Pimavanserin for Rigid-compulsive Symptoms in Autism Spectrum Disorder

Inclusion Criteria:

• Participant must be at least 16 years old and no greater than 40 years old.

• Participants 18 years of age or older or a legally acceptable representative must beable and willing to sign an informed consent document indicating understanding ofthe protocol and procedures and willingness to participate in full. For adultparticipants, a parent, caregiver, or other adult informant must also sign aninformed consent document indicating understanding the requirements for completingtheir portion of the study and their willingness to participate. For a participantwho is under 18 years of age, a parent or guardian must sign an informed consentdocument indicating understanding the protocol and procedures and willingness toparticipate in full. Signed assent indicating understanding and willingness toparticipate is required of participants under 18 years of age.

• Participant must have a diagnosis of Autism Spectrum Disorder, according to DSM-5criteria, made by a licensed study psychiatrist or psychologist and supported by theAutism Diagnostic Observation Schedule 2 (ADOS-2) completed at screening or withinthe past 12 months prior to screening by an appropriately trained professional.

• Participant must have a Clinical Global Impression of Severity for RepetitiveBehavior of 4 or greater, as rated by the study psychiatrist or psychologist atScreening and at Baseline

• Participant must have a non-verbal IQ of greater than or equal to 70 as determinedby the 4-subtest Wechsler Abbreviated Scale of Intelligence.

• Participant must be able to speak and understand English in order to complete studymeasures.

• Participant must live with a parent, primary caregiver, or other adult informant whocan complete study measures on the basis of spending an average of at least 4 hoursper day with the participant

• Parent, primary caregiver, or other adult informant must speak and understandEnglish in order to complete study measures.

• Participant must be able to self-administer study medication or haveparent/caregiver be able to administer study medication.

• Participant must be able to swallow study medication whole with liquid.

• Participant or legally acceptable representative must be willing to continue currentmedication(s) and behavioral intervention(s) and to not add or change medication(s)or behavioral intervention(s) over the full course of the study.

Exclusion Criteria:

• Participant is judged by the Investigator to be unable to perform or comply with allstudy specific requirements.

• Participant is an employee of an investigator with direct involvement in theproposed study or other studies under the direction of a study investigator, or is afamily member of an investigator.

• Participant has a history of any severe or unstable psychiatric condition (e.g.,schizophrenia or other psychotic disorder, bipolar disorder, major depressivedisorder) that, in the opinion of the Investigator, could confound theinterpretation of the study results or put the participant at undue risk. An acuteepisode of a mood disorder will be considered exclusionary; a participant with ahistory of mild to moderate mood disorder may be included in the study under thediscretion of the Investigator. Other stable psychiatric conditions are permitted atthe discretion of the Investigator (e.g., attention deficit hyperactivity disorder,generalized anxiety disorder, etc.).

• Participant has a current or recent history of clinically significant suicidalideation within the past 6 months, corresponding to a score of 3 or higher (activesuicidal ideation with some intent to act, without specific plan) on the ColumbiaSuicide Severity Rating Scale (C-SSRS), or a history of suicidal behavior within thepast year, as validated by the C-SSRS at screening or Day 1.

• Participant has met DSM-5 criteria for a substance abuse disorder within the last 6months prior to Screening, except for disorders related to caffeine or nicotine.

• Participant has a positive test for an illicit drug or cannabis at Screening orBaseline. Participants who test positive for cannabis and who have a validprescription may be rescreened if they agree to abstain from the cannabis for thelength of their participation in the study. The repeat test must be negative forthem to participate in the study.

• Participant is taking a serotonin reuptake inhibitor or antipsychotic medication.

• Participant has had a change to psychotropic medications within the last 2 months

• Participant has received electroconvulsive therapy (ECT) in the last 6 months.

• Participant has received new-onset psychotherapy or has had a change in theintensity of psychotherapy within the 2 months prior to Screening.

• Participant has known allergies, hypersensitivity, or intolerance to Pimavanserin orits excipients.

• Participant has received an investigational drug or used an investigational medicaldevice within 3 months before the planned start of study or is currently enrolled inan investigational study.

• Participant has a body mass index (BMI) <17 or >40 at Screening.

• Participant has a known history of long QT syndrome or family history of suddendeath.

• Participant has a history of myocardial infarction, unstable angina, acute coronarysyndrome, or cerebrovascular accident (CVA) within the last 4 months. Has greaterthan NYHA Class 2 congestive heart failure or Class 2 angina pectoris, sustainedventricular tachycardia (VT), ventricular fibrillation, torsade de pointes, orsyncope due to an arrhythmia.

• Participant has a history of neuroleptic malignant syndrome/serotonin syndrome.

• Participant has had a seizure within the past 12 months. Individuals with seizuredisorders who are on stable seizure medications (i.e., without seizures in the past 12 months) are permitted at the discretion of the Investigator.

• Participant is pregnant or breast-feeding, or planning to become pregnant orbreastfeed while enrolled in this study or within 3 months after the last dose ofstudy drug.

• Participant has current evidence, or a history within the previous 3 months prior toscreening, of a serious and/or unstable neurologic, cardiovascular, respiratory,gastrointestinal, renal, hepatic, hematologic, or other medical disorder, that, inthe opinion of the Investigator, would jeopardize the safe participation of theParticipant in the study.

• Participant has a history of malignancy within 5 years before screening (exceptionsare squamous and basal cell carcinomas of the skin and carcinoma in situ of thecervix, or malignancy that in the opinion of the Investigator, is considered curedwith minimal risk of recurrence).

• Participant has a known history of a positive hepatitis C virus (HCV) or humanimmunodeficiency virus (HIV) test.

• Participant has a Screening or Baseline ECG with a QTcF>450ms when the QRS durationis <120 ms or has a Screening or Baseline ECG with a QTcF>470 ms when the QRSduration is >120 ms.

• Participant has laboratory evidence of hypothyroidism at Screening, as measured bythyroid stimulating hormone (TSH) and reflex free thyroxine (T4). If TSH is abnormaland the reflex free T4 is normal, the Participant may be enrolled.

• Participant has current unstable diabetes or glycosylated hemoglobin (HbAIc) >8% atScreening.

• Participant has other clinically significant laboratory abnormalities that, in theopinion of the Investigator, would jeopardize the safe participation of the studyParticipant.