Randomized Placebo Controlled Trial Evaluating the Efficacy of Pimavanserin, a Selective Serotonin 5-HydroxyTryptamine-2A (5HT2A) Inverse Agonist, to Treat Impulse Control Disorders in Parkinson's Disease.

Inclusion Criteria:

1. Patient with PD according to the UKPDSBB criteria for at least 1 year beforerandomization

2. Patient, man or woman, aged from 35 to 75 years old

3. Patient with moderately severe ICD assessed by QUIP-RS (each item being rated 0-16)defined as:

• a combined ICD total score (defined as the sum of the 4 ICD sub-scores (pathological gambling + buying + hypersexuality + eating)) superior or equalto 10 or,

• at least one of the 4 ICD sub-scores in the following range:

1. "pathological gambling" sub-score from 6 to 12 (included),

2. "buying" sub-score from 8 to 12 (included),

3. "hypersexuality" sub-score from 8 to 12 (included),

4. "eating" sub-score from 7 to 12 (included) (Weintraub et al., 2012). Theuse of "lower" margins will guarantee that the patient experiencesbehavioral disturbances severe enough to justify pimavanserin treatment.On the other hand, the use of "upper" margins will guarantee that thepatients included in the trial will not suffer from ICD severe enough toquestion ethically the use of placebo during the 8 weeks of the treatment.Eligibility of patients with QUIP-RS sub-scores above 12 will be assessedupon investigator's request by an adjudication committee composed byindependent experts external to the study (cf IX.3 AdjudicationCommittee).

5. ICD onset after PD onset and after initiation of dopaminergic drugs

6. Patient treated by dopaminergic drugs for at least 3 months before randomization

7. Patient treated with a stable regimen of levodopa, dopamine agonists, COMT and MAOBinhibitors, amantadine, anticholinergic, antidepressant and benzodiazepine for atleast 1 month before the randomization and be willing to remain on the same dosesthroughout the course of their participation in the trial (Papay et al., 2014)

8. Patient with health insurance

9. Patient/ guardian / curator who sign the written informed consent

10. For women of childbearing potential, use of an effective contraception method* forat least 1 month prior to randomization until 8 weeks after the last dose of studydrug administration. Women who do not have an effective contraception* must : havehad her last natural menstruation ≥24 months prior to the selection visit, or havebeen surgically sterilized prior to the selection visit, or have had a hysterectomyprior to the selection visit.

Exclusion Criteria:

1. Patient suffering from another parkinsonian syndrome (multiple system atrophy,progressive supranuclear palsy, Lewy body dementia, corticobasal degeneration)

2. Patient who have a known hypersensitivity to the study treatment, based on knownallergies to drugs of the same class

3. Stroke, uncontrolled serious medical illness, myocardial infarction, congestiveheart failure, cardiac function disorders, within 6 months before randomization

4. Patient with history of long QT syndrome

5. Patient with long QTcB detected with ECG at inclusion visit (> 450 ms)

6. Patient treated with antipsychotic drugs during the last three months beforerandomization

7. Patient treated with concomitant medication leading to torsade de pointes (TdP)without discontinuation ≥ 5 half-lives before randomization (please refer tomedications list with known risks of TdP on appendix XVII.5.10 and check websitehttps://crediblemeds.org/index.php/tools/ for the most up-to-date information)

8. Patient with hydro-electrolytics troubles, particularly hypokaliemia or hypocalcemianot corrected, at inclusion visit or assessed no later than 8 days beforerandomization. To be eligible, the patient's electrolyte values should be within thefollowing limits:

3.5 ≤ K+ ≤ 5 mmol/L 135 ≤ Na+ ≤ 145 mmol/L 2,20 ≤ Ca2+ ≤ 2,60 mmol/L

9. Patient treated with a strong or moderate CYP3A4 inducer: carbamazepine, rifampicin,phenytoin, modafinil, efavirenz or a strong inhibitor of CYP3A4: azole antifungals,protease inhibitors, macrolids, without discontinuation ≥ 5 half-lives beforerandomization

10. Patient treated with medicinal plants interacting with CYP3A4 withoutdiscontinuation ≥ 5 half-lives before randomization (Echinacea (E.pupurea,E.angustifolia and E.pallida), Piperina, Artemisia, St. John's Wort and Ginkgo

11. Patient with Montreal Cognitive Assessment (MoCA) (Nasreddine et al., 2005) score < 20 (to exclude patients likely with dementia) at inclusion visit (Papay et al., 2014).

12. Patient suffering from severe depression or marked suicidal thoughts (score > 3 onthe suicidal thoughts item of the MADRS) at inclusion visit (Papay et al., 2014)

13. History of DBS within the past year before randomization, or change in stimulationparameters less than one month prior to randomization

14. Hematologic or solid malignancy diagnosis within 5 years prior to randomization.

[Note: Subjects with a history of localized skin cancer, basal cell or squamous cellcarcinoma, may be enrolled in the study as long as they are cancer free prior torandomization. Subjects with other localized cancers (without metastatic spread) whohave previously completed their course of treatment more than 5 years prior torandomization, are not currently receiving treatment and have been in remission maybe enrolled only if, in the opinion of the Investigator, there is no expectation forrecurrence or further cancer treatment during the study period. Antihormonal therapy (e.g., tamoxifen) is allowed if the subject's cancer is in remission and the subjectis on stable maintenance therapy to reduce their risk of recurrence.]

15. Patient suffering from severe renal impairment define as CrCL<30 mL/min,Cockcroft-Gault at inclusion visit or assessed no later than 8 days beforerandomization

16. Clinically significant hepatic impairment

17. Concurrent participation in another research involving a drug or medical device

18. Patient with language barriers precluding adequate understanding or co-operation orwho, in the opinion of the investigator, should not participate in the trial

19. Treatment with an investigational treatment within 30 days prior to randomization

20. Woman pregnant, nursing or of childbearing potential age without effectivecontraception methods* or intends to become pregnant.

• an effective contraception method is defined as implants, oraloestro-progestative contraceptives or progestative which inhibit ovulationcontraceptives (e.g, desogestrel), or double barrier method (condom plusspermicide or diaphragm plus spermicide) or levonorgestrel intrauterinedevices, or vasectomized partner (confirmed with two negative spermograms).