participate in the clinical trial (that is., with a Global Deterioration Scale [GDS] score of 3 or less or a Clinical Dementia Rating [CDR] of 0.5 or less within 3 months prior to screening)

1. Females who are planning for pregnancy, pregnant or breastfeeding

2. Prior use of safinamide

3. If participants have previously taken medication such as COMT inhibitor and/or MAO-B inhibitor, they have to take appropriate wash-out period for each medication (3 days for COMT inhibitor; 14 days for MAO-B inhibitor)

4. Use of medications for depression or psychosis within 5 weeks prior to screening

5. History of allergic response to levodopa, or other anti-Parkinsonian agents

6. Hypersensitivity or contraindications to MAO-B inhibitors

7. Confirmed ophthalmologic history including any of the following conditions: albino participants, family history of hereditary retinal disease, progressive and/or severe diminution of visual acuity (that is, 20/70 on Snellen Chart), retinitis pigmentosa, retinal pigmentation due to any cause, any active retinopathy or ocular inflammation (uveitis), or diabetic retinopathy

8. Participants who did not consent to having at least 7 days of washout period prior to visit 2, if known to take narcotic analgesics 7 days prior to screening visit (example, pethidine hydrochloride-containing products, tramadol hydrochloride, or tapentadol hydrochloride)

9. History of serotonergic medications administration (example, tricyclic antidepressants, tetracyclic antidepressants, selective serotonin reuptake inhibitors, serotonin-noradrenaline reuptake inhibitors, selective noradrenaline reuptake inhibitor, or noradrenergic and serotonergic antidepressant) within 5 weeks prior to screening visit

10. Administering central nervous system stimulants (example, methylphenidate hydrochloride, lisdexamfetamine mesilate)

11. Administering dextromethorphan

12. Participants with clinically significant liver function abnormalities defined as greater than (>) 1.5 times of the upper limit of the normal range of total bilirubin or >3 times of the upper limit of the normal range of Alanine Aminotransferase (ALT) or Aspartate Aminotransferase (AST); re-examination and re-screening are allowed once within the screening period

13. Have a history of hypersensitivity to any of the ingredients of the product

14. Currently enrolled in another clinical trial or used any investigational drug/biologics or device within 30 days or 5*the half-life, whichever is longer, preceding informed consent