The study's purpose is to evaluate the efficacy and safety of troriluzole as adjunctive therapy compared to placebo in subjects with Obsessive Compulsive Disorder (OCD)

Inclusion Criteria:

1. Primary diagnosis of obsessive-compulsive disorder (OCD) as per Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition as confirmed by the MINI at Screening; The duration of the subject's illness must be ≥ 1 year
2. An inadequate response to current Standard of Care medication defined as selective serotonin reuptake inhibitor (excluding fluvoxamine) or clomipramine treatment at an adequate and stable dose for at least 8 weeks prior to screening and at least 12 weeks at baseline (adequate dose defined by USPI labeling); an inadequate response as defined per the MGH-TRQ-OCD, there has been minimal or no meaningful clinical benefit as perceived by the subject
3. Determined by the investigator to be medically stable at baseline/randomization as assessed by medical history, physical examination, laboratory test results, and electrocardiogram testing. Subjects must be physically able and expected to complete the trial as designed

Exclusion Criteria:

1. Subjects with a history of more than two (2) previous failed or inadequate treatment classes given for an adequate duration at an adequate dose as defined by the MGH-TRQ-OCD.
2. Current or prior history of: bipolar I or II disorder, schizophrenia or other psychotic disorders, schizoaffective disorder, autism or autistic spectrum disorders, borderline personality disorder, antisocial personality disorder, Tourette's disorder, body dysmorphic disorder, hoarding disorder; or psychosurgery, Deep Brain Stimulation (DBS) or Electroconvulsive Therapy (ECT); or general medical condition that may confound safety and/or efficacy results
3. Previous treatment in a study with troriluzole